Literature variant report for SLC26A4

In this report you find an overview of the most relevant scientific literature for the relation of gene SLC26A4 to hearing loss terms. It includes all abstracts in which variations for this gene have been described.

  • First all the abstracts for SLC26A4 are collected based on the occurrence of and its synonyms in MEDLINE abstracts.
  • All abstracts are then ordered based on a 'variation' score. This score is obtained with a TenWise proprietary machine learning algorithm that has been trained for the classification of abstracts that describe genetic variations.
  • All abstracts are then highligted with three types of terms. These represent the genes and its synonyms, terms related to hearing loss and terms related to genetic variation.
A general liteature overview for SLC26A4 can be found on the TenWise MLQUERY server.

References
Segregation of a new mutation in SLC26A4 and p.E47X mutation in GJB2 within a consanguineous Tunisian family affected with Pendred syndrome. Mariem Ben Said;Houria Dhouib;Zeineb BenZina;Abdelmoneem Ghorbel;Felipe Moreno;Saber Masmoudi;Hammadi Ayadi;Mounira Hmani-Aifa. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22429511

OBJECTIVE: Recessive mutations of the SLC26A4 (PDS) gene on chromosome 7q31 can cause sensorineural hearing loss with goiter (Pendred syndrome) or non-syndromic autosomal recessive hearing loss (DFNB4). Furthermore, mutations in the GJB2 gene results in autosomal recessive (DFNB1) and dominant (DFNA3) non-syndromic hearing loss. The aim of the present study was to characterize a family with Pendred syndrome affected by severe to profound HL and presenting goiter. METHODS: Affected members underwent detailed audiologic examination and characterization. DNA samples from family members were genotyped with polymorphic microsatellite markers and sequencing of the SLC26A4 and GJB2 genes was performed. A total of 25 families with non-syndromic hearing loss were screened for the common p.E47X mutation in the GJB2 gene by direct dideoxy sequencing. RESULTS: Genetic microsatellite analysis showed linkage to the 7q22-q31 chromosomal region and mutation analysis revealed a novel frameshift mutation (c.451delG) in the SLC26A4 gene. Screening of the GJB2 gene in one patient, displayed a homozygous p.E47X mutation, together with a heterozygous c.451delG mutation. Screening of 25 families with HL showed frequent segregation of the p.E47X mutation, which was homozygous in five of these families. Haplotype analysis using microsatellite markers and single nucleotide polymorphisms (SNPs) closely flanking the GJB2 gene, revealed the presence of two disease-associated-haplotypes suggesting the presence of at least, two founder effects carrying the p.E47X non-sense mutation in the Tunisian population. CONCLUSIONS: The segregation of both SLC26A4 and GJB2 mutations in the family illustrates once again the unexpected intra-familial genetic heterogeneity in consanguineous families and highlights the difficulty of genetic counselling in such families. In addition, our results disclose the existence of founder effects in the Tunisian population.
Prevalent SLC26A4 mutations in patients with enlarged vestibular aqueduct and/or Mondini dysplasia: a unique spectrum of mutations in Taiwan, including a frequent founder mutation. Chen-Chi Wu;Te-Huei Yeh;Pei-Jer Chen;Chuan-Jen Hsu. 2005. Laryngoscope. 115. PMID: 15933521

OBJECTIVES/HYPOTHESIS: The purpose of the study is to elucidate the mutation spectrum of SLC26A4 among patients with enlarged vestibular aqueduct and/or Mondini dysplasia in Taiwan and to explore the origin of the most common mutation, IVS7-2A>G. The correlation between the genotypes and the phenotypes is also investigated, with special emphasis placed on comparison between the genotypes and hearing levels. STUDY DESIGN: A 3-year prospective clinical genetic study at a tertiary care university hospital. METHOD: Mutations on SLC26A4 were screened in 38 families that fulfilled the criteria of enrollment, and single nucleotide polymorphisms (SNPs) in the vicinity of IVS7-2A>G were typed. The presence of goiter, radiologic findings, and audiologic results of the probands were then compared according to the genotypes. RESULTS: A total of eight mutations were detected in 33 families, and IVS7-2A>G accounted for 84% (48/57) of the mutated alleles. SNP analysis confirmed the founder effect of IVS7-2A>G. Meanwhile, no obvious correlation was observed between SLC26A4 genotypes and phenotypes. CONCLUSION: The present study disclosed the unique SLC26A4 mutation spectrum in Taiwan, confirmed that IVS7-2A>G arose from a common ancestor, and demonstrated the lack of correlation between genotypes and phenotypes. High prevalence of certain SLC26A4 mutations in East Asians, as revealed here and previously, might largely facilitate mutation screening and genetic counseling in these areas.
Identification of a founder mutation for Pendred syndrome in families from northwest Iran. Marzieh Mohseni;Asal Honarpour;Reza Mozafari;Behzad Davarnia;Hossein Najmabadi;Kimia Kahrizi. 2014. Int J Pediatr Otorhinolaryngol. 78. PMID: 25239229

OBJECTIVE: Mutations in the SLC26A4 gene cause both Pendred syndrome and autosomal recessive nonsyndromic hearing loss (ARNSHL) at the DFNB4 locus. The SLC26A4 mutations vary among different communities. Previous studies have shown that mutations in the SLC26A4 gene are responsible for the more common syndromic hereditary hearing loss in Iran. This study assesses the possibility of a founder mutation for Pendred syndrome in northwest Iran. MATERIALS AND METHODS: In this study, we performed comprehensive clinical and genetic evaluations in two unrelated families from northwest Iran with nine members affected by hearing loss (HL). After testing short tandem repeat (STR) markers to confirm linkage to the SLC26A4 locus, we screened the SLC26A4 gene by Sanger sequencing of all 21 exons, exon-intron boundaries and the promoter region for any causative mutation. We identified the same causative mutation in these two families as we had detected earlier in two other Azeri families from northwest Iran. To investigate the possibility of a founder effect in these four families, we conducted haplotype analysis, and 14 single nucleotide polymorphisms (SNPs) throughout the SLC26A4 gene were genotyped. RESULTS: Patients in the two families showed the phenotype of Pendred syndrome. A known frameshift mutation (c.965insA, p.N322Fs7X) in exon 8 was identified in the two families, which was the same mutation that we detected previously in two other Azeri families. The results of haplotype analysis showed that all 15 patients from four families shared the founder mutation. Common haplotypes were not observed in noncarrier members. CONCLUSIONS: Based on the results of our two studies, the c.965insA mutation has only been described in Iranian families from northwest Iran, so there is evidence for a founder mutation originating in this part of Iran.
Simultaneous multi‑gene mutation screening using SNPscan in patients from ethnic minorities with nonsyndromic hearing‑impairment in Northwest China. Shi-Hong Duan;Jian-Li Ma;Xiao-Long Yang;Yu-Fen Guo. 2017. Mol Med Rep. 16. PMID: 28901477

The present study aimed to investigate the molecular etiology of nonsyndromic hearing impairment (HI) in hearing impaired populations of Hui, Tibetan, and Tu ethnicities in northwest China. A total of 283 unrelated subjects with HI who attended special education schools in northwest China were enrolled in the present study. Single-nucleotide polymorphisms (SNPs) in three common deafness‑related genes, gap junction protein β2 (GJB2), solute carrier family 26 member 4 (SLC26A4) and mitochondrially encoded 12S RNA (mtDNA12SrRNA), were detected using a SNPscan technique. GJB2 mutations were detected in 14.89% of Hui patients, 9.37% of Tibetan patients and 11.83% of Tu patients. The most prevalent GJB2 mutation in the Hui and Tu patients was c.235delC. In the Tibetan patients, the c.109G>A SNP exhibited the highest allele frequency. SLC26A4 mutations were detected in 10.64% of Hui patients, 6.25% of Tibetan patients, and 8.6% of Tu patients. The most common SLC26A4 mutation was c.919‑2A>Gin the Hui, Tibetan, and Tu patients, and the second most common SLC26A4 mutations in these patients were c.1517T>G, c.1226G>A andc.2168A>G, respectively. The mutation rates ofmtDNA12SrRNA in the Hui, Tibetan, and Tu patients were 1.06, 5.21, and 5.38%, respectively. These findings demonstrate that the mutation spectra of these deafness‑related genes are unique amongst these three ethnic groups. This information will be helpful in designing a protocol for genetic testing for deafness and for achieving accurate molecular diagnoses in northwest China.
Optimization of simultaneous screening of the main mutations involved in non-syndromic deafness using the TaqMan® OpenArray™ Genotyping platform. Fábio Tadeu Arrojo Martins;Priscila Zonzini Ramos;Maria Carolina Costa Melo Svidnicki;Arthur Menino Castilho;Edi Lúcia Sartorato. 2013. BMC Med Genet. 14. PMID: 24156272

BACKGROUND: Hearing loss is the most common sensory deficit in humans, affecting approximately 10% of the global population. In developed countries, one in every 500 individuals suffers from severe to profound bilateral sensorineural hearing loss. For those up to 5 years old, the proportion is higher, at 2.7 in 1000 individuals, and for adolescents the average is 3.5 in 1000. Among the causes of hearing loss, more than 50% are related to genetic factors. To date, nearly 150 loci and 64 genes have been associated with hearing loss. Mutations in the GJB2 gene, which encodes connexin 26, constitute the main genetic cause. So far, more than 300 variations have been described in this gene.As a response to the clinical and genetic heterogeneity of hearing loss and the importance of correct molecular diagnosis of individuals with hereditary hearing loss, this study worked in the optimization for a diagnostic protocol employing a high-throughput genotyping technology. METHODS: For this work, was used the TaqMan® OpenArray™ Genotyping platform. This is a high performance, high-throughput technology based on real-time PCR, which enables the evaluation of up to 3072 SNPs (Single Nucleotide Polymorphisms), point mutations, small deletions, and insertions, using a single genotyping plate. For the study, were selected the layout allowing to analyze 32 alterations in 96 individuals simultaneously. In the end, the generated results were validated by conventional techniques, as direct sequencing, Multiplex PCR and RFLP-PCR. RESULTS: A total of 376 individuals were analyzed, of which 94 were healthy controls, totaling 4 plates in duplicate. All 31 of the changes analyzed were present in the nuclear genes GJB2, GJB6, CRYL1, TMC1, SLC26A4, miR-96, and OTOF, and in the mitochondrial genes MT-RNR1 and MT-TS1. The reactions were subsequently validated by established techniques (direct sequencing, multiplex PCR, and RFLP-PCR) that had previously been used to perform molecular screening of hearing loss at the Human Genetics Laboratory of the Center for Molecular Biology and Genetic Engineering (CBMEG), at the State University of Campinas (UNICAMP). In total, 11,656 genotyping reactions were performed. Of these, only 351 reactions failed, representing approximately 3.01% of the total. The average accuracy of genotyping using the OpenArray™ plates was 96.99%. CONCLUSIONS: The results demonstrated the accuracy, low cost, and good reproducibility of the technique, indicating that the TaqMan® OpenArray™ Genotyping Platform is a useful and reliable tool for application in molecular diagnostic testing of hearing loss.
A rapid method for simultaneous multi-gene mutation screening in children with nonsyndromic hearing loss. Wan Du;Jing Cheng;Hui Ding;Zhengwen Jiang;Yufen Guo;Huijun Yuan. 2014. Genomics. 104. PMID: 25149764

Hearing loss (HL) is a common genetically heterogeneous sensory disorder, occurring in 1 to 3 per 1000 live births. In spite of the extraordinary genetic heterogeneity, variants in GJB2, MT-RNR1, and SLC26A4 genes have been considered as the main reasons of nonsyndromic hearing loss in Chinese population. We developed a rapid multiplex genetic screening system called the SNPscan assay technique which could detect the 115 mutations of the above three genes. This technique is a high-throughput and cost-saving SNP genotyping method. We found that the carrier rate of mutations in the GJB2 gene, MT-RNR1 gene, and SLC26A4 gene was 26.21%, 1.86%, and 25.46% of the patients with nonsyndromic hearing loss, respectively. Using this method, up to 50% of the patients in our study were identified to have hereditary HL caused by mutations in the three genes. It is applicable to not only genetic diagnosis of HL, but also molecular screening of other inherited diseases.
Research of genetic bases of hereditary non-syndromic hearing loss. Aslı Subaşıoğlu;Duygu Duman;Aslı Sırmacı;Güney Bademci;Fehime Carkıt;Mehmet Akif Somdaş;Mustafa Erkan;Mustafa Tekin;Munis Dündar. 2017. Turk Pediatri Ars. 52. PMID: 29062245

AIM: Hearing loss is the most common sensory disorder that affects approximately one per 1000 live births. With this project, we aimed to identify gene variants that were common causes of hearing loss in Turkey to contribute to the planning of genetic screening programs for hearing loss, as well as to improve genetic counseling to affected families. MATERIAL AND METHODS: Twenty-one families with at least two affected individuals and parental consanguinity who presented with non-syndromic severe-to-profound sensorineural hearing loss were included in this study. We first screened for mutations in GJB2 and mitochondrial DNA 12S RNA genes. Subsequently, we genotyped the TMIE c.250C>T and SNP markers flanking the SLC26A4, MYO7A, MYO15A, OTOF, CDH23, TMIE, TECTA, PCDH15, TMC1, TMPRSS3, TMHS genes in the remaining twelve families without mutations in GJB2. RESULTS: Screening for mutations in GJB2 gene showed c.[35delG];[35delG] mutation in four families, c.[35delG];[507C>A] mutation in two families, c.[35delG];[-23+1G>A] mutation in one family, and c.457G>A heterozygous mutation in one family. Genotyping SNP markers showed the c.[250C>T];[250C>T] mutation in TMIE in one family. A homozygous region with SNP genotypes was detected with the OTOF gene in one family, the TMPRSS3 gene in another family, and also a homozygous region was detected with TMHS, OTOF, and TMPRSS3 genes in another family. CONCLUSIONS: Further research will be required to determine the genetic bases of hearing loss in families with non-syndromic hearing loss.
GJB2, SLC26A4, and mitochondrial DNA12S rRNA hot-spots in 156 subjects with non-syndromic hearing loss in Tengzhou, China. Yalin Ma;Yun Xiao;Xiaohui Bai;Fengguo Zhang;Daogong Zhang;Xinmao Xu;Lei Xu;Haibo Wang. 2016. Acta Otolaryngol. 136. PMID: 27066914

CONCLUSION: In this cohort of 156 non-syndromic hearing-impaired subjects of Tengzhou area, the most common deafness-associated genes GJB2, SLC26A4 and mtDNA 12S rRNA were investigated by SNPscan efficiently. GJB2 c.235delC and SLC26A4 c.IVS7-2A > G were the most common mutation sites. OBJECTIVES: Until now, there is no systematic gentic analysis in patients with non-syndromic hearing loss for Tengzhou area, so we evaluated the molecular etiology to investigate the hot-sports. METHODS: Peripheral blood samples were obtained from 156 patients with severe-to-profound non-syndromic deafness in Tengzhou. The SNP scan assay technique was performed for a rapid multiplex genetic screening to detect the 115 mutations of the most common three genes. All results were statistically analyzed with SPSS software. RESULTS: Among the 156 analyzed patients, 60 patients were demonstrated with deafness genes, accounting for 38.46% (60/156), including GJB2 (22.44%, 35/156), SLC26A4 (13.66%, 22/156), and mtDNA 12S rRNA (2.56%, 4/156). In this study, we confirmed 23 deafness-causing mutations and 27 different allelic combinations including GJB2 (eight variants, 11 allelic combinations), SLC26A4 (13 variants, 16 allelic combinations) and mtDNA 12S rRNA (two variants). The occurrence rates of these deafness-causing mutations GJB2 c.235delC and SLC26A4 c.IVS7-2A > G were significantly higher than other mutation sites (p < 0.01).
Prevalence of Mutations in Deafness-Causing Genes in Cochlear Implanted Patients with Profound Nonsyndromic Sensorineural Hearing Loss in Shandong Province, China. Jianfen Luo;Xiaohui Bai;Fengguo Zhang;Yun Xiao;Lintao Gu;Yuechen Han;Zhaomin Fan;Jianfeng Li;Lei Xu;Haibo Wang. 2017. Ann Hum Genet. 81. PMID: 28786104

The mutations of GJB2, SLC26A4, and mtDNA12SrRNA are the most common inherited causes of nonsyndromic sensorineural hearing loss (NSHL) in China, yet previous genetic screenings were mainly carried on patients with moderate-to-profound impairment. We aimed to detect the mutation frequencies in NSHL population within a more specified range of severity. Patients with profound NSHL who had undergone cochlear implantation in the Shandong Provincial Hospital (Shandong, China) were recruited. The majority (n  =  472) were between 0.7 and 6 years old, and the remaining (n  =  63) were between 6 and 70 years old. In total, 115 mutation alleles of the three genes were screened with SNP scan assay. Of the patients, 19.44% (104/535) were found to have GJB2 mutations, and the most common allele was c.235delC, followed by c.299_300delAT and c.109G>A. SLC26A4 mutations were detected in 13.46% patients (72/535), and the most common allele was c.919-2A>G (IVS7-2A>G), followed by c.1174A>T and c.2168A>G. Seven patients (1.31%) carried mutations in mtDNA12SrRNA, with the alleles of m.1555A>G and m.1494C>T. We found the allele frequency of c.109G>A (GJB2) was relatively lower in the profound NSHL population in comparison to the moderate-to-profound ones, and the c.1174A>T (SLC26A4) relatively higher. It suggests those mutations may be connected with the degree of deafness, which needs more observations and analyses to support.
Refining the DFNB17 interval in consanguineous Indian families. Yingshi Guo;Valentina Pilipenko;Lynne H Y Lim;Hongwei Dou;Liane Johnson;C R Srikumari Srisailapathy;Arabandi Ramesh;Daniel I Choo;Richard J H Smith;John H Greinwald. 2004. Mol Biol Rep. 31. PMID: 15293785

We previously mapped the DFNB17 locus to a 3-4 cM interval on human chromosome 7q31 in a large consanguineous Indian family with congenital profound sensorineural hearing loss. To further refine this interval, 30 new highly polymorphic markers and 8 SNPs were analyzed against the pedigree. Re-analysis in the original DFNB 17 family and additional data from a second unrelated consanguineous family with congenital deafness found to map to the interval, limited the area of shared homozygosity-by-descent (HBD) to approximately 4 megabase (Mb) between markers D7S2453 and D7S525. Nineteen known genes and over 20 other cDNAs have been identified in the refined DFNB 17 interval, including the SLC26A4 gene. We have analyzed 4 other cochlear-expressed genes that map to the DFNB17 interval as candidate genes. Analysis of coding and splice site regions of these cochlear expressed genes did not reveal any disease causing mutations. Further study of other candidate genes is currently underway.
A novel synonymous mutation causing complete skipping of exon 16 in the SLC26A4 gene in a Korean family with hearing loss. Yoonjung Kim;Hui Ram Kim;Juwon Kim;Joong-Wook Shin;Hong-Joon Park;Jae Young Choi;Un-Kyung Kim;Kyung-A Lee. 2012. Biochem Biophys Res Commun. 430. PMID: 23246836

INTRODUCTION: Mutations in PDS (or SLC26A4) cause both Pendred syndrome (PS) and DFNB4, two autosomal recessive disorders that share hearing loss as a common feature. PS and DFNB4 are genetically homogeneous disorders caused by bi-allelic SLC26A4 mutations. Here, we report a novel synonymous mutation (c.1803G>A, p.Lys601Lys), that caused aberrant splicing in two Korean family members who were clinically considered to have DFNB4, along with congenital hearing loss and dilated vestibular aqueducts (DVA). METHODS: After extracting DNA from whole blood using standard procedures, the 21 exons and flanking introns of SLC26A4 were amplified with PCR. To evaluate the implication of a novel synonymous mutation (c.1803G>A), we used The Berkeley Drosophila Genome Project (BDGP) (http://www.fruitfly.org/) as a splice site prediction program and performed exon trapping analysis. RESULTS: In molecular analysis of the 21 exons of SCL26A4, we detected a known splicing mutation (c.919-2A>G, heterozygote) and a novel variant (c.1803G>A, heterozygote) in the patients (II-1 and II-2). According to in silico analysis, the novel variant (c.1803G>A) affects canonical splice donor nucleotide positioning. To define the transcript level effects of this novel 1803G>A variant, we performed exon trapping and confirmed that exon 16 is completely skipped in this variant type. CONCLUSION: We report a novel synonymous mutation (c.1803G>A) causing complete exon 16 skipping in the SLC26A4 gene in two Korean family members with hearing loss. This is the first case of a synonymous SNP (c.1803G>A) affecting vestibulocochlear organs through altering splicing accuracy by causing a complete skipping of exon 16. An important issue raised by this study is that synonymous mutations that have been previously ignored in clinical diagnoses must now be considered as potential pathogenic mutations.
A unique case of de novo 5q33.3-q34 triplication with uniparental isodisomy of 5q34-qter. Atsushi Fujita;Hiroshi Suzumura;Mitsuko Nakashima;Yoshinori Tsurusaki;Hirotomo Saitsu;Naoki Harada;Naomichi Matsumoto;Noriko Miyake. 2013. Am J Med Genet A. 161A. PMID: 23824987

De novo triplication together with uniparental disomy (UPD) is a rare genomic rearrangement, and, to our knowledge, co-occurrence has previously only been reported in two individuals. We encountered a patient with a suspected karyotype of 46,XX,del(5)(q33.1q33.3),dup(5)(q31.3q33.3) or (q33.1q35.1). Genetic analysis revealed tetrasomy of 5q33.3-q34 caused by de novo middle inverted triplication and uniparental isodisomy of 5q34-qter. Most clinical features in the patient were observed in previously reported cases of duplication overlapping with 5q33.3-q34, with the exception of hearing loss. The FOXI1 gene, which causes autosomal recessive deafness (OMIM 600791, DFNB4) when mutated, was contained within the uniparental isodisomy region (5q34-qter). However, no mutations were identified following Sanger sequencing of FOXI1. This is the first report of a patient with de novo triplication together with uniparental isodisomy of chromosome 5q. As segmental isodisomy is a post-fertilization error, it is thought to have occurred during mitosis just after fertilization via a U-type exchange, while inverted duplication could have occurred during meiosis or mitosis. This study reaffirms that the single nucleotide polymorphism (SNP) array is a powerful tool to screen for UPD in a single experiment, especially in cases of isodisomy.
Lack of significant association between mutations of KCNJ10 or FOXI1 and SLC26A4 mutations in Pendred syndrome/enlarged vestibular aqueducts. Priya Landa;Ann-Marie Differ;Kaukab Rajput;Lucy Jenkins;Maria Bitner-Glindzicz. 2013. BMC Med Genet. 14. PMID: 23965030

BACKGROUND: Pendred syndrome is a common autosomal recessive disorder causing deafness. Features include sensorineural hearing impairment, goitre, enlarged vestibular aqueducts (EVA) and occasionally Mondini dysplasia. Hearing impairment and EVA may occur in the absence of goitre or thyroid dyshormonogensis in a condition known as non-syndromic EVA. A significant number of patients with Pendred syndrome and non-syndromic EVA show only one mutation in SLC26A4. Two genes, KCNJ10, encoding an inwardly rectifying potassium channel and FOXI1, a transcriptional factor gene, are thought to play a role in the disease phenotypes. METHODS: Using Polymerase Chain Reaction and Sanger sequencing, sixty-eight patients with monoallelic mutations of SLC26A4 were tested for mutations in KCNJ10 and FOXI1. RESULTS: Two variants were observed in the KCNJ10 gene, p.Arg271Cys in three patients and p.Arg18Gln in one patient; only one variant, p.Arg123Trp was observed in the FOXI1 gene in a single patient. Both p.Arg271Cys and p.Arg18Gln are likely to be polymorphisms as judged by their frequency in the general population. CONCLUSION: Therefore we found no evidence for a significant association between mutations of KCNJ10 and FOXI1 with SLC26A4. It was also observed that the variant, p.Arg271Cys in KCNJ10, previously thought to have a protective effect against seizure susceptibility, was found in a patient with Pendred syndrome with co-existing epilepsy.
Molecular and functional characterization of human pendrin and its allelic variants. Silvia Dossena;Charity Nofziger;Grazia Tamma;Emanuele Bernardinelli;Simone Vanoni;Christoph Nowak;Elisabeth Grabmayer;Sonja Kössler;Susanne Stephan;Wolfgang Patsch;Markus Paulmichl. 2011. Cell Physiol Biochem. 28. PMID: 22116358

Pendrin (SLC26A4, PDS) is an electroneutral anion exchanger transporting I(-), Cl(-), HCO(3)(-), OH(-), SCN(-) and formate. In the thyroid, pendrin is expressed at the apical membrane of the follicular epithelium and may be involved in mediating apical iodide efflux into the follicle; in the inner ear, it plays a crucial role in the conditioning of the pH and ion composition of the endolymph; in the kidney, it may exert a role in pH homeostasis and regulation of blood pressure. Mutations of the pendrin gene can lead to syndromic and non-syndromic hearing loss with EVA (enlarged vestibular aqueduct). Functional tests of mutated pendrin allelic variants found in patients with Pendred syndrome or non-syndromic EVA (ns-EVA) revealed that the pathological phenotype is due to the reduction or loss of function of the ion transport activity. The diagnosis of Pendred syndrome and ns-EVA can be difficult because of the presence of phenocopies of Pendred syndrome and benign polymorphisms occurring in the general population. As a consequence, defining whether or not an allelic variant is pathogenic is crucial. Recently, we found that the two parameters used so far to assess the pathogenic potential of a mutation, i.e. low incidence in the control population, and substitution of evolutionary conserved amino acids, are not always reliable for predicting the functionality of pendrin allelic variants; actually, we identified mutations occurring with the same frequency in the cohort of hearing impaired patients and in the control group of normal hearing individuals. Moreover, we identified functional polymorphisms affecting highly conserved amino acids. As a general rule however, we observed a complete loss of function for all truncations and amino acid substitutions involving a proline. In this view, clinical and radiological studies should be combined with genetic and molecular studies for a definitive diagnosis. In performing genetic studies, the possibility that the mutation could affect regions other than the pendrin coding region, such as its promoter region and/or the coding regions of functionally related genes (FOXI1, KCNJ10), should be taken into account. The presence of benign polymorphisms in the population suggests that genetic studies should be corroborated by functional studies; in this context, the existence of hypo-functional variants and possible differences between the I(-)/Cl(-) and Cl(-)/HCO(3)(-) exchange activities should be carefully evaluated.
An association study of the SLC26A4 gene in children with mental retardation. Jun Li;Fuchang Zhang;Jianjun Gao;Zhen Cai;Qian Zhao;Yi Xing;Jie Xu;Yun Liu;Liyan Shao;Ronglin Che;Zhiyun Wei;Lin He. 2009. Neurosci Lett. 457. PMID: 19429184

It is generally considered that iodine deficiency is the single most common cause of preventable mental retardation (MR) and brain damage. The SLC26A4 gene is expressed at the apical surface of thyrocytes and its product forms an efficient iodide-trapping mechanism. To investigate whether variability in the SLC26A4 gene influences the risk of iodine-deficiency based MR, we undertook an association study between SLC26A4 and MR. Participants were recruited from a relatively isolated and traditionally iodine-deficient region with a high prevalence of MR. The SNPs we selected from the dbSNP and HapMap were identified using ARMS-PCR and sequencing methods. Singular-locus and haplotype association analysis indicated no association between the SLC26A4 gene and MR (p>0.05). The negative results suggest that the SLC26A4 gene has no measurable impact on iodine-deficiency based MR. In view of the characteristics of our samples, our study may provide a good reference for research into the transport features of pendrin in the thyrocyte apical surface.
[A novel technique for simultaneous multi-gene mutation screening in 225 patients with nonsyndromic hearing loss]. Di Zhang;Hong Duan;Peng Lin;Jing Cheng;Cuicui Wang;Yuanxu Ma;Yan Cheng;Hui Zhao;Wei Wang;Kaixu Xu;Dongyi Han;Huijun Yuan. 2016. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 51. PMID: 27033575

OBJECTIVE: Using simultaneous multi-gene mutation screening to investigate the new method molecular epidemiological basis of 225 patients with nonsyndromic hearing loss in Tianjin, and verifying the for simultaneous multi-gene mutation screening. METHODS: Two hundred and twenty-five patients with severe non-syndromic deafness from Tianjin CDPF and Association of the Deaf were included in the study. The single nucleotide polymorphisms scan, (SNPscan) technique was used for screening the 115 spots mutations in three common deafness-related genes (GJB2, SLC26A4, mtDNA 12S rRNA) of patients with nonsyndromic hearing loss in Tianjin. We verified the results by Sanger sequencing. RESULTS: Among the 225 patients, there were 111 cases of deafness caused by mutation (49.3%). Using this method, up to 50% of the patients in our study were identified to have hereditary HL caused by mutations in the three genes. 56 patients with the GJB2 mutations were detected (24.9%), including 30 cases of homozygous mutations (13.3%), 26 patients (11.6%) of compound heterozygous mutations, and 21 cases (9.33%) of single heterozygous mutations. 50 patients with the SLC26A4 mutations were detected (22.2%), including 22 cases of homozygous mutations(9.8%), 28 patients (12.4%) of compound heterozygous mutations, and 22 cases (9.8%) of single heterozygous mutations. mtDNA 12S rRNA A1555G mutation was detected in 5 patients (2.2%). mtDNA 12S rRNA 1494C>T mutation was not detected. We verified the results by Sanger sequencing. The accuracy of the sequencing results was 100%. The SNPscan cost eight hours and 160 yuan (each sample). CONCLUSIONS: Applying SNPscan technology can be accurate, rapid and cost-effective diagnostic screening in patients with hearing loss for etiology investigation. It is expected to become an effective means of large-scale genetic testing for hereditary deafness.
[Studies of the strategy for newborn gene screening]. Qiu-Ju Wang;Ya-Li Zhao;Lan Lan;Cui Zhao;Ming-Kun Han;Dong-Yi Han. 2008. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 42. PMID: 18300440

OBJECTIVE: To discuss and analyze the feasibility and strategy for perform the newborn gene screening in the process of newborn hearing screening in order to supply the defects or limitation in the hearing screening. METHODS: Four hundreds and sixty newborn babies from December 2006 to April 2007 accepted the simultaneous hearing and gene screening. Otoacoustic emission (OAE) was used for the first step hearing screening and OAE combined with auto auditory brainstem response (AABR) detection for the second step screening. Newborn genetic disease screening cards were used for collecting the blood spot from the umbilical cord within the moment of newborn. The cards could be directly performed the polymerase chain reaction (PCR) for screening the mitochondrial 12SrRNA 1555G and GJB2 as well as SLC26A4 genes mutations. The restriction enzyme Alw26I was used to recognize the point mutation of 12SrRNA A1555G. The samples with the possible 12SrRNA A1555G mutation were then sequenced to verify. The PCR products from the GJB2 coding region and SLC26A4 IVS7-2A > G hot spot region were sequenced directly. The software of DNAStar was used to analysis the sequence. RESULTS: The first step of hearing screening of 460 newborn babies showed " refer" on the left ear of nine babies and on the right ear of three babies. Seven showed "refer" on bilateral with the the total of babies 19. After 42 days, they accepted the second step for hearing screening. 16 of the 19 were showed "pass" with OAE and AABR. One baby showed "pass" on the left ear, "refer" on the right ear with the OAE detection but bilateral "pass" with AABR. Two babies failed to accept the re-examination. The newborn gene screening showed five of the 460 babies had the positive response on the A1555G restriction enzyme assay. Of the five babies, one was proved to be the 12SrRNA A1555G mutation and three were the C1556T mutations and one sequence was normal. For the SLC26A4 gene screening, five were the heterozygote of IVS7-2A > G mutation were found and one was carrier the polymorphism of IVS7-18T > G and another was IVS6-62_63insGT heterozygote carrier. For the GJB2 gene screening, eight were 235delC heterozygote carriers, four were G109A heterozygote carriers. All the gene screening found 23 newborn babies of the 460 harbored the changes in the three genes. Of those, one was the 12SrRNA A1555G. pathogenic mutation and 13 were pathogenic heterozygote carriers, nine were the polymorphisms. It was worth to pay more attentions that A1555G mutation was found in the baby whose hearing screening was "pass" in the hearing screening as well as the 13 heterozygote carrier for GJB2 and SLC26A4 gene. CONCLUSIONS: It might be one of the powerful strategy for adding the concept of newborn gene screening into the hearing screening for the purpose of early diagnosis and discovery the prelingual or late-onset or the high risk as well as the pathogenic carriers. On the basis of the research progress, it was necessary to develop the national newborn gene screening into the process of newborn hearing screening.
Whole Exome Sequencing Reveals Homozygous Mutations in RAI1, OTOF, and SLC26A4 Genes Associated with Nonsyndromic Hearing Loss in Altaian Families (South Siberia). Alexander Y Сhurbanov;Tatiana M Karafet;Igor V Morozov;Valeriia Yu Mikhalskaia;Marina V Zytsar;Alexander A Bondar;Olga L Posukh. 2016. PLoS One. 11. PMID: 27082237

Hearing loss (HL) is one of the most common sensorineural disorders and several dozen genes contribute to its pathogenesis. Establishing a genetic diagnosis of HL is of great importance for clinical evaluation of deaf patients and for estimating recurrence risks for their families. Efforts to identify genes responsible for HL have been challenged by high genetic heterogeneity and different ethnic-specific prevalence of inherited deafness. Here we present the utility of whole exome sequencing (WES) for identifying candidate causal variants for previously unexplained nonsyndromic HL of seven patients from four unrelated Altaian families (the Altai Republic, South Siberia). The WES analysis revealed homozygous missense mutations in three genes associated with HL. Mutation c.2168A>G (SLC26A4) was found in one family, a novel mutation c.1111G>C (OTOF) was revealed in another family, and mutation c.5254G>A (RAI1) was found in two families. Sanger sequencing was applied for screening of identified variants in an ethnically diverse cohort of other patients with HL (n = 116) and in Altaian controls (n = 120). Identified variants were found only in patients of Altaian ethnicity (n = 93). Several lines of evidences support the association of homozygosity for discovered variants c.5254G>A (RAI1), c.1111C>G (OTOF), and c.2168A>G (SLC26A4) with HL in Altaian patients. Local prevalence of identified variants implies possible founder effect in significant number of HL cases in indigenous population of the Altai region. Notably, this is the first reported instance of patients with RAI1 missense mutation whose HL is not accompanied by specific traits typical for Smith-Magenis syndrome. Presumed association of RAI1 gene variant c.5254G>A with isolated HL needs to be proved by further experimental studies.
Identification of SLC26A4 gene mutations in Iranian families with hereditary hearing impairment. Kimia Kahrizi;Marzieh Mohseni;Carla Nishimura;Niloofar Bazazzadegan;Stephanie M Fischer;Atefeh Dehghani;Morteza Sayfati;Maryam Taghdiri;Payman Jamali;Richard J H Smith;Fereydoun Azizi;Hossein Najmabadi. 2008. Eur J Pediatr. 168. PMID: 18813951

Mutations in the SLC26A4 gene at the DFNB4 locus are responsible for Pendred syndrome and non-syndromic hereditary hearing loss (DFNB4). This study included 80 nuclear families with two or more siblings segregating presumed autosomal recessive hearing loss. All deaf persons tested negative for mutations in GJB2 at the DFNB1 locus and were, therefore, screened for autozygosity by descent (ABD) using short tandem repeat polymorphisms (STRPs) that flanked SLC26A4. In 12 families, homozygosity for STRPs suggested possible ABD in this genomic region. Affected individuals in five families had a positive perchlorate discharge test. Sequence analysis of SLC26A4 identified ten mutations in eight families (T420I, 1197delT, G334V, R409H, T721M, R79X, S448L, L597S, 965insA and L445W), of which, four are novel (T420I, G334V, 965insA and R79X). These results imply that Pendred syndrome is the most prevalent form of syndromic hereditary hearing loss in Iran.
Genetic analysis of presbycusis by arrayed primer extension. Juan Rodriguez-Paris;Charles Ballay;Michelle Inserra;Katrina Stidham;Tahl Colen;Joseph Roberson;Phyllis Gardner;Iris Schrijver. 2008. Ann Clin Lab Sci. 38. PMID: 18988928

Using the Hereditary Hearing Loss arrayed primer extension (APEX) array, which contains 198 mutations across 8 hearing loss-associated genes (GJB2, GJB6, GJB3, GJA1, SLC26A4, SLC26A5, 12S-rRNA, and tRNA Ser), we compared the frequency of sequence variants in 94 individuals with early presbycusis to 50 unaffected controls and aimed to identify possible genetic contributors. This cross-sectional study was performed at Stanford University with presbycusis samples from the California Ear Institute. The patients were between ages 20 and 65 yr, with adult-onset sensorineural hearing loss of unknown etiology, and carried a clinical diagnosis of early presbycusis. Exclusion criteria comprised known causes of hearing loss such as significant noise exposure, trauma, ototoxic medication, neoplasm, and congenital infection or syndrome, as well as congenital or pediatric onset. Sequence changes were identified in 11.7% and 10% of presbycusis and control alleles, respectively. Among the presbycusis group, these solely occurred within the GJB2 and SLC26A4 genes. Homozygous and compound heterozygous pathogenic mutations were exclusively seen in affected individuals. We were unable to detect a statistically significant difference between our control and affected populations regarding the frequency of sequence variants detected with the APEX array. Individuals who carry two mild mutations in the GJB2 gene possibly have an increased risk of developing early presbycusis.
Mutation analysis of the SLC26A4, FOXI1 and KCNJ10 genes in individuals with congenital hearing loss. Lynn M Pique;Marie-Luise Brennan;Colin J Davidson;Frederick Schaefer;John Greinwald;Iris Schrijver. 2014. PeerJ. 2. PMID: 24860705

Pendred syndrome (PDS) and DFNB4 comprise a phenotypic spectrum of sensorineural hearing loss disorders that typically result from biallelic mutations of the SLC26A4 gene. Although PDS and DFNB4 are recessively inherited, sequencing of the coding regions and splice sites of SLC26A4 in individuals suspected to be affected with these conditions often fails to identify two mutations. We investigated the potential contribution of large SLC26A4 deletions and duplications to sensorineural hearing loss (SNHL) by screening 107 probands with one known SLC26A4 mutation by Multiplex Ligation-dependent Probe Amplification (MLPA). A heterozygous deletion, spanning exons 4-6, was detected in only one individual, accounting for approximately 1% of the missing mutations in our cohort. This low frequency is consistent with previously published MLPA results. We also examined the potential involvement of digenic inheritance in PDS/DFNB4 by sequencing the coding regions of FOXI1 and KCNJ10. Of the 29 probands who were sequenced, three carried nonsynonymous variants including one novel sequence change in FOXI1 and two polymorphisms in KCNJ10. We performed a review of prior studies and, in conjunction with our current data, conclude that the frequency of FOXI1 (1.4%) and KCNJ10 (3.6%) variants in PDS/DFNB4 individuals is low. Our results, in combination with previously published reports, indicate that large SLC26A4 deletions and duplications as well as mutations of FOXI1 and KCNJ10 play limited roles in the pathogenesis of SNHL and suggest that other genetic factors likely contribute to the phenotype.
Sensorineural hearing loss caused by mutations in two alleles of both GJB2 and SLC26A4 genes. Shasha Huang;Dongyi Han;Guojian Wang;Yongyi Yuan;Yueshuai Song;Mingyu Han;Zhengyi Chen;Pu Dai. 2012. Int J Pediatr Otorhinolaryngol. 77. PMID: 23266159

BACKGROUND: Most studies of the molecular etiology of sensorineural hearing loss have described deafness as a monogenic disease encompassing double-allele mutations for patients with autosomal recessive deafness. Here, we report the first case of autosomal recessive genetic deafness in an enlarged vestibular aqueduct syndrome (EVAS) patient with biallelic mutations in two deafness genes. METHODS: Temporal computed tomography (CT), complete physical and otoscopic examinations, and an audiological study, including tympanometry, pure-tone audiometry or auditory steady-state response (ASSR), were carried out. Exon 2 of GJB2 and the coding exons of SLC26A4 were sequenced. RESULTS: A patient with an enlarged vestibular aqueduct was found to carry c.1229C>T/c.1079C>T compound heterozygous mutations in SLC26A4.This individual also carried c.257C>G/c.299-300delAT compound heterozygous mutations in GJB2. As a result, the recurrent risk of the patient's siblings increased significantly from 25% for typical autosomal recessive deafness to 43.75%. CONCLUSIONS: The findings of the present study challenge the traditional diagnostic strategy in which testing is generally considered complete upon identification of a double-allele mutation within one gene, with significant implications for genetic counseling and risk prediction. Our results suggest that, with advances in sequencing technology, it will be possible and necessary to test all known deafness genes in the near future, as this will likely allow more accurate genetic counseling of patients.
Hypo-functional SLC26A4 variants associated with nonsyndromic hearing loss and enlargement of the vestibular aqueduct: genotype-phenotype correlation or coincidental polymorphisms? Byung Yoon Choi;Andrew K Stewart;Anne C Madeo;Shannon P Pryor;Suzanne Lenhard;Rick Kittles;David Eisenman;H Jeffrey Kim;John Niparko;James Thomsen;Kathleen S Arnos;Walter E Nance;Kelly A King;Christopher K Zalewski;Carmen C Brewer;Thomas Shawker;James C Reynolds;John A Butman;Lawrence P Karniski;Seth L Alper;Andrew J Griffith. 2009. Hum Mutat. 30. PMID: 19204907

Hearing loss with enlargement of the vestibular aqueduct (EVA) can be associated with mutations of the SLC26A4 gene encoding pendrin, a transmembrane Cl(-)/I(-)/HCO(3)(-) exchanger. Pendrin's critical transport substrates are thought to be I(-) in the thyroid gland and HCO(3)(-) in the inner ear. We previously reported that bi-allelic SLC26A4 mutations are associated with Pendred syndromic EVA whereas one or zero mutant alleles are associated with nonsyndromic EVA. One study proposed a correlation of nonsyndromic EVA with SLC26A4 alleles encoding pendrin with residual transport activity. Here we describe the phenotypes and SLC26A4 genotypes of 47 EVA patients ascertained since our first report of 39 patients. We sought to determine the pathogenic potential of each variant in our full cohort of 86 patients. We evaluated the trafficking of 11 missense pendrin products expressed in COS-7 cells. Products that targeted to the plasma membrane were expressed in Xenopus oocytes for measurement of anion exchange activity. p.F335L, p.C565Y, p.L597S, p.M775T, and p.R776C had Cl(-)/I(-) and Cl(-)/HCO(3)(-) exchange rate constants that ranged from 13 to 93% of wild type values. p.F335L, p.L597S, p.M775T and p.R776C are typically found as mono-allelic variants in nonsyndromic EVA. The high normal control carrier rate for p.L597S indicates it is a coincidentally detected nonpathogenic variant in this context. We observed moderate differential effects of hypo-functional variants upon exchange of HCO(3)(-) versus I(-) but their magnitude does not support a causal association with nonsyndromic EVA. However, these alleles could be pathogenic in trans configuration with a mutant allele in Pendred syndrome.
Enlarged vestibular aqueduct: Audiological and genetical features in children and adolescents. C Aimoni;A Ciorba;L Cerritelli;S Ceruti;P H Skarżyński;S Hatzopoulos. 2017. Int J Pediatr Otorhinolaryngol. 101. PMID: 28780189

BACKGROUND: Enlarged Vestibular Aqueduct (EVA) is one of the most common congenital malformations associated with sensorineural or mixed hearing loss. The association between hearing loss and EVA is described in syndromic (i.e. Pendred Syndrome, BOR, Waardenburg) and non-syndromic disorders, as isolate or familiar mutations of the SLC26A4 gene. The audiological phenotype of the EVA syndrome is heterogeneous, the type and entity of hearing loss may vary and vertigo episodes might also be present. OBJECTIVE: The aim of this retrospective study was to describe the clinical and genetic features of a group of adolescent subjects presenting an EVA clinical profile, considering the presence of SLC26A4 gene mutations. METHODS: 14 Caucasian patients were assessed (24 ears in total; 4 patients presented a monolateral EVA), 10 females and 4 males. Their age at the time of diagnosis was between 1 and 6 years (mean age 2.5 years). Subjects were assessed by an ENT microscopy evaluation with a complete audiometric assessment, CT & MRI scans and genetic tests for the evaluation of the pendrin gene mutations (SLC26A4). RESULTS: Considering the presence of SLC26A4 mutations and thyroid function, we could identify three sub-groups of patients: group 1, non syndromic EVA (ns EVA, no SLC26A4 mutation and no thyroid dysfunction); group 2, EVA with DFNB4 (single SLC26A4 gene mutation and no thyroid dysfunction); group 3, EVA with Pendred Syndrome (two pathological mutation of SLC26A4 and thyromegaly with thyroid dysfunction). Patients of group 1 (ns-EVA) showed various degrees of hearing loss from mild (55%) to severe-profound (45%). In groups 2 (DFNB4) and 3 (PDS), the degree of hearing loss is severe to profound in 70-75% of the cases; middle and high frequencies are mainly involved. CONCLUSIONS: The phenotypic expressions associated with the EVA clinical profile are heterogeneous. From the available data, it was not possible to identify a representative audiological profile, in any of the three sub-groups. The data suggest that: (i) a later onset of hearing loss is usually related to EVA, in absence of SLC26A4 gene mutations; and (ii) hearing loss is more severe in patients with SLC26A4 gene mutations (groups 2 and 3 of this study).
Screening of SLC26A4, FOXI1, KCNJ10, and GJB2 in bilateral deafness patients with inner ear malformation. Kaitian Chen;Xianren Wang;Liang Sun;Hongyan Jiang. 2012. Otolaryngol Head Neck Surg. 146. PMID: 22412181

OBJECTIVE: Bilateral nonsyndromic sensorineural hearing loss associated with inner ear malformation is closely related to genetics. SLC26A4 is considered to be the major involved gene. Recently, FOXI1 and KCNJ10 mutations have been linked to enlarged vestibular aqueducts and GJB2 mutations linked to temporal bone malformation. The authors aimed to investigate the mutation spectrums of these genes in Chinese patients with bilateral hearing impairment associated with inner ear malformation. STUDY DESIGN: Cross-sectional study. SETTING: Affiliated hospital of the university. SUBJECTS AND METHODS: The authors analyzed the GJB2, SLC26A4, FOXI1, and KCNJ10 gene sequences in 43 patients presenting with bilateral hearing impairment associated with inner ear malformation using pyrosequencing and direct DNA sequencing. RESULTS: In total, 74.4% (32/43) of patients carried at least 1 of 14 pathogenic SLC26A4 mutations, including 6 novel mutations and 4 polymorphisms. Patients with enlarged vestibular aqueducts had a higher rate of SLC26A4 mutation than Mondini dysplasia patients. No FOXI1 or KCNJ10 potential pathogenic mutation was present, and GJB2 biallelic pathogenic mutations were uncommon (2.3%; 1/43). No significant correlation was observed between the genotype and phenotype of SLC26A4 mutations. CONCLUSION: SLC26A4 accounts for 74.4% of inner ear malformations in our cohort, whereas FOXI1, KCNJ10, and GJB2 mutations are not common. Other possible genes or external factors may contribute to this multibranch abnormality.
A systematic review and meta-analysis of common mutations of SLC26A4 gene in Asian populations. Wan Du;Yufen Guo;Changlan Wang;Yanli Wang;Xiaowen Liu. 2013. Int J Pediatr Otorhinolaryngol. 77. PMID: 23958391

OBJECTIVES: The IVS7-2A>G (c.919-2A>G) and p.H723R (c.2168A>G) mutations of SLC26A4 gene are recognized as a risk factor for the non-syndromic hearing loss. To elucidate the variable results, a meta-analysis and systematic review was performed from all case-control studies by pooling data on them. METHODS: The case-control studies were assessed with a modification of the Newcastle-Ottawa Scale (NOS). The strength of association between c.919-2A>G, c.2168A>G and hearing loss risk was measured by odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: We included 14 case-control studies and 16 case series studies in present study. There was a higher prevalence of the c.919-2A>G mutation in the case group than that in the control group (12.4% vs 0.9%; OR = 13.05, 95% CI: 8.41-20.23, Z = 11.47, P<0.00001). CONCLUSIONS: In conclusion, the results from this meta-analysis suggest that NSHL patients have an increased risk of the c.919-2A>G mutation of SLC26A4 gene in Asians, especially in Chinese.
Genetic polymorphisms of SCN10A are associated with functional dyspepsia in Japanese subjects. Tomiyasu Arisawa;Tomomitsu Tahara;Hisakazu Shiroeda;Takahiro Minato;Yasuhiro Matsue;Takashi Saito;Tomoki Fukuyama;Toshimi Otsuka;Atsushi Fukumura;Masakatsu Nakamura;Tomoyuki Shibata. 2012. J Gastroenterol. 48. PMID: 22618805

BACKGROUND: Visceral sensory impulses are transmitted via C-fibers from the gastrointestinal tract to the central nervous system. The tetrodotoxinresistant (TTX-r) sodium channel, Na(V) 1.8/SNS (sensory-neuron specific), encoded by SCN10A, has been identified on C-fibers. We attempted to clarify the association between functional dyspepsia (FD) and SCN10A non-synonymous polymorphisms (2884 A>G, 3218 C>T and 3275 T>C). METHODS: The study was performed in 642 subjects (345 with no symptoms and 297 with FD). We employed a multiplex polymerase chain reaction single-strand confirmation polymorphism (PCR-SSCP) method to detect the gene polymorphisms. RESULTS: The 3218 CC homozygotes had a reduced risk for the development of FD [odds ratio (OR) 0.589; 95 % confidence interval (CI) 0.402-0.864; p = 0.0067]. In addition, both 2884 A>G and 3275 T>C, which were in linkage disequilibrium, were also associated with the development of FD (p = 0.039 and 0.028, respectively). Each 2884 G carrier, 3218 CC homozygote, and 3275 C carrier had a reduced risk for the development of both epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS). The subjects with the 2884 G allele, 3275 C allele, and no 3218 T allele had a reduced risk for FD (OR 0.618; 95 % CI 0.448-0.853; p = 0.0034). This haplotype was associated with a reduced risk for both EPS and PDS (p = 0.0011 and 0.0056, respectively). In addition, there was a significant association between FD and this haplotype in Helicobacter pylori-negative subjects (OR 0.463; 95 % CI 0279-0.9768; p = 0.0029). CONCLUSION: We conclude that genetic polymorphisms of SCN10A are closely associated with FD (both EPS and PDS), especially in H. pylori-negative subjects, in Japanese.
[Genetic analysis and prenatal diagnosis for non-syndromic hearing impairment]. Li Wang;Hui-ru Zhao;Shixiu Liao;Yan-li Yang;Tao Li;Bing Zhang;Xue-bing Ding;Song Ma;Hong-jian Liu. 2013. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 30. PMID: 24078562

OBJECTIVE: To detect genetic mutations underlying non-syndromic hearing impairment (NSHI) and establish a method for prenatal diagnosis. METHODS: Sixty six NSHI patients were included in this study. DNA was extracted from peripheral blood. Genetic mutations were detected by gene chip analysis and direct sequencing of GJB2 gene. For 7 pregnant women at high risk, prenatal genetic diagnosis was provided. RESULTS: Fourteen cases (21.21%) were found to have GJB2 mutations by both methods (homozygous 235delC mutation in 3 cases, homozygous 176del16 mutation in 2 cases, 235delC and 299delAT compound heterozygous mutation in 2 cases, 299delAT and 176del16 compound heterozygous mutation in 1 case, c.339T > G and 313del12bp compound heterozygous mutation 1 case, and 235delC heterozygous mutation in 5 cases). 13 (19.70%) had SLC26A4 mutations (IVS7-2 A >G homozygous mutation in 2 cases, IVS7-2 A > G homozygous mutation in 2 cases, IVS7-2 A > G and 2168A > G compound heterozygous mutation in 3 cases, 2168A>G heterozygous mutation in 3 cases, and IVS7-2 heterozygous mutation in 3 cases); and 3 had mtDNA12S rRNA mutation (1555A > G mutation in 2 cases, 1494C > T mutation in 1 case). Prenatal diagnosis suggested that 3 fetuses have carried a heterozygous mutation. Two fetuses were detected as normal and confirmed to have normal hearing after birth. Two fetuses were found to have carried compound mutations of GJB2. CONCLUSION: Gene chip combined with GJB2 gene analysis is an accurate and effective method for the diagnosis of NSHI. The results can facilitate accurate prenatal diagnosis.
Phenotype and genotype of deaf patients with combined genomic and mitochondrial inheritance models. Shasha Huang;Guojian Wang;Yi Jiang;Yongyi Yuan;Dongyi Han;Yueshuai Song;Pu Dai. 2013. Mitochondrion. 13. PMID: 23688906

In most studies, sensorineural hearing loss is reported as a single-gene disease with autosomal dominant or autosomal recessive or with X-linked or maternal inheritance. It is uncommon that the hearing impairment is caused by a combined inheritance model including genomic and mitochondrial models. Here, we report six patients with sensorineural hearing loss caused by co-existing mutations in GJB2 or SLC26A4 and the mitochondrial gene. And there was no significant difference in hearing phenotypes between the six patients and the controls. The results indicate the complicated genetic etiology of, and may impact the diagnostic strategy for, hereditary hearing impairment. All patient siblings will carry mitochondrial DNA A1555G or C1494T mutations, and 25% of siblings may carry the same homozygous or compound heterozygote mutations in GJB2 or SLC26A4. Although this combined inheritance is not common in the Chinese deaf population (0.10%), our findings will have great impact in genetic counseling and risk prediction for deafness.
Large scale newborn deafness genetic screening of 142,417 neonates in Wuhan, China. Zongjie Hao;Denggang Fu;Yang Ming;Jinlong Yang;Qi Huang;Weilong Lin;Huan Zhang;Bin Zhang;Aifen Zhou;Xijiang Hu;Cong Yao;Yunping Dong;Huijun Z Ring;Brian Z Ring. 2018. PLoS One. 13. PMID: 29634755

Almost one third of the three million people in China suffering severe deafness are children, and 50% of these cases are believed to have genetic components to their etiology. Newborn hearing genetic screening can complement Universal Neonatal Hearing Screening for the diagnosis of congenital hearing loss as well as identifying children at risk for late-onset and progressive hearing impairment. The aim of this joint academic and Ministry of Health project was to prototype a cost effective newborn genetic screen in a community health setting on a city-wide level, and to ascertain the prevalence of variation at loci that have been associated with non-syndromic hearing loss. With the participation of 143 local hospitals in the city of Wuhan, China we screened 142,417 neonates born between May 2014 and Dec. 2015. The variants GJB2 c.235delC, SLC26A4 c.919-2A>G, and mitochondrial variants m.1555A>G and m.1494C>T were assayed using real time PCR. Newborns found to carry a variant were re-assayed by sequencing in duplicate. Within a subset of 707 newborns we assayed using real-time PCR and ARMS-PCR to compare cost, sensitivity and operating procedure. The most frequent hearing loss associated allele detected in this population was the 235delC variant in GJB2 gene. In total, 4289 (3.01%) newborns were found to carry at least one allele of either GJB2 c.235delC, SLC26A4 c.919-2A>G or two assayed MT-RNR1 variants. There was complete accordance between the real-time PCR and the ARMS PCR, though the real-time PCR had a much lower failure rate. Real-time PCR had a lower cost and operating time than ARMS PCR. Ongoing collaboration with the participating hospitals will determine the specificity and sensitivity of the association of the variants with hearing loss at birth and arising in early childhood, allowing an estimation of the benefits of newborn hearing genetic screening in a large-scale community setting.
Different cortical metabolic activation by visual stimuli possibly due to different time courses of hearing loss in patients with GJB2 and SLC26A4 mutations. Hideaki Moteki;Yasushi Naito;Keizo Fujiwara;Ryosuke Kitoh;Shin-ya Nishio;Kazuhiro Oguchi;Yutaka Takumi;Shin-ichi Usami. 2011. Acta Otolaryngol. 131. PMID: 21728752

CONCLUSION: We have demonstrated differences in cortical activation with language-related visual stimuli in patients who were profoundly deafened due to genetic mutations in GJB2 and SLC26A4. The differences in cortical processing patterns between these two cases may have been influenced by the differing clinical courses and pathogenesis of hearing loss due to genetic mutations. Our results suggest the importance of hearing during early childhood for the development of a normal cortical language network. OBJECTIVES: To investigate the cortical activation with language-related visual stimuli in patients who were profoundly deafened due to genetic mutations in GJB2 and SLC26A4. METHODS: The cortical activity of two adult patients with known genetic mutations (GJB2, SLC26A4) was evaluated with fluorodeoxyglucose-positron emission tomography (FDG-PET) with a visual language task and compared with that of normal-hearing controls. RESULTS: A patient with a GJB2 mutation showed activation in the right auditory association area [BA21, BA22], and the left auditory association area [BA42] even with visual language task; in contrast, a patient with an SLC26A4 mutation showed no significant activation in the corresponding area.
Mutation spectrum and genotype-phenotype correlation of hearing loss patients caused by SLC26A4 mutations in the Japanese: a large cohort study. Maiko Miyagawa;Shin-Ya Nishio;Shin-Ichi Usami; . 2014. J Hum Genet. 59. PMID: 24599119

Mutations in SLC26A4 cause a broad phenotypic spectrum, from typical Pendred syndrome to nonsyndromic hearing loss associated with enlarged vestibular aqueduct. Identification of these mutations is important for accurate diagnosis, proper medical management and appropriate genetic counseling and requires updated information regarding spectrum, clinical characteristics and genotype-phenotype correlations, based on a large cohort. In 100 patients with bilateral enlarged vestibular aqueduct among 1511 Japanese hearing loss probands registered in our gene bank, goiter data were available for 79, of whom 15 had Pendred syndrome and 64 had nonsyndromic hearing loss. We clarified the mutation spectrum for the SLC26A4 mutations and also summarized hearing levels, progression, fluctuation and existence of genotype-phenotype correlation. SLC26A4 mutations were identified in 82 of the 100 patients (82.0%). Of the Pendred syndrome patients, 93% (14/15) were carriers, as were 77% (49/64) of the nonsyndromic hearing loss patients. Clinical characteristics of patients with SLC26A4 mutations were congenital, fluctuating and progressive hearing loss usually associated with vertigo and/or goiter. We found no genotype-phenotype correlations, indicating that, unlike in the case of GJB2 mutations, the phenotype cannot be predicted from the genotype. Our mutation analysis confirmed the importance of mutations in the SLC26A4 gene among hearing loss patients with enlarged vestibular aqueduct and revealed the mutation spectrum, essential information when performing genetic testing.
[An analysis of the mutation in GJB2,GJB3,SLC26A4 and mtDNA12SrRNA in new born]. F Chai;H L Zhao;S Q Qiu. None. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 31. PMID: 29871341

Objective:To analyze deafness gene mutation in GJB2,GJB3,SLC26A4 and mtDNA12SrRNA in newborn and to explore the significance of genetic test and potential correlations between the genotype and clinical phenotype.Method:Blood samples were collected with a standard protocol and DNA templates are extracted from 501 newborn in Longgang of Shenzhen.MALDI-TOF-MS Technology was used to detect the coding region twenty mutations sites of GJB2,GJB3,SLC26A4 AND mtDNA12SrRNA,includingSLC26A4(1226G>A,1229C>T,281C>T,589G>A,IVS7-2A>T,1174A>T,IVS15+5G>A,1975G>C,2027T>A,2162C>T,2168A>G),GJB2(176-191del16,35delG,167delT,235 delC,299-300 delAT),GJB3(547G>A,538C>T),mtDNA12SrRNA(1555A>G,1494C>T).While two-step hearing screening was carried by using AABR(automatedauditory brainstem response)and DPOAE. Result:In the 501 newborns,26 cases were found have one or two allele mutations of deafness-susceptibility genes.GJB2 gene mutation(n=9,1.796%) all were 235 delC single heterozygosity mutation.GJB3 gene mutation(n=3,0.599%). SLC26A4 gene mutation(n=12,2.395%) included IVS7-2A>G heterozygosity mutation(n=5). MtDNA 12Rrna gene mutation was found in 3 child(n=3,0.599%). Finally one of 26 infants was diagnosed enlarged vestibular aqueduct syndrome. The infant was detected 2168A>G heterozygosity mutation. Conclusion:235delC is the main mutation form of GJB2 gene,while it is the hottest mutation in People. But SLC26A4 gene mutations are the main type in newborn. MtDNA 12Rrna gene mutation was found in 3 child.This genetic epidemiological study demonstrated that genetic screening is helpful for determining high risk individuals and early discovering possible late-onset hearing loss. Moreover pationts and family member can acquire more effective genetic counseling.
Prevalence of Connexin 26 (GJB2) and Pendred (SLC26A4) mutations in a population of adult cochlear implant candidates. Jordan B Hochman;Tracy L Stockley;D Shipp;Vincent Y W Lin;Joseph M Chen;Julian M Nedzelski. 2010. Otol Neurotol. 31. PMID: 20601923

OBJECTIVE: To assess the prevalence of Connexin 26 (GJB2), Connexin 30 (GJB6), and Pendred (SLC26A4) mutations in a population of adult cochlear implant patients with a history of either early idiopathic or hereditary progressive sensorineural deafness. BACKGROUND: Significant efforts have been applied in defining the epidemiology of Connexin 26 (GJB2)-associated hearing impairment in the pediatric population, yet the issue remains ambiguous for adult patients. Causation is important in this population because there are implications to prognosis, risk of associated medical manifestations, and for genetic counseling purposes. PATIENTS: Adult patients meeting criteria for cochlear implantation with early-onset hearing loss assessed at an adult cochlear implant center from November 2007 to April 2009. INTERVENTION: Genomic DNA samples from whole blood were tested with bidirectional sequence analysis for mutations in the coding region of the GJB2 and SLC26A4 genes and tested for large deletions of the GJB6 gene. RESULTS: Fifty-seven patients were analyzed for GJB2 mutations. Eight patients (14%) were found to have GJB2-related hearing impairment; 5 patients were homozygous for the c.35delG mutation (genotype c.35delG/c.35delG), and 3 additional patients were compound heterozygotes with 2 different GJB2 mutations. Of these 8 patients with GJB2-related hearing impairment, 3 had serviceable hearing into their teenage years. One additional patient had 1 GJB2 variant (p.Met195Ile, heterozygous). None had GJB6 mutations. Of the 57 patients, 30 were also analyzed for SLC26A4 mutations. Three of these patients were compound heterozygotes for disease-causing SLC26A4 mutations, confirming SLC26A4-related hearing impairment. Three additional patients were found to have a single variant in SLC26A4. CONCLUSION: The prevalence of GJB2- and SLC26A4-related hearing impairment in an adult population with early-onset severe sensorineural hearing loss is significant, suggesting the need for routine assessment for genetic etiologies in this group. We also note 3 individuals with causal connexin 26 mutations with subjective serviceable hearing into adolescence in our cohort.
The SLC26A4 c.706C>G (p.Leu236Val) Variant is a Frequent Cause of Hearing Impairment in Filipino Cochlear Implantees. Charlotte M Chiong;Ma Rina T Reyes-Quintos;Talitha Karisse L Yarza;Celina Ann M Tobias-Grasso;Anushree Acharya;Suzanne M Leal;Karen L Mohlke;Nanette L Mayol;Eva Maria Cutiongco-de la Paz;Regie Lyn P Santos-Cortez. 2018. Otol Neurotol. 39. PMID: 30113565

HYPOTHESIS: Variants in SLC26A4 are an important cause of congenital hearing impairment in the Philippines. BACKGROUND: Cochlear implantation is a standard rehabilitation option for congenital hearing impairment worldwide, but places a huge cost burden in lower-income countries. The study of risk factors such as genetic variants that may help determine genetic etiology of hearing loss and also predict cochlear implant outcomes is therefore beneficial. METHODS: DNA samples from 29 GJB2-negative Filipino cochlear implantees were Sanger-sequenced for the coding exons of SLC26A4. Exome sequencing was performed to confirm results. RESULTS: Four cochlear implantees with bilaterally enlarged vestibular aqueducts (EVA) were homozygous for the pathogenic SLC26A4 c.706C>G (p.Leu236Val) variant, which has a minor allele frequency of 0.0015 in Filipino controls. In patients with the SLC26A4 variant there was no association between cochlear implant outcome and age at implantation or duration of implant. There was also no association between the occurrence of the SLC26A4 variant and postsurgical audiometric thresholds and parents' evaluation of aural/oral performance of children (PEACH) scores. On the other hand, the SLC26A4 variant increased presurgical median audiometric thresholds (p = 0.01), particularly at 500 to 2000 Hz. CONCLUSION: The SLC26A4 c.706C>G (p.Leu236Val) variant is a frequent cause of congenital hearing impairment in Filipinos and is associated with bilateral EVA and increased presurgical audiometric thresholds, but does not adversely affect post-implant outcomes.
Short communication: Confirmation of candidate causative variants on milk composition and cheesemaking properties in Montbéliarde cows. M P Sanchez;V Wolf;M El Jabri;E Beuvier;O Rolet-Répécaud;Y Gaüzère;S Minéry;M Brochard;A Michenet;S Taussat;A Barbat-Leterrier;A Delacroix-Buchet;C Laithier;S Fritz;D Boichard. 2018. J Dairy Sci. . PMID: 30219425

In a previous study, we identified candidate causative variants located in 24 functional candidate genes for milk protein and fatty acid composition in Montbéliarde, Normande, and Holstein cows. We designed these variants on the custom part of the EuroG10K BeadChip (Illumina Inc., San Diego, CA), which is routinely used for genomic selection analyses in French dairy cattle. To validate the effects of these candidate variants on milk composition and to estimate their effects on cheesemaking properties, a genome-wide association study was performed on milk protein, fatty acid and mineral composition, as well as on 9 cheesemaking traits (3 laboratory cheese yields, 5 coagulation traits, and milk pH). All the traits were predicted from midinfrared spectra in the Montbéliarde cow population of the Franche-Comté region. A total of 194 candidate variants located in 24 genes and 17 genomic regions were imputed on 19,862 cows with phenotypes and genotyped with either the BovineSNP50 (Illumina Inc.) or the EuroG10K BeadChip. We then tested the effect of each SNP in a mixed linear model including random polygenic effects estimated with a genomic relationship matrix. We confirm here the effects of candidate causative variants located in 17 functional candidate genes on both cheesemaking properties and milk composition traits. In each candidate gene, we identified the most plausible causative variant: 4 are missense in the ALPL, SLC26A4, CSN3, and SCD genes, 7 are located in 5'UTR (AGPAT6), 3' untranslated region (GPT), or upstream (CSN1S1, CSN1S2, PAEP, DGAT1, and PICALM) regions, and 6 are located in introns of the SLC37A1, MGST1, CSN2, BRI3BP, FASN, and ANKH genes.
Molecular and functional studies of 4 candidate loci in Pendred syndrome and nonsyndromic hearing loss. Valentina Cirello;Claudia Bazzini;Valeria Vezzoli;Marina Muzza;Simona Rodighiero;Pierangela Castorina;Antonia Maffini;Guido Bottà;Luca Persani;Paolo Beck-Peccoz;Giuliano Meyer;Laura Fugazzola. 2012. Mol Cell Endocrinol. 351. PMID: 22285650

Patients with PS or non-syndromic deafness were submitted to genetic/functional analyzes of SLC26A4, of its binding domain for FOXI1 (FOXI1-DBD), of the transcription activator FOXI1, and of the potassium channel KCNJ10. SLC26A4 was the most frequently mutated gene. An altered intracellular localization with immunocytochemistry, and a hampered maturation process were demonstrated for two novel SLC26A4 variants. Biochemical and immunocytochemical analyzes led to the development of a more sensitive fluorometric functional assay able to reveal the partial loss-of-function of SLC26A4 mutations. A novel missense variant was found in FOXI1 gene, though functional analysis showed no significant impairment in the transcriptional activation of SLC26A4. Finally, 3 patients were found to harbor a variant in KCNJ10, which was classified as polymorphism. The novelty of the study resides in the analysis of all the 4 candidate genetic loci linked to PS/non-syndromic deafness, and in the precise definition of the thyroid phenotype. PS was invariably associated with biallelic mutations of SLC26A4, whereas the genetic origin of non-syndromic deafness remained largely undetermined, since monoallelic SLC26A4 variants accounted for one fourth of the cases and FOXI1 and KCNJ10 were not involved in this series.
Newborn hearing concurrent gene screening can improve care for hearing loss: a study on 14,913 Chinese newborns. Qiu-Ju Wang;Ya-Li Zhao;Shao-Qi Rao;Yu-Fen Guo;Yao He;Lan Lan;Wei-Yan Yang;Qing-Yin Zheng;Robert J Ruben;Dong-Yi Han;Yan Shen. 2011. Int J Pediatr Otorhinolaryngol. 75. PMID: 21329993

OBJECTIVE: Newborn hearing screening has been widely adopted and made an achievement to some degree. Current screening protocols rely solely on detecting existing auditory disorders at the time of screening and are unable to identify individuals susceptible to auditory disorders in later life. Even if the hearing loss newborn is referred, most cases could not be diagnosed until 6-12 months old with no etiology being elucidated. This study reports the first effort to combine traditional hearing screening with genetic screening to improve the efficacy of newborn hearing screening. METHODS: This study was undertaken in 12 regional hospitals located in 11 provinces of China. 14,913 newborn babies received hearing concurrent genetic screening. The hearing screening was performed with OAE or AABR. Blood sample was collected with a universal newborn genetic screening card. And three common gene, mtDNA 12S rRNA, GJB2 and SLC26A4 were screened with standard protocol. RESULTS: Among all the 14,913 newborns, 86.1% (12,837/14,913) individuals passed the first-step hearing screening, 7.8% (1168/14,913) babies passed only one side, and the other 6.1% (908/14,913) were bilaterally referred. Gene screening found 306 individuals had one or two mutant alleles, the carrier rate is 2.05% (306/14,913) among the entire newborn population. The risk for hearing loss was 100% (7/7) for those newborns carrying causative GJB2 or SLC26A4 mutations (homozygotes or compound heterozygotes), 14.4% (23/160) for GJB2 heterozygote carriers, 12.3% (15/122) for SLC26A2 heterozygous carriers, and the total prevalence of referral hearing screening was approximately 14.7% (45/306). However, 85.3% (261/306) newborns passed hearing screening among these carriers including 18 newborns with 12S rRNA mt.1555A>G pathogenic mutation, who would suffer from sudden hearing loss once applying aminoglycoside drugs. CONCLUSION: The cohort studies provided the essential population parameters for developing effective programs for hearing care of newborns in China. Hearing concurrent gene screening in newborns may confirm the abnormal results from hearing screening tests, help to find the etiologic of the hearing loss, and better recognize infants at risk for late-onset hearing loss occurring prior to speech and language development. In conclusion, a survey on 14,913 Chinese newborns proved that concurrent genetic screening could improve newborn hearing screening for hearing defects.
Genotype-phenotype correlations for SLC26A4-related deafness. Hela Azaiez;Tao Yang;Sai Prasad;Jessica L Sorensen;Carla J Nishimura;William J Kimberling;Richard J H Smith. 2007. Hum Genet. 122. PMID: 17690912

Pendred syndrome (PS) and non-syndromic enlarged vestibular aqueduct (EVA) are two recessive disorders characterized by the association of sensorineural hearing loss (SNHL) with inner ear malformations that range from isolated EVA to Mondini Dysplasia, a complex malformation that includes a cochlear dysplasia and EVA. Mutations in the SLC26A4 gene, coding for the protein pendrin, have been implicated in the pathophysiology of both disorders. In order to determine whether SLC26A4 genotypes can be correlated to the complexity and severity of the phenotypes, we ascertained 1,506 deaf patients. Inner ear abnormalities were present in 474 patients (32%). Mutation screening of SLC26A4 detected two mutations in 16% of patients, one mutation in 19% of patients and zero mutation in 65% of patients. When the distribution of SLC26A4 genotypes was compared across phenotypes, a statistically significant difference was found between PS patients and non-syndromic EVA-Mondini patients (P = 0.005), as well as between EVA patients and Mondini patients (P = 0.0003). There was a correlation between phenotypic complexity of inner ear malformations and genetic heterogeneity--PS patients have the most severe phenotype and the most homogeneous etiology while EVA patients have the least severe phenotype and the most heterogeneous etiology. For all patients, variability in the degree of hearing loss is seen across genotypes implicating other genetic and/or environmental factors in the pathogenesis of the PS-Mondini-EVA disease spectrum.
Auditory screening concurrent deafness predisposing genes screening in 10,043 neonates in Gansu province, China. Zhewen Zhang;Wenjuan Ding;Xiaowen Liu;Baicheng Xu;Wan Du;Shuling Nan;Yufen Guo. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22510577

OBJECTIVE: The aim of our study was to evaluate the effectiveness of combining newborn hearing screening with screening for genetic mutations associated with deafness. METHODS: Ten thousand forty-three newborn babies, born between December 2009 and April 2011 in Gansu province, China, were screened for hearing loss using the otoacoustic emissions test or automatic auditory brainstem response test and genetic mutations associated with deafness using a standard protocol. RESULTS: In the hearing screening, the referral rate for hearing loss in the first-step screening was 14.4% (1409/9786), decreasing significantly to 3.8% (362/9506) upon retesting. After the second-step screening, a total of 537 newborns were lost to follow-up. The genetic screening found that about 2.29% (230/10,043) individuals carried one or more recessive risk alleles or the mitochondrial mutation. Among them, 18 babies had the pathogenic mitochondrial DNA mutation, 92 babies were SLC26A4 heterozygote carriers, one case with both SLC26A4 and 12S rRNA 1555A>G mutation, 117 babies were GJB2 heterozygote carriers, and two babies were GJB2 homozygote carriers. However, 83.5% (192/230) neonates passed the conventional hearing screening among these carriers. CONCLUSIONS: It might be effective to complement the conventional hearing screening with gene screening for the purpose of early diagnosis and discovery of the late-onset hearing loss.
SLC26A4 mutations are associated with a specific inner ear malformation. Suat Fitoz;Levent Sennaroğlu;Armağan Incesulu;Filiz Başak Cengiz;Yasemin Koç;Mustafa Tekin. 2007. Int J Pediatr Otorhinolaryngol. 71. PMID: 17197040

BACKGROUND AND AIM: Inner ear anomalies have been reported in approximately 30% of children with early onset deafness. Identification of causative genetic factors in a large proportion of these patients was not successful. Mutations in the SLC26A4 gene have been detected in individuals with enlarged vestibular aqueduct (EVA) or Mondini dysplasia. We aimed to characterize the inner ear anomalies associated with SLC26A4 mutations. METHODS: The SLC26A4 gene has been screened for mutations in 16 subjects from 14 unrelated Turkish families with a variety of inner ear anomalies ranging from Michel aplasia to incomplete partition-II and EVA. None of the patients was diagnosed to have a recognizable genetic syndrome. Additional four patients with Pendred syndrome from three families were included. RESULTS: Only one patient with EVA was found to have a heterozygous mutation (c.1586delT) in SLC26A4. All patients with Pendred syndrome had homozygous mutations and were noted to have either EVA or EVA associated with incomplete partition-II on the computed tomography of the temporal bone. CONCLUSION: SLC26A4 mutations are not associated with a large spectrum of inner ear anomalies. They, instead, result in a specific morphological appearance consistent with EVA or incomplete partition-II.
Association of SLC6A4 5-HTTLPR and TRPV1 945G>C with functional dyspepsia in Korea. Sung Wook Hwang;Nayoung Kim;Hye-Kyung Jung;Ji Hyun Park;Yoon Jin Choi;Heebal Kim;Jaemin Kim;Joo Sung Kim;Hyun Chae Jung. 2014. J Gastroenterol Hepatol. 29. PMID: 24720453

BACKGROUND AND AIM: The association of various genetic polymorphisms with functional dyspepsia (FD) has been suggested, but the results were still controversial. The aim of the present study was to assess the association of GNB3 825C>T, SLC6A4 5-HTTLPR, ADRA2A-1291C>G, CCK-1R intron 779T>C, and TRPV1 945G>C polymorphisms with FD based on Rome III criteria in Korea. METHODS: Study subjects were prospectively recruited from visitors to Seoul National University Bundang Hospital between 2009 and 2012. One hundred and twelve FD patients and 269 controls were enrolled. RESULTS: In SLC6A4 5-HTTLPR polymorphism, the frequency of S/S genotype was significantly lower than that of L/L + L/S genotype in FD compared to controls (P < 0.05). After stratification according to Helicobacter pylori infection, the S/S genotype was significantly associated with H. pylori-positive epigastric pain syndrome (EPS) patients (adjusted odds ratio (OR) 0.46; 95% confidence interval (CI) 0.22-0.99; P = 0.048). In TRPV1 945G>C polymorphism, the frequency of C/C genotype was lower in FD compared to controls (P = 0.057). The C carrier and C/C genotype was significantly associated with postprandial distress syndrome (PDS) and EPS, respectively (adjusted OR 0.47 and 0.43; 95% CI 0.25-0.90 and 0.20-0.93; P = 0.021 and 0.033). After stratification, the significant associations remained in H. pylori-positive PDS and EPS patients (adjusted OR 0.37 and 0.28; 95% CI 0.16-0.88 and 0.09-0.85; P = 0.024 and 0.025). CONCLUSIONS: The genetic polymorphism of SLC6A4 5-HTTLPR and TRPV1 945G>C could be one of the pathophysiological factors of FD, especially in the case of H. pylori-positive patients in Korea.
Genetic mutations in nonsyndromic deafness patients of Chinese minority and Han ethnicities in Yunnan, China. Feng Xin;Yongyi Yuan;Xiaoming Deng;Mingyu Han;Guojian Wang;Jiandong Zhao;Xue Gao;Jun Liu;Fei Yu;Dongyi Han;Pu Dai. 2013. J Transl Med. 11. PMID: 24341454

BACKGROUND: Each year in China, 30,000 babies are born with congenital hearing impairment. However, the molecular etiology of hearing impairment in the Yunnan Province population where more than 52 minorities live has not been thoroughly investigated. To provide appropriate genetic testing and counseling to these families, we investigated the molecular etiology of nonsyndromic deafness in this population. METHODS: Unrelated students with hearing loss (n = 235) who attended Kunming Huaxia secondary specialized school in Yunnan enrolled in this study. Three prominent deafness-related genes, GJB2, SLC26A4 and mtDNA 12S rRNA, were analyzed. High-resolution temporal bone computed tomography (CT) scan examinations were performed in 100 cases, including 16 cases with SLC26A4 gene variants, and 37 minorities and 47 Han cases without any SLC26A4 gene mutation. RESULTS: The GJB2 mutation was detected in 16.67% (7/42) of minority patients and 17.62% (34/193) of Chinese Han patients (P > 0.05). 235delC was the hotspot mutation in nonsyndromic hearing loss (NSHL) patients, whereas 35delG was not found. The 431_450del19 mutation was detected for the first time in Han NSHL patients, which resulted in a premature stop codon and changed the protein. The SLC26A4 mutation was found in 9.52% (4/42) of minority patients and 9.84% (19/193) of Han Chinese patients (P > 0.05). The frequencies of mtDNA 12S rRNA mutation in minority and Han Chinese patients were 11.90% (5/42) and 7.77% (15/193; P > 0.05), respectively. Sixteen (16/23, 69.57%) patients with SLC26A4 mutations received temporal bone CT scan, and 14 patients were diagnosed with enlarged vestibular aqueducts (EVAs); the other 2 patients had normal inner ear development. The ratio of EVA in the minorities was 14.63% (6/41). CONCLUSIONS: In this study, a total of 35.74% deaf patients showed evidence of genetic involvement, based on either genetic screening or family history; 17.45%, 9.79%, and 8.51% of the patients were determined to have inherited hearing impairment caused by GJB2, SLC26A4, and mtDNA 1555A > G mutations. There was no significant difference in deafness associated gene mutational spectrum and frequency between the Yunnan minority and Han patients.
Screening of SLC26A4 gene in autoimmune thyroid diseases. R Kallel;M Niasme-Grare;S Belguith-Maalej;M Mnif;M Abid;H Ayadi;S Masmoudi;L Jonard;H Hadj Kacem. 2013. Int J Immunogenet. 40. PMID: 23280318

The Pendred syndrome (PS) gene, SLC26A4, was involved in the genetic susceptibility of autoimmune thyroid disease (AITD) in Tunisian population. Recently, functional assays have shown a differential expression of SLC26A4 gene between Graves' disease (GD) and Hashimoto's thyroiditis (HT). Here, by the mean of DHPLC and HRM, we explored the 21 exons and their flanking intronic sequences of 128 patients affected with GD (n = 64) or HT (n = 64). The pathogenic effect of identified variations on splice was investigated using the web server HSF. Eighteen allelic variations were identified and ranged on missense, sens and splice variations. Nine identified variations (c.-66C>G, c.898A>C, c.1002-9A>C, c.1061T>C, c.1544 + 9G>T, c.1545-5T>G, c.1790T>C, c.1826T>G, c.2139T>G) were previously reported in hearing impairment studies. Forty-seven per cent (30/64) of GD patients and 37,5% (24/64) of HT patients present at least one variant in the explored sequences. Moreover, the analysis of the variant distribution between HT (9 (5'UTR), 12 exonic and 13 intronic) and GD (18 (5'UTR), 13 exonic and 5 intronic) patients showed a significant difference (χ² = 6.54, 2df, P = 0.03). Interestingly, missense changes (I300L, p.M283I, F354S and p.L597S) affected conserved residues of pendrin. On the other hand, the HSF analyses ascertain that some variants identified in HT disease are predicted to have a pathogenic effect on splice. In conclusion, our analysis of SLC26A4 sequence variations suggested a distinct genetics basis between HT and GD patients, which should be confirmed on a large cohort.
An effective screening strategy for deafness in combination with a next-generation sequencing platform: a consecutive analysis. Naoko Sakuma;Hideaki Moteki;Masahiro Takahashi;Shin-ya Nishio;Yasuhiro Arai;Yukiko Yamashita;Nobuhiko Oridate;Shin-ichi Usami. 2016. J Hum Genet. 61. PMID: 26763877

The diagnosis of the genetic etiology of deafness contributes to the clinical management of patients. We performed the following four genetic tests in three stages for 52 consecutive deafness subjects in one facility. We used the Invader assay for 46 mutations in 13 genes and Sanger sequencing for the GJB2 gene or SLC26A4 gene in the first-stage test, the TaqMan genotyping assay in the second-stage test and targeted exon sequencing using massively parallel DNA sequencing in the third-stage test. Overall, we identified the genetic cause in 40% (21/52) of patients. The diagnostic rates of autosomal dominant, autosomal recessive and sporadic cases were 50%, 60% and 34%, respectively. When the sporadic cases with congenital and severe hearing loss were selected, the diagnostic rate rose to 48%. The combination approach using these genetic tests appears to be useful as a diagnostic tool for deafness patients. We recommended that genetic testing for the screening of common mutations in deafness genes using the Invader assay or TaqMan genotyping assay be performed as the initial evaluation. For the remaining undiagnosed cases, targeted exon sequencing using massively parallel DNA sequencing is clinically and economically beneficial.
Pendred syndrome: evidence for genetic homogeneity and further refinement of linkage. E Gausden;B Coyle;J A Armour;R Coffey;A Grossman;G R Fraser;R M Winter;M E Pembrey;P Kendall-Taylor;D Stephens;L M Luxon;P D Phelps;W Reardon;R Trembath. 1997. J Med Genet. 34. PMID: 9039988

Pendred syndrome is the association between congenital sensorineural deafness and goitre. The disorder is characterised by the incomplete discharge of radioiodide from a primed thyroid following perchlorate challenge. However, the molecular basis of the association between hearing loss and a defect in organification of iodide remains unclear. Pendred syndrome is inherited as an autosomal recessive trait and has recently been mapped to 7q31 coincident with the non-syndromic deafness locus DFNB4. To define the critical linkage interval for Pendred syndrome we have studied five kindreds, each with members affected by Pendred syndrome. All families support linkage to the chromosome 7 region, defined by the microsatellite markers D7S501-D7S523. Detailed haplotype analysis refines the Pendred syndrome linkage interval to a region flanked by the marker loci D7S501 and D7S525, separated by a genetic distance estimated to be 2.5 cM. As potential candidate genes have as yet not been mapped to this interval, these data will contribute to a positional cloning approach for the identification of the Pendred syndrome gene.
[DNA microarray screening analysis in children with profound hearing impairment in Hubei province]. Yue Zhan;Xia Wu;Yujuan Hu;Xiang Huang;Jiade Duan;Haihua Chen;Jing Jin;Dan Li;Wen Xie;Weijia Kong. 2014. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 28. PMID: 25129964

OBJECTIVE: To investigate characteristics of molecular etiology of children with profound sensorineural hearing loss in Hubei province, and to provide reference for deafness treatment and genetic counseling. METHOD: Three hundred and six children with profound sensorineural hearing loss in Hubei province were enrolled, their genomic DNA were extracted from peripheral blood and a deafness gene test chip was used to screen nine hot spot mutation in the GJB2, GJB3, SLC26A4, and mitochondria 12SrRNA gene. All patients with SLC26A4 gene mutation were given temporal bone CT scan. RESULT: One hundred and thirty-two (43.14%) out of 306 children were found carrying at least one pathogenic gene mutation. The mutation rates of GJB2, SLC26A4 and mitochondria DNA 12SrRNA gene were 29.41% (90/306), 13.72% (42/306) and 0.65% (2/306), respectively. None out of 306 children was detected GJB3 gene mutation. Thirty-six patients carrying SLC26A4 gene mutation were detected enlarged vestibular aqueduct by CT scan. CONCLUSION: Mutations of GJB2 and SLC26A4 gene are two major pathogenic gene for genetic hearing loss in children. 235delC mutation is the main mutation type, followed by IVS7-2A> G mutation type. The screening of SLC26A4 gene common mutations contribute to the diagnosis of enlarged vestibular aqueduct syndrome.
The influence of mutations in the SLC26A4 gene on the temporal bone in a population with enlarged vestibular aqueduct. Colm Madden;Mark Halsted;Jareen Meinzen-Derr;Dianna Bardo;Mark Boston;Ellis Arjmand;Carla Nishimura;Tao Yang;Corning Benton;Vijay Das;Richard Smith;Daniel Choo;John Greinwald. 2007. Arch Otolaryngol Head Neck Surg. 133. PMID: 17309986

OBJECTIVE: To correlate genetic and audiometric findings with a detailed radiologic analysis of the temporal bone in patients with enlarged vestibular aqueduct (EVA) to ascertain the contribution of SLC26A4 gene mutations to this phenotype. DESIGN: A retrospective review of patients with EVA identified in a database of pediatric hearing-impaired patients. SETTING: A tertiary care pediatric referral center. PATIENTS: Seventy-one children with EVA and screening results for SLC26A4 mutations. MAIN OUTCOME MEASURES: Genetic screening results, audiometric thresholds, and radiographic temporal bone measurements. RESULTS: Seventy-one children with EVA were screened for SLC26A4 mutations. Mutations were found in 27% of children overall, while only 8% had biallelic mutations. The mean initial pure-tone average (PTA) was 59 dB; the mean final PTA was 67 dB. A bilateral EVA was found in 48 (67%) of the children; a unilateral EVA was found in 23 (33%). Progressive hearing loss (in at least 1 ear) was seen in 29 (41%) of the patients. The strongest genotype-phenotype interaction was seen in children with a bilateral EVA. Among children with SLC26A4 mutations, there was a significantly wider vestibular aqueduct at the midpoint and a wider vestibule width (P < .05) than in children without the mutation. Among patients with a bilateral EVA, children with any SLC26A4 mutation were more likely to have a more severe final PTA (64 dB vs 32 dB), larger midpoint measurement (2.1 vs 1.1 mm), and larger operculum measurement (3.0 vs 2.0 mm) than those without the mutation in their better-hearing ear (P < .05). CONCLUSIONS: In a population of pediatric patients with an EVA and hearing loss, SLC26A4 mutations are a contributor to the phenotype. Our data suggest that other genetic factors also have important contributions to this phenotype. The presence of an abnormal SLC26A4 allele, even in the heterozygous state, was associated with greater enlargement of the vestibular aqueduct, abnormal development of the vestibule, and possibly a stable hearing outcome.
[Genetic testing and mutation analysis for the cochlear implantation children and their normal auditory phenotype parents]. Ming Shi;Yibing Yang;Mei Zhao;Jin Gao;Wang Li;Yanming He;Biao Ruan;Pu Dai. 2013. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 26. PMID: 23285950

OBJECTIVE: To investigate the characteristics and significant of mutations of GJB2 gene, SLC26A4 gene and mitochondrial 12S rRNA in deaf children who received cochlear implantation (CI) in Yunnan and to provide the data for diagnoses and research of recovery in C1 children. METHOD: Genomic DNA was extracted from the peripheral blood samples collected from 46 children and their parents (110 cases). All the children received the CI. Their parents had normal auditory phenotype. PCR was performed and the products were sequenced by automated DNA sequencer to detect the hot spots of mutations. RESULT: The detection rates of GJB2 235delC (13.0%) and 109G>A (24.0%) mutations were significantly higher than other mutations. SLC26A was the secondary major mutation (13.0%). We found out that no patient carried the mitochondrial 12S rRNA mutations. Leukoencephalopathy, hyperbilirubinemia and hypoxic-ischemic injure were disclosed in 7 patients (15.2%). The rate of mutations in parents was 36.0% (23/64). There had no difference between Han and other racial minorities (P>0.05). CONCLUSION: The CI recipients in Yunnan with a high frequency of 235 delC and 109 G>A mutation, IVS7-2A>G (6.5%) is also a common mutation related hearing loss; aminoglycoside antibiotics may not be the main reason which induced congenital deaf in CI children; environment facts was suggested to contribute another important cause. The hot-spots gene screening for the C1 children could offer an accurate genetic counseling for early diagnosis and treatment, it also provide evidences for the clinical analysis between mutations and curative effect.
Molecular and hereditary mechanisms of sensorineural hearing loss with focus on selected endocrinopathies. I Masindova;L Varga;J Stanik;L Valentinova;M Profant;I Klimes;D Gasperikova. 2012. Endocr Regul. 46. PMID: 22808909

Hearing loss is one of the most widespread sensory disorders. The incidence of deafness in general population is 1:1000 newborns. About one half of the cases of the congenital sensorineural hearing loss (SNHL) is inherited. Recessive mutations in the gap junction beta 2 (GJB2) gene are the most common genetic causes of the nonsyndromic SNHL. The GJB2 encodes a protein connexin 26 which forms a subunit of gap junction essential for the correct function of the inner ear. The syndromic SNHL is associated with a wide range of other symptoms, which encompass also dysfunctions of endocrine organs. The Pendred syndrome associated with the hearing impairment is characterized by a prelingual, bilateral sever to profound SNHL, goiter, and iodine organification defect. It is an autosomal recessive disorder, which develops due to mutations in pendrin, an anion channel encoded by SLC26A4 gene. Another important type of syndromic hearing loss is the Maternally Inherited Diabetes and Deafness syndrome, which is caused by several mitochondrial DNA mutations. These mutations are clinically manifested by a hearing impairment with development of the diabetes in the adult age. Hearing impairment occurs during puberty when sensation of high frequency tones is affected following with further progress to profound bilateral sensorineural hearing impairment in the whole frequency range. This review deals with the molecular mechanisms of common genetic causes of the hereditary SNHL along with the selected endocrinopathies emphasizing that the DNA analyses along with the functional studies significantly contribute to the early SNHL diagnosis followed by personalized therapy and genetic counseling.
Outcomes of cochlear implantation for the patients with specific genetic etiologies: a systematic literature review. Shin-Ya Nishio;Shin-Ichi Usami. 2017. Acta Otolaryngol. 137. PMID: 28498079

CONCLUSION: Most of the cases with gene mutations of intra-cochlear etiology showed relatively good CI outcomes. To progress toward more solid evidence-based CI intervention, a greater number of reports including CI outcomes for specific gene mutations are desired. BACKGROUND: Cochlear implantation (CI) is the most important and effective treatment for patients with profound sensorineural hearing loss. However, the outcomes of CI vary among patients. One of the reasons of this heterogeneous outcome for cochlear implantation is thought to be the heterogeneous nature of hearing loss. Indeed, genetic factors, the most common etiology in severe-to-profound hearing loss, might be one of the key determinants of outcomes for CI and electric acoustic stimulation (EAS). Patients with genetic causes involving an 'intra-cochlear' etiology show good CI/EAS outcomes. REVIEW: This review article aimed to summarize the reports on CI/EAS outcomes in patients with special genetic causes as well as to assist in future clinical decision-making. Most of the cases were suspected of an intra-cochlear etiology, such as those with GJB2, SLC26A4, and OTOF mutations, which showed relatively good CI outcomes. However, there have only been a limited number of reports on patients with other gene mutations.
A novel insertion-induced frameshift mutation of the SLC26A4 gene in a Korean family with Pendred syndrome. Borum Sagong;Jun Ho Seok;Tae-Jun Kwon;Un-Kyung Kim;Sang-Heun Lee;Kyu-Yup Lee. 2012. Gene. 508. PMID: 22884721

Pendred syndrome (PS) is an autosomal recessive disorder characterized by congenital bilateral sensorineural hearing loss, goiter, and incomplete iodide organification. Patients with PS also have structural anomalies of the inner ear such as enlarged vestibular aqueducts (EVA) and Mondini's malformation. The goiter, which is a major clinical manifestation of PS, usually develops around adolescence. PS is caused by biallelic mutations of the SLC26A4 gene, while nonsyndromic bilateral EVA is associated with zero or one SLC26A4 mutant allele. We report here a Korean family including a young female with PS who had goiter and progressive, fluctuating sensorineural hearing loss that could be partially recovered by oral steroid treatment. Genetic investigation revealed compound heterozygous mutations for p.R677AfsX11, a novel frameshift mutation, and p.H723R in the SLC26A4 gene. Our findings provide detailed information regarding the distribution of mutant alleles for PS and may serve as a foundation for studies to comprehend the genetic portion of syndromic hearing loss.
[Common deafness gene mutations of non-syndromic hearing loss in Liaoning]. Ying Tian;Zheng Wang;Ning Yang;Lian Hui;Xuejun Jiang. 2014. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 28. PMID: 25464568

OBJECTIVE: Investigate common deafness gene mutations in patients with severe and profound non-syndromic hearing loss in Liaoning in order to understand their hereditary etiologies and characteristics at the molecular level. METHOD: Peripheral blood samples were obtained and the DNA templates were extracted from 128 non-syndromic hearing loss patients who are sporadic in clinics. The deafness gene chip was applied to detect hot-spot deafness gene mutations including GJB2, GJB3, SLC26A4 and mitochondrial 12S rRNA. Deafness etiology questionnaires, pure tone audiometry, auditory brainstem response, tympanometry and temporal bone CT were also applied. RESULT: Various types of gene locus mutations were seen in 52 of the 128 patients (40.6%); (1) GJB2 gene mutations (n=22) included c. 235 del C homozygous mutation (n=10), c. 235 del C heterozygous mutation (n=5); c. 176_191 del 16 heterozygous mutation (n=l); c 35 del G heterozygous mutation (n=l); c. 235 del C/c. 299_300 del AT mutation (n=l), c. 235 del C/c. 176_191 del 16 mutation (n=l), c. 35 del G/c. 176_191 del 16 mutation (n=l); c. 299_300 del AT/c. 919-2 A>G mutation (n=l), c. 235 del C/c. 919-2 A>G mutation (n=l). (2) SLC26A4 gene mutations (n=30) included c. 919-2 A>G homozygous mutation (n=6), c. 919-2 A>G heterozygous mutation (n=17), c. 2168 A>G homozygous mutation (n=l), c. 2168 A>G heterozygous mutation (n=2), c. 2168 A>G/c. 919-2 A>G mutation (n=2), c. 919-2 A>G/GJB2 c. 235 del C mutation (n=2); (3) No GJB3 and mitochondrial 12S rRNA mutation. Genetic deafness was confirmed at the gene level in 24 cases (18.8%) and 28 patients (21.9%) were diagnosed as carriers of genetic deafness gene mutations. CONCLUSION: Genetic deafness occupies a large population in deaf community in Liaoning. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss and provide theoretical guidance.
[Common deafness gene mutations of non-syndromic hearing loss in Liaoning]. Ying Tian;Zheng Wang;Ning Yang;Lian Hui;Xuejun Jiang. 2014. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 28. PMID: 25508199

OBJECTIVE: Investigate common deafness gene mutations in patients with severe and profound non-syndromic hearing loss in Liaoning in order to understand their hereditary etiologies and characteristics at the molecular level. METHOD: Peripheral blood samples were obtained and the DNA templates were extracted from 128 non-syndromic hearing loss patients who are sporadic in clinics. The deafness gene chip was applied to detect hot-spot deafness gene mutations including GJB2, GJB3, SLC26A4 and mitochondrial 12S rRNA. Deafness etiology questionnaires, pure tone audiometry, auditory brainstem response, tympanometry and temporal bone CT were also applied. RESULT: Various types of gene locus mutations were seen in 52 of the 128 patients (40.6%); (1) GJB2 gene mutations (n=22) included c. 235 del C homozygous mutation (n=10), c. 235 del C heterozygous mutation (n=5); c. 176_191 del 16 heterozygous mutation (n=l); c 35 del G heterozygous mutation (n=l); c. 235 del C/c. 299_300 del AT mutation (n=l), c. 235 del C/c. 176_191 del 16 mutation (n=l), c. 35 del G/c. 176_191 del 16 mutation (n=l); c. 299_300 del AT/c. 919-2 A>G mutation (n=l), c. 235 del C/c. 919-2 A>G mutation (n=l). (2) SLC26A4 gene mutations (n=30) included c. 919-2 A>G homozygous mutation (n=6), c. 919-2 A>G heterozygous mutation (n=17), c. 2168 A>G homozygous mutation (n=l), c. 2168 A>G heterozygous mutation (n=2), c. 2168 A>G/c. 919-2 A>G mutation (n=2), c. 919-2 A>G/GJB2 c. 235 del C mutation (n=2); (3) No GJB3 and mitochondrial 12S rRNA mutation. Genetic deafness was confirmed at the gene level in 24 cases (18.8%) and 28 patients (21.9%) were diagnosed as carriers of genetic deafness gene mutations. CONCLUSION: Genetic deafness occupies a large population in deaf community in Liaoning. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss and provide theoretical guidance.
Novel mutations in the SLC26A4 gene. Micol Busi;Alessandro Castiglione;Marina Taddei Masieri;Anna Ravani;Valeria Guaran;Laura Astolfi;Patrizia Trevisi;Alessandra Ferlini;Alessandro Martini. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22717225

OBJECTIVES: Mutations in the SLC26A4 gene (7q22.3-7q31.1) are considered one of the most common causes of genetic hearing loss. There are two clinical forms related to these mutations: syndromic and non-syndromic deafness. The first one is named Pendred Syndrome (PS) when deafness is associated with thyroid goiter; the second is called DFNB4, when no other symptoms are present. Both are transmitted as an autosomal recessive trait, but simple heterozygotes can develop both forms of deafness. Actually it is thought that Pendred Syndrome occurs when both alleles of SLC26A4 gene are mutated; DFNB4 seems due to monoallelic mutations. PS and DFNB4 can be associated with inner ear malformations. In most of the cases (around 80%), these consist in Enlarged Vestibular Aqueduct (EVA). EVA can also be present without SLC26A4 mutations. Understanding the role of new SLC26A4 variants should facilitate clinical assessment, as well as diagnostic and therapeutic approaches. This investigation aims to detect and report genetic causes of two unrelated Italian boys with hearing loss. METHODS: Patients and family members underwent clinical, audiological and genetic evaluations. To identify genetic mutations, DNA sequencing of SLC26A4 gene (including all 21 exons, exon-intron boundaries and promoter region) was carried out. RESULTS: Both probands were affected by congenital, progressive and fluctuating mixed hearing loss. Temporal bone imaging revealed a bilateral EVA with no other abnormalities in both cases. Probands were heterozygotes for previously undescribed mutations in the SLC26A4 gene: R409H/IVS2+1delG (proband 1) and L236P/K590X (proband 2). No other mutations were detected in GJB2, GJB6 genes or mitochondrial DNA (mit-DNA). CONCLUSIONS: The IVS2+1delG and K590X mutations have not yet been described in literature but there is some evidence to suggest that they have a pathological role. The results underlined the importance of considering the complete DNA sequencing of the SLC26A4 gene for differential molecular diagnosis of deafness, especially in those patients affected by congenital, progressive and fluctuating mixed hearing loss with bilateral EVA.
Intrafamilial phenotypic variability in families with biallelic SLC26A4 mutations. Mee Hyun Song;Joong-Wook Shin;Hong-Joon Park;Kyung-A Lee;Yoonjung Kim;Un-Kyung Kim;Ju Hyun Jeon;Jae Young Choi. 2013. Laryngoscope. 124. PMID: 24338212

OBJECTIVES/HYPOTHESIS: Enlarged vestibular aqueduct (EVA) and hearing loss are known to be caused by SLC26A4 mutations, but large phenotypic variability exists among patients with biallelic SLC26A4 mutations. Intrafamilial phenotypic variability was analyzed in multiplex EVA families carrying biallelic SLC26A4 mutations to identify the contribution of SLC26A4 mutations and other genetic or environmental factors influencing the clinical manifestations. STUDY DESIGN: Retrospective case series. METHODS: Eleven multiplex Korean families with EVA and hearing loss that carry biallelic mutations of the SLC26A4 gene were included. Genetic analysis for SLC26A4 and other genes including FOXI1, FOXI1-DBD, and KCNJ10 was performed. The auditory and other phenotypes were compared among siblings with the same SLC26A4 mutations. RESULTS: The difference in the auditory phenotypes was identified between siblings in approximately half of the EVA families. Families with SLC26A4 mutations other than H723R homozygous mutations demonstrated more phenotypic variability, especially in those carrying IVS7-2A>G splice site mutation. Cochlear malformation was a consistent finding among siblings with the same SLC26A4 mutations. No mutation was identified in the FOXI1, FOXI1-DBD, and KCNJ10 genes in the tested families. CONCLUSIONS: The possibility of variability concerning auditory phenotype should be considered even within family members carrying the same SLC26A4 mutations when providing genetic counseling to multiplex EVA families. Mutations in the currently known genes associated with EVA other than SLC26A4 were not found to be responsible for the intrafamilial phenotypic variability. Modifier genes or environmental factors other than the currently known genes seem to play a role in the phenotypic expressions of EVA patients.
Resolving the genetic heterogeneity of prelingual hearing loss within one family: Performance comparison and application of two targeted next generation sequencing approaches. Yu Lu;Xueya Zhou;Zhanguo Jin;Jing Cheng;Weidong Shen;Fei Ji;Liyang Liu;Xuegong Zhang;Michael Zhang;Ye Cao;Dongyi Han;KwongWai Choy;Huijun Yuan. 2014. J Hum Genet. 59. PMID: 25231367

Here, we report an unconventional Chinese pedigree consisting of three branches all segregating prelingual hearing loss (HL) with unclear inheritance pattern. After identifying the cause of one branch as maternally inherited aminoglycoside-induced HL, targeted next generation sequencing (NGS) was applied to identify the genetic causes for the other two branches. One affected subject from each branch was subject to targeted NGS whose genomic DNA was enriched either by whole-exome capture (Agilent SureSelect All Exon 50 Mb) or by candidate genes capture (Agilent SureSelect custom kit). By NGS analysis, we identified that patients from Branch A were compound heterozygous for p.E1006K and p.D1663V in the CDH23 (DFNB12) gene; and patients from Branch B were homozygous for IVS7-2A>G in the SLC26A4 (DFNB4) gene. Both CDH23 mutations altered conserved calcium binding sites of the extracellular cadherin domains. The co-occurrence of three different genetic causes in this family was exceedingly rare but fully compatible with the mutation spectrum of HL. Our study has also raised several technical and analytical issues when applying the NGS technique to genetic testing.
[Prenatal screening and diagnosis of genetic deafness by microarray]. Lian-hua Sun;Lei Li;Xiao-wen Wang;Ya-zhong Zhu;Yong-chuan Chai;Xiao-hua Li;Hao Wu;Tao Yang. 2013. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 47. PMID: 23328038

OBJECTIVE: To evaluate a microarray-based mutation screening method for genetic deafness and its application in prenatal diagnosis. METHODS: Mutation screening of common deafness genes was performed in pregnant women and volunteers spouses. Nine common mutations in four major deafness genes, GJB2, GJB3, SLC26A4 and mitochondrial 12S rRNA, were detected simultaneously by a microarray-based method. Genetic counseling was given based on their testing results. RESULTS: 5.11% of pregnant women carried at least one mutation. Among them, seven carried mutation in the mitochondria 12S rRNA gene and were offered aminoglycoside-induced ototoxicity warning. For other mutation carriers of GJB2 or SLC26A4 genes, additional mutation screening was performed in their husbands by direct sequencing. A total of 20 couples were at risk of giving birth to children with genetic deafness. Of five couples who selected to undergo prenatal diagnostic testing of the fetus, four were diagnosed as wild type or heterozygous for the tested genes and one as p.V37I/c.235delC compound heterozygous for GJB2. CONCLUSIONS: DNA microarray is a quick, easy and reliable method to screen mutations in genetic deafness genes. Application of this method in prenatal screening and diagnosis might effectively reduce the occurrence of genetic deafness.
Distribution and frequencies of PDS (SLC26A4) mutations in Pendred syndrome and nonsyndromic hearing loss associated with enlarged vestibular aqueduct: a unique spectrum of mutations in Japanese. Koji Tsukamoto;Hiroaki Suzuki;Daisuke Harada;Atsushi Namba;Satoko Abe;Shin-ichi Usami. 2003. Eur J Hum Genet. 11. PMID: 14508505

Molecular diagnosis makes a substantial contribution to precise diagnosis, subclassification, prognosis, and selection of therapy. Mutations in the PDS (SLC26A4) gene are known to be responsible for both Pendred syndrome and nonsyndromic hearing loss associated with enlarged vestibular aqueduct, and the molecular confirmation of the PDS gene has become important in the diagnosis of these conditions. In the present study, PDS mutation analysis confirmed that PDS mutations were present and significantly responsible in 90% of Pendred families, and in 78.1% of families with nonsyndromic hearing loss associated with enlarged vestibular aqueduct. Furthermore, variable phenotypic expression by the same combination of mutations indicated that these two conditions are part of a continuous category of disease. Interestingly, the PDS mutation spectrum in Japanese, including the seven novel mutations revealed by this study, is very different from that found in Caucasians. Of the novel mutations detected, 53% were the H723R mutation, suggesting a possible founder effect. Ethnic background is therefore presumably important and should be noted when genetic testing is being performed. The PDS gene mutation spectrum in Japanese may be representative of those in Eastern Asian populations and its elucidation is expected to facilitate the molecular diagnosis of a variety of diseases.
[A literature review of epidemiological studies on mutation hot spots of Chinese population with non-syndromic hearing loss]. Haibo Li;Qiong Li;Hong Li;Ying Chen. 2012. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 26. PMID: 23002642

OBJECTIVE: To identify the regional mutation hot spots characteristics, and then to establish a regional genetic screening programs. METHOD: Molecular epidemiological literatures about Chinese deafness gene GJB2, SLC26A4, mitochondrial DNA mutations from 2006 to the first half of 2011 were retrieved in Wanfang and Pubmed literature database. The primary data of these studies including the number of samples, demographic characteristics, mutation frequencies and so on,were analyzed statically. RESULT: Of 46 papers, 42 were included in this study. The patients all had non-syndromic sensorineural hearing loss and lived in 20 regions of China. A total of 18094 were counted and the average mutation frequencies were approximately 42.0%. The mutation frequencies of 235 delC were 16.34%, 299-300 delAT were 4.75% in GJB2 gene and IVS7-2A > G were 12.60%, 2168A > G were 2.32% in SLC26A4 gene and the mutation frequencies of 1555A > G, 1494C > T in mtDNA were 5.21%, 1.11% respectively. The statistical discrepancy was significant among mutation frequencies in different regions by chi2-test (P < 0.05). CONCLUSION: Molecular epidemiological statistics show that the 6 locus are the mutation hot spots in Chinese people with non-syndromic hearing loss and can be used for genetic screening according to the specific regional mutation characteristics.
[Audiological and genetic studies on 130 infants with hearing loss]. Da-yong Wang;Qiu-ju Wang;Lan Lan;Wei Shi;Cui Zhao;Pei-lin Hui;Shao-qi Rao;Dong-yi Han. 2009. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 44. PMID: 19558853

OBJECTIVE: To investigate the genetic etiologies in the 0- 3-years-old infants with hearing loss and to analyze the interaction between genetics and environmental factors. METHODS: Total of 130 infants were performed detailed audiological evaluation as well as the detection of the popular deafness gene mutations in GJB2 gene, SLC26A4 and mtDNA12SrRNA. Of them, 84 cases were performed the computer tomography or magnetic resonance imaging examinations. RESULTS: Of the 130 cases, 54 infants were diagnosed as large vestibular aqueduct syndrome, while seven of 130 were as auditory neuropathy and the others were diagnosed as sensorineural hearing loss. Considering of the risks of etiologies for hearing loss, 85 of them had the experiences of the high risk factors at birth (65.4%, 85/130), while 23 of them had the exposure of aminoglycoside antibiotics, and 13 had the family history background as well as two cases were from the consanguineous families. In the causative genes screening, 42 infants were caused by the mutations of SLC26A4 gene (32.3%), but 14 infants found the mutations in GJB2 gene (4.6%), and no infants carried the mutation in mtDNA 12SrRNA 1555G and 1494T points in our studies. CONCLUSIONS: In our studies, about 36.9% infants hearing loss cases can be found the mutations in SLC26A4 and GJB2 genes. It is essential to put the idea into the hearing evaluation combined with genetic testing for the diagnoses of hearing loss. It is also helpful for exploring the etiologies of hearing loss and performing the target genetic consulting for decreasing the prevalence of deafness in the future.
Genetic Screening of GJB2 and SLC26A4 in Korean Cochlear Implantees: Experience of Soree Ear Clinic. Joong-Wook Shin;Seung-Chul Lee;Ho-Ki Lee;Hong-Joon Park. 2012. Clin Exp Otorhinolaryngol. 5 Suppl 1. PMID: 22701767

OBJECTIVES: Genetic hearing loss is highly heterogeneous and more than 100 genes are predicted to cause this disorder in humans. In spite of this large genetic heterogeneity, mutations in SLC26A4 and GJB2 genes are primarily responsible for the major etiologies of genetic hearing loss among Koreans. The purpose of this study is to investigate the genetic cause of deafness in Korean cochlear implantees by performing a genetic screening of the SLC26A4 and GJB2 genes. METHODS: The study cohort included 421 unrelated Korean patients with sensorineural hearing loss (SNHL) and who had received cochlear implants (CI) at Soree Ear Clinic from July 2002 to December 2010. Among 421 CI patients, we studied 230 cases who had received the genetic screening for SLC26A4 or GJB2 genes. Written informed consent was obtained from all participants. All patients had severe to profound, bilateral hearing loss. For 56 patients who showed enlarged vestibular aqueduct on their computed tomography (CT) scan, we analyzed SLC26A4. For 174 CT negative patients, GJB2 gene was sequenced. RESULTS: For the 56 SLC26A4 patients, 32 (57.1%) had two pathogenic recessive mutations in SLC26A4. A single recessive SLC26A4 mutation was identified in 14 patients (25%). H723R and IVS7-2A>G were the most commonly found mutations, accounting for 60.3% (47/78) and 30.8% (24/78) of the mutated alleles, respectively. For the 174 GJB2 patients, 20 patients (11.5%) had two pathogenic recessive mutations in GJB2. 235delC was the most common mutation, accounting for 43.0% (31/72) of mutant alleles. CONCLUSION: The two major genes, SLC26A4 and GJB2, contribute major causes of deafness in CI patients. Continuous studies are needed to identify new genes that can cause hearing loss to Korean CI patients.
[Study of generational risk in deafness inflicted couples using deafness gene microarray technique]. Ping Wang;Jia Zhao;Shu-yuan Yu;Peng Jin;Wei Zhu;Bo DU. 2011. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 46. PMID: 21924098

OBJECTIVE: To explored the significance of screening the gene mutations of deafness related in deaf-mute (deaf & dumb) family using DNA microarray. METHODS: Total of 52 couples of deaf-mute were recruited from Changchun deaf-mute community. With an average age of (58.3 ± 6.7) years old (x(-) ± s). Blood samples were obtained with informed consent. Their genomic DNA was extracted from peripheral blood and PCR was performed. Nine of hot spot mutations in four most common deafness pathologic gene were examined with the DNA microarray, including GJB2, GJB3, PDS and mtDNA 12S rRNA genes. At the same time, the results were verified with the traditional methods of sequencing. Fifty of normal people served as a control group. RESULTS: All patients were diagnosed non-syndromic sensorineural hearing loss by subjective pure tone audiometry. Thirty-two of 104 cases appeared GJB2 gene mutation (30.7%), the mutation sites included 35delG, 176del16, 235delC and 299delAT. Eighteen of 32 cases of GJB2 mutations were 235delC (59.1%). Seven of 104 cases appeared SLC26A4 gene IVS7-2 A > G mutation. Questionnaire survey and gene diagnosis revealed that four of 52 families have deaf offspring (7.6%). When a couple carries the same gene mutation, the risk of their children deafness was 100%. The results were confirmed with the traditional methods of sequencing. CONCLUSIONS: There is a high risk of deafness if a deaf-mute family is planning to have a new baby. It is very important and helpful to avoid deaf newborns again in deaf-mute family by DNA microarray.
Association of intronic repetition of SLC26A4 gene with Hashimoto thyroiditis disease. Salima Belguith-Maalej;Rihab Kallel;Mouna Mnif;Mohamed Abid;Hammadi Ayadi;Hassen Hadj Kacem. 2013. Genet Res (Camb). 95. PMID: 23452581

Intronic microsatellites repeats were implicated in the pathogenic mechanisms of several diseases. SLC26A4 gene, involved in the genetic susceptibility of autoimmune thyroid disease (AITD), harbours large non-coding introns. Using the tandem repeat finder (TRF) Software, two new polymorphic microsatellite markers, rs59736472 and rs57250751, located at introns 10 and 20, respectively, were identified. A case-control design including 308 patients affected with AITD (146 GD, 90 HT and 72 PIM) and 212 unmatched healthy controls were performed for each marker (rs59736472, D7S2459 and rs57250751). Furthermore, we used PHASE 2.0 version to reconstruct haplotypes, Kolmogorov-Smirnov (KS) and the Clump analysis program for multivariate analysis. The fluorescent genotyping revealed three alleles (106,112 and 115 bp) for rs57250751 and 12 alleles for both D7S2459 and rs59736472 ranging from 134 to 156 bp and from 144 to 168 bp, respectively. The case-control analysis confirmed the positive association of D7S2459 with Hashimoto thyroiditis (HT) disease previously reported. Moreover, a significant association was found only with rs59736472 and HT disease. Haplotype-specific analysis showed that the 140-148-115 haplotype may increase the risk of HT (χ2=9.8, 1 df, P=0.0017, OR=2.07, IC [1.27-3.36]). Consequently, considering the number of repetitions of both D7S2459 and rs59736472, we found 15 alleles ranging from 45 to 59 repetitions. The case-control analysis showed a significant association of the 55 repetition with HT disease (χ2=6.32, 1 df, p c=0.012, OR=1.74, IC [1.1-2.76]). In conclusion, we suggest the association of longer alleles of intron 10 of SLC26A4 gene with HT disease.
Combination of hearing screening and genetic screening for deafness-susceptibility genes in newborns. Gen-Dong Yao;Shou-Xia Li;Ding-Li Chen;Hai-Qin Feng;Su-Bin Zhao;Yong-Jie Liu;Li-Li Guo;Zhi-Ming Yang;Xiao-Fang Zhang;Cai-Xia Sun;Ze-Hui Wang;Wei-Yong Zhang. 2013. Exp Ther Med. 7. PMID: 24348793

The aim of this study was to determine the clinical significance of the results of screening of newborn hearing and the incidence of deafness-susceptibility genes. One thousand newborn babies in the Handan Center Hospital (Handan, China) underwent screening of hearing and deafness-susceptibility genes. The first screening test was carried out using otoacoustic emissions (OAEs). Babies with hearing loss who failed to pass the initial screening were scheduled for rescreening at 42 days after birth. Cord blood was used for the screening of deafness-susceptibility genes, namely the GJB2, SLC26A4 and mitochondrial 12S rRNA (MTRNR1) genes. Among the 1,000 neonates that underwent the first hearing screening, 25 exhibited left-sided hearing loss, 21 exhibited right-sided hearing loss and 15 cases had binaural hearing loss. After rescreening 42 days later, only one of the initial 61 cases exhibited hearing loss under OAE testing. The neonatal deafness gene tests showed two cases with 1555A>G mutation and two cases with 1494C>T mutation of the MTRNR1 gene. In the SLC26A4 gene screening, four cases exhibited the heterozygous IVS7-2A>G mutation and one case exhibited heterozygous 1226G>A mutation. In the GJB2 gene screening, two cases exhibited the homozygous 427C>T mutation and 10 exhibited the heterozygous 235delC mutation. The genetic screening revealed 21 newborns with mutations in the three deafness-susceptibility genes. The overall carrier rate was 2.1% (21/1,000). The association of hearing and gene screening may be the promising screening strategy for the diagnosis of hearing loss.
Massively parallel DNA sequencing successfully identifies new causative mutations in deafness genes in patients with cochlear implantation and EAS. Maiko Miyagawa;Shin-ya Nishio;Takuo Ikeda;Kunihiro Fukushima;Shin-ichi Usami. 2013. PLoS One. 8. PMID: 24130743

Genetic factors, the most common etiology in severe to profound hearing loss, are one of the key determinants of Cochlear Implantation (CI) and Electric Acoustic Stimulation (EAS) outcomes. Satisfactory auditory performance after receiving a CI/EAS in patients with certain deafness gene mutations indicates that genetic testing would be helpful in predicting CI/EAS outcomes and deciding treatment choices. However, because of the extreme genetic heterogeneity of deafness, clinical application of genetic information still entails difficulties. Target exon sequencing using massively parallel DNA sequencing is a new powerful strategy to discover rare causative genes in Mendelian disorders such as deafness. We used massive sequencing of the exons of 58 target candidate genes to analyze 8 (4 early-onset, 4 late-onset) Japanese CI/EAS patients, who did not have mutations in commonly found genes including GJB2, SLC26A4, or mitochondrial 1555A>G or 3243A>G mutations. We successfully identified four rare causative mutations in the MYO15A, TECTA, TMPRSS3, and ACTG1 genes in four patients who showed relatively good auditory performance with CI including EAS, suggesting that genetic testing may be able to predict the performance after implantation.
A rapid method for simultaneous screening of multi-gene mutations associated with hearing loss in the Korean population. Borum Sagong;Jeong-In Baek;Se-Kyung Oh;Kyung Jin Na;Jae Woong Bae;Soo Young Choi;Ji Yun Jeong;Jae Young Choi;Sang-Heun Lee;Kyu-Yup Lee;Un-Kyung Kim. 2013. PLoS One. 8. PMID: 23469187

Hearing loss (HL) is a congenital disease with a high prevalence, and patients with hearing loss need early diagnosis for treatment and prevention. The GJB2, MT-RNR1, and SLC26A4 genes have been reported as common causative genes of hearing loss in the Korean population and some mutations of these genes are the most common mutations associated with hearing loss. Accordingly, we developed a method for the simultaneous detection of seven mutations (c.235delC of GJB2, c.439A>G, c.919-2A>G, c.1149+3A>G, c.1229C>T, c.2168A>G of SLC26A4, and m.1555A>G of the MT-RNR1 gene) using multiplex SNaPshot minisequencing to enable rapid diagnosis of hereditary hearing loss. This method was confirmed in patients with hearing loss and used for genetic diagnosis of controls with normal hearing and neonates. We found that 4.06% of individuals with normal hearing and 4.32% of neonates were heterozygous carriers. In addition, we detected that an individual is heterozygous for two different mutations of GJB2 and SLC26A4 gene, respectively and one normal hearing showing the heteroplasmy of m.1555A>G. These genotypes corresponded to those determined by direct sequencing. Overall, we successfully developed a robust and cost-effective diagnosis method that detects common causative mutations of hearing loss in the Korean population. This method will be possible to detect up to 40% causative mutations associated with prelingual HL in the Korean population and serve as a useful genetic technique for diagnosis of hearing loss for patients, carriers, neonates, and fetuses.
[Etiologic analysis of severe to profound hearing loss patients from Chifeng city in Inner Mongolia]. Yong-yi Yuan;Pu Dai;Xiu-hui Zhu;Dong-yang Kang;Xin Zhang;De-liang Huang. 2009. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 44. PMID: 19558834

OBJECTIVE: To investigate the etiology of patients with severe to profound hearing loss and to identify the ratio of hereditary hearing loss in Chifeng area in Northern China. METHODS: DNA were extracted from peripheral blood of 134 deaf patients from Chifeng special educational school and 100 normal hearing controls in Northern China. Audiology examinations showed that all patients had severe to profound bilateral sensorineural hearing impairment. Sequence analysis of the whole coding areas of GJB2, GJB3, GJB6, SLC26A4, mtDNA12SrRNA and mtDNAtRNASer(UCN) were performed. Individuals carrying SLC26A4 mutation were given further temporal bone CT scan. RESULTS: The ratio of hearing loss related to genetic factors in this population was 60.45% (81/134). About 33.58% (45/134) of the patients were given accurate genetic diagnosis. GJB2 mutations were responsible for approximately 17.16% of the cases in ChiFeng area. By screening SLC26A4 followed by temporal bone CT scan, we diagnosed 20 cases of enlarged vestibular aqueduct (EVA) and/or other inner ear malformation. SLC26A4 mutations account for about 14.93% of the cases. The aminoglycoside-related mtDNA 1555A>G mutation accounted for 0.76% of the cases in Chifeng area. In addition, another 13.43% (18/134) of the cases carried heterozygous GJB2 mutation and their hearing loss may be related to GJB2. 6.72% (9/134) of the cases carried heterozygous SLC26A4 mutation who were not found EVA by temporal bone CT or not took CT examination for some reasons. However, their hearing loss may also be SLC26A4-related. About 2.24% (3/134) of the cases carried mtDNA 12SrRNA 1095 T>C which may also be an aminoglycoside-related mutation and very likely be the cause of hearing loss. GJB3 might participate in the pathomechanism of hearing loss in 1.49% (2/134) of the patients. GJB6 mutation was not detected in this population. CONCLUSIONS: The ratio of hearing loss related to genetic factors in the sample drawing population from Chifeng was 60.45% (81 cases). GJB2 is the most common gene and SLC26A4 is the second common gene next to GJB2 that cause deafness in this area.
Identification of allelic variants of pendrin (SLC26A4) with loss and gain of function. Silvia Dossena;Aigerim Bizhanova;Charity Nofziger;Emanuele Bernardinelli;Josef Ramsauer;Peter Kopp;Markus Paulmichl. 2011. Cell Physiol Biochem. 28. PMID: 22116359

BACKGROUND: Pendrin is a multifunctional anion transporter that exchanges chloride and iodide in the thyroid, as well as chloride and bicarbonate in the inner ear, kidney and airways. Loss or reduction in the function of pendrin results in both syndromic (Pendred syndrome) and non-syndromic (non-syndromic enlarged vestibular aqueduct (ns-EVA)) hearing loss. Factors inducing an up-regulation of pendrin in the kidney and the lung may have an impact on the pathogenesis of hypertension, chronic obstructive pulmonary disease (COPD) and asthma. Here we characterize the ion transport activity of wild-type (WT) pendrin and seven of its allelic variants selected among those reported in the single nucleotide polymorphisms data base (dbSNPs), some of which were previously identified in a cohort of individuals with normal hearing or deaf patients belonging to the Spanish population. METHODS: WT and mutated pendrin allelic variants were functionally characterized in a heterologous over-expression system by means of fluorometric methods evaluating the I(-)/Cl(-) and Cl(-)/OH(-) exchange and an assay evaluating the efflux of radiolabeled iodide. RESULTS: The transport activity of pendrin P70L, P301L and F667C is completely abolished; pendrin V609G and D687Y allelic variants are functionally impaired but retain significant transport. Pendrin F354S activity is indistinguishable from WT, while pendrin V88I and G740S exhibit a gain of function. CONCLUSION: Amino acid substitutions involving a proline always result in a severe loss of function of pendrin. Two hyperfunctional allelic variants (V88I, G740S) have been identified, and they may have a contributing role in the pathogenesis of hypertension, COPD and asthma.
Genetic heterogeneity of congenital hearing impairment in Algerians from the Ghardaïa province. Sonia Talbi;Crystel Bonnet;Zied Riahi;Farid Boudjenah;Malika Dahmani;Jean-Pierre Hardelin;Fabienne Wong Jun Tai;Malek Louha;Fatima Ammar-Khodja;Christine Petit. 2018. Int J Pediatr Otorhinolaryngol. 112. PMID: 30055715

BACKGROUND: Consanguinity rate is high in Algeria, and the population is thus at high risk for genetic diseases transmitted on an autosomal recessive mode. Inherited congenital hearing impairment (HI) is a highly heterogeneous disorder, which affects approximately 1 in 800 Algerian newborns. Several hundreds of genes responsible for deafness have been reported among which more than one hundred are responsible for isolated deafness, of which 19 have already been reported to be involved in the Algerian population. This study focuses on patients from the Ghardaïa province, an ethnically and geographically isolated region of Southern Algeria that has the highest consanguinity rate in the country (56%). METHODS: Eleven families, with at least two related members experiencing moderate to profound congenital HI, were recruited and screened for mutations in known HI genes. RESULTS: A preliminary screening for common mutations in GJB2 and GJB6 identified the prevalent GJB2:c.35delG mutation in four families. Targeted exome sequencing further identified the causal mutations in the remaining seven families: CIB2:c.97C > T; p.(Arg33*), MYO7A:c.470+1G > A; p.(?), and SLC26A4:c.410C > T; p.(Ser137Leu) biallelic mutations in two families each, and a TECTA:c.2743 A > G; p.(Ile915Val) monoallelic mutation in the only family with autosomal dominant transmission of the HI. Of note, the missense mutations of SLC26A4 and TECTA had not been previously reported. CONCLUSION: These results further substantiate the genetic heterogeneity of HI, even in reportedly isolated populations. However, several families may harbor the same mutations as a result of a long history of marriages between relatives. This study has important implications for the HI molecular diagnosis strategy, and to develop genetic counseling for families originating from the Ghardaïa province of Algeria.
[The clinical application of gene chips combined with CT examination in the diagnosis of large vestibular aqueduct syndrome patients]. Feng Zhou;Ying Lin;Qiong Luo;Xiaoke Chen;Lifen Huang;Zijian Liang;Haitao Wang;Feng Yu. 2014. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 27. PMID: 24417166

OBJECTIVE: To explore the feasibility and superiority of the gene chip method and temporal bone CT in diagnosis of large vestibular aqueduct syndrome. METHOD: One hundred and eighty-eight cases of deaf students in Guangzhou were selected,the microarray detection of the SLC26A4 gene locus was performed,and the 26 cases of students with detected SLC26A4 gene mutations received temporal bone CT imaging. RESULT: Among the detected 26 cases of patients with hearing loss, IVS7-2A>G homozygous mutation was found in 7 cases, 17 cases were heterozygous mutation, 2168A>G heterozygous mutation presented in three cases, including one case of IVS7-2A>G and 2168A>G compound heterozygous mutations. Temporal bone CT findings of 25 cases among the 26 patients showed bilateral large vestibular aqueduct,among which 9 cases exhibited bilateral cochlear malformations, and 1 case was normal. CONCLUSION: Among the different SLC26A4 gene mutations, IVS7-2A>G point mutation rates the highest, followed by 2168A>G. Most of the CT examination prompted the expansion of the vestibular aqueduct. Deafness gene chip hotspot detection of SLC26A4 gene mutations can diagnose such patients before CT examination,which can be used for screening people with high risk of deafness prenatal screening. The early detection and early diagnosis can guide proper precautionary measures in advance to prevent the occurrence of prelingual deafness.
SLC26A4 gene is frequently involved in nonsyndromic hearing impairment with enlarged vestibular aqueduct in Caucasian populations. Sébastien Albert;Hélène Blons;Laurence Jonard;Delphine Feldmann;Pierre Chauvin;Nathalie Loundon;Annie Sergent-Allaoui;Muriel Houang;Alain Joannard;Sébastien Schmerber;Bruno Delobel;Jacques Leman;Hubert Journel;Hélène Catros;Hélène Dollfus;Marie-Madeleine Eliot;Albert David;Catherine Calais;Valérie Drouin-Garraud;Marie-Françoise Obstoy;Patrice Tran Ba Huy;Didier Lacombe;Françoise Duriez;Christine Francannet;Pierre Bitoun;Christine Petit;Eréa-Noël Garabédian;Rémy Couderc;Sandrine Marlin;Françoise Denoyelle. 2006. Eur J Hum Genet. 14. PMID: 16570074

Sensorineural hearing loss is the most frequent sensory deficit of childhood and is of genetic origin in up to 75% of cases. It has been shown that mutations of the SLC26A4 (PDS) gene were involved in syndromic deafness characterized by congenital sensorineural hearing impairment and goitre (Pendred's syndrome), as well as in congenital isolated deafness (DFNB4). While the prevalence of SLC26A4 mutations in Pendred's syndrome is clearly established, it remains to be studied in large cohorts of patients with nonsyndromic deafness and detailed clinical informations. In this report, 109 patients from 100 unrelated families, aged from 1 to 32 years (median age: 10 years), with nonsyndromic deafness and enlarged vestibular aqueduct, were genotyped for SLC26A4 using DHPLC molecular screening and sequencing. In all, 91 allelic variants were observed in 100 unrelated families, of which 19 have never been reported. The prevalence of SLC26A4 mutations was 40% (40/100), with biallelic mutation in 24% (24/100), while six families were homozygous. All patients included in this series had documented deafness, associated with EVA and without any evidence of syndromic disease. Among patients with SLC26A4 biallelic mutations, deafness was more severe, fluctuated more than in patients with no mutation. In conclusion, the incidence of SLC26A4 mutations is high in patients with isolated deafness and enlarged vestibular aqueduct and could represent up to 4% of nonsyndromic hearing impairment. SLC26A4 could be the second most frequent gene implicated in nonsyndromic deafness after GJB2, in this Caucasian population.
Vestibular function is associated with residual low-frequency hearing loss in patients with bi-allelic mutations in the SLC26A4 gene. Jinsei Jung;Young Wook Seo;Jae Young Choi;Sung Huhn Kim. 2016. Hear Res. 335. PMID: 26900070

DFNB4 is non-syndromic, autosomal recessive type of hearing loss with an enlarged vestibular aqueduct (EVA) caused by mutations in SLC26A4/pendrin. Although the characteristics of hearing loss are well known in DFNB4, vestibular function remains inconclusive. We evaluated the vestibular function of 31 patients with bi-allelic mutations in SLC26A4/pendrin and analyzed genetic, radiological, and audiological correlations with vestibular function. In a caloric test, unilateral and bilateral vestibulopathies were detected in 45.2% and 6.4% of patients, respectively; however, only 22.6% had subjective vertigo symptoms. While vestibular phenotype was not significantly associated with specific mutations in genetic alleles or the sizes of the endolymphatic sac and vestibular aqueduct, a residual hearing threshold at a low frequency (500 Hz) was definitely correlated with vestibular function in DFNB4 (p = 0.005). These findings may indicate that vestibular function in DFNB4 deteriorates unilaterally in ears when hearing loss occurs. In conclusion, DFNB4 shows vestibular dysfunction, which is strongly linked to hearing loss at low frequencies without any allelic or anatomical predisposing factor.
Molecular heterogeneity in two families with auditory pigmentary syndromes: the role of neuroimaging and genetic analysis in deafness. D Shears;H Conlon;T Murakami;K Fukai;R Alles;R Trembath;M Bitner-Glindzicz. 2004. Clin Genet. 65. PMID: 15099345

We report two cases in which the probands presented with deafness and a family history of a dominantly inherited auditory pigmentary syndrome, yet the cause of deafness in each proband was not associated with the pigmentary abnormalities but was a result of mutations in SLC26A4, the gene mutated in Pendred's syndrome. The first case is a young woman with congenital sensorineural hearing loss and a family history of piebaldism. Despite showing no pigmentary abnormalities, the proband was found to harbor the same KIT mutation as her relatives affected by piebaldism, as well as two mutations in the SLC26A4 gene. In the second case, 2-year-old identical twin boys born to deaf parents presented with congenital sensorineural deafness and an extensive maternal family history of Waardenburg's syndrome type I (WSI). Their father had recessively inherited deafness associated with dilated vestibular aqueducts and a clinical diagnosis of Pendred's syndrome was made in him, which was confirmed molecularly. As the twin boys did not have features of WSI, both the mother and children were tested for mutations in SLC26A4 which showed the mother to be a carrier of a single mutation and both boys to be compound heterozygotes, illustrating pseudodominant inheritance of the condition.
Government-funded universal newborn hearing screening and genetic analyses of deafness predisposing genes in Taiwan. Chun-Wei Chu;Yann-Jang Chen;Yi-Hui Lee;Sian-Jang Jaung;Fei-Peng Lee;Hung-Meng Huang. 2015. Int J Pediatr Otorhinolaryngol. 79. PMID: 25724631

OBJECTIVE: To investigate the association of eight connexin genes (GJB2, GJB4, GJA1P1, GJB6, GJB3, GJA1, GJB1, and GJC3) and the SLC26A4 gene with congenital hearing impairment among infants in a universal newborn hearing screening program. METHOD: From September 2009 to October 2013, the consecutive neonates born in all six branches of Taipei City Hospital were enrolled. Infants who failed the newborn hearing screening and were diagnosed with hearing impairment underwent the genetic analyses. RESULT: 15,404 neonates were born at Taipei City Hospital, and 15,345 neonates underwent newborn hearing screening. Among them, 32 infants were diagnosed with unilateral or bilateral hearing impairment. 26 of them underwent analyses of the connexin genes and the SLC26A4 gene. Of the connexin genes, two infants carried a GJB3 mutation (heterozygous c.580G>A and heterozygous c.520G>A, respectively). Only one infant carried a GJB2 mutation (homozygous c.235delC). One infant carried a GJA1P1 mutation (heterozygous c.929delC) and another carried a GJB4 mutation (heterozygous c.302G>A). Additionally, one infant carried a GJA1P1 novel variant (heterozygous c.1081C>T). Another infant carried a GJA1 novel variant (heterozygous c.1-33C>G). Of the SLC26A4 gene, one infant carried heterozygous c.919-2A>G mutation and a novel variant (heterozygous c.164+1G>C), and high-resolution computed tomography (HRCT) of the temporal bone revealed bilateral enlarged vestibular aqueducts. One infant carried heterozygous c.919-2A>G mutation and no inner ear anomalies were demonstrated by HRCT of the temporal bone. Another infant carried a novel variant (heterozygous c.818C>T). CONCLUSION: These results provide a genetic profile of the connexin genes and SLC26A4 gene among infants with hearing impairment detected by a universal newborn hearing screening program in Taiwan. Further studies and long-term follow up of this cohort are warranted to determine the pathogenicity of each variants and the long-term hearing consequence.
Genetic basis of hearing loss associated with enlarged vestibular aqueducts in Koreans. H-J Park;S-J Lee;H-S Jin;J O Lee;S-H Go;H S Jang;S-K Moon;S-C Lee;Y-M Chun;H-K Lee;J-Y Choi;S-C Jung;A J Griffith;S K Koo. 2005. Clin Genet. 67. PMID: 15679828

Sensorineural hearing loss associated with enlargement of the vestibular aqueduct (EVA) can be associated with mutations of the SLC26A4 gene. In western populations, less than one-half of the affected individuals with EVA have two mutant SLC26A4 alleles, and EVA is frequently caused by unknown genetic or environmental factors alone or in combination with a single SLC26A4 mutation as part of a complex trait. In this study, we ascertained 26 Korean probands with EVA and performed nucleotide sequence analysis to detect SLC26A4 mutations. All subjects had bilateral EVA, and 20 of 26 were sporadic (simplex) cases. Fourteen different mutations were identified, including nine novel mutations. Five mutations were recurrent and accounted for 80% of all mutant alleles, providing a basis for the design and interpretation of cost-efficient mutation detection algorithms. Two mutant alleles were identified in 21 (81%), one mutant allele was detected in three (11%), and zero mutant allele was detected in two (8%) of 26 probands. The high proportion of Korean probands with two SLC26A4 mutations may reflect a reduced frequency of other genetic or environmental factors causing EVA in comparison to western populations.
Newborn genetic screening for high risk deafness-associated mutations with a new Tetra-primer ARMS PCR kit. Bing Han;Liang Zong;Qian Li;Zhidong Zhang;Dayong Wang;Lan Lan;Jingxin Zhang;Yali Zhao;Qiuju Wang. 2013. Int J Pediatr Otorhinolaryngol. 77. PMID: 23815884

OBJECTIVE: Previous epidemiological studies indicate that GJB2, SLC26A4 or mtDNA 12S rRNA mutations were chiefly responsible for the hearing loss in children. A cost-effective method for screening deafness-associated mutations at early age is needed. This study aimed to develop a simple kit for screening of high risk deafness-associated mutations in newborns using tetra-primer amplification refractory mutation system PCR. METHODS: The screening kit was designed to detect high risk deafness-associated mutations (GJB2 c.235delC, SLC26A4 c.919-2A>G, mtDNA 12S rRNA mt.1555A>G and mt.1494C>T). The kit was able to amplify both wild-type and mutant alleles with a control fragment. The proposed method was conducted to genotype the above four deafness gene mutations in four PCR reactions. Each mutation was genotyped by a set of four primers, two allele-specific inner primers, and two common outer primers. A mismatch at the penultimate or antepenult nucleotide of the 3' terminus was introduced in order to maximize specificity. The 16 primers were used for the amplification of genomic DNA as a template. Amplified fragments were separated by electrophoresis. We designed and validated the kit with wild and mutant type DNA samples that had been previously been confirmed by Sanger sequencing. Then 1181 newborns were enrolled, and those samples with mutations were further validated with sequencing too. RESULTS: Among 1181 newborns, 29 individuals had one or two mutant alleles, with the carrier rate being 2.46% (29/1181). For GJB2 c.235delC mutation, one case was homozygote and 12 cases were heterozygote carriers. For SLC26A4 c.919-2A>G mutation, 12 cases were heterozygotes carriers, and no homozygotes were found; for mtDNA 12S rRNA mt.1555A>G mutation, one case was identified; three cases of mtDNA 12S rRNA mt.1494C>T mutation were detected. All mutations were detected with high specificity. Mutation samples were confirmed via Sanger sequencing. No false positive was found. CONCLUSION: A user-friendly screening kit for deafness-associated mutations was successfully developed. It provided rapid, reproducible, and cost-effective detection of deafness gene mutation without special equipment. The kit allowed the detection of the four high risk deafness-associated mutations with only 4 single tube PCR reactions. In the future, the kit could be applied to large population-based epidemiological studies for newborn hearing defects screening.
Spectrum and frequency of GJB2, GJB6 and SLC26A4 gene mutations among nonsyndromic hearing loss patients in eastern part of India. Bidisha Adhikary;Sudakshina Ghosh;Silpita Paul;Biswabandhu Bankura;Arup Kumar Pattanayak;Subhradev Biswas;Biswanath Maity;Madhusudan Das. 2015. Gene. 573. PMID: 26188157

Genetically caused nonsyndromic hearing loss is highly heterogeneous. Inspite of this large heterogeneity, mutations in the genes GJB2, GJB6 and SLC26A4 are major contributors. The mutation spectrum of these genes varies among different ethnic groups. Only a handful of studies focused on the altered genetic signature of these genes in different demographic regions of India but never focused on the eastern part of the country. Our study for the first time aimed to characterize the mutation profile of these genes in hearing loss patients of West Bengal state, India. Mutations in GJB2, GJB6 and SLC26A4 genes were screened by bidirectional sequencing from 215 congenital nonsyndromic hearing loss patients. Radiological diagnosis was performed in patients with SLC26A4 mutations by temporal bone CT scan. The study revealed that 4.65% and 6.97% patients had monoallelic and biallelic GJB2 mutations respectively. Six mutations were identified, p.W24X being the most frequent one accounting for 71.05% of the mutated alleles. Mutations in GJB6 including the previously identified deletion mutation (GJB6-D13S1830) were not identified in our study. Further, no patients harbored biallelic mutations in the SLC26A4 gene or the common inner ear malformation Enlarged Vestibular Aqueduct (EVA). The mutation profile of GJB2 in our study is distinct from other parts of India, suggesting that the mutation spectrum of this gene varies with ethnicity and geographical origin. The absence of GJB6 mutations and low frequency of SLC26A4 mutations suggest that additional genetic factors may also contribute to this disease.
Intrafamilial variability of the deafness and goiter phenotype in Pendred syndrome caused by a T416P mutation in the SLC26A4 gene. Ulrike Napiontek;Guntram Borck;Wiebke Müller-Forell;Nicole Pfarr;Andrea Bohnert;Annerose Keilmann;Joachim Pohlenz. 2004. J Clin Endocrinol Metab. 89. PMID: 15531480

Pendred syndrome (PS) is the most common cause of syndromic deafness, accounting for more than 5% of all autosomal-recessive hearing loss cases. It is characterized by bilateral sensorineural hearing loss and by goiter with or without hypothyroidism. Mutations in the SLC26A4 gene cause both classical PS and deafness associated with an enlarged vestibular aqueduct without goiter. To investigate a possible genotype-phenotype correlation in PS, we performed a detailed clinical and genetic study in three adult German sibs with typical PS caused by a common homozygous SLC26A4 mutation, T416P. An audiological long-term follow-up of 23 yr showed that the mutation T416P is associated with a distinct type of hearing loss in each of the three sibs: moderate-to-profound progressive deafness, profound nonprogressive deafness, and a milder but more rapidly progressing form. We show that these phenotypic differences are not caused by either different degrees of inner ear malformations or sequence variations in the GJB2/connexin 26 gene. Because the thyroid phenotype was also highly variable within the family, with thyroid sizes ranging from normal to large goiters requiring thyroidectomy, this study leads to the conclusion that other environmental and/or genetic factors have an impact on the PS phenotype.
Diagnostic application of targeted resequencing for familial nonsyndromic hearing loss. Byung Yoon Choi;Gibeom Park;Jungsoo Gim;Ah Reum Kim;Bong-Jik Kim;Hyo-Sang Kim;Joo Hyun Park;Taesung Park;Seung-Ha Oh;Kyu-Hee Han;Woong-Yang Park. 2013. PLoS One. 8. PMID: 23990876

Identification of causative genes for hereditary nonsyndromic hearing loss (NSHL) is important to decide treatment modalities and to counsel the patients. Due to the genetic heterogeneity in sensorineural genetic disorders, the high-throughput method can be adapted for the efficient diagnosis. To this end, we designed a new diagnostic pipeline to screen all the reported candidate genes for NSHL. For validation of the diagnostic pipeline, we focused upon familial NSHL cases that are most likely to be genetic, rather than to be infectious or environmental. Among the 32 familial NSHL cases, we were able to make a molecular genetic diagnosis from 12 probands (37.5%) in the first stage by their clinical features, characteristic inheritance pattern and further candidate gene sequencing of GJB2, SLC26A4, POU3F4 or mitochondrial DNA. Next we applied targeted resequencing on 80 NSHL genes in the remaining 20 probands. Each proband carried 4.8 variants that were not synonymous and had the occurring frequency of less than three among the 20 probands. These variants were then filtered out with the inheritance pattern of the family, allele frequency in normal hearing 80 control subjects, clinical features. Finally NSHL-causing candidate mutations were identified in 13(65%) of the 20 probands of multiplex families, bringing the total solve rate (or detection rate) in our familial cases to be 78.1% (25/32) Damaging mutations discovered by the targeted resequencing were distributed in nine genes such as WFS1, COCH, EYA4, MYO6, GJB3, COL11A2, OTOF, STRC and MYO3A, most of which were private. Despite the advent of whole genome and whole exome sequencing, we propose targeted resequencing and filtering strategy as a screening and diagnostic tool at least for familial NSHL to find mutations based upon its efficacy and cost-effectiveness.
A mutational analysis of the SLC26A4 gene in Spanish hearing-impaired families provides new insights into the genetic causes of Pendred syndrome and DFNB4 hearing loss. Alejandra Pera;Manuela Villamar;Antonio Viñuela;Marta Gandía;Carme Medà;Felipe Moreno;Concepción Hernández-Chico. 2008. Eur J Hum Genet. 16. PMID: 18285825

Pendred syndrome (PS) and DFNB4, a non-syndromic sensorineural hearing loss with enlargement of the vestibular aqueduct (EVA), are caused by mutations in the SLC26A4 gene. Both disorders are recessive, and yet only one mutated SLC26A4 allele, or no mutations, are identified in many cases. Here we present the genetic characterization of 105 Spanish patients from 47 families with PS or non-syndromic EVA and 20 families with recessive non-syndromic hearing loss, which segregated with the DFNB4 locus. In this cohort, two causative SLC26A4 mutations could be characterized in 18 families (27%), whereas a single mutated allele was found in a patient with unilateral hearing loss and EVA in the same ear. In all, 24 different causative mutations were identified, including eight novel mutations. The novel p.Q514K variant was the most prevalent mutation in SLC26A4, accounting for 17% (6/36) of the mutated alleles identified in this study, deriving from a founder effect. We also characterized a novel multiexon 14 kb deletion spanning from intron 3 to intron 6 (g.8091T_22145Cdel). This study also revealed the first case of a de novo recessive mutation p.Q413P causing PS that arose in the proband's paternal allele, the maternal one carrying the p.L445W. The relevance of our results for genetic diagnosis of PS and non-syndromic EVA hearing loss is discussed.
Outcome of Cochlear Implantation in Prelingually Deafened Children According to Molecular Genetic Etiology. Joo Hyun Park;Ah Reum Kim;Jin Hee Han;Seong Dong Kim;Shin Hye Kim;Ja-Won Koo;Seung Ha Oh;Byung Yoon Choi. 2017. Ear Hear. 38. PMID: 28841141

OBJECTIVES: About 60% of Korean pediatric cochlear implantees could be genetically diagnosed (GD) and we previously reported that a substantial portion of undiagnosed cases by deafness gene panel sequencing were predicted to have a nongenetic or complex etiology. We aimed to compare the outcomes of cochlear implantation (CI) in GD and genetically undiagnosed (GUD) patients and attempted to determine CI outcomes according to etiology. DESIGN: Ninety-three pediatric cochlear implantees underwent molecular genetic testing. Fifty-seven patients carried pathogenic variants and 36 patients remained GUD after panel sequencing of 204 known or potential deafness genes (TRS-204). Among them, 55 cochlear implantees with reliable speech evaluation results with a follow-up of longer than 24 months were recruited. Longitudinal changes in the audiologic performance were compared between the GD (n = 31) and GUD (n = 24) groups. The GD group was subdivided into cochlear implantee with SLC26A4 mutations (group 1) and cochlear implantee with other genetic etiology (group 2), and the GUD group was subdivided into groups 3 and 4, that is, patients with or without inner ear anomaly, respectively. RESULTS: Group 1 related to SLC26A4 mutations had the highest categories of auditory perception scores among all groups pre- and postoperatively. Group 4 with inner ear anomaly had the lowest categories of auditory perception scores. At 24 months post-CI, the group 2 with another genetic etiology had significantly better outcomes than molecularly undiagnosed group 3, which had with the same condition as group 2 except that the candidate gene was not detected. This finding was recapitulated when we limited cases to those that underwent CI before 24 months of age to minimize age-related bias at implantation. Furthermore, on extending the follow-up to 36 months postoperatively, this tendency became more prominent. Additionally, our preliminary clinical data suggest a narrower sensitive window period for good CI outcomes for implantees with OTOF mutation rather than the GJB2 and other genes. CONCLUSIONS: Current molecular genetic testing including deafness panel sequencing helps to predict the 2-year follow-up outcomes after CI in prelingually deafened children. GD cochlear implantees show better functional outcomes after CI than undiagnosed cochlear implantees as determined by deafness panel sequencing, suggesting a genotype-functional outcome correlation. The genetic testing may provide a customized optimal window period in terms of CI timing for favorable outcome according to genetic etiology.
[Diagnostic methods and clinic application for mtDNA A1555G and GJB2 and SLC26A4 genes in deaf patients]. Pu Dai;Fei Yu;Dong-yang Kang;Xin Zhang;Xin Liu;Wen-Zong Mi;Ju-Yang Cao;Hui-jun Yuan;Wei-yan Yang;Bai-lin Wu;Dong-yi Han. 2006. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 40. PMID: 16408730

OBJECTIVE: To establish the method of clinic genetic testing for common deaf genes such as mtDNA nt1555, GJB2 gene and SLC26A4 (Pendrin's syndrome gene, PDS) gene. METHODS: Three hundred and sixty seven sporadic patients with hearing loss from out-patient department of General Hospital of Chinese People's Liberation Army, 60 patients with history of maternal inherited hearing loss from 27 family, 20 congenital deaf patients from special educational school for deaf and dumb, 3 deaf patients with enlarged vestibular aqueduct (EVA) confirmed by CT scan, 50 control individuals with normal bone conductive hearing were analyzed. The genetic testing kit for mtDNA A1555G mutation was used to detect mtDNA A1555G mutation. The whole gene sequencing were accomplished in 20 congenital deaf patients. In 3 patients with EVA, fragments covering all exons of PDS gene were analyzed by denatured high productive liquid chromatogram and special exons were sequenced when DHPLC showed abnormal wave patterns of amplicons covering these exons. RESULTS: Fifty nine patients from 26 family and 5 sporadic patients were found to carry mtDNA A1555G mutation. Among 20 congenital deaf patients, 2 cases were found to have homozygous GJB2 235 del C mutation, 1 case had compound 235del C and 299-300 del AT mutation. Other 2 cases carried heterozygous 109 A-G mutation. Among 3 patients with EVA, 1 case was found to have heterozygous PDS G316X mutation and other 2 cases had homozygous 919-2 A-G mutation. CONCLUSIONS Genetic testing for deafness is feasible procedure with remarkable clinic significance.
Genetic counseling for patients with nonsyndromic hearing impairment directed by gene analysis. Dingyuan Ma;Jingjing Zhang;Chunyu Luo;Ying Lin;Xiuqing Ji;Ping Hu;Zhengfeng Xu. 2016. Mol Med Rep. 13. PMID: 26783197

The aim of the present study was to investigate the genetic etiology of patients with nonsyndromic hearing impairment through gene analysis, and provide accurate genetic counseling and prenatal diagnosis for deaf patients and families with deaf children. Previous molecular etiological studies have demonstrated that the most common molecular changes in Chinese patients with nonsyndromic hearing loss (NSHL) involved gap junction protein β 2, solute carrier family 26, member 4 (SLC26A4), and mitochondrial DNA 12S rRNA. A total of 117 unrelated NSHL patients were included. Mutation screening was performed by Sanger sequencing in GJB2, 12S rRNA, and the hot‑spot regions of SLC26A4. In addition, patients with a single mutation of SLC26A4 in the hot‑spot regions underwent complete exon sequencing to identify a mutation in the other allele. A total of 36 of the 117 deaf patients were confirmed to have two pathogenic mutations, which included 4 deaf couples, husband or wife in 11 deaf couples and 17 deaf individuals. In addition, prenatal diagnoses was performed in 7 pregnant women at 18‑21 weeks gestation who had previously given birth to a deaf child, and the results showed that two fetal genotypes were the same as the proband's genotypes, four fetuses carried one pathogenic gene from their parents, and one fetus was identified to have no mutations. Taken together, the genetic testing of deaf patients can provide reasonable guidance to deaf patients and families with deaf children.
[Genetic analysis of family constellation for cochlear implant recipients]. Chu-Qin Zhang;Bo-Bei Chen;Jia-Yun Huang;Dong-Mei Sun;Ying-Ying Chen;Song-Jie Xiang;Min-Xin Guan. 2008. Yi Chuan. 30. PMID: 19073547

GJB2, SLC26A4 (PDS) and mitochondrial DNA (mtDNA) have been associated with sensorineural hearing loss. In the present study, the clinical, genetic and molecular analysis of 14 cochlear implant recipients and their parents was studied from April 2006 to September 2007. Of the 14 subjects, 35.7% had gene mutations; 28.6% had homozygous GJB2 235delC mutation, whose parents carried heterozygous GJB2 235delC mutation; and 7.1% had mtDNA A1555G mutation, whose mother carried mtDNA A1555G mutation too. There was no SLC26A4 (PDS) mutation. These results strongly suggested that the mutation in GJB2 gene was a major cause of deafness in cochlear implant recipients and the mutation of mtDNA A1555G was another important cause. Genetic test of hot-spots and analysis of family constellation can offer an accurate genetic counseling to deaf family and reduce the incidence of hearing loss.
Comprehensive molecular etiology analysis of nonsyndromic hearing impairment from typical areas in China. Yongyi Yuan;Yiwen You;Deliang Huang;Jinghong Cui;Yong Wang;Qiang Wang;Fei Yu;Dongyang Kang;Huijun Yuan;Dongyi Han;Pu Dai. 2009. J Transl Med. 7. PMID: 19744334

BACKGROUND: Every year, 30,000 babies are born with congenital hearing impairment in China. The molecular etiology of hearing impairment in the Chinese population has not been investigated thoroughly. To provide appropriate genetic testing and counseling to families, we performed a comprehensive investigation of the molecular etiology of nonsyndromic deafness in two typical areas from northern and southern China. METHODS: A total of 284 unrelated school children with hearing loss who attended special education schools in China were enrolled in this study, 134 from Chifeng City in Inner Mongolia and the remaining 150 from Nangtong City in JiangSu Province. Screening was performed for GJB2, GJB3, GJB6, SLC26A4, 12S rRNA, and tRNAser(UCN) genes in this population. All patients with SLC26A4 mutations or variants were subjected to high-resolution temporal bone CT scan to verify the enlarged vestibular aqueduct. RESULTS: Mutations in the GJB2 gene accounted for 18.31% of the patients with nonsyndromic hearing loss, 1555A>G mutation in mitochondrial DNA accounted for 1.76%, and SLC26A4 mutations accounted for 13.73%. Almost 50% of the patients with nonsyndromic hearing loss in these typical Chinese areas carried GJB2 or SLC26A4 mutations. No significant differences in mutation spectrum or prevalence of GJB2 and SLC26A4 were found between the two areas. CONCLUSION: In this Chinese population, 54.93% of cases with hearing loss were related to genetic factors. The GJB2 gene accounted for the etiology in about 18.31% of the patients with hearing loss, SLC26A4 accounted for about 13.73%, and mtDNA 1555A>G mutation accounted for 1.76%. Mutations in GJB3, GJB6, and mtDNA tRNAser(UCN) were not common in this Chinese cohort. Conventionally, screening is performed for GJB2, SLC26A4, and mitochondrial 12S rRNA in the Chinese deaf population.
Simultaneous screening of multiple mutations by invader assay improves molecular diagnosis of hereditary hearing loss: a multicenter study. Shin-ichi Usami;Shin-ya Nishio;Makoto Nagano;Satoko Abe;Toshikazu Yamaguchi; . 2012. PLoS One. 7. PMID: 22384008

Although etiological studies have shown genetic disorders to be a common cause of congenital/early-onset sensorineural hearing loss, there have been no detailed multicenter studies based on genetic testing. In the present report, 264 Japanese patients with bilateral sensorineural hearing loss from 33 ENT departments nationwide participated. For these patients, we first applied the Invader assay for screening 47 known mutations of 13 known deafness genes, followed by direct sequencing as necessary. A total of 78 (29.5%) subjects had at least one deafness gene mutation. Mutations were more frequently found in the patients with congenital or early-onset hearing loss, i.e., in those with an awareness age of 0-6 years, mutations were significantly higher (41.8%) than in patients with an older age of awareness (16.0%). Among the 13 genes, mutations in GJB2 and SLC26A4 were mainly found in congenital or early-onset patients, in contrast with mitochondrial mutations (12S rRNA m.1555A>G, tRNA(Leu(UUR)) m.3243A>G), which were predominantly found in older-onset patients. The present method of simultaneous screening of multiple deafness mutations by Invader assay followed by direct sequencing will enable us to detect deafness mutations in an efficient and practical manner for clinical use.
Genetic Linkage Analysis of DFNB4, DFNB28, DFNB93 Loci in Autosomal Recessive Non-syndromic Hearing Loss: Evidence for Digenic Inheritance in GJB2 and GJB3 Mutations. Marzieh Naseri;Masoud Akbarzadehlaleh;Marjan Masoudi;Najmeh Ahangari;Ali Akbar Poursadegh Zonouzi;Ahmad Poursadegh Zonouzi;Leila Shams;Azim Nejatizadeh. 2018. Iran J Public Health. 47. PMID: 29318123

Background: Autosomal recessive non-syndromic hearing loss (ARNSHL) a most frequent hereditary type of hearing impairment, exhibit tremendous genetic heterogeneity. We aimed to determine the contribution of three common DFNB loci (DFNB4, DFNB28, and DFNB93), and mutation analysis of Gap Junction Beta-2 gene (GJB2) and GJB3 genes in ARNSHL subjects in southern Iran. Methods: Thirty-six large ARNSHL pedigrees (167 individuals) with at least two affected subjects (72 patients) were included in this descriptive study from Hormozgan Province of Iran, during 2014 - 2015. The variation of GJB2 and GJB3 genes were screened using direct sequencing method. The negative samples for GJB2 and GJB3 genes mutations were analyzed for the linkage to DFNB4, DFNB28, and DFNB93 loci by genotyping the corresponding short tandem repeat (STR) markers using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE) methods. Results: DNA sequencing of GJB2 were identified heterozygous mutation (964 C/T) in 13.88% of the studied families. Three missense mutations (788G/A, 284C/T and 973G/C) were also detected in coding region of the GJB3 gene. The 284C/T mutation in the GJB3 occurs in compound heterozygosity along with the 964T/C mutation in the GJB2 in one family. Finally, we found no evidence of linkage to either of DFNB4, DFNB93 and DFNB28 loci. Conclusion: Highlighting the hypothesis that a genetic interaction between GJB2 and GJB3 genes could be lead to ARNSHL, however, no evidence of linkage to the DFNB loci was found. 284C/T variant in GJB3 gene might be pathogenic when accompanied by variant in GJB2 in a digenic pattern. However, further large-scale familial and functional studies are required to challenge this hypothesis.
[Results of molecular genetic testing in Russian patients with Pendred syndrome and allelic disorders]. O L Mironovich;E A Bliznetz;T G Markova;E N Geptner;M R Lalayants;E I Zelikovich;G A Tavartkiladze;A V Polyakov. 2018. Genetika. 53. PMID: 29372807

Pendred syndrome is an autosomal recessive inherited disorder characterized by a combination of sensorineural hearing impairment and euthyroid goiter; its clinical manifestation in children is hardly distinguishable from nonsyndromic hearing loss. Pendred syndrome is one of the most frequent types of syndromic hearing loss. Hearing impairment is accompanied by abnormal development of the bony labyrinth—enlarged vestibular aqueduct (EVA) and occasionally combined with Mondini dysplasia. Mutations in the SLC26A4 gene, which encodes the pendrin protein, are responsible for both Pendred syndrome and for allelic disorder (nonsyndromic enlarged vestibular aqueduct). The present study for the first time conducted molecular genetic analysis in 20 Russian patients with Pendred syndrome, EVA and/or Mondini dysplasia. As a result, six pathogenic mutations in the SLC26A4 gene were revealed in four patients. The mutation c.222G>T (p.Trp74Cys) was detected for the first time. Mutations were found in patients with Pendred syndrome and nonsyndromic EVA with or without Mondini dysplasia. Mutations were not detected in patients with isolated Mondini dysplasia. One proband with clinical diagnosis Pendred syndrome was homozygous for the c.35delG mutation in the GJB2 gene. The absence of frequent mutations, including well-known ones or “hot” exons in the SLC26A4 gene, was reported. Therefore, the optimal method to search for mutations in the SLC26A4 gene in Russian patients is Sanger sequencing of all exons and exon-intron boundaries in the SLC26A4 gene.
Genetic mutations in non-syndromic deafness patients in Hainan Province have a different mutational spectrum compared to patients from Mainland China. Bangqing Huang;Mingyu Han;Guojian Wang;ShaSha Huang;Jialing Zeng;Yongyi Yuan;Pu Dai. 2018. Int J Pediatr Otorhinolaryngol. 108. PMID: 29605365

OBJECTIVES: To provide appropriate genetic testing and counseling for non-syndromic hearing impairment patients in Hainan Province, an island in the South China Sea. METHODS: 299 unrelated students with non-syndromic hearing loss who attended a special education school in Hainan Province were enrolled in this study. Three prominent deafness-related genes (GJB2, SLC26A4, and mtDNA 12S rRNA) were analyzed using Sanger sequencing. RESULTS: GJB2 mutations were detected in 32.78% (98/299) of the entire cohort; however, only 5.69% (17/299) had two confirmed pathogenic mutations. The most common mutation observed in this population was c.109G > A in the GJB2 gene, with an allelic frequency of 15.05% (90/598), which is significantly higher than that reported in previous cohorts. A total of 16 patients had two confirmed pathogenic SLC26A4 gene mutations, and 16 patients had one. The IVS7-2A > G mutation was the most commonly observed, with an allelic frequency of 3.51% (21/598). Three patients had a m.1555A > G mutation in the mtDNA 12S rRNA gene. CONCLUSIONS: These results reveal that genetic etiology occurred in 11.71% (35/299) of patients, suggesting that Hainan province have a different mutational spectrum compare to Mainland China in non-syndromic deafness patients, which provide useful information to genetic counseling in Hainan province.
Integration of human and mouse genetics reveals pendrin function in hearing and deafness. Amiel A Dror;Zippora Brownstein;Karen B Avraham. 2011. Cell Physiol Biochem. 28. PMID: 22116368

Genomic technology has completely changed the way in which we are able to diagnose human genetic mutations. Genomic techniques such as the polymerase chain reaction, linkage analysis, Sanger sequencing, and most recently, massively parallel sequencing, have allowed researchers and clinicians to identify mutations for patients with Pendred syndrome and DFNB4 non-syndromic hearing loss. While thus far most of the mutations have been in the SLC26A4 gene coding for the pendrin protein, other genetic mutations may contribute to these phenotypes as well. Furthermore, mouse models for deafness have been invaluable to help determine the mechanisms for SLC26A4-associated deafness. Further work in these areas of research will help define genotype-phenotype correlations and develop methods for therapy in the future.
Application of deafness diagnostic screening panel based on deafness mutation/gene database using invader assay. Satoko Abe;Toshikazu Yamaguchi;Shin-Ichi Usami. 2007. Genet Test. 11. PMID: 17949297

Despite progress in identification of deafness genes, clinical application has lagged due to the genetic heterogeneity of deafness. We designed and tested a comprehensive and simple diagnostic strategy to simultaneously detect deafness gene mutations based on a mutation/gene database followed by Invader assay screening of 41 known mutations of nine known deafness genes. Three hundred thirty-eight Japanese patients with congenital or childhood-onset (up to age 10) bilateral sensorineural hearing loss participated in this study. A total of 100 (29.6%) subjects had at least one mutation in GJB2, SLC26A4, and/or the mitochondrial 12S rRNA, indicating that these are the three major causative genes in Japanese deafness patients. The present study demonstrated that the Invader assay has excellent sensitivity and accuracy, and its application to deafness mutation screening will greatly improve medical management and facilitate extensive genetic counseling for hearing impairment.
Compound Heterozygosity for Two Novel SLC26A4 Mutations in a Large Iranian Pedigree with Pendred Syndrome. Nasrin Yazdanpanahi;Mohammad Amin Tabatabaiefar;Effat Farrokhi;Narges Abdian;Nader Bagheri;Shirin Shahbazi;Zahra Noormohammadi;Morteza Hashemzadeh Chaleshtori. 2013. Clin Exp Otorhinolaryngol. 6. PMID: 24353858

OBJECTIVES: The aim of this study was to detect the genetic cause of deafness in a large Iranian family. Due to the importance of SLC26A4 in causing hearing loss, information about the gene mutations can be beneficial in molecular detection and management of deaf patients. METHODS: We investigated the genetic etiology in a large consanguineous family with 9 deaf patients from Fars province of Iran with no GJB2 mutations. Initially, linkage analysis was performed by four DFNB4 short tandem repeat markers. The result showed linkage to DFNB4 locus. Following that, DNA sequencing of all 21 exons, their adjacent intronic sequences and the promoter of SLC26A4 was carried out for mutation detection. RESULTS: Two novel mutations (c.863-864insT and c.881-882delAC) were identified in exon 7 of the gene, in both homozygous and compound heterozygous state in patients. CONCLUSION: Our results supported the importance of the SLC26A4 mutations in the etiology of hearing loss among the Iranian patients and therefore its mutation screening should be considered after GJB2 in the molecular diagnostics of hearing loss, especially when enlarged vestibular aqueduct or goiter is detected.
Genetic characteristics in children with cochlear implants and the corresponding auditory performance. Chen-Chi Wu;Tien-Chen Liu;Shih-Hao Wang;Chuan-Jen Hsu;Che-Ming Wu. 2011. Laryngoscope. 121. PMID: 21557232

OBJECTIVES/HYPOTHESIS: To explore the genetic characteristics of children with cochlear implants (CIs) and to correlate the auditory performance after implantation to the genetic diagnosis of children with CIs. STUDY DESIGN: Prospective cohort study. METHODS: Mutations of four common deafness-associated genes, GJB2, SLC26A4, the mitochondrial 12S rRNA gene, and OTOF, were screened in 743 unrelated children with idiopathic sensorineural hearing impairment, including 180 and 563 children with and without CIs, respectively. The allele frequencies and audiologic features were compared between both groups. The Categories of Auditory Performance (CAP) scores at 3 years after implantation were then analyzed according to the genotypes. RESULTS: A definitive genetic diagnosis was made in 37 (20.6%) of the 180 CI children. A significant difference in allele frequencies between CI and non-CI children was found in GJB2 mutations (chi-square test, P < .01), but not in SLC26A4 mutations, mitochondrial 12S rRNA mutations, or OTOF mutations (all P > .05). Further analysis revealed that the difference might have resulted from distinct audiological features in each group. Among the 110 CI children who had received more than 3 years of rehabilitation after implantation, the 35 children with mutations had better CAP scores than the 75 children without mutations. CONCLUSIONS: A significant prevalence of genetic mutations was identified in children with CIs, suggesting the need for routine genetic assessments. The frequencies of common deafness-associated mutations were different between children with and without CIs. The presence of genetic mutations was associated with an excellent long-term auditory performance outcome after implantation.
Common molecular etiology of patients with nonsyndromic hearing loss in Tibetan, Tu nationality, and Mongolian patients in the northwest of China. Xiao-Long Yang;Xu Bai-Cheng;Xing-Jian Chen;Bian Pan-Pan;Ma Jian-Li;Liu Xiao-Wen;Zhe-Wen Zhang;Du Wan;Yi-Ming Zhu;Yu-Fen Guo. 2013. Acta Otolaryngol. 133. PMID: 23834103

CONCLUSION: In the northwest of China, the prevalence of mutations of the three prominent deafness-related genes, GJB2, SLC26A4, and mitochondrial DNA (mtDNA) 12S rRNA, among Tibetan, Tu nationality, and Mongolian subjects is high, at 19%, 28.57%, and 21.05%, respectively. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss. OBJECTIVE: To analyze the prevalence of the three common deafness genes GJB2, mtDNA, and SLC26A4 gene mutations in Tibetan, Tu nationality, and Mongolian patients with nonsyndromic hearing impairment in the Northwest region of China. METHODS: Genomic DNA was extracted from a total of 189 Tibetan, Tu nationality, and Mongolian probands from the northwest of China. PCR and direct sequencing were used to analyze the coding region of GJB2, mtDNA, and SLC26A4 genes. RESULTS: The mutant allele rate of GJB2 gene was 6.2% in Tibetan and 11.22% in Tu nationality patients, c.235delC was the most prevalent mutation, accounting for 75% of the mutant GJB2 alleles. Mutant allele frequency of SLC26A4 in Tibetan, Tu nationality, and Mongolian subjects was 4.54%, 6.12%, and 15.79% respectively; p.IVS7-2A>G was the most common form. Mongolian cases were significantly higher than Tibetan cases (χ² = 7.281, p = 0.007 and p < 0.05). mtDNA A1555G mutation was detected in six Tibetan, five Tu nationality, and one Mongolian subject; one Tibetan patient carried the C1494T mutation.
Screening of genetic alterations related to non-syndromic hearing loss using MassARRAY iPLEX® technology. Maria Carolina Costa Melo Svidnicki;Sueli Matilde Silva-Costa;Priscila Zonzini Ramos;Nathalia Zocal Pereira dos Santos;Fábio Tadeu Arrojo Martins;Arthur Menino Castilho;Edi Lúcia Sartorato. 2015. BMC Med Genet. 16. PMID: 26399936

BACKGROUND: Recent advances in molecular genetics have enabled to determine the genetic causes of non-syndromic hearing loss, and more than 100 genes have been related to the phenotype. Due to this extraordinary genetic heterogeneity, a large percentage of patients remain without any molecular diagnosis. This condition imply the need for new methodological strategies in order to detect a greater number of mutations in multiple genes. In this work, we optimized and tested a panel of 86 mutations in 17 different genes screened using a high-throughput genotyping technology to determine the molecular etiology of hearing loss. METHODS: The technology used in this work was the MassARRAY iPLEX® platform. This technology uses silicon chips and DNA amplification products for accurate genotyping by mass spectrometry of previous reported mutations. The generated results were validated using conventional techniques, as direct sequencing, multiplex PCR and RFLP-PCR. RESULTS: An initial genotyping of control subjects, showed failures in 20 % of the selected alterations. To optimize these results, the failed tests were re-designed and new primers were synthesized. Then, the specificity and sensitivity of the panel demonstrated values above 97 %. Additionally, a group of 180 individuals with NSHL without a molecular diagnosis was screened to test the diagnostic value of our panel, and mutations were identified in 30 % of the cases. In 20 % of the individuals, it was possible to explain the etiology of the HL. Mutations in GJB2 gene were the most prevalent, followed by other mutations in in SLC26A4, CDH23, MT-RNR1, MYO15A, and OTOF genes. CONCLUSIONS: The MassARRAY technology has the potential for high-throughput identification of genetic variations. However, we demonstrated that optimization is required to increase the genotyping success and accuracy. The developed panel proved to be efficient and cost-effective, being suitable for applications involving the molecular diagnosis of hearing loss.
A1555G homoplasmic mutation from A1555G heteroplasmic mother with Pendred syndrome. Moo Kyun Park;Borum Sagong;Jong Dae Lee;Seung-Hyun Bae;Byeonghyeon Lee;Kwang Shik Choi;Yeon-Sik Choo;Kyu-Yup Lee;Un-Kyung Kim. 2014. Int J Pediatr Otorhinolaryngol. 78. PMID: 25223473

Hearing loss (HL) is genetically heterogeneous and can be caused by mutations in multiple gene lesions. Pendred syndrome, caused by mutation of SLC26A4, is one of the common causes of recessive syndromic profound HL. Mitochondrial mutation is another rare cause of genetic HL, resulting in late onset sensorineural HL. Recently, we evaluated a young woman representing bilateral progressive moderate HL with delayed language development, along with her family. Hearing test, temporal bone computed tomography, and genetic evaluation of GJB2, MT-RNR1, SLC26A4 gene mutations were performed on each family member. Her mother was prelingually deaf and displayed enlarged vestibular aqueduct (EVA) along with goiter. Interestingly, subject's mother showed both SLC26A4 mutation and mitochondrial A1555G heteroplasmic mutation at the same time. The sisters did not display EVA or goiter. Although the subject's older sister showed both prelingual deafness and mitochondrial A1555G heteroplasmy, her younger sister showed only A1555G homoplasmy, which suggests A1555G homoplasmy as the genetic cause of hearing loss. This is the first report of HL caused by mitochondrial A1555G homoplasmy from a mother with Pendred syndrome coexistent with A1555G heteroplasmy in the Korean population.
Association of SLC26A4 mutations with clinical features and thyroid function in deaf infants with enlarged vestibular aqueduct. Satoshi Iwasaki;Koji Tsukamoto;Shinichi Usami;Kiyoshi Misawa;Kunihiro Mizuta;Hiroyuki Mineta. 2006. J Hum Genet. 51. PMID: 16924389

Pendred syndrome and non-syndromic recessive deafness associated with enlarged vestibular aqueduct (NSRD with EVA) are caused by mutations in the SLC26A4 (PDS) gene. Unlike NSRD with EVA, Pendred syndrome is characterized by goiter, which may be present after early adulthood. However, the clinical diagnosis of these two disorders is difficult in deaf children. Expression of the SLC26A4 gene may be responsible for iodide transport in the thyroid as well as for formation and function of the inner ear. Here, we analyzed the SLC26A4 gene and performed thyroid function tests (FT3, FT4, TSH, and Thyroglobulin) on six congenitally deaf infants (mean age 2.7 years) with EVA. Mutation of the SLC26A4 gene was identified in five patients: four were compound heterozygous (H723R/919-2A>G, H723R/IVS15+5G>A, H723R/R581S, IVS7-2A>G/IVS8+1G>A), the fifth had a frameshift mutation (322delC). All the patients demonstrated an elevation of serum thyroglobulin level. FT3 level was elevated in four of the five patients. The patient who did not have a detectable gene mutation showed normal thyroid function. We conclude that the mutations in the SLC26A4 gene identified here are highly associated with high serum thyroglobulin levels in congenital and deafness infants. These mutations may be of value for the diagnosis of Pendred syndrome and NSRD with EVA.
Mutational analysis of the SLC26A4 gene in Chinese sporadic nonsyndromic hearing-impaired children. Xiangyang Hu;Fenghe Liang;Min Zhao;Angela Gong;Emily R Berry;Yang Shi;Yanxiao Wang;Yan Chen;Aishu Liu;Chunyan Qu. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22796198

OBJECTIVE: To investigate the mutations of SLC26A4 gene and the relevant phenotype in Chinese sporadic nonsyndromic hearing-impaired children. METHODS: 195 Chinese sporadic nonsyndromic hearing-impaired children were subjected to microarray-based mutation detection for 9 hot spot mutations in four of the most common deafness-related genes (GJB2, SLC26A4, GJB3, and 12s rRNA). Subsequently, twenty-one patients with one SLC26A4 mutation detected by microarray were subjected to sequencing analysis of the whole SLC26A4 coding region and the splice sites in order to identify the second mutant allele. The inner ear malformation and hearing loss level were compared among different genotypes. RESULTS: The incidence of genetic mutations was found to be 43.59% (85/195) in this patient group using CapitalBio Deafness Gene Mutation Detection Array Kit. A total of 34 children (17.44%) were found carrying the mutant SLC26A4 sequences. Thirteen (6.67%) children carried two mutant alleles of SLC26A4 and 21 (10.77%) children carried one mutant allele of SLC26A4. After the application of subsequent sequencing analysis, 13 mutational variants including 4 novel variants, two missense (p.D661G, p.N457D), one splice site mutation (IVS15+1G>A) and one frameshift mutation (624_632del9insACTTGGC), were identified in SLC26A4 gene in 15 of the 21 previously monoallelic patients. No second mutation was identified in the remaining 6 children. Biallelic mutations of SLC26A4 were identified in 20 of 21 children with enlarged vestibular aqueduct. CONCLUSIONS: Our results demonstrated that genetic factors were important causes for sporadic nonsyndromic hearing loss in Chinese pediatric cases. Mutation of SLC26A4 is one of the major genetic causes in nonsyndromic hearing loss with inner ear malformation. IVS7-2A>G, 2168A>G and 1229C>T were the most frequent mutations identified in our studies. The combination of microarray testing and sequencing analysis is a useful and high-throughput method for the diagnosis of genetic hearing loss.
Establishment of a Gene Detection System for Hotspot Mutations of Hearing Loss. Chao Wang;Shengzhou Wang;Hongyan Chen;Daru Lu. 2018. Biomed Res Int. 2018. PMID: 29707576

Hearing loss is an etiologically heterogeneous trait with a high incidence in China. Though conventional newborn hearing screening program has been widely adopted, gene detection can significantly improve the means of early discovering genetic risk factors. Thus, simple and efficient methods with higher sensitivity and lower cost for detecting hotspot mutations of hearing loss are urgently requested. Here we established a mutation detection system based on multiple fluorescent probe technique, which can detect and genotype nine hotspot mutations of four prominent hearing loss-related genes in two reactions on a four-channel real-time PCR instrument, including GJB2 (rs750188782, rs80338943, rs1110333204, and rs80338939), GJB3 (rs74315319), SLC26A4 (rs111033313 and rs121908362), and mtDNA 12S rRNA (rs267606617 and rs267606619). This system is with high sensitivity that enables detecting as low as 10 DNA copies samples per reaction. A comparison study in 268 clinical samples showed that the detection system had 100% concordance to Sanger sequencing. Besides, blood and saliva samples can be directly detected without DNA extraction process, which greatly simplifies the manipulation. The new system with high sensitivity, accuracy, and specimen type compatibility can be expectedly a reliable tool in clinical application.
Hearing impairment in Estonia: an algorithm to investigate genetic causes in pediatric patients. R Teek;K Kruustük;R Žordania;K Joost;T Kahre;N Tõnisson;M Nelis;O Zilina;L Tranebjaerg;T Reimand;K Ounap. 2013. Adv Med Sci. 58. PMID: 24222258

PURPOSE: The present study was initiated to establish the etiological causes of early onset hearing loss (HL) among Estonian children between 2000-2009. METHODS: The study group consisted of 233 probands who were first tested with an arrayed primer extension assay, which covers 199 mutations in 7 genes (GJB2, GJB6, GJB3, SLC26A4, SLC26A5 genes, and two mitochondrial genes - 12S rRNA, tRNASer(UCN)). From probands whose etiology of HL remained unknown, DNA analysis of congenital cytomegalovirus (CMV) infection and G-banded karyotype and/or chromosomal microarray analysis (CMA) were performed. RESULTS: In 110 (47%) cases, the etiology of HL was genetic and in 5 (2%) congenital CMV infection was diagnosed. We found mutations with clinical significance in GJB2 (100 children, 43%) and in 2 mitochondrial genes (2 patients, 1%). A single mutation in SLC26A4 gene was detected in 5 probands (2.2%) and was considered diagnostic. In 4 probands a heterozygous IVS2-2A>G change in the SLC26A5 gene was found. We did not find any instances of homozygosity for this splice variant in the probands. CMA identified in 4 probands chromosomal regions with the loss of one allele. In 2 of them we were able to conclude that the found abnormalities are definitely pathogenic (12q13.3-q14.2 and 17q22-23.2 microdeletion), but the pathogenity of 2 other findings (3p26.2 and 1p33 microdeletion) remained unknown. CONCLUSION: This practical diagnostic algorithm confirmed the etiology of early onset HL for 115 Estonian patients (49%). This algorithm may be generalized to other populations for clinical application.
[The molecular epidemiology analysis of heavy-profound hearing loss in Nangtong]. Qiang Wang;Yiwen You;Qicheng Zhang. 2013. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 27. PMID: 23833990

OBJECTIVE: To investigate the etiology of deafness and the common disease-causing genes among patients with sensorineural hearing loss in Nangtong and to explore the proportion of genetic factors in this region. METHOD: One hundred and fifty cases with hearing loss from three schools for deaf-mutes in Nangtong received sequence analysis of GJB2, GJB3, SLC26A4, mtDNA12SrRNA and mtDNA tRNASer(UCN), and individuals carrying SLC26A4 mutation were given further temporal bone CT scan. We investigated the etiology of deafness by analyzing the genes testing results and questionnaires. RESULT: GJB2 mutations were responsible for approximately 19.33% of the cases in Nangtong area. Nineteen cases (12.67%) were diagnosed with EVA (enlarged vestibular aqueduct) by screening SLC26A4 followed by temporal bone CT scan. The aminoglycoside-related mtDNA 1555A > G mutation accounted for 2.67% (4/150) of the cases in this area. In addition, 27 cases (18%) may relate to genetic factors in this group. CONCLUSION: By genetic screening we find that genetic deafness occupies a large proportion in deaf community. Our data demonstrate that gene testing has important role in clarifying etiology for hearing loss population.
[Clinical implications of molecular genetic research in otorhinolaryngology]. N Gürtler. 2003. Ther Umsch. 60. PMID: 14502856

Molecular-genetic research in Otolaryngology has seen a rapid advancement during the last ten years, especially in the fields of otology and head and neck tumors. The results of this basic research have now started to be implemented in the clinic. In otology the understanding of auditive function has dramatically improved. The syndromic and non-syndromic forms of hereditary hearing impairment can be subdivided into their underlying genetic defects, as more and more genes are identified. Diagnostic of syndromic hearing loss has been improved and can be done earlier. But the molecular-genetic analysis is still time-consuming and difficult. Currently, in our clinic, only patients with suspected Pendred-syndrome, representing the most frequent syndrome with hearing impairment, undergo a routine search for mutation detection in the corresponding gene SLC26A4. A multitude of genes and mutations are seen in the non-syndromic forms of hereditary hearing impairment. The gene gap-junction-protein beta2, encoding connexin 26, is encountered most frequently. Its prevalence in Switzerland is high with about 20% in the non-syndromic group. A molecular-genetic analysis of connexin 26 is offered in cases of congenital hearing loss. Another analysis, which has been implemented in the clinic, is the sequencing of Wolfram-syndrome gene 1 in familial low-frequency hearing loss. This gene seems to be involved in the majority of families with this type of hearing loss. Gene therapy for hearing loss is currently not an option in the clinical field. The different steps in carcinogenesis of head and neck cancer have further been elucidated by molecular-genetic research. Clinical applications are the establishment of risk-profiles for tumor-development and defining prognostic markers as well as the development of new treatment strategies based on genetic therapy.
[Genetic screening of mutation hot-spots for nonsyndromic hearing loss in southern Jiangsu province with SNaPshot]. Hong Li;Hai-bo Li;Jun Mao;Min-juan Liu;Hong-bo Cheng;Shi-lin Li;Ying Chen. 2011. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 28. PMID: 21811975

OBJECTIVE: To investigate the mutation frequency in 7 mutation hot-spots of deafness gene in southern Jiangsu province and verify the performance of the SNaPshot technology platform, designed for genetic screening of non-syndromic hearing loss (NSHL) in Chinese. METHODS: One hundred and twenty-five NSHL patients were enrolled. Amplification of 235delC, 299-300delAT in GJB2 gene, IVS7-2A>G, 2168 A>G in SLC26A4 gene, and 1555A>G, 7445 A>G and 3243 A>G in mitochondrial DNA (mtDNA) was performed using multiplex polymerase chain reaction (PCR) technology. Afterwards, the sequence-specific probe interrogated each locus and labeled it at the 3' end using fluorescent dideoxynucleotide chemistry by the SNaPshot Multiplex Kit, the resulting products were then separated electrophoretically in ABI PRISM R 3130 Genetic Analyzer and analyzed in the presence of a fifth-dye-labeled size standard. Finally, the genotyping results were verified by direct sequencing or PCR-restriction fragment length polymorphism (PCR-RFLP). RESULTS: (1) The total mutation frequency for the 7 mutation hot-spots was 53.6%. The mutation frequency of 235delC was 24.0%, 299-300delAT was 5.6% in the GJB2 gene, IVS7-2A>G was 15.2%, 2168A>G was 3.2% in the SLC26A4 gene. The mutation frequency of 1555A>G and 7445 A>G in mtDNA was 4.8% and 0.8% respectively. The mutation 3243 A>G was not detected. (2) The SNaPshot results were consistent with that from direct sequencing or PCR-RFLP, and the specificity and sensitivity of detection were 100%. CONCLUSION: (1) More than half of the patients with deafness in southern Jiangsu province carry the mutations of the seven hot-spots. (2) The genetic screening technology platform based on SNaPshot can detect 7 mutations in one reaction, and is efficient and suitable for clinical practice.
Assessment of the genetic causes of recessive childhood non-syndromic deafness in the UK - implications for genetic testing. T Hutchin;N N Coy;H Conlon;E Telford;K Bromelow;D Blaydon;G Taylor;E Coghill;S Brown;R Trembath;X Z Liu;M Bitner-Glindzicz;R Mueller. 2005. Clin Genet. 68. PMID: 16283880

Approximately one in 2000 children is born with a genetic hearing impairment, mostly inherited as a non-syndromic, autosomal recessive trait, for which more than 30 different genes have been identified. Previous studies have shown that one of these genes, connexin 26 (GJB2), accounts for 30-60% of such deafness, but the relative contribution of the many other genes is not known, especially in the outbred UK population. This lack of knowledge hampers the development of diagnostic genetic services for deafness. In an effort to determine the molecular aetiology of deafness in the population, 142 sib pairs with early-onset, non-syndromic hearing impairment were recruited. Those in whom deafness could not be attributed to GJB2 mutations were investigated further for other mapped genes. The genetic basis of 55 cases (38.7%) was established, 33.1% being due to mutations in the GJB2 gene and 3.5% due to mutations in SLC26A4. None of the remaining 26 loci investigated made a significant contribution to deafness in a Caucasian population. We suggest that screening the GJB2 and SLC26A4 genes should form the basis of any genetic testing programme for childhood deafness and highlight a number of important issues for consideration and future work.
Long-Term Cochlear Implant Outcomes in Children with GJB2 and SLC26A4 Mutations. Che-Ming Wu;Hui-Chen Ko;Yung-Ting Tsou;Yin-Hung Lin;Ju-Li Lin;Chin-Kuo Chen;Pei-Lung Chen;Chen-Chi Wu. 2015. PLoS One. 10. PMID: 26397989

OBJECTIVES: To investigate speech and language outcomes in children with cochlear implants (CIs) who had mutations in common deafness genes and to compare their performances with those without mutations. STUDY DESIGN: Prospective study. METHODS: Patients who received CIs before 18 years of age and had used CIs for more than 3 years were enrolled in this study. All patients underwent mutation screening of three common deafness genes: GJB2, SLC26A4 and the mitochondrial 12S rRNA gene. The outcomes with CIs were assessed at post-implant years 3 and 5 using the Categories of Auditory Performance (CAP) scale, Speech Intelligibility Rating (SIR) scale, speech perception tests and language skill tests. RESULTS: Forty-eight patients were found to have confirmative mutations in GJB2 or SLC26A4, and 123 without detected mutations were ascertained for comparison. Among children who received CIs before 3.5 years of age, patients with GJB2 or SLC26A4 mutations showed significantly higher CAP/SIR scores than those without mutations at post-implant year 3 (p = 0.001 for CAP; p = 0.004 for SIR) and year 5 (p = 0.035 for CAP; p = 0.038 for SIR). By contrast, among children who received CIs after age 3.5, no significant differences were noted in post-implant outcomes between patients with and without mutations (all p > 0.05). CONCLUSION: GJB2 and SLC26A4 mutations are associated with good post-implant outcomes. However, their effects on CI outcomes may be modulated by the age at implantation: the association between mutations and CI outcomes is observed in young recipients who received CIs before age 3.5 years but not in older recipients.
Familial nonsyndromic hearing loss with incomplete partition type II caused by novel DSPP gene mutations. Wan-Xin Li;Hong Peng;Le Yang;Qing-Qing Hao;Wei Sun;Fei Ji;Wei-Wei Guo;Shi-Ming Yang. 2018. Acta Otolaryngol. 138. PMID: 29741433

BACKGROUND: Familial nonsyndromic hearing loss (NSHL) with incomplete partition type II (IP-II) is a very rare condition. AIMS/OBJECTIVES: To determine the audiological feature, inheritance patterns and genetic etiology of familial NSHL with IP-II in a Chinese family with eight family members. MATERIAL AND METHODS: Clinical data were collected from all eight family members, selected deafness genes were sequenced in proband and whole genome sequencing of seven family members was performed. RESULTS: The proband were a pair of male nonidentical twins (III:1, III:2). Three patients in this family, including the twins and their father (II:1), were diagnosed with bilateral NSHL with IP-II, and no mutation was found in the genes of SLC26A4, GJB2, GJB3, mitochondrial 12S rRNA, and MITF. Whole genome sequencing data indicated de novo mutations of the gene DSPP, c.3085A > G and c.3087C > T, which resulted in p.N1029D and co-segregated with deafness phenotype, were the underlying genetic etiology. CONCLUSION AND SIGNIFICANCE: Familial NSHL with IP-II is extremely rare. In this family, de novo DSPP gene mutations, were considered to be the most probable genetic etiology. And this is the first report to reveal DSPP gene mutations leading to familial NSHL with IP-II.
Prospective mutation screening of three common deafness genes in a large Taiwanese Cohort with idiopathic bilateral sensorineural hearing impairment reveals a difference in the results between families from hospitals and those from rehabilitation facilities. Chen-Chi Wu;Pei-Jer Chen;Yu-Hsun Chiu;Ying-Chang Lu;Ming-Chueh Wu;Chuan-Jen Hsu. 2007. Audiol Neurootol. 13. PMID: 18075246

Accurate epidemiological data on common deafness genes are essential to improve the efficiency and to reduce the cost of molecular diagnosis. They may depend on several factors, including a clear delineation of the source of patients being studied. In the present study, we hypothesize that patients with idiopathic sensorineural hearing loss recruited from different sources might reveal discrepancies in the epidemiological results of genetic screening, because patients from different sources might demonstrate distinct clinical or audiologic features and thus result in biased selection of subjects. To elucidate the relative importance of common deafness genes in Taiwanese and to verify our hypothesis, we conducted a prospective project screening mutations in GJB2, SLC26A4 and mitochondrial 12S rRNA gene in a total of 420 Taiwanese families with idiopathic bilateral sensorineural hearing loss, of which 325 families were recruited from hospitals and 95 from hearing rehabilitation facilities. Allele frequencies of common mutations in these three genes and distributions of the corresponding genotypes were then compared between the two groups. The allele frequencies of mutations in SLC26A4, GJB2 and mitochondrial 12S rRNA in the probands of the 420 families were 14.4, 21.7 and 3.8%, respectively. The allele frequency of SLC26A4 mutations in the hospital group was significantly higher than that in the rehabilitation facility group (16.2 vs. 8.4%, chi(2)-test, p < 0.05), whereas no difference in the frequencies of GJB2 mutations and mitochondrial 12S rRNA mutations was found between the two groups. Distributions of probands classified by SLC26A4 genotypes were also different between the two groups (chi(2)-test, p < 0.05). Accordingly, a discrepancy in the genetic screening results might exist between different sources of idiopathic hearing-impaired patients. Further analysis of audiological results and construction of a logistic regression model showed that different audiological features, namely hearing levels and hearing loss patterns, might be responsible for the unequal distributions of mutations and probands between the hospital and rehabilitation facility groups.
Deafness gene variations in a 1120 nonsyndromic hearing loss cohort: molecular epidemiology and deafness mutation spectrum of patients in Japan. Shin-Ya Nishio;Shin-Ichi Usami. 2015. Ann Otol Rhinol Laryngol. 124 Suppl 1. PMID: 25788563

OBJECTIVES: To elucidate the molecular epidemiology of hearing loss in a large number of Japanese patients analyzed using massively parallel DNA sequencing (MPS) of target genes. METHODS: We performed MPS of target genes using the Ion PGM system with the Ion AmpliSeq and HiSeq 2000 systems using SureSelect in 1389 samples (1120 nonsyndromic hearing loss cases and 269 normal hearing controls). We filtered the variants identified using allele frequencies in a large number of controls and 12 predication program scores. RESULTS: We identified 8376 kinds of variants in the 1389 samples, and 409 835 total variants were detected. After filtering the variants, we selected 2631 kinds of candidate variants. The number of GJB2 mutations was exceptionally high among these variants, followed by those in CDH23, SLC26A4, MYO15A, COL11A2, MYO7A, and OTOF. CONCLUSIONS: We performed a large number of MPS analyses and clarified the genetic background of Japanese patients with hearing loss. This data set will be a powerful tool to discover rare causative gene mutations in highly heterogeneous monogenic diseases and reveal the genetic epidemiology of deafness.
[Molecular genetic analysis of SLC26A4 2168A > G mutations in sensorineural hearing loss with unknown reason in Henan province]. Yunhua Zhu;Lingling Neng;Meisheng Li;Mingmin Dong. 2009. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 22. PMID: 19266817

OBJECTIVE: To survey the etiology of sensorineural hearing loss with unknown reason and the incidence of the mutation of SLC26A4 2168A > G in Henan province. METHOD: The evaluation of hearing loss, etiologic survey, the molecular genetic analysis and temporal bone CT examination for genes common to hereditary hearing disorders were performed in 95 hearing-impaired patients in Henan province. RESULT: In the deafness group, the incidence of large vestibular aqueduct syndrome (LVAS) which correlates with SLC26A4 2168A > G is 6.32%. The incidence of the gene diagnosis conformed to the clinical one is 83.3%. CONCLUSION: There is a high incidence of SLC26A4 2168 A > G mutation in sensorineural hearing loss with unknown reason. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss.
The responsible genes in Japanese deafness patients and clinical application using Invader assay. Shin-Ichi Usami;Michio Wagatsuma;Hisakuni Fukuoka;Hiroaki Suzuki;Keita Tsukada;Shinya Nishio;Yutaka Takumi;Satoko Abe. 2008. Acta Otolaryngol. 128. PMID: 18368581

Discovery of deafness genes has progressed but clinical application lags because of the genetic heterogeneity. To establish clinical application strategy, we reviewed the frequency and spectrum of mutations found in Japanese hearing loss patients and compared them to those in populations of European ancestry. Screening revealed that in Japanese, mutations in GJB2, SLC26A4, and CDH23, and the mitochondrial 12S rRNA are the major causes of hearing loss. Also, mutations in KCNQ4, TECTA, COCH, WFS1, CRYM, COL9A3, and KIAA1199 were found in independent autosomal dominant families. Interestingly, spectrums of GJB2, SLC26A4, and CDH23 mutations in Japanese were quite different from those in Europeans. Simultaneous screening of multiple deafness mutations based on the mutation spectrum of a corresponding population using an Invader panel revealed that approximately 30% of subjects could be diagnosed. This assay will enable us to detect deafness mutations in an efficient and practical manner in the clinical platform. We conclude that specific racial populations may have unique deafness gene epidemiologies; therefore, ethnic background should be considered when genetic testing is performed. Simultaneous examination of multiple mutations based on a population's spectrum may be appropriate and effective for detecting deafness genes, facilitating precise clinical diagnosis, appropriate counseling, and proper management.
Patient with an SLC26A4 gene mutation who had low-frequency sensorineural hearing loss and endolymphatic hydrops. T Yoshida;M Sone;S Naganawa;T Nakashima. 2015. J Laryngol Otol. 129. PMID: 25572613

OBJECTIVE: To report magnetic resonance imaging findings in a patient with an SLC26A4 gene mutation who had low-frequency sensorineural hearing loss. CASE REPORT: A 13-year-old girl had bilateral and symmetric low-frequency sensorineural hearing loss. Upon genetic testing, a heterozygous c.1105A > G (p.K369E) mutation of the SLC26A4 gene was detected. Mild endolymphatic hydrops in the right cochlea and marked endolymphatic hydrops in the left vestibulum were seen by magnetic resonance imaging 4 hours after an intravenous gadolinium injection. CONCLUSION: This is the first reported case of a patient with the SLC26A4 gene mutation c.1105A > G (p.K369E) who had low-frequency sensorineural hearing loss. Co-occurrence of cochlear and vestibular endolymphatic hydrops suggests an association with that pathology.
Two novel SLC26A4 mutations in Iranian families with autosomal recessive hearing loss. Nasrin Yazdanpanahi;Morteza Hashemzadeh Chaleshtori;Mohammad Amin Tabatabaiefar;Zahra Noormohammadi;Effat Farrokhi;Hossein Najmabadi;Shirin Shahbazi;Azam Hosseinipour. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22444735

OBJECTIVE: Due to the fact that SLC26A4 has been suggested as the second cause of hearing loss (HL) in Iran as well as many other countries, obtaining more comprehensive information about SLC26A4 mutations can facilitate more efficient genetic services to the patients with hereditary hearing loss. This investigation aims to detect genetic cause of two Iranian families with hearing loss. METHODS: In the present study, genetic linkage analysis via 4 short tandem repeat markers linked to SLC26A4 was performed for two consanguineous families originating from Hormozgan and Chaharmahal va Bakhtiari provinces of Iran, co-segregating autosomal recessive hearing loss and showed no GJB2 mutations in our preliminary investigation. For identification of mutations, DNA sequencing of SLC26A4 including all the 21 exons, exon-intron boundaries and the promoter was carried out. RESULTS: The results showed linkage to this gene in both families. After sequencing, two novel SLC26A4 mutations (c.65-66insT in exon 2 and c.2106delG in exon 19) were revealed in the two studied families. CONCLUSION: Results of this study stress the necessity of considering the analysis of SLC26A4 in molecular diagnosis of deafness especially when phenotypes such as goiter or enlarged vestibular aqueduct are present.
Identification of PENDRIN (SLC26A4) mutations in patients with congenital hypothyroidism and "apparent" thyroid dysgenesis. Peter Kühnen;Serap Turan;Sebastian Fröhler;Tülay Güran;Saygin Abali;Heike Biebermann;Abdullah Bereket;Annette Grüters;Wei Chen;Heiko Krude. 2013. J Clin Endocrinol Metab. 99. PMID: 24248179

CONTEXT: Congenital hypothyroidism, the most frequent endocrine congenital disease, can occur either based on a thyroid hormone biosynthesis defect or can predominantly be due to thyroid dysgenesis. However, a genetic cause could so far only be identified in less than 10% of patients with a thyroid dysgenesis. OBJECTIVES: Exome sequencing was used for the first time to find additional genetic defects in thyroid dysgenesis. PATIENTS AND METHODS: In a consanguineous family with thyroid dysgenesis, exome sequencing was applied, and findings were further validated by Sanger sequencing in a cohort of 94 patients with thyroid dysgenesis. RESULTS: By exome sequencing we identified a homozygous missense mutation (p.Leu597Ser) in the SLC26A4 gene of a patient with hypoplastic thyroid tissue, who was otherwise healthy. In the cohort of patients with thyroid dysgenesis, we observed a second case with a homozygous missense mutation (p.Gln413Arg) in the SLC26A4 gene, who was additionally affected by severe hearing problems. Both mutations were previously described as loss-of-function mutations in patients with Pendred syndrome and nonsyndromic enlarged vestibular aqueduct. CONCLUSION: We unexpectedly identified SLC26A4 mutations that were hitherto diagnosed in thyroid dyshormonogenesis patients, now for the first time in patients with structural thyroid defects. This result resembles the historic description of thyroid atrophy in patients with the so-called myxedematous form of cretinism after severe iodine deficiency. Most likely the thyroid defect of the two homozygous SLC26A4 gene mutation carriers represents a kind of secondary thyroid atrophy, rather than a primary defect of thyroid development in the sense of thyroid agenesis. Our study extends the variable clinical spectrum of patients with SLC26A4 mutations and points out the necessity to analyze the SLC26A4 gene in patients with apparent thyroid dysgenesis in addition to the known candidate genes TSHR, PAX8, NKX2.1, NKX2.5, and FOXE1.
Genotypes and phenotypes of a family with a deaf child carrying combined heterozygous mutations in SLC26A4 and GJB3 genes. Yunlong Li;Baosheng Zhu. 2016. Mol Med Rep. 14. PMID: 27176802

Mutations in the SLC26A4 gene have been shown to cause a type of deafness referred to as large vestibular aqueduct syndrome (LVAS), whereas mutations in the GJB3 gene have been associated with nonsyndromic deafness. However, the clinical phenotypes of these mutations vary and remain to be fully elucidated. The present study performed genetic analysis of a Chinese family, in which the child was deaf and the parents were healthy. Sanger sequencing demonstrated that the affected individual harbored three heterogeneous mutations in the SLC26A4 and GJB3 genes, as follows: SLC26A4 IVS-2 A>G, SLC26A4 c.2168 A>G and GJB3 c.538 C>T. The affected individual exhibited hearing loss and was diagnosed with LVAS by computed tomography scan. The mother and father of the affected individual harbored the heterogeneous mutations of SLC26A4 IVS-2 A>G and GJB3 c.538 C>T, and the heterozygous mutation of SLC26A4 c.2168 A>G, respectively. Neither parents exhibited any hearing loss. The results obtained from the deaf patient provided genetic and clinical evidence that carrying combined heterogeneous mutations in the GJB3 and SLC26A4 genes may be involved in the etiology of severe hearing loss, of which the mechanism requires further examination.
Functional Testing of SLC26A4 Variants-Clinical and Molecular Analysis of a Cohort with Enlarged Vestibular Aqueduct from Austria. Sebastian Roesch;Emanuele Bernardinelli;Charity Nofziger;Miklós Tóth;Wolfgang Patsch;Gerd Rasp;Markus Paulmichl;Silvia Dossena. 2018. Int J Mol Sci. 19. PMID: 29320412

The prevalence and spectrum of sequence alterations in the SLC26A4 gene, which codes for the anion exchanger pendrin, are population-specific and account for at least 50% of cases of non-syndromic hearing loss associated with an enlarged vestibular aqueduct. A cohort of nineteen patients from Austria with hearing loss and a radiological alteration of the vestibular aqueduct underwent Sanger sequencing of SLC26A4 and GJB2, coding for connexin 26. The pathogenicity of sequence alterations detected was assessed by determining ion transport and molecular features of the corresponding SLC26A4 protein variants. In this group, four uncharacterized sequence alterations within the SLC26A4 coding region were found. Three of these lead to protein variants with abnormal functional and molecular features, while one should be considered with no pathogenic potential. Pathogenic SLC26A4 sequence alterations were only found in 12% of patients. SLC26A4 sequence alterations commonly found in other Caucasian populations were not detected. This survey represents the first study on the prevalence and spectrum of SLC26A4 sequence alterations in an Austrian cohort and further suggests that genetic testing should always be integrated with functional characterization and determination of the molecular features of protein variants in order to unequivocally identify or exclude a causal link between genotype and phenotype.
Identification of SLC26A4 mutations p.L582LfsX4, p.I188T and p.E704K in a Chinese family with large vestibular aqueduct syndrome (LVAS). Yunlong Li;Baosheng Zhu;Jie Su;Yifei Yin;Fangqing Yu. 2016. Int J Pediatr Otorhinolaryngol. 91. PMID: 27863619

Large vestibular aqueduct syndrome (LVAS) is a type of hearing loss characterized by an autosomal recessive inheritance. LVAS has been shown to be associated with mutations in SLC26A4 gene. In the present study, we report the clinical, genetic and molecular characterization of a Chinese family with LVAS. By using the targeted sequence capture and next-generation sequencing, we identified heterozygous mutations of SLC26A4 p.I188T (c.563T > C), p.L582LfsX4 (c.1746 delG) and p.E704K (c.2110G > A) in the affected individual of this family, of which SLC26A4 p.E704K is a novel mutation associated with LVAS. By tracing the transmission and functional prediction of these mutations in the pedigree, the heterozygous mutations of p.I188T, p.L582LfsX4 and p.E704K in SLC26A4 gene were responsible for the LVAS of the affected individual. This is the first case of LVAS caused by these mutations.
Distinct and novel SLC26A4/Pendrin mutations in Chinese and U.S. patients with nonsyndromic hearing loss. Pu Dai;Andrew K Stewart;Fouad Chebib;Ann Hsu;Julia Rozenfeld;Deliang Huang;Dongyang Kang;Va Lip;Hong Fang;Hong Shao;Xin Liu;Fei Yu;Huijun Yuan;Margaret Kenna;David T Miller;Yiping Shen;Weiyan Yang;Israel Zelikovic;Orah S Platt;Dongyi Han;Seth L Alper;Bai-Lin Wu. 2009. Physiol Genomics. 38. PMID: 19509082

Mutations of the human SLC26A4/PDS gene constitute the most common cause of syndromic and nonsyndromic hearing loss. Definition of the SLC26A4 mutation spectrum among different populations with sensorineural hearing loss is important for development of optimal genetic screening services for congenital hearing impairment. We screened for SLC26A4 mutations among Chinese and U.S. subjects with hearing loss, using denaturing HPLC (DHPLC) and direct DNA sequencing. Fifty-two of 55 Chinese subjects with deafness accompanied by enlargement of the vestibular aqueduct (EVA) exhibited at least one mutant SLC26A4 allele, whereas SLC26A4 mutations were found in only 2 of 116 deaf Chinese patients without EVA. The spectrum of SLC26A4 mutations differed among Chinese and U.S. subjects and included 10 previously unreported SLC26A4 variants: 4 in the Chinese population (p.E303Q, p.X329, p.X467, p.X573) and 6 in the U.S. population (p.V250A, p.D266N, p.F354S, p.D697A, p.K715N, p.E737D). Among the seven novel in-frame missense mutations, five encoded SLC26A4 proteins with substantially reduced Cl(-)/anion exchange activity as expressed and measured in Xenopus oocytes, but four of these were sufficiently active to allow study of anion selectivity. The only mutant polypeptide exhibiting complete loss of anion exchange function, p.E303Q, was expressed at or near the oocyte surface at near-wild-type levels. Two variants, p.F354S and p.E737D, displayed selective reduction in relative rate of Cl(-)/HCO(3)(-) exchange compared with similarly measured rates of Cl(-)/Cl(-) and Cl(-)/I(-) exchange. Our data show that mutation analysis of the SLC26A4 gene is of high diagnostic yield among subjects with deafness and bilateral EVA in both China and the U.S. However, the pathogenicity of monoallelic SLC26A4 gene variants in patients with hearing loss remains unclear in many instances.
Screening of 38 genes identifies mutations in 62% of families with nonsyndromic deafness in Turkey. Duygu Duman;Asli Sirmaci;F Basak Cengiz;Hilal Ozdag;Mustafa Tekin. 2010. Genet Test Mol Biomarkers. 15. PMID: 21117948

More than 60% of prelingual deafness is genetic in origin, and of these up to 95% are monogenic autosomal recessive traits. Causal mutations have been identified in 1 of 38 different genes in a subset of patients with nonsyndromic autosomal recessive deafness. In this study, we screened 49 unrelated Turkish families with at least three affected children born to consanguineous parents. Probands from all families were negative for mutations in the GJB2 gene, two large deletions in the GJB6 gene, and the 1555A>G substitution in the mitochondrial DNA MTRNR1 gene. Each family was subsequently screened via autozygosity mapping with genomewide single-nucleotide polymorphism arrays. If the phenotype cosegregated with a haplotype flanking one of the 38 genes, mutation analysis of the gene was performed. We identified 22 different autozygous mutations in 11 genes, other than GJB2, in 26 of 49 families, which overall explains deafness in 62% of families. Relative frequencies of genes following GJB2 were MYO15A (9.9%), TMIE (6.6%), TMC1 (6.6%), OTOF (5.0%), CDH23 (3.3%), MYO7A (3.3%), SLC26A4 (1.7%), PCDH15 (1.7%), LRTOMT (1.7%), SERPINB6 (1.7%), and TMPRSS3 (1.7%). Nineteen of 22 mutations are reported for the first time in this study. Unknown rare genes for deafness appear to be present in the remaining 23 families.
[The clinical definition and etiology of Pendred syndrome (a review of the literature and clinical observations)]. T G Markova;E N Geptner;M R Lalayants;E I Zelikovich;T I Chugunova;O L Mironovich;E A Bliznetz;A V Polyakov;G A Tavartkiladze. 2017. Vestn Otorinolaringol. 81. PMID: 28091472

The aim of this work was a clinical study of the patients with mutations in the SLC26A4 gene and clinical diagnosis of the Pendred syndrome. The Pendred syndrome is a hereditary autosomal recessive disorder characterized by combined pathology of the inner ear and the thyroid gland. CT of the temporal bones demonstrates the Mondini-type structural anomaly in the inner ear and enlarged vestibular aqueduct. Examination of the thyroid gland reveals hypothyroidism and euthyroid goiter. A total of 20 unrelated children at the age from 2 to 16 years presenting with the hearing loss of different severity were available for the examination. High-resolution CT of the temporal bones demonstrated abnormal development of the inner ear including the Mondini-type structural anomaly and enlarged vestibular aqueduct. Five children with congenital hypothyroidism suffered from bilateral sensorineural impairment of hearing. The routine methods of audiological and molecular genetic examination were used throughout the study. RESULTS: As a result of molecular genetic studies, four out of the 20 patients were found to carry six recessive mutations of the SLC26A4 gene in the compound heterozygous and one such gene in the homozygous state which confirmed the hereditary nature of the disease. The children suffered the hearing loss of varying severity diagnosed at different age. The thyroid hypofunction in one child was identified when it was 2 years of age, and in two children at the age of 8 and 9 years. CONCLUSION: The first step in the diagnosis of the Pendred syndrome among children with congenital hearing loss was a CT scan of the temporal bones that showed incomplete separation of the curls of the cochlea and enlarged vestibular aqueduct. It is necessary to continue to study epidemiology, clinical and molecular genetics of the Pendred syndrome in the Russian population.
Mutations of KCNJ10 together with mutations of SLC26A4 cause digenic nonsyndromic hearing loss associated with enlarged vestibular aqueduct syndrome. Tao Yang;Jose G Gurrola;Hao Wu;Sui M Chiu;Philine Wangemann;Peter M Snyder;Richard J H Smith. 2009. Am J Hum Genet. 84. PMID: 19426954

Mutations in SLC26A4 cause nonsyndromic hearing loss associated with an enlarged vestibular aqueduct (EVA, also known as DFNB4) and Pendred syndrome (PS), the most common type of autosomal-recessive syndromic deafness. In many patients with an EVA/PS phenotype, mutation screening of SLC26A4 fails to identify two disease-causing allele variants. That a sizable fraction of patients carry only one SLC26A4 mutation suggests that EVA/PS is a complex disease involving other genetic factors. Here, we show that mutations in the inwardly rectifying K(+) channel gene KCNJ10 are associated with nonsyndromic hearing loss in carriers of SLC26A4 mutations with an EVA/PS phenotype. In probands from two families, we identified double heterozygosity in affected individuals. These persons carried single mutations in both SLC26A4 and KCNJ10. The identified SLC26A4 mutations have been previously implicated in EVA/PS, and the KCNJ10 mutations reduce K(+) conductance activity, which is critical for generating and maintaining the endocochlear potential. In addition, we show that haploinsufficiency of Slc26a4 in the Slc26a4(+/-) mouse mutant results in reduced protein expression of Kcnj10 in the stria vascularis of the inner ear. Our results link KCNJ10 mutations with EVA/PS and provide further support for the model of EVA/PS as a multigenic complex disease.
Application of allele-specific primer extension-based microarray for simultaneous multi-gene mutation screening in patients with non-syndromic hearing loss. Soo-Young Choi;Kyu-Yup Lee;Young-Eun Kim;Jae-Woong Bae;Se-Kyung Oh;So-Yeon Kim;Sang-Joon Hwang;Un-Kyung Kim;Sang-Heun Lee. 2010. Int J Mol Med. 25. PMID: 20127034

Congenital hearing loss (HL) is the most common sensory disorder in humans, affecting one in 1000 infants at birth. A high degree of genetic heterogeneity makes it difficult to screen for mutations in all known deafness genes in clinical applications. We have improved a genotyping microarray using the multiplex PCR-based allele-specific primer extension (ASPE) reaction and applied this method for the genetic diagnosis of congenital HL in Korea. Seven different mutations in the GJB2, SLC26A4 and mitochondrial 12S rRNA genes, which were identified on the basis of a previous study in a Korean population, were selected for the study. These genes were used to evaluate the accuracy of the microarray. The test for validation of the current version of HL genotyping microarray was fully concordant with the results of DNA sequencing in which 51 subjects with non-syndromic HL were originally genotyped. Furthermore, the blind test of the genotyping microarray detected four different mutations in 10 out of 65 patients, and the accuracy of microarray was calculated as 98% (64/65). Therefore, our results suggest that this HL genotyping microarray will be useful in clinical applications for the genetic diagnosis of HL.
Molecular analysis of the GJB2, GJB6 and SLC26A4 genes in Korean deafness patients. K Y Lee;S Y Choi;J W Bae;S Kim;K W Chung;D Drayna;U K Kim;S H Lee. 2008. Int J Pediatr Otorhinolaryngol. 72. PMID: 18585793

OBJECTIVES: Mutations in the GJB2, GJB6 and SLC26A4 genes are a frequent cause of hearing loss in a number of populations. However, little is known about the genetic causes of hearing loss in the Korean population. METHODS: We sequenced the GJB2 and GJB6 genes to examine the role of mutations in these genes in 22 hearing loss patients. We also sequenced the SLC26A4 gene in seven patients with inner ear malformations, including enlarged vestibular aqueduct (EVA) revealed by computer tomography. RESULTS: Coding sequence mutations in GJB2 were identified in 13.6% of the patients screened. Two different mutations, 235delC and T86R were found in three unrelated patients. The 235delC was the most prevalent mutation with an allele frequency of 6.9% in our patient group. No mutations, including 342-kb deletion, were found in GJB6 gene. Three different variants of SLC26A4 were identified in the EVA patients, including one novel mutation. Four EVA patients carried two mutant alleles of SLC26A4, and at least one allele in all patients was the H723R mutation, which accounted for 75% of all mutant alleles. CONCLUSIONS: Our results suggest that GJB2 and SLC26A4 mutations together make up a major cause of congenital hearing loss in the Korean population. Further studies may be able to identify other common variants that account for a significant fraction of hearing loss in the Korean population.
Predominance of genetic diagnosis and imaging results as predictors in determining the speech perception performance outcome after cochlear implantation in children. Chen-Chi Wu;Yi-Chin Lee;Pei-Jer Chen;Chuan-Jen Hsu. 2008. Arch Pediatr Adolesc Med. 162. PMID: 18316665

OBJECTIVE: To investigate the roles of genetic diagnosis and imaging studies, as well as other prognostic factors, in predicting outcomes in children with cochlear implant. DESIGN: Prospective cohort study. SETTING: Tertiary referral center. PARTICIPANTS: Sixty-seven consecutive children with sensorineural hearing impairment who had at least 3 years of experience with cochlear implant. INTERVENTIONS: Imaging of the inner ear was done with high-resolution computed tomography, and mutations were screened in 3 genes commonly associated with pediatric hearing impairment: GJB2, SLC26A4, and the mitochondrial 12S ribosomal RNA gene. Speech perception performance was compared according to genetic diagnosis and imaging data. A general linear model was constructed to demonstrate the predictive values of specific genetic and imaging results after adjusting for other factors. Main Outcome Measure Recognition scores on speech perception tests. RESULTS: Twenty-two children (33%) showed genetic mutations: 18 with SLC26A4 and 4 with GJB2 mutations. According to imaging findings, 33 children (49%) showed inner ear malformations: 9 with a narrow internal auditory canal and 24 with other malformations. All children with SLC26A4 or GJB2 mutations exhibited excellent speech recognition scores, whereas a narrow internal auditory canal was associated with poorer outcomes (P < .001 in all recognition scores). The general linear model confirmed that both a narrow internal auditory canal (P < .001) and SLC26A4 mutations (P = .04) correlated with speech perception outcome. CONCLUSIONS: Genetic diagnosis and imaging results are the 2 predominant factors determining the outcome in children with cochlear implants. In pediatric candidates for cochlear implantation, both genetic examination and imaging studies should be included in the battery of preoperative evaluations.
Hearing loss associated with enlarged vestibular aqueduct and zero or one mutant allele of SLC26A4. Jane Rose;Julie A Muskett;Kelly A King;Christopher K Zalewski;Parna Chattaraj;John A Butman;Margaret A Kenna;Wade W Chien;Carmen C Brewer;Andrew J Griffith. 2016. Laryngoscope. 127. PMID: 27859305

OBJECTIVES/HYPOTHESIS: To characterize the severity and natural history of hearing loss, and the prevalence of having a cochlear implant in a maturing cohort of individuals with enlarged vestibular aqueduct (EVA) and zero or one mutant allele of SLC26A4. STUDY DESIGN: Prospective cohort study of subjects ascertained between 1998 and 2015 at the National Institutes of Health Clinical Center. METHODS: Study subjects were 127 individuals (median age, 8 years; range, 0-59 years) with EVA in at least one ear. RESULTS: Ears with EVA and zero or one mutant allele of SLC26A4 had mean 0.5/1/2/4-kHz pure-tone averages of 62.6 and 52.9 dB HL, respectively, in contrast to EVA ears with two mutant alleles of SLC26A4 (88.1 dB HL; P < .01). This association was independent of age, sex, or side of EVA (P < .001). Natural history of hearing loss was not associated with number of mutant alleles (P = .94). The prevalence of having a cochlear implant was nine (12%) of 76, two (13%) of 15, and 12 (38%) of 32 subjects with zero, one, and two mutant alleles, respectively (P = .00833). This association was not independent (P = .534) but reflected underlying correlations with age at time of first audiogram (P = .003) or severity of hearing loss (P = .000). CONCLUSIONS: Ears with EVA and zero or one mutant allele of SLC26A4 have less severe hearing loss, no difference in prevalence of fluctuation, and a lower prevalence of cochlear implantation in comparison to ears with two mutant alleles of SLC26A4. LEVEL OF EVIDENCE: NA Laryngoscope, 127:E238-E243, 2017.
SLC26A4 mutation spectrum associated with DFNB4 deafness and Pendred's syndrome in Pakistanis. Saima Anwar;Saima Riazuddin;Zubair M Ahmed;Saba Tasneem; Ateeq-ul-Jaleel;Shahid Y Khan;Andrew J Griffith;Thomas B Friedman;Sheikh Riazuddin. 2009. J Hum Genet. 54. PMID: 19287372

Pendred's syndrome (PDS) is an autosomal-recessive disorder characterized by sensorineural hearing loss and goiter. PDS is caused by mutations of the SLC26A4 gene encoding pendrin, a transmembrane exchanger of Cl(-), I(-) and HCO(3)(-), which is expressed in the thyroid and inner ear. SLC26A4 mutations can also be associated with non-syndromic deafness, DFNB4. The goal of our study was to define the identities and frequencies of SLC26A4 mutations in 563 large, consanguineous Pakistani families segregating severe-to-profound recessive deafness. Sequence analyses of SLC26A4 in 46 unreported families segregating deafness linked to DFNB4/PDS revealed 16 probable pathogenic variants, 8 of which are novel. The novel variants include three missense substitutions (p.R24L, p.G139V and p.V231M), two splice site mutations (c.304+2T>C and c.1341+3A>C), one frameshift (p.C565MfsX8) and two different genomic deletions affecting exons 1-2 and 11-18. Each of six pathogenic variants (p.V239D, p.Q446R, p.S90L, p.Y556C, p.R24L and p.K715N) was found in more than one family and haplotype analyses suggest that they are founder mutations. Combined with earlier reported data, SLC26A4 mutations were identified in 56 (7.2%; 95% CI: 5.6-9.2%) of 775 families. Therefore, SLC26A4 mutations are the most common known cause of genetic deafness in this population. As p.V239D (30%), p.S90L (18%) and p.Q446R (18%) account for approximately two-third of the mutant alleles of SLC26A4, hierarchical strategies for mutation detection would be feasible and cost-efficient genetic tests for DFNB4 deafness and PDS in Pakistanis.
[Identification of novel common mutations among patients with non-syndromic hearing loss with high-throughput gene capture technology]. Yongan Zhou;Hongyan Zeng;Xiangshao Li;Huifang Yang;Wei Guo;Ziqi Hao;Pengli Li;Jiao Li;Xiaoli Zhao;Xiang Wang;Li Xia;Siqi Ma. 2016. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 33. PMID: 27984600

OBJECTIVE: To identify novel common mutations among patients with non-syndromic hearing loss (NSHL). METHODS: High-throughput gene capture technology was used to analyze 18 patients with NSHL in whom common mutations of deafness genes including GJB2, SLC26A4, GJB3, and mtDNA were excluded. Suspected mutation was verified with Sanger sequencing. RESULTS: Next generation sequencing has identified 62 mutations in 29 genes associated with hearing loss, which included 54 missense mutations, 4 splicing mutations, 3 deletional mutations, and 1 nonsense mutation. Mutations occurring more than twice in the 18 patients were verified by Sanger sequencing. This has confirmed 15 mutations in 8 genes, including 3 missense mutations (p.C2184G, p.L2825P, p.H1888Y) which have not been reported previously. Meanwhile, p.L445W, p.D866N, and IVS919-2A>G were common causative mutations. CONCLUSION: A number of common causative mutations, e.g., p.L445W, p.D866N, IVS919-2A>G, have been identified by high-throughput capture technology, which may facilitate the research and genetic diagnosis for hearing loss.
[Study of newborn hearing and genetic screening in Jinan]. Lili Xiang;Qian Lin;Wenying Nie;Qian Hou;Hui Li;Yinghui Li;Xinjie Liu. 2015. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 50. PMID: 26178053

OBJECTIVE: In this study, we employed newborn hearing screening and gene screening concurrently to explore the hearing loss associated with mutations in the city of Jinan. METHODS: A total of 3 288 newborns born between March 2013 and December 2013 in Jinan Maternity and Child Care Hospital received hearing concurrent genetic screening. Transiently evoked otoacoustic emissions (TEOAE) was used in rooming-in newborns, while TEOAE and auto auditory brainstem response (AABR) was used in infants in neonatal intensive care unit (NICU). Two drops of heel blood were harvested with filter paper. Nine mutations [GJB2 (235delC, 35delG, 299delAT, 176del16), SLC26A4 (IVS7-2A>G,2168 A>G), GJB3 (538 C>T), 12SrRNA (1555 A>G, 1494C>T)] of 4 frequent genes associated with Chinese hearing loss were determined by gene chip in these dried blood samples. RESULTS: Among 3 288 newborns, 363 cases failed to pass the hearing screening, and 36 cases of these 363 newborns carried mutations, with a carrier rate of 9.91%. 2 925 cases passed the hearing screening, of which 113 carried mutations, with a carrier rate of 3.86%. There was a significantly statistic difference (χ2=8.67, P=0.000) in carrier rate between two groups. 149 (4.53%) infants were detected to carry at least one mutation allele,among which 113 cases passed the hearing screening and 36 cases failed. Seven cases were diagnosed to have hearing loss. Homozygous GJB2 mutation was detected in 2 cases, compound heterozygous GJB2 mutation was detected in 1 case, and heterozygous GJB2 mutation in 88 cases. There were 91 cases carried GJB2 mutations totally, with a total rate of 2.76%. There were 40 cases were detected to carry heterozygous SLC26A4 mutation, with a carrier rate of 1.22%. Nine cases had heterozygous GJB3 mutation, with a carrier rate of 0.27%. Six cases had homogeneous mitochondria 12SrRNA mutation, and 1 had heterogeneous mutations. There were 7 cases totally, with a total rate of 0.21%. 142 infants with gene mutation should be follow-up. CONCLUSION: A follow-up system in infants, passed hearing screening,with single heterozygous mutation and mutations associated with drug-induced hearing loss, can help to detect infants with hearing defects early and effectively prevent late-onset hearing impairment.
Whole-exome sequencing identifies MYO15A mutations as a cause of autosomal recessive nonsyndromic hearing loss in Korean families. Hae-Mi Woo;Hong-Joon Park;Jeong-In Baek;Mi-Hyun Park;Un-Kyung Kim;Borum Sagong;Soo Kyung Koo. 2013. BMC Med Genet. 14. PMID: 23865914

BACKGROUND: The genetic heterogeneity of hearing loss makes genetic diagnosis expensive and time consuming using available methods. Whole-exome sequencing has recently been introduced as an alternative approach to identifying causative mutations in Mendelian disorders. METHODS: To identify the hidden mutations that cause autosomal recessive nonsyndromic hearing loss (ARNSHL), we performed whole-exome sequencing of 13 unrelated Korean small families with ARNSHL who were negative for GJB2 or SLC26A4 mutations. RESULTS: We found two novel compound heterozygous mutations, IVS11 + 1 and p.R2146Q, of MYO15A in one (SR903 family) of the 13 families with ARNSHL. In addition to these causative mutations, 13 nonsynonymous variants, including variants with uncertain pathogenicity (SR285 family), were identified in the coding exons of MYO15A from Korean exomes. CONCLUSION: This is the first report of MYO15A mutations in an East Asian population. We suggest that close attention should be paid to this gene when performing genetic testing of patients with hearing loss in East Asia. The present results also indicate that whole-exome sequencing is a valuable method for comprehensive medical diagnosis of a genetically heterogeneous recessive disease, especially in small-sized families.
Microarray-based mutation detection of pediatric sporadic nonsyndromic hearing loss in China. Chunyan Qu;Xibin Sun;Yang Shi;Angela Gong;Shuang Liang;Min Zhao;Yan Chen;Fenghe Liang. 2011. Int J Pediatr Otorhinolaryngol. 76. PMID: 22154049

OBJECTIVE: To investigate the molecular etiologic causes of sporadic nonsyndromic hearing loss in Chinese children. METHODS: 179 sporadic nonsyndromic hearing loss children were subjected to microarray-based mutation detection for nine hot spot mutations in four of the most common deafness-related genes, including GJB2, SLC26A4, GJB3, and 12s rRNA. RESULTS: The incidence of positive genetic errors was 43.58% with the current set of target genes in sporadic nonsyndromic hearing loss children. Among them, 25.14% of cases had genetic defects in GJB2, 16.76% of cases had pathogenic mutations in SLC26A4, 1.12% of cases were caused by 12s rRNA mutations, and GJB3 mutation was detected in 0.56% of this group of patients. CONCLUSIONS: Our results demonstrated that genetic factors were important causes for sporadic nonsyndromic hearing loss in Chinese pediatric cases. Mutations of GJB2 and SLC26A4 are two major genetic causes, whereas mutations of GJB3 and 12s rRNA result in the development of hearing loss in a small percentage of sporadic nonsyndromic hearing loss cases. Microarray testing is a helpful and instrumental screening method in the diagnosis of genetic hearing loss.
Clinical data analysis of genotypes and phenotypes of deafness gene mutations in newborns: A retrospective study. Yating Du;Lihui Huang;Xueyao Wang;Qingjia Cui;Xiaohua Cheng;Liping Zhao;Tingting Ni. 2017. Biosci Trends. 11. PMID: 28717060

We retrospectively analyzed newborns with deafness gene mutations and summarized the relationship between genotype and phenotype to provide a basis for genetic counseling. We studied 582 subjects positive for deafness gene mutations that were treated in the otology outpatient department of Beijing Tongren Hospital, Capital Medical University, between April 2012 and April 2016. The subjects were divided into 3 categories: a diagnosed group (group A), which was further subdivided into subgroups A1 (homozygous and compound heterozygous GJB2 mutations) and A2 (homozygous and compound heterozygous SLC26A4 mutations); a drug-induced deafness group (group B, mitochondrial (Mt) gene mutations); and a mutation carrier group (group C), which was further subdivided into the subgroups C1 (GJB2 heterozygous mutations), C2 (SLC26A4 heterozygous mutations), C3 (GJB3 heterozygous mutations), and C4 (double gene mutations). Partial sequences positive for GJB2 or SLC26A4 were sequenced and analyzed for mutations. Subjects underwent otoscopic examination and comprehensive audiological evaluation, and temporal bone computerized tomography and/or inner ear magnetic resonance imaging were performed. GJB2 235delC was the most common mutation locus. The highest proportion of deafness detected during universal newborn hearing screening was for drug-induced deafness, whereas the lowest was for the diagnosed group. GJB2 gene mutations mainly resulted in flat-type, profound-to-severe sensorineural hearing loss (SNHL). SLC26A4 gene mutation was mainly associated with high-frequency drop-type and profound-severe SNHL and was closely related to enlargement of the vestibular aqueduct.
Comparative study of mutation spectrums of MT-RNR1 m.1555A>G, GJB2, and SLC26A4 between familial and sporadic patients with nonsyndromic sensorineural hearing loss in Chinese Han. Qian Li;Yubin Ji;Bing Han;Liang Zong;Lan Lan;Yali Zhao;Hongyang Wang;Dayong Wang;Qiuju Wang. 2014. Chin Med J (Engl). 127. PMID: 25266519

BACKGROUND: The mutation frequencies of three common deafness genes (MT-RNR1 m.1555A>G, GJB2, and SLC26A4) among patients with nonsyndromic sensorineural hearing loss (NSHL) were different in previous studies. Inconsistent selection criteria for recruiting patients could have led to differences in estimating the frequencies of genetic mutations thus resulting in different mutation frequencies among these studies. The aim of this study was to reveal the differences in the mutation spectrums of the three common genes between familial and sporadic Chinese Han patients. METHODS: Totally, 301 familial probands and 703 sporadic patients with NSHL were enrolled in this study. Three genes, MT-RNR1 m.1555A>G, GJB2, and SLC26A4, were screened for mutation in our study cohort. A χ(2) test was performed to compare the mutation frequencies between the two groups. RESULTS: The study showed that the disease-causing mutation frequencies of MT-RNR1 m.1555A>G, GJB2, and SLC26A4 were 12.29%, 14.62%, and 18.27% in familial probands and 3.56%, 18.63%, and 18.92% in sporadic patients, respectively. The mutation frequency of MT-RNR1 m.1555A>G in familial probands was significantly higher than in sporadic patients (χ(2) test, P = 0.000), while there were no significant differences in the mutation frequencies of GJB2 and SLC26A4 between the familial and sporadic groups (χ(2) test, P > 0.05). CONCLUSIONS: It is necessary to reveal the differences in gene mutation frequencies between patients of different sources or characteristics by comparative studies in order to avoid selection bias. The mutations of GJB2, SLC26A4, and MT-RNR1 m.1555A>G are the most important etiological factors in Chinese Han patients, among which SLC26A4 might be the most frequent.
Mutation analysis of common GJB2, SCL26A4 and 12S rRNA genes among 380 deafness patients in northern China. Jing Pan;Ping Xu;Weibo Tang;Zhongtao Cui;Miao Feng;Chunying Wang. 2017. Int J Pediatr Otorhinolaryngol. 98. PMID: 28583500

OBJECTIVES: The molecular etiology of nonsyndromic deafness in Chinese population has not been investigated systematically, our study is aim to investigate the molecular etiology of nonsyndromic deafness patients from Northern China (Heilongjiang province), in order to provide genetic test and counseling to families. METHODS: 380 unrelated patients with hearing loss who attended to the Department of Otolaryngology, The Fourth Affiliated Hospital of Harbin Medical University were enrolled to our study. All patients were diagnosed with nonsyndromic deafness by audiologic evaluation, 202 normal-hearing individuals were taken as controls. Mutations in three common deafness-causing genes (GJB2, SLC26A4 and 12S rRNA) were screened by direct sequencing. RESULTS: Mutations (homozygote or compound heterozygote) in GJB2 accounted for 8.9% (34/380) of the patients, mutations in SLC26A4 accounted for 10.0% (38/380) of the patients screened. Only one case was found to carry 12S rRNA 1555A > G (1/380, 0.26%). Five types of mutations in GJB2 were identified, GJB2 235delC was the most prevalent mutation in our patient group (76/380, 20.0%), followed by 299-300delAT with a frequency of 7.4% (28/380). Two types of mutations in SLC26A4 were detected in our patient group (IVS7-2A > G and 2168A > G). IVS7-2A > G was identified in 27 patients (27/380, 7.1%) and 2168A > G was identified in 14 patients (14/380, 3.7%). CONCLUSIONS: Our results demonstrate that 19.2% patients with nonsyndromic deafness were caused by mutations in three common deafness genes (GJB2, SLC26A4 and 12S rRNA) in our northern China patient group. GJB2 235delC was the most prevalent mutation, same as in the most Asian populations. These data enrich the database of deafness mutations and provide the standard for clinical diagnose, treatment and genetic counseling in Northern China population.
Identification of SLC26A4 c.919-2A>G compound heterozygosity in hearing-impaired patients to improve genetic counseling. Qi Li;Qing-wen Zhu;Yong-yi Yuan;Sha-sha Huang;Dong-yi Han;De-liang Huang;Pu Dai. 2012. J Transl Med. 10. PMID: 23151025

BACKGROUND: Mutations in the SLC26A4 gene, which encodes the anion transporter, pendrin, are a major cause of autosomal recessive non-syndromic hearing loss (NSHL) in some Asian populations. SLC26A4 c.919-2A>G (IVS7-2A>G) is the most common mutation in East Asian deaf populations. To provide a basis for improving the clinical diagnosis of deaf patients, we evaluated 80 patients with the SLC26A4 c.919-2A>G monoallelic mutation from 1065 hearing-impaired subjects and reported the occurrence of a second mutant allele in these patients. METHODS: The occurrence of a second mutant allele in these 80 patients with a single c.919-2A>G mutation was investigated. Mutation screening was performed by bidirectional sequencing in SLC26A4 exons 2 to 6 and 9 to 21. RESULTS: We found that 47/80 patients carried another SLC26A4 c.919-2A>G compound mutation. The five most common mutations were: p.H723R, p.T410M, 15+5G>A (c.1705+5G>A), p.L676Q and p.N392Y. We found a Chinese-specific SLC26A4 mutation spectrum and an associated SLC26A4 contribution to deafness. CONCLUSION: Our study illustrates that mutation analysis of other SLC26A4 exons should be undertaken in deaf patients with a single heterozygous SLC26A4 mutation. Moreover, a model of compound heterozygosity may partially explain the disease phenotype.
[Genetic counseling and intervention for families with deaf-mute patients based on genetic testing: analysis of 5 families]. Pu Dai;Bing Han;Yong-yi Yuan;Zheng-ce Jin;Yi Wang;Yang Xiang;Fei Yu;Xin Liu;Guo-jian Wang;Dong-yang Kang;Xin Zhang;Mei Li;Suo-qiang Zhai;De-liang Huang;Dong-yi Han. 2007. Zhonghua Yi Xue Za Zhi. 87. PMID: 17672986

OBJECTIVE: To analyze the molecular genetic mechanisms of pathogenesis of deafness in the families with deaf-mute patients and analyze the strategies of genetic counseling and intervention for these families. METHODS: Peripheral blood samples were collected from the probands with deaf-muteness and their parents of five families and genetic tests were conducted to analyze the GJB2, SLC26A4 (PDS), and mitochondrial DNA (mtDNA) A 1555G genes for the existence of mutation. Families 1-3 had one child with hearing loss each while the parents had normal hearing and the mothers had been pregnant for 6-18 weeks. Both parents of family 4 were deaf-mute, and the wife of family 5 was deaf-mute while her husband had normal hearing. RESULTS: The proband from family 1 was proven to carry compound GJB2 mutations while his parents carried a single GJB2 mutation; prenatal testing showed that the fetus only carried the paternal mutation. The proband from family 2 was proven to carry compound SLC26A4 (PDS) mutations while his parents carried a single SLC26A4 (PDS) mutation; prenatal testing showed that the fetus only carried the paternal mutation. The proband from family 3 and his parents didn't carry any GJB2, SLC26A4 and mtDNA A1555G mutation. Observation showed that the new born babies of these three families all had normal hearing revealed by new born hearing screening and ABR test. The husband from family 4 was homozygous GJB2 235delC while his wife was mtDNA A1555G positive. This couple was advised to strictly avoid the administration of aminoglycoside antibiotics to their future offspring. In family 5, the wife carried compound SLC26A4 (PDS) mutations while her husband carried a single SLC26A4 (PDS) mutation; and they were told about the 50% risk of their offspring's suffering from enlarged vestibular aqueduct syndrome. CONCLUSION: Genetic testing with prenatal testing and relevant intervention for the families with deaf-mute patients can be applied to prevent another deaf-mute member from being born.
SLC26A4 genotype, but not cochlear radiologic structure, is correlated with hearing loss in ears with an enlarged vestibular aqueduct. Kelly A King;Byung Yoon Choi;Christopher Zalewski;Anne C Madeo;Ani Manichaikul;Shannon P Pryor;Anne Ferruggiaro;David Eisenman;H Jeffrey Kim;John Niparko;James Thomsen;John A Butman;Andrew J Griffith;Carmen C Brewer. 2009. Laryngoscope. 120. PMID: 19998422

OBJECTIVES/HYPOTHESIS: Identify correlations among SLC26A4 genotype, cochlear structural anomalies, and hearing loss associated with enlargement of the vestibular aqueduct (EVA). STUDY DESIGN: Prospective cohort survey, National Institutes of Health, Clinical Center, a federal biomedical research facility. METHODS: Eighty-three individuals, 11 months to 59 years of age, with EVA in at least one ear were studied. Correlations among pure-tone hearing thresholds, number of mutant SLC26A4 alleles, and the presence of cochlear anomalies detected by computed tomography or magnetic resonance imaging were examined. RESULTS: Linear mixed-effects model indicated significantly poorer hearing in ears with EVA in individuals with two mutant alleles of SLC26A4 than in those with EVA and a single mutant allele (P = .012) or no mutant alleles (P = .007) in this gene. There was no detectable relationship between degree of hearing loss and the presence of structural cochlear anomalies. CONCLUSIONS: The number of mutant alleles of SLC26A4, but not the presence of cochlear anomalies, has a significant association with severity of hearing loss in ears with EVA. This information will be useful for prognostic counseling of patients and families with EVA.
[Rapid detection of the hot spot gene mutations in Chinese patients with nonsyndromic hearing loss by polymerase chain reaction-restrictive fragment length polymorphism]. Juan Zhao;Ling-qian Wu;Yong Feng;Hao Hu;Qian Pan;Le-qin Xiong;De-sheng Liang. 2009. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 26. PMID: 19806571

OBJECTIVE: To develop a rapid genetic diagnosis technique for the patients with hereditary hearing loss by screening hot spots of mutations, namely 235delC of the GJB2 gene, IVS7-2A>G of the SLC26A4 gene, and 1555A>G of mitochondrial 12S rRNA. METHODS: Multiple PCR amplification of the three fragments covering the expected mutations in GJB2, SLC26A4 and 12S were carried out and the amplified products were analyzed by restriction fragment length polymorphism (RFLP). RESULTS: Eighteen homozygous and 18 heterozygous 235delC, 2 homozygous and 13 heterozygous IVS7-2A>G, and 8 homogeneous 1555A>G were detected in the 200 patients with hearing loss. All the results were confirmed by sequencing. The detection rate of the three mutant alleles was 21.7% (71/400 + 8/200 = 0.217) and the genetic diagnosis rate was 14% [(18+2+8)/200 = 0.14]. CONCLUSION: It is a convenient, efficient and economical method to screen the hot spots of mutation in the patient with hereditary hearing loss by using PCR-RFLP.
Mutations in OTOF, CLDN14 & SLC26A4 genes as major causes of hearing impairment in Dhadkai village, Jammu & Kashmir, India. Nishtha Pandey;Tabassum Rashid;Rajeev Jalvi;Meenakshi Sharma;Raghunath Rangasayee;Khurshid Iqbal Andrabi;Anuranjan Anand. 2018. Indian J Med Res. 146. PMID: 29434063

Background & objectives: A high incidence of hearing impairment is reported from the village of Dhadkai in the State of Jammu and Kashmir, India. Prevalence of endogamy in this community suggested a common genetic basis for the disorder. A genetic study was undertaken to ascertain the basis for the high incidence of hearing impairment in this region. Methods: In a two-step approach to identify the causative mutation/s, a whole-genome-based linkage analysis of an extended family of 45 members was carried out, which included 23 affected and 22 unaffected members. Mutational analysis for the candidate deafness genes helped reveal causative mutations in the family. In addition, seven deafness-causing genes, Cx26, SLC26A4, CLDN14, TMPRSS3, TMC1, TMIE and USH1C, were analyzed in smaller families with hearing impairment. Results: In the 45-member extended family, the critical chromosomal region mapped to 2p24-p22.The c.2122C>T (p.R708X) mutation in OTOF in 2p24-p22was identified as being the causal change. Linkage to 2p24-p22 locus was not observed in a particular branch of this extended family. Analysis of seven known deafness-causing genes in this branch revealed a mutation, c.254T>A (p.V85D), in CLDN14. Among seven small families unrelated to the 45-member extended family, hearing loss was attributable to p.R708X in OTOF in three families and to p.V85D in CLDN14 in one family; a new mutation c.1668T>A (p.Y556X) SLC26A4 was identified in two families and the causative change could not be identified in one family. Interpretation & conclusions: This study suggested considerable genetic heterogeneity in the causation of hearing loss in Dhadkai. Recessive mutations were observed in at least three genes causing hearing loss: OTOF (p.R708X), SLC26A4 (p.Y556X) and CLDN14 (p.V85D). Mutation p.R708X appeared to be the major cause of hearing impairment in Dhadkai.
Simultaneous multigene mutation detection in patients with sensorineural hearing loss through a novel diagnostic microarray: a new approach for newborn screening follow-up. Phyllis Gardner;Eneli Oitmaa;Anna Messner;Lies Hoefsloot;Andres Metspalu;Iris Schrijver. 2006. Pediatrics. 118. PMID: 16950989

OBJECTIVE: The advent of universal newborn hearing screening in the United States and other countries, together with the identification of genes involved in the process of hearing, have led to an increase in both the need and opportunity for accurate molecular diagnosis of patients with hearing loss. Deafness and hearing impairment have a genetic cause in at least half the cases. The molecular genetic basis for the majority of these patients remains obscure, however, because of the absence of associated clinical features in approximately 70% (ie, nonsyndromic hearing loss) of patients, genetic heterogeneity, and the lack of molecular genetic tests that can evaluate a large number of mutations across multiple genes. DESIGN: We report on the development of a diagnostic panel with 198 mutations underlying sensorineural (mostly nonsyndromic) hearing loss. This panel, developed on a microarray, is capable of simultaneous evaluation of multiple mutations in 8 genes (GJB2, GJB6, GJB3, GJA1, SLC26A4, SLC26A5 and the mitochondrial genes encoding 12S rRNA and tRNA-Ser[UCN]). RESULTS: The arrayed primer extension array for sensorineural hearing loss is based on a versatile platform technology and is a robust, cost-effective, and easily modifiable assay. Because hearing loss is a major public health concern and common at all ages, this test is suitable for follow-up after newborn hearing screening and for the detection of a genetic etiology in older children and adults. CONCLUSIONS: Comprehensive and relatively inexpensive genetic testing for sensorineural hearing loss will improve medical management for affected individuals and genetic counseling for their families.
Targeted Next-Generation Sequencing Analysis of a Pendred Syndrome-Associated Thyroid Carcinoma. Guo-Xia Tong;Qing Chang;Diane Hamele-Bena;John Carew;Richard S Hoffman;Marina N Nikiforova;Yuri E Nikiforov. 2016. Endocr Pathol. 27. PMID: 26744121

Pendred syndrome is an autosomal recessive disorder characterized by hearing loss and goiter and is caused by bi-allelic mutations (homozygous or compound heterozygous) of the PDS (SLC26A4) gene. The incidence of Pendred syndrome is 7.5-10/100,000 in the general population, and it carries a 1 % risk of developing thyroid carcinoma. Herein, we report a case of a patient with Pendred syndrome who developed a follicular variant of papillary thyroid carcinoma (FVPTC)-that is approximately at an odd of 1/1,000,000. Targeted next-generation sequencing with ThyroSeq v2 was performed on the tumor, and only a TP53 mutation (TP53 p.R175H) was identified. The mutation was limited to the tumor nodule of FVPTC as shown by immunohistochemistry. This report represents the first extensive molecular study of a Pendred syndrome-associated thyroid carcinoma. The evidences support that thyroid carcinomas arising from dyshormonogenetic goiter require additional genetic alteration in addition to the purported thyroid-stimulating hormone (TSH) overstimulation. It is intrigue to note that the mutant p53 is involved in the development of a low-grade malignant thyroid tumor as FVPTC in this patient.
[Prenatal genetic test and clinical guidance for 213 hereditary deaf families]. Ming-yu Han;Yan-ping Lu;Xu-ming Bian;Long-xia Wang;Sha-sha Huang;Guo-jian Wang;Yi Wang;Dong-yang Kang;Xin Zhang;Pu Dai. 2012. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 47. PMID: 22455811

OBJECTIVE: To summarize the workflow, strategy and experience of prenatal genetic test for deafness based on the 6-year clinical practice. METHODS: There were 213 families who received prenatal test from 2005 to 2011. Among the 213 families, 205 families had had one deaf child, including 204 couples with normal hearing and one couple of the deaf husband and normal wife, 8 families including 6 couples with normal hearing and 2 deaf couples, had no child before test. Genomic and mitochondrial DNA of each subject was extracted from whole blood. The etiology and recurrent risks in 212 families were confirmed by means of the genetic test of GJB2, SLC26A4 and mtDNA 12sRNA, but one family carried POU3F4 c.647G > A heterozygous mutation causing X-linked hereditary hearing impairment confirmed by pedigree study. The prenatal test was carried out during the pregnancy of all mothers from 11 to 30 weeks, and the following genetic information and counseling were supplied based on the results. RESULTS: The recurrent risk was 25% in 209 families, including 204 families with one deaf child and 5 families without child, among which all couples were GJB2 or SLC26A4 mutation carriers and deaf children were caused by homozygous or compound GJB2/SLC26A4 mutations; The recurrent risk was 50% in 3 families, the father and his child in one family had compound SLC26A4 mutations and the mother with heterozygous SLC26A4 mutation, the wife had POU3F4 c.647G > A heterozygous mutation in another one family, and the husband with compound SLC26A4 mutations and the wife with mtDNA A1555G mutation and heterozygous SLC26A4 mutation simultaneously happened in the rest one family; The recurrent risk was 100% in one family of the deaf couple who were both found to carry homozygous or compound GJB2 mutations, and the deaf wife got pregnant by artificial insemination with the sperm from the local Human Sperm Bank. 226 times of prenatal test were applied in all 213 families that 11 families of them received prenatal test twice, and one family received three times. 46 times of prenatal testing showed that the fetuses carried parental mutations simultaneously or the same mutations with probands; while 180 times of prenatal test showed that the fetuses carried only one parental mutation or did not carry any mutation from parents. The following visit showed that all of these 180 families had given birth to babies who were all revealed to have normal hearing by new born hearing screening test. CONCLUSIONS: Prenatal diagnosis for deafness assisted by genetic test can provide efficient information about offspring's hearing condition, and the normative workflow and precise strategy highly guarantee the safe and favorable implementation of prenatal diagnosis.
CT-scans of cochlear implant patients with characteristics of Pendred syndrome. Sebastian Roesch;Gerhard Moser;Gerd Rasp;Miklós Tóth. 2014. Cell Physiol Biochem. 32. PMID: 24429823

BACKGROUND: Sensorineural hearing loss (SNHL) in newborns is estimated with an incidence around 1:10,000 per year and is divided into syndromic and non-syndromic forms. In case of present retrocochlear function' cochlear implantation allows speech and cognitive development in affected children, comparable to that of normal hearing children. Pathogenesis of SNHL remains unclear in many cases. Imaging of the temporal bone, such as computed tomography (CT) and magnetic resonance imaging (MRI), can reveal conspicuous findings, e.g. enlarged vestibular aqueduct (EVA) and Mondini malformation (MM) of the cochlea. These malformations can be a clinical sign for Pendred syndrome. METHODS: We screened CT scans of 75 cochlear implant patients for EVA and MM. RESULTS: Six patients were observed to have either EVA alone (n=3), or MM alone (n=2), or a combination of both (n=1). Further malformations of the temporal bone could be found within the whole group, as well. CONCLUSION: Our results confirm the general opinion on EVA and MM, being commonly found in patients with SNHL. A possible association with Pendred syndrome needs to be confirmed by genetic investigations with search for mutations in the SLC26A4 gene and further clinical tests, such as Perchlorate test for surveillance of thyroid function.
A study of deafness-related genetic mutations as a basis for strategies to prevent hereditary hearing loss in Hebei, China. Junzhen Zhu;Qinying Cao;Ning Zhang;Jun Ge;Donglan Sun;Qingqi Feng. 2015. Intractable Rare Dis Res. 4. PMID: 26361564

Hearing loss is the most common sensory disorder, and at least 50% of cases are due to a genetic etiology. Two-thirds of individuals with congenital deafness are nonsyndromic. Among the nonsyndromic forms, the large majority are monogenic autosomal recessive traits. The current work summarizes mutations in the GJB2, SLC26A4, 12SrRNA, and GJB3 and their prevalence in 318 students with autosomal recessive nonsyndromic hearing loss at schools for the deaf or special needs schools in 9 cities in Hebei Province, China. Deafness gene mutations were identified in 137 students via a gene chip, time-of-flight mass spectrometry, fluorescence quantitative PCR, and gene sequencing. Mutations were detected at a rate of 43.08%. A homozygous mutation of the GJB2 gene was found in 16 students (5.03%), a heterozygous mutation of that gene was found in 38 (11.95%), a homozygous mutation of the SLC26A4 gene was found in 22 (6.92%), a heterozygous mutation of that gene was found in 59 (18.55%), and a heterozygous mutation of the mitochondrial 12SrRNA gene was found in 2 (0.63%). In addition, there were 15 families in which a student's parents had normal hearing. Compound heterozygous mutations of the GJB2 gene were found in 3 families (20%) and mutations of the SLC26A4 gene were found in 9 (60%). Thus, this study has provided a molecular diagnostic basis for the causes of deafness, and this study has also provided a scientific basis for the early prevention of and intervention in deafness.
Mono-allelic mutations of SLC26A4 is over-presented in deaf patients with non-syndromic enlarged vestibular aqueduct. Xiuhong Pang;Yongchuan Chai;Penghui Chen;Longxia He;Xiaowen Wang;Hao Wu;Tao Yang. 2015. Int J Pediatr Otorhinolaryngol. 79. PMID: 26100058

OBJECTIVES: Recessive mutations of SLC26A4 are the major cause of hearing impairment associated with enlarged vestibular aqueduct (EVA). In a significant percentage of non-syndromic EVA patients, however, only mono-allelic mutations of SLC26A4 can be identified. In this study, we aimed to evaluate whether presence of mono-allelic mutations of SLC26A4 in those patients was coincidental or etiologically associated with the disorder. METHODS: The exons and flanking splicing sites of SLC26A4 were sequenced in 150 Chinese Han deaf probands with non-syndromic EVA. c.919-2A >G and p.H723R, two frequent mutations of SLC26A4 in Chinese Hans, were screened by an allele-specific PCR-based array in 3056 ethnically-matched normal hearing controls. The frequency of mono-allelic c.919-2A >G and p.H723R mutations was determined in each group. The statistical significance of the difference was analyzed by Fisher's exact test. RESULTS: Bi-allelic, mono-allelic and no mutation of SLC26A4 were detected in 98 (65.3%), 18 (12%) and 34 (22.67%) deaf probands with non-syndromic EVA, respectively. The frequency of mono-allelic c.919-2A >G and p.H723R mutations were significantly higher in the 150 deaf probands with non-syndromic EVA (8.67%) than in the 3056 normal hearing controls (1.4%, P=1.8×10(-6)). CONCLUSION: Presence of mono-allelic mutations of SLC26A4 in non-syndromic EVA patients is etiologically associated with this disorder. Additional genetic or environmental causes may be present in those patients and demand further investigation and consideration during the genetic diagnosis and counseling.
SLC26A4 gene polymorphism and late-onset Alzheimer's disease in a Han Chinese population from Qingdao, China. Jifang Zhang;Yantuan Li. 2013. Neural Regen Res. 8. PMID: 25206722

In a recent genome-wide association study, the SLC26A4 gene rs2072064 polymorphism was found to be associated with late-onset Alzheimer's disease in Caucasians. Here, we investigated this association in a large Northern Han Chinese cohort consisting of 599 sporadic late-onset Alzheimer's disease patients and 598 healthy controls matched for sex and age in a Northern Han Chinese population from Qingdao, China. Genotyping by the polymerase chain reaction-ligase detection reaction revealed that there were significant differences in the genotype (P = 0.017) and allele (P = 0.007) frequencies of the rs2072064 polymorphism between late-onset Alzheimer's disease patients and controls. The A allele of this polymorphism was significantly associated with a reduced risk of late-onset Alzheimer's disease (odds ratio (OR) = 0.792, 95% confidence interval (CI) = 0.670-0.937, P = 0.007). When the data were stratified by the apolipoprotein E ε4 status, there was a significant difference only among apolipoprotein E ε4 non-carriers (genotypic P = 0.001, allelic P = 0.001). Furthermore, the association between rs2072064 and late-onset Alzheimer's disease remained significant by logistic regression analysis after adjustment for age, gender, and the apolipoprotein E ε4 carrier status (dominant model: OR = 0.787, 95% CI = 0.619-1.000, P = 0.050; recessive model: OR = 0.655, 95% CI = 0.448-0.959, P = 0.030; additive model: OR = 0.792, 95% CI = 0.661-0.950, P = 0.012). These findings suggest that SLC26A4 is a susceptibility gene for late-onset Alzheimer's disease in a Northern Han Chinese population from the Qingdao area.
[Prenatal genetic counseling and instruction for deaf families by genetic test]. Ming-yu Han;Sha-sha Huang;Guo-jian Wang;Yong-yi Yuan;Dong-yang Kang;Xin Zhang;Pu Dai. 2012. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 46. PMID: 22335977

OBJECTIVE: Analyzed the molecular pathogenesis of probands by means of genetic test and assisted the local Family Planning Institute by providing prenatal genetic counseling and instruction for deaf families who eager to have more baby. METHODS: Total of forty-three deaf families were recruited by two institutes for family planning from Guangzhou and Weifang. Forty-two families had one deaf child with normal hearing parents. One family was that parents and their child were all deaf. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) 12SrRNA were firstly performed in probands and their parents, following medical history, physical examination, auditory test and CT scan of temporal bone were completed. And then the genetic information and instruction were provided to each deaf family. RESULTS: Fifteen of these 43 families had positive results of genetic test. In fifteen families, one family was confirmed that the parents and their child all carried homozygous GJB2 mutations and the recurrence risk was 100%. Twelve families were confirmed that the probands carried homozygous/compound GJB2 or SLC26A4 mutations while their parents were GJB2 or SLC26A4 carriers, and the recurrence risk was 25%. One family was confirmed that the proband, diagnosed with enlarged vestibular aqueduct syndrome (EVAS) by CT scan, carried heterozygous SLC26A4 mutation from the mother, and the recurrence risk was still 25% based on the hereditary pattern of EVAS although another SLC26A4 mutation from the father was not found. One family was confirmed that the proband carried a heterozygous GJB2 mutation from the mother and the possibility to be GJB2 carrier for offsprings was 50%. The rest 28 families were that all probands and their parents did not carry GJB2, SLC26A4 and mtDNA 12SrRNA pathological mutation. CONCLUSIONS: Genetic testing can provide more accurate and useful prenatal genetic counseling and instruction to deaf families. Meanwhile, it is an ideal way to develop a cooperative relationship with the institute for family planning.
Heterogeneity of Hereditary Hearing Loss in Iran: a Comprehensive Review. Maryam Beheshtian;Mojgan Babanejad;Hela Azaiez;Niloofar Bazazzadegan;Diana Kolbe;Christina Sloan-Heggen;Sanaz Arzhangi;Kevin Booth;Marzieh Mohseni;Kathy Frees;Mohammad Hossein Azizi;Ahmad Daneshi;Mohammad Farhadi;Kimia Kahrizi;Richard Jh Smith;Hossein Najmabadi. 2016. Arch Iran Med. 19. PMID: 27743438

A significant contribution to the causes of hereditary hearing impairment comes from genetic factors. More than 120 genes and 160 loci have been identified to be involved in hearing impairment. Given that consanguine populations are more vulnerable to most inherited diseases, such as hereditary hearing loss (HHL), the genetic picture of HHL among the Iranian population, which consists of at least eight ethnic subgroups with a high rate of intermarriage, is expected to be highly heterogeneous. Using an electronic literature review through various databases such as PubMed, MEDLINE, and Scopus, we review the current picture of HHL in Iran. In this review, we present more than 39 deafness genes reported to cause non-syndromic HHL in Iran, of which the most prevalent causative genes include GJB2, SLC26A4, MYO15A, and MYO7A. In addition, we highlight some of the more common genetic causes of syndromic HHL in Iran. These results are of importance for further investigation and elucidation of the molecular basis of HHL in Iran and also for developing a national diagnostic tool tailored to the Iranian context enabling early and efficient diagnosis of hereditary hearing impairment.
SNaPshot reveals high mutation and carrier frequencies of 15 common hearing loss mutants in a Chinese newborn cohort. Y Chen;Y Cao;H-B Li;J Mao;M-J Liu;Y-H Liu;B-J Wang;D Jiang;Q Zhu;Y Ding;W Wang;H Li;K W Choy. 2014. Clin Genet. 87. PMID: 24989646

Genetic causes account for more than half of congenital hearing loss cases. The most frequent mutations found in non-syndromic hearing loss patients occur in GJB2 and SLC26A4. Mitochondrial genome mutations are also prevalent. However, the frequency of common hearing loss mutations in the Chinese population has not yet been well estimated. Here, we implemented the SNaPshot genotyping method to investigate the carrier frequency of 15 commonly reported hearing loss mutations in GJB2, SLC26A4 and the mitochondrial genome based on a cohort of 5800 neonates in China. Up to 15.9% (923/5800) of the newborns carry at least one mutant allele. The top three were GJB2-c.109G>A, GJB2-c.235delC, and SLC26A4-c.919A>G, with notably high carrier frequencies of 1/10, 1/53 and 1/62 respectively, and mt-7444G>A with 1/141 was the most frequent allele in the mitochondrial genome. In this cohort, 0.48% (28/5800) of neonates were genetically diagnosed with hearing loss, from which seven cases failed an OAE test. This is the first epidemiological study of non-syndromic hearing loss in Chinese newborns indicating a notably high carrier frequency (1 per 6.3 newborns) among these 15 mutant alleles. Our carrier frequency data also aid in effective risk assessment and genetic counseling for hearing loss patients in the Chinese population.
[Screening of SLC26A4 (PDS) gene mutation in cochlear implant recipients with inner ear malformation]. Dong-ye Chen;Xiao-wei Chen;Xin Jin;Jin Zuo;Chao-gang Wei;Ke-li Cao;Fu-de Fang. 2008. Zhonghua Yi Xue Za Zhi. 87. PMID: 18167283

OBJECTIVE: To determine the prevalence of SLC26A4 (PDS) gene mutations in cochlear implant recipients with inner ear malformation, and the correlation between SLC26A4 (PDS) gene mutation and inner ear malformation and intra-operative testing of the electrically evoked auditory nerve compound action potentials (ECAP). METHODS: Peripheral blood samples were collected from 48 cochlear implant recipients with temporal bone malformation and 50 healthy controls. Genomic DNA was extracted from the blood; PCR and direct sequencing were used to detect the mutations of SLC26A4 (PDS) gene. During the implantation of artificial cochlea the 48 recipients underwent intraoperative neural response telemetry (NRT) to measure the electrically evoked auditory nerve compound action potentials (ECAP). RESULTS: SLC26A4 (PDS) mutations were detected in 70.3% (26/37) of the patients with enlarged vestibular aqueduct (EVA), and 18.2% (2/11) of the patients with other malformations of inner ear. Fifteen different mutations were identified, 8 of which had never been previously reported. The IVS7-2A>G mutation was the most prevalent mutation of SLC26A4 (PDS) gene, accounting for 45.9% (17/37) in the EVA patients. No association was detected between SLC26A4 mutation and ECAP. CONCLUSION: Mutations in the SLC26A4 (PDS) gene is a major cause of EVA, with IVS7-2A>G as the most common mutation form.
Prevalence and range of GJB2 and SLC26A4 mutations in patients with autosomal recessive non‑syndromic hearing loss. Hua Jiang;Jia Chen;Xin-Ji Shan;Ying Li;Jian-Guo He;Bei-Bei Yang. 2014. Mol Med Rep. 10. PMID: 24737404

The frequency and distribution of genetic mutations that cause deafness differ significantly according to ethnic group and region. Zhejiang is a province in the southeast of China, with an exceptional racial composition of the population caused by mass migration in ancient China. The purpose of the present study was to investigate the prevalence and spectrum of gap junction‑β2 (GJB2), solute carrier family 26 (anion exchanger) member 4 (SLC26A4) and GJB3 mutations in patients with autosomal recessive non‑syndromic hearing loss (ARNHL) in this area. A total of 176 unrelated pediatric patients with ARNHL were enrolled in the study. A genomic DNA sample was extracted from the peripheral blood. Polymerase chain reaction was employed, and the products were sequenced to screen for mutations in GJB2. In addition, a SNaPshot sequencing method was utilized to detect four hotspot mutations in SLC26A4 (IVS7‑2A>G and c.2168A>G) and GJB3 (c.538C>T and c.547G>A). All patients were subjected to a temporal bone computed tomography scan to identify enlarged vestibular aqueducts (EVA). In total, 14 different mutations, including two new mutations (p.W44L and p.D66N) of GJB2, were detected. The most common pathogenic mutation of GJB2 was c.235delC (15.1%), followed by c.176_191del16 (1.7%), c.299_300delAT (1.7%), c.508_511dup (0.85%) and c.35delG (0.28%) of the total alleles. Mutation analysis of SLC26A4 demonstrated that 13.6% (24/176) of patients carried at least one mutant allele. The patients with EVA (84.2%) had SLC26A4 mutations, and 31% had homozygous mutations. Only one patient carried a heterozygous mutation of GJB3 (c.538C>T). Compared with the other regions of China, in the present population cohort, the prevalence and spectrum of mutations in GJB2 was unique, and in patients with EVA the frequency of a homozygous mutation in SLC26A4 was significantly lower. These findings may be of benefit in genetic counseling and risk assessment for families from this area of China.
GJB2, SLC26A4 and mitochondrial DNA A1555G mutations in prelingual deafness in Northern Chinese subjects. Yu-Fen Guo;Xiao-Wen Liu;Jing Guan;Ming-Kun Han;Da-Yong Wang;Ya-Li Zhao;Shao-Qi Rao;Qiu-Ju Wang. 2008. Acta Otolaryngol. 128. PMID: 18274916

CONCLUSION: This genetic epidemiological study demonstrated that 26.65% of the prelingual deafness in Northern Chinese patients can be detected at younger ages by genetic testing of three common hearing loss genes (GJB2, SLC26A4 and mtDNA A1555G), and thus, early intervention measures could be undertaken to help them in language acquisition. OBJECTIVES: The GJB2, SLC26A4 and mtDNA A1555G mutations are the prevalent causes of prelingual deafness worldwide. Numerous studies have revealed that the forms and frequencies of the mutations in the three genes are largely dependent on the ethnic or geographic origins. Hence, this study aimed to characterize the mutation profiles of the three genes in prelingual deafness in Northern Chinese patients. SUBECTS AND METHODS: An investigation of 514 patients with prelingual deafness and 117 controls with normal hearing was conducted. Bidirectional sequencing (or enzyme digestion) was applied to identify sequence variations. RESULTS: This study revealed that 26.65% patients had two mutated alleles (homozygote or compound heterozygote) of GJB2 (9.14%) or SLC26A4 (8.95%) and/or an mtDNA A1555G (8.56%) mutation. In detail, 19.26% patients carried GJB2 mutations including 10.12% single mutant carriers. 235delC was the most common type, making up 69.18% of all mutants for GJB2. The mutant carrier rate for SLC26A4 was 15.2%, including 6.23% single mutant carriers. The two most common types (IVS7-2A > G and H723R) accounted for 51.61% and 33.06% mutations, respectively. Forty-five patients had mtDNA A1555G, giving a frequency of 8.75%. In the control group with normal hearing, 2.56%, 1.71% and 0% of the subjects carried a single mutant for GJB2, SLC26A4 and mtDNA A1555G, respectively.
Genetic mutations in non-syndromic deafness patients of Uyghur and Han Chinese ethnicities in Xinjiang, China: a comparative study. Yu Chen;Mayila Tudi;Jie Sun;Chao He;Hong-Li Lu;Qing Shang;Di Jiang;Pilidong Kuyaxi;Bin Hu;Hua Zhang. 2011. J Transl Med. 9. PMID: 21917135

BACKGROUND: The deafness-associated gene mutation profile varies greatly among regions and races. Due to the multi-ethnic coalition of over one thousand years, non-syndromic deafness (NSD) patients of Uyghur ethnicity may exhibit a unique deafness-associated gene mutation spectrum as compared to Han Chinese deaf population. METHODS: In order to characterize nine loci of four deafness-associated genes of Uyghur NSD patients in comparison with Chinese Han deaf population, NSD patients (n = 350) were enrolled, including Uyghur (n = 199) and Han Chinese (n = 151). Following the history taking, blood samples were collected for DNA extraction. DNA microarray was performed on nine loci of four deafness-associated genes, including 35delG, 176-191del16, 235delC, 299-300delAT, 538C > T, 1555A > G, 1494C > T, 2168A > G, and IVS7-2A > G. The samples that showed the absence of both wild and mutant probe signals were tested for further DNA sequencing analysis. RESULTS: The mutations in the nine loci of prevalent deafness-associated genes were detected in 13.06% of Uyghur NSD patients and 32.45% of Han Chinese patients (P < 0.05), respectively. GJB2 mutation was detected in 9.05% of Uyghur patients and 16.56% of Han Chinese patients (P > 0.05), respectively. 235delC was the hotspot mutation region in NSD patients of the two ethnicities, whereas 35delG was the mutation hotspot in Uyghur patients. 187delG mutation was detected for the first time in Uyghur NSD patients and considered as an unreported pathological variant of GJB2. SLC26A4 mutation was found in 2.01% of Uyghur patients and 14.57% of Han Chinese patients (P < 0.05), respectively. The frequencies of mtDNA 12S rRNA mutation in Uyghur and Han Chinese patients were 2.01% and 2.65% (P > 0.05), respectively. The NSD patients exhibited a low frequency of GJB3 mutation regardless of ethnicity. CONCLUSION: Prevalent deafness-associated gene mutations in the nine loci studied were less frequently detected in Uyghur NSD patients than in Han Chinese patients. GJB2 was the most common mutant gene in the two ethnicities, whilst the two ethnicities differed substantially in hotspot mutations. A low-frequency SLC26A4 mutation was detected in Uyghur NSD patients. Uyghur NSD patients differed significantly from Han Chinese patients in gene mutation profile.
Mutation Analysis of the Common Deafness Genes in Patients with Nonsyndromic Hearing Loss in Linyi by SNPscan Assay. Fengguo Zhang;Yun Xiao;Lei Xu;Xue Zhang;Guodong Zhang;Jianfeng Li;Huaiqing Lv;Xiaohui Bai;Haibo Wang. 2016. Biomed Res Int. 2016. PMID: 27247933

Hearing loss is a common sensory disorder, and at least 50% of cases are due to a genetic etiology. Although hundreds of genes have been reported to be associated with nonsyndromic hearing loss, GJB2, SLC26A4, and mtDNA12SrRNA are the major contributors. However, the mutation spectrum of these common deafness genes varies among different ethnic groups. The present work summarized mutations in these three genes and their prevalence in 339 patients with nonsyndromic hearing loss at three different special education schools and one children's hospital in Linyi, China. A new multiplex genetic screening system "SNPscan assay" was employed to detect a total of 115 mutations of the above three genes. Finally, 48.67% of the patients were identified with hereditary hearing loss caused by mutations in GJB2, SLC26A4, and mtDNA12SrRNA. The carrying rate of mutations in the three genes was 37.76%, 19.75%, and 4.72%, respectively. This mutation profile in our study is distinct from other parts of China, with high mutation rate of GJB2 suggesting a unique mutation spectrum in this area.
Nuclear and mitochondrial genes mutated in nonsyndromic impaired hearing. Josef Finsterer;Johannes Fellinger. 2005. Int J Pediatr Otorhinolaryngol. 69. PMID: 15850684

Half of the cases with congenital impaired hearing are hereditary (HIH). HIH may occur as part of a multisystem disease (syndromic HIH) or as disorder restricted to the ear and vestibular system (nonsyndromic HIH). Since nonsyndromic HIH is almost exclusively caused by cochlear defects, affected patients suffer from sensorineural hearing loss. One percent of the total human genes, i.e. 300-500, are estimated to cause syndromic and nonsyndromic HIH. Of these, approximately 120 genes have been cloned thus far, approximately 80 for syndromic HIH and 42 for nonsyndromic HIH. In the majority of the cases, HIH manifests before (prelingual), and rarely after (postlingual) development of speech. Prelingual, nonsyndromic HIH follows an autosomal recessive trait (75-80%), an autosomal dominant trait (10-20%), an X-chromosomal, recessive trait (1-5%), or is maternally inherited (0-20%). Postlingual nonsyndromic HIH usually follows an autosomal dominant trait. Of the 41 mutated genes that cause nonsyndromic HIH, 15 cause autosomal dominant HIH, 15 autosomal recessive HIH, 6 both autosomal dominant and recessive HIH, 2 X-linked HIH, and 3 maternally inherited HIH. Mutations in a single gene may not only cause autosomal dominant, nonsyndromic HIH, but also autosomal recessive, nonsyndromic HIH (GJB2, GJB6, MYO6, MYO7A, TECTA, TMC1), and even syndromic HIH (CDH23, COL11A2, DPP1, DSPP, GJB2, GJB3, GJB6, MYO7A, MYH9, PCDH15, POU3F4, SLC26A4, USH1C, WFS1). Different mutations in the same gene may cause variable phenotypes within a family and between families. Most cases of recessive HIH result from mutations in a single locus, but an increasing number of disorders is recognized, in which mutations in two different genes (GJB2/GJB6, TECTA/KCNQ4), or two different mutations in a single allele (GJB2) are involved. This overview focuses on recent advances in the genetic background of nonsyndromic HIH.
Genetic testing for sporadic hearing loss using targeted massively parallel sequencing identifies 10 novel mutations. X Gu;L Guo;H Ji;S Sun;R Chai;L Wang;H Li. 2014. Clin Genet. 87. PMID: 24853665

The genetic heterogeneity of non-syndromic hearing loss (NSHL) has hampered the identification of its pathogenic mutations. Several recent studies applied targeted genome enrichment (TGE) and massively parallel sequencing (MPS) to simultaneously screen a large set of known hearing loss (HL) genes. However, most of these studies were focused on familial cases. To evaluate the effectiveness of TGE and MPS on screening sporadic NSHL patients, we recruited 63 unrelated sporadic NSHL probands, who had various levels of HL and were excluded for mutations in GJB2, MT-RNR1, and SLC26A4 genes. TGE and MPS were performed on 131 known HL genes using the Human Deafness Panel oto-DA3 (Otogenetics Corporation., Norcross, GA). We identified 14 pathogenic variants in STRC, CATSPER2, USH2A, TRIOBP, MYO15A, GPR98, and TMPRSS3 genes in eight patients (diagnostic rate = 12.7%). Among these variants, 10 were novel compound heterozygous mutations. The identification of pathogenic mutations could predict the progression of HL, and guide diagnosis and treatment of the disease.
[Genetic counseling and instruction of marriage for deaf young people: study of 115 cases]. Bing Han;Pu Dai;Guo-Jian Wang;Yong-Yi Yuan;Qi Li;Xin Zhang;Dong-Yang Kang;Dong-Yi Han. 2009. Zhonghua Yi Xue Za Zhi. 89. PMID: 19595061

OBJECTIVE: To invesigate the molecular pathogenesis of deafness among the youth by means of genetic testing so as to provide pre-marriage genetic counseling and instruction for the deaf youth. METHODS: 217 deaf young people, 126 males and 91 females, aged 18.9 (16 - 26), from Yunnan and Guizhou provinces, underwent history taking, auditory testing, and collection of peripheral blood samples. Genomic DNA and mitochondrial DNA were extracted to undergo sequence analysis of the entire gene GJB2, common point mutation of SLC26A4 gene, and mutation of mtDNA A1555G. Genetic prediction and marriage instruction were provided to each subject based on these results. RESULTS: Twenty-three of the 117 persons (10.5%), 13 males and 10 females, were mtDNA A1555G mutation carriers and they were instructed that they, their maternal relatives, and the offspring of the female carriers, should they be born, should strictly avoid the administration of amino glycoside antibiotics. Twenty eight of the 115 persons (12.9%), were confirmed to carry homozygous or compound GJB2 mutations, 5 individuals (2.3%) carried heterozygous GJB2 mutation, 19 (8.8%) carried homozygous or compound SLC26A4 mutations, and one (0.5%) carried heterozygous SLC26A4 mutation. The suggestion for them was to avoid getting married with deaf partners caused by the same deaf gene or with individuals carrying mutations in the same deaf gene. Meanwhile, suggestions such as avoiding aggressive exercises and head injury were provided to the deaf young people with SLC26A4 mutations. CONCLUSION: Genetic testing can provide more accurate and useful genetic counseling and instruction to deaf young people for their partner selection and eugenics.
Cordblood-Based High-Throughput Screening for Deafness Gene of 646 Newborns in Jinan Area of China. Shou-Xia Li;Ding-Li Chen;Su-Bin Zhao;Li-Li Guo;Hai-Qin Feng;Xiao-Fang Zhang;Li-Li Ping;Zhi-Ming Yang;Cai-Xia Sun;Gen-Dong Yao. 2015. Clin Exp Otorhinolaryngol. 8. PMID: 26330914

OBJECTIVES: Infants with slight/mild or late-onset hearing impairment might be missed in universal newborn hearing screening (UNHS). We identified the mutation hot spot of common deaf gene in the newborns in Jinan area population by screening the mutation spot with neonate cord blood, in order to make clear whether the neonate cord blood for screening is feasible. METHODS: Six hundred and forty-six newborns were subjected to both UNHS and genetic screening for deafness by using neonate cord blood. The newborn genetic screening targeted four deafness-associated genes, which were commonly found in the Chinese population including gap junction beta-2 protein (GJB2), gap junction beta-3 protein (GJB3), solute carrier family 26 member 4 (SLC26A4), and mtDNA 12S rRNA. The most common 20 spot mutations in 4 deaf genes were detected by MassARRAY iPLEX platform and mitochondrial 12S rRNA A1555G and C1494T mutations were sequenced using Sanger sequencing. RESULTS: Among the 646 newborns, 635 cases passed the UNHS and the other 11 cases (1.7%) did not. Of the 11 failures, two cases were found to carry homozygous GJB2 p.R143W pathogenic mutation, one case was found to have heterozygous GJB2 235delC mutation, and another one case carried heterozygous GJB3 p.R180X pathogenic mutation. Six hundred and thirty-five babies passed the newborn hearing screening, in which 25 babies were identified to carry pathogenic mutations, including 12 heterozygotes (1.9%) for GJB2 235delC, eight heterozygotes (1.3%) for SLC26A4 IVS7-2A>G, one heterozygote (0.2%) for p.R409H, two homozygotes (0.3%) for m.1494C>T, and two homozygotes (0.3%) for m.1555A>G. CONCLUSION: Newborn genetic screening through the umbilical cord blood for common deafness-associated mutations may identify carriers sensitive to aminoglycoside antibiotic, and can effectively prevent or delay hearing loss occurs.
Genetic Predisposition to Sporadic Congenital Hearing Loss in a Pediatric Population. Jinsei Jung;Joon Suk Lee;Kyeong Jee Cho;Seyoung Yu;Joo-Heon Yoon;Heon Yung Gee;Jae Young Choi. 2017. Sci Rep. 7. PMID: 28383030

Discriminating between inherited and non-inherited sporadic hearing loss is challenging. Here, we attempted to delineate genetic inheritance in simplex cases of severe-to-profound congenital hearing loss in Korean children. Variations in SLC26A4 and GJB2 in 28 children with bilateral severe-to-profound non-syndromic hearing loss (NSHL) without familial history were analyzed using Sanger sequencing. Genetic analysis of individuals without mutations in SLC26A4 and GJB2 was performed by whole exome sequencing (WES). Bi-allelic mutations in SLC26A4 and GJB2 were identified in 12 and 3 subjects, respectively. Of the 13 individuals without mutations in SLC26A4 and GJB2, 2 and 1 carried compound heterozygous mutations in MYO15A and CDH23, respectively. Thus, 64.3% (18/28) of individuals with NSHL were determined to be genetically predisposed. Individuals with sporadic severe-to-profound NSHL were found to mostly exhibit an autosomal recessive inheritance pattern. Novel causative candidate genes for NSHL were identified by analysis of WES data of 10 families without mutations in known causative genes. Bi-allelic mutations predisposing to NSHL were identified in 64.3% of subjects with sporadic severe-to-profound NSHL. Given that several causative genes for NSHL are still unidentified, genetic inheritance of sporadic congenital hearing loss could be more common than that indicated by our results.
Strategy for the customized mass screening of genetic sensorineural hearing loss in koreans. Mun Young Chang;Byung Yoon Choi. 2014. Korean J Audiol. 18. PMID: 25279224

Hearing loss is one of the most common sensorineural disorder. More than half of congenital bilateral profound deafness cases have been estimated to be attributed to genetic cause. Identification of genetic cause can provide valuable information. We developed new diagnostic strategy combining phenotype-driven candidate gene approach and targeted exome sequencing to find out the causative mutation of hearing loss. The causative mutation detection rates of this strategy were 78.1% and 54.8% in Korean multiplex families and sporadic severe to profound hearing loss families, respectively. The most frequent causative genes of Korean multiplex families were SLC26A4 and POU3F4. The other causative genes were MRNR1, WFS1, COCH, TECTA, MYO6, COL11A2, EYA4, GJB3, OTOF, STRC, MYO3A, and GJB2. The most frequent causative gene of Korean sporadic severe to profound hearing loss families was SLC26A4 followed by GJB2, CHD7, and CDH23. Based upon the results, the value of this strategy as a diagnostic tool seems to be promising. Although whole genome and exome sequencing have advanced as the development of next-generation sequencing, this new strategy could be a good screening and diagnostic tool to find the causative mutations.
Mutation analysis of SLC26A4 in mainland Chinese patients with enlarged vestibular aqueduct. Samuel Reyes;Guojian Wang;Xiaomei Ouyang;Bing Han;Li Lin Du;Hui Jun Yuan;Denise Yan;Pu Dai;Xue-Zhong Liu. 2009. Otolaryngol Head Neck Surg. 141. PMID: 19786220

OBJECTIVE: We have characterized the spectrum of SLC26A4 mutations and clinical features in a population of mainland Chinese patients with nonsyndromic sensorineural hearing loss (SNHL) and enlarged vestibular aqueduct (EVA). STUDY DESIGN: Cross-sectional clinical genetic study. SETTING: Tertiary care outpatient otolaryngology clinic. METHODS: A total of 32 subjects identified with bilateral EVA using high-resolution CT were screened for mutations in SLC26A4 by denaturing high-performance liquid chromatography and direct sequencing methods. RESULTS: A total of 13 different mutations were identified in the SLC26A4 gene, five of which are novel. A total of 88 percent of the patients harbored biallelic mutations, 11 patients were homozygotes, and 17 were compound heterozygotes. Four patients were found to carry a single SLC26A4 mutation. The IVS7-2A>G mutation was the most frequent, accounting for 60 percent of the mutant alleles. We have not found any correlations between the type of SLC26A4 mutations and the type, degree, and progression of hearing loss. There are significant proportions of patients with asymmetric (26%), progressive (32%), or fluctuating hearing loss (21%). CONCLUSION: Our data confirm the high prevalence of SLC26A4 mutations in Chinese patients with SNHL and EVA. We could not establish any relationship between genotype and phenotype. However, the high incidence of asymmetric, progressive, and fluctuating hearing loss found in the current study indicates that patients with those features should be routinely screened for SLC26A4 mutation in addition to diagnosis of EVA using CT or MRI.
Two Compound Heterozygous Were Identified in SLC26A4 Gene in Two Chinese Families With Enlarged Vestibular Aqueduct. Yongbo Yu;Yang Yang;Jie Lu;Yaqiong Jin;Yeran Yang;Enyu Hong;Jin Shi;Feng Chen;Shujing Han;Ping Chu;Yongli Guo;Xin Ni. None. Clin Exp Otorhinolaryngol. . PMID: 30086623

Objectives: To investigate the genetic causes of hearing loss with enlarged vestibular aqueduct (EVA) in two children from unrelated two Chinese families. Methods: Sanger sequencing of all coding exons in SLC26A4 (encoding Pendrin protein) was performed on the two patients, their sibling and parents respectively. To predict and visualize the potential functional outcome of the novel variant, model building, structure analysis, and in silico analysis were further conducted. Results: The results showed that the proband from family I harbored a compound heterozygote of SLC26A4 c.1174A>T (p.N392Y) mutation and c.1181delTCT (p.F394del) variant in exon 10, potentially altering Pendrin protein structure. In family II, the proband was identified in compound heterozygosity with a known mutation of c.919-2A>G in the splice site of intron 7 and a novel mutation of c.1023insC in exon 9, which results in a frameshift and translational termination, consequently leading to truncated Pendrin protein. Sequence homology analysis indicated that all the mutations localized at high conservation sites, which emphasized the significance of these mutations on Pendrin spatial organization and function. Conclusion: In summary, this study revealed two compound heterozygous mutations (c.1174A>T/c.1181delTCT; c.919- 2A>G/c.1023insC) in Pendrin protein, which might account for the deafness of the two probands clinically diagnosed with EVA. Thus this study contributes to improve understanding of the causes of hearing loss associated with EVA and develop a more scientific screening strategy for deafness.
Hearing loss associated with an unusual mutation combination in the gap junction beta 2 (GJB2) gene in a Chinese family. Aiping Huang;Yongyi Yuan;Naichao Duan;Xinxia Jiang;Baoshan Wang;Yanping Liu;Dongyang Kang;Xin Zhang;Qingwen Zhu;Pu Dai. 2014. Int J Pediatr Otorhinolaryngol. 78. PMID: 24503448

OBJECTIVE: To assess the molecular etiology of nonsyndromic sensorineural hearing loss (NSHL) in members of an affected Chinese family. METHODS: Common hearing-related genes including gap junction beta 2 (GJB2), SLC26A4, mitochondrial DNA 12S rRNA, GJB3 and GJB6 were examined in a family consisting of a normal hearing father, an NSHL-affected mother, one normal-hearing child and three NSHL-affected children. Specific primers were used in polymerase chain reactions to amplify the coding regions of the above genes from the peripheral blood DNA from each family member, and the genes were analyzed by direct sequencing. The subjects were evaluated for phenotypic characterization using audiometric testing and radiological examination of the inner ear. RESULTS: Pathogenic mutations in the GJB2 gene were identified. The affected mother showed a heterozygous G→A transition at nucleotide 232, resulting in an alanine to threonine substitution at codon 78 (p.A78T), and the normal hearing father had a c.35insG insertion mutation. The three affected children displayed heterozygosity for the GJB2 mutations, showing a previously unreported combination of c.35insG and c.232G>A. CONCLUSIONS: The GJB2 mutations account for a significant proportion of NSHL in affected individuals worldwide. Genetic and audiological data analysis of a Chinese family with NSHL revealed a novel c.35insG/c.232G>A compound heterozygous state. Our results highlight the complexity of the GJB2 genotypes and phenotypes.
Genetic causes of moderate to severe hearing loss point to modifiers. Sadaf Naz;Ayesha Imtiaz;Ghulam Mujtaba;Azra Maqsood;Rasheeda Bashir;Ihtisham Bukhari;Muhammad R Khan;Memoona Ramzan;Amara Fatima;Atteeq U Rehman;Muddassar Iqbal;Taimur Chaudhry;Merete Lund;Carmen C Brewer;Robert J Morell;Thomas B Friedman. 2016. Clin Genet. 91. PMID: 27573290

The genetic underpinnings of recessively inherited moderate to severe sensorineural hearing loss are not well understood, despite its higher prevalence in comparison to profound deafness. We recruited 92 consanguineous families segregating stable or progressive, recessively inherited moderate or severe hearing loss. We utilized homozygosity mapping, Sanger sequencing, targeted capture of known deafness genes with massively parallel sequencing and whole exome sequencing to identify the molecular basis of hearing loss in these families. Variants of the known deafness genes were found in 69% of the participating families with the SLC26A4, GJB2, MYO15A, TMC1, TMPRSS3, OTOF, MYO7A and CLDN14 genes together accounting for hearing loss in 54% of the families. We identified 20 reported and 21 novel variants in 21 known deafness genes; 16 of the 20 reported variants, previously associated with stable, profound deafness were associated with moderate to severe or progressive hearing loss in our families. These data point to a prominent role for genetic background, environmental factors or both as modifiers of human hearing loss severity.
Screening of deafness-causing DNA variants that are common in patients of European ancestry using a microarray-based approach. Denise Yan;Guangxin Xiang;Xingping Chai;Jie Qing;Haiqiong Shang;Bing Zou;Rahul Mittal;Jun Shen;Richard J H Smith;Yao-Shan Fan;Susan H Blanton;Mustafa Tekin;Cynthia Morton;Wanli Xing;Jing Cheng;Xue Zhong Liu. 2017. PLoS One. 12. PMID: 28273078

The unparalleled heterogeneity in genetic causes of hearing loss along with remarkable differences in prevalence of causative variants among ethnic groups makes single gene tests technically inefficient. Although hundreds of genes have been reported to be associated with nonsyndromic hearing loss (NSHL), GJB2, GJB6, SLC26A4, and mitochondrial (mt) MT-RNR1 and MTTS are the major contributors. In order to provide a faster, more comprehensive and cost effective assay, we constructed a DNA fluidic array, CapitalBioMiamiOtoArray, for the detection of sequence variants in five genes that are common in most populations of European descent. They consist of c.35delG, p.W44C, p.L90P, c.167delT (GJB2); 309kb deletion (GJB6); p.L236P, p.T416P (SLC26A4); and m.1555A>G, m.7444G>A (mtDNA). We have validated our hearing loss array by analyzing a total of 160 DNAs samples. Our results show 100% concordance between the fluidic array biochip-based approach and the established Sanger sequencing method, thus proving its robustness and reliability at a relatively low cost.
A novel missense mutation in the SLC26A4 gene causes nonsyndromic hearing loss and enlarged vestibular aqueduct. Xiaoguang He;Qi Peng;Siping Li;Pengyuan Zhu;Chunqiu Wu;Chunbao Rao;Jiang Chang;Mingyu Xie;Baimao Zhong;Xiaomei Lu. 2017. Int J Pediatr Otorhinolaryngol. 95. PMID: 28576516

OBJECTIVES: We aimed to investigate the genetic causes of hearing loss in a Chinese proband with nonsyndromic hearing loss and enlarged vestibular aqueduct syndrome. METHODS: We conducted clinical and genetic evaluations in a deaf proband and his normal-hearing parents. Multiplex PCR technology combined with Ion Torrent™ next-generation sequencing technology was used to detect the pathogenic mutations. As a control, a group of 1500 previously studied healthy newborns from the same ethnic background were subjected to deafness gene screening using the same method as in our previous study. RESULTS: The proband harbored two mutations in the SLC26A4 gene in the form of compound heterozygosity. He was found to be heterozygous for a novel mutation named c.1742 G > T (p.Arg581Met) in exon 13 and for the known mutation c.589 G > A (p.Gly197Arg). These variants were carried in the heterozygous state by the parents and therefore co-segregated with the genetic disease. The c.1742 G > T (p.Arg581Met) mutation was absent in 1500 healthy newborns. Protein alignment indicated high evolutionary conservation of the p.R581 residue, and this mutation was predicted by PolyPhen-2 and other online tools to be damaging. CONCLUSION: This study demonstrates that the novel mutation c.1742 G > T (p.Arg581Met) in compound heterozygosity with c.589 G > A in the SLC26A4 gene is the main cause of deafness in a family clinically diagnosed with enlarged vestibular aqueduct (EVA). Our study will provide a basic foundation for further investigations to elucidate the SLC26A4-related mechanisms of hearing loss.
Developing regional genetic counseling for southern Chinese with nonsyndromic hearing impairment: a unique mutational spectrum. Kaitian Chen;Ling Zong;Min Liu;Xianren Wang;Wei Zhou;Yuan Zhan;Hui Cao;Chang Dong;Haocheng Tang;Hongyan Jiang. 2014. J Transl Med. 12. PMID: 24612839

BACKGROUND: Racial and regional factors are important for the clinical diagnosis of non-syndromic hearing impairment. Comprehensive genetic analysis of deaf patients in different regions of China must be performed to provide effective genetic counseling. To evaluate the mutational spectrum of south Chinese families, we performed genetic analysis for non-syndromic hearing impairment in this population. METHODS: Complete clinical evaluations were performed on 701 unrelated patients with non-syndromic hearing impairment from six provinces in south China. Each subject was screened for common mutations, including SLC26A4 c.IVS7-2A > G, c.2168A > G; mitochondrial DNA m.1555A > G, m.1494C > T, m.7444G > A, m.7445A > G; GJB3 c.538C > T, c.547G > A; and WFS1 c.1901A > C, using pyrosequencing. GJB2 and SLC26A4 coding region mutation detection were performed using Sanger sequencing. RESULTS: Genetic analysis revealed that among the etiology of non-syndromic hearing impairment, GJB2, SLC26A4, and mitochondrial m.1555A > G mutations accounted for 18.0%, 13.1%, and 0.9%, respectively. Common mutations included GJB2 c.235delC, c.109G > A, SLC26A4 c.IVS7-2A > G, c.1229 T > C, and mitochondrial m.1555A > G. The total mutation rate was 45.1% in all patients examined in south China. Overall, the clear contribution of GJB2, SLC26A4, and mitochondrial m.1555A > G to the etiology of the non-syndromic deafness population in south China was 32.0%. CONCLUSIONS: Our study is the first genetic analysis of non-syndromic hearing impairment in south China, and revealed that a clear genetic etiology accounted for 32.0% of non-syndromic hearing cases in patients from these regions. The mutational spectrum of non-syndromic hearing impairment in the south Chinese population provides useful and targeted information to aid in genetic counseling.
Newborn genetic screening for hearing impairment: a preliminary study at a tertiary center. Chen-Chi Wu;Chia-Cheng Hung;Shin-Yu Lin;Wu-Shiun Hsieh;Po-Nien Tsao;Chien-Nan Lee;Yi-Ning Su;Chuan-Jen Hsu. 2011. PLoS One. 6. PMID: 21811586

Universal newborn hearing screening (UNHS) is of paramount importance for early identification and management of hearing impairment in children. However, infants with slight/mild, progressive, or late-onset hearing impairment might be missed in conventional UNHS. To investigate whether genetic screening for common deafness-associated mutations could assist in identifying these infants, 1017 consecutive newborns in a tertiary hospital were subjected to both newborn hearing screening using a two-step distortion-product otoacoustic emissions (DPOAE) screening and newborn genetic screening (NGS) for deafness. The NGS targeted 4 deafness-associated mutations commonly found in the Taiwanese population, including p.V37I (c.109G>A) and c.235delC of the GJB2 gene, c.919-2A>G of the SLC26A4 gene, and mitochondrial m.1555A>G of the 12S rRNA gene. The results of the NGS were then correlated to the results of the NHS. Of the 1017 newborns, 16 (1.6%) had unilateral DPOAE screening failure, and 22 (2.2%) had bilateral DPOAE screening failure. A total of 199 (19.6%) babies were found to have at least 1 mutated allele on the NGS for deafness, 11 (1.1%) of whom were homozygous for GJB2 p.V37I, 6 (0.6%) compound heterozygous for GJB2 p.V37I and c.235delC, and 1 (0.1%) homoplasmic for m.1555A>G, who may potentially have hearing loss. Among them, 3 babies, 5 babies, and 1 baby, respectively, passed the NHS at birth. Comprehensive audiological assessments in the 9 babies at 3 months identified 1 with slight hearing loss and 2 with mild hearing loss. NGS for common deafness-associated mutations may identify infants with slight/mild or potentially progressive hearing impairment, thus compensating for the inherent limitations of the conventional UNHS.
Deafness gene mutations in newborns in Beijing. Shujing Han;Xiaojian Yang;Yi Zhou;Jinsheng Hao;Adong Shen;Fang Xu;Ping Chu;Yaqiong Jin;Jie Lu;Yongli Guo;Jin Shi;Haihong Liu;Xin Ni. 2016. Acta Otolaryngol. 136. PMID: 26766211

OBJECTIVE: To determine the incidence of congenital hearing loss (HL) in newborns by the rate of deafness-related genetic mutations. DESIGN: Clinical study of consecutive newborns in Beijing using allele-specific polymerase chain reaction-based universal array. STUDY SAMPLE: This study tested 37 573 newborns within 3 days after birth, including nine sites in four genes: GJB2 (35 del G, 176 del 16, 235 del C, 299 del AT), SLC26A4 (IVS7-2 A > G, 2168 A > G), MTRNR1 (1555 A > G, 1494 C > T), and GJB3 (538 C > T). The birth condition of infants was also recorded. RESULTS: Of 37 573 newborns, 1810 carried pathogenic mutations, or 4.817%. The carrier rates of GJB2 (35 del G, 176 del 16, 235 del C, 299 del AT), GJB3 (538 C > T), SLC26A4 (IVS7-2 A > G, 2168 A > G), and MTRNR1 (1555 A > G, 1494 C > T) mutations were 0.005%, 0.104%, 1.924%, 0.551%, 0.295%, 0.253%, 1.387%, 0.024%, and 0.274%, respectively. Logistic regression analysis indicated no statistically significant relationship between mutations and infant sex, premature delivery, twin status, or birth weight. CONCLUSIONS: The 235delC GJB2 mutation was the most frequent deafness-related mutation in the Chinese population. Genetic screening for the deafness gene will help detect more cases of newborn congenital HL than current screening practices.
[Genetic counseling and instruction for deaf couples directed by genetic testing]. Bing Han;Pu Dai;Guo-jian Wang;Dong-yang Kang;Xin Zhang;Yong-yi Yuan;Qing-wen Zhu;Zheng-ce Jin;Mei Li;Suo-qiang Zhai;De-liang Huang;Dong-yi Han. 2007. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 42. PMID: 17886676

OBJECTIVE: To analyze the molecular pathogenesis of deaf couples by means of genetic testing. To provide accurate genetic counseling and instruction for deaf couples with different etiology based upon results of genetic testing. METHODS: Four deaf families from July 2005 to May 2006. Each subject was with moderate to profound hearing loss. Genomic and mitochondrial DNA (mtDNA) of each subject were extracted from whole blood. Genetic testing of GJB2, SLC26A4 (PDS) and mtDNA A1555G mutation were offered to each individuals. RESULTS: The husband from family 1 didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation while his wife was confirmed to carry compound SLC26A4 mutations. The possibility of their offspring's to be SLC26A4 single mutation carrier was 100%. The couple from family 2 both didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation. The possibility of their offspring's having hereditary deafness caused by GJB2, SLC26A4 and mtDNA A1555G mutation was excluded. The husband from family 3 was confirmed to carry homozygous GJB2 mutations and a single SLC26A4 mutation while his wife who was diagnosed with enlarged vestibular aqueduct syndrome (EVAS) by CT scan was proven to carry a single SLC26A4 mutation. The risk of their offspring's suffering EVAS was 50%. The husband from family 4 was mtDNA A1555G positive while his wife who was diagnosed with cochlear malformation by CT scan didn't carry GJB2, SLC26A4 and mtDNA A1555G mutation. The risk of their offspring's having hereditary deafness caused by GJB2, SLC26A4 and mtDNA A1555G mutation was excluded. CONCLUSIONS: Genetic testing could be applied to offer the more accurate genetic counseling and instruction to deaf couples.
[External quality survey results of newborn deafness gene mutations in China]. Wei Wang;Kun Zhong;Falin He;Yan Zhang;Yan Zhao;Zhiguo Wang. 2015. Zhonghua Yi Xue Za Zhi. 95. PMID: 25877242

OBJECTIVE: To evaluate the external quality survey results of newborn hereditary deafness gene mutations to improve and enhance the testing quality of hereditary deafness gene mutations. METHODS: Each of 30 voluntarily participating laboratories testing newborn hereditary deafness gene mutations received 15 lots of quality control blood spots in this survey at May 2013, including mitochondria DNA 12SrRNA 1555A>G (201311-201315), SLC26A4 IVS7-2A>G (201321-201325) and GJB2 235delC (201331-201335). The testing results, methods, equipments and reagent information were submitted for analyses of Clinet EQA, Microsoft Excel 2007 and SPSS 13.0. The rates of correction (number of correct results/total number of submitted results) were used for evaluating the performance of laboratories. RESULTS: Among them, 24 laboratories submitted the testing results of mitochondria DNA 12SrRNA 1555A>G and the rate of submission was 80.0% (24/30). The rates of correction for each lot were 95.8% (23/24), 95.8% (23/24), 100% (24/24), 95.8% (23/24) and 95.8% (23/24) respectively and the overall rate was 96.7% (116/120). And 23 laboratories submitted the other two kinds of genetic test results, the rate of submission was 76.7% (23/30); the rates of correction for each lot of SLC26A4 IVS7-2A>G genetic test were 95.7% (22/23), 95.7% (22/23), 100% (23/23), 95.7% (22/23) and 95.7% (22/23) respectively and the overall rate was 96.5% (111/115); the genetic test results of GJB2 235delC were all correct (23/23). In this survey, 2/3 laboratories employed fluorescent polymerase chain reaction (PCR) and the remainder microarray chips. CONCLUSIONS: The survey of newborn deafness gene mutation testing results is generally satisfactory. Only mitochondria DNA 12SrRNA and SLC26A4 have some errors. The laboratories of gene testing should improve their quality control system, correct mistakes during the test period without any delay and boost the rate of correction for newborn hereditary deafness gene testing.
Construction of a DNA chip for screening of genetic hearing loss. Soo-Young Choi;Young-Eun Kim;Dong-Bin Ahn;Tae-Hoon Kim;Jae-Hyuk Choi;Hye-Ryung Lee;Sang-Joon Hwang;Un-Kyung Kim;Sang-Heun Lee. 2009. Clin Exp Otorhinolaryngol. 2. PMID: 19434291

OBJECTIVES: Hearing loss is the most common sensory disorder in humans and genetic causes are estimated to cause more than 50% of all incidents of congenital hearing loss. To develop an efficient method for a genetic diagnosis of hearing loss, we have developed and validated a genetic hearing loss DNA chip that allows the simultaneous analysis of 7 different mutations in the GJB2, SLC26A4, and the mtDNA 12S rRNA genes in Koreans. METHODS: A genotyping microarray, based on the allele-specific primer extension (ASPE) method, was used and preliminary validation was examined from the five patients and five controls that were already known their genotypes by DNA sequencing analysis. RESULTS: The cutoff Genotyping index (GI) of genotyping for each mutation was set up and validated to discriminate among the genotypes. The result of the DNA chip assay was identical to those of previous results. CONCLUSION: We successfully designed the genetic hearing loss DNA chip for the first time in Korea and it would be useful for a clinical genetic diagnosis of hearing loss. Further consideration will be needed in order to examine the accuracy of this DNA chip with much larger patient sample numbers.
[Analysis of positive rate of common genetic mutations in 1448 cases with different hearing phenotype]. Guojian Wang;Yongyi Yuan;Rong Li;Mingyu Han;Shasha Huang;Dongyang Kang;Xin Zhang;Min Dong;Pu Dai;Dongyi Han. 2011. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 25. PMID: 21809555

OBJECTIVE: To analyze the positive rate of common genetic mutations in Chinese non-syndromic sensorineural hearing loss groups with different hearing phenotype. METHOD: One thousand four hundred and forty-eight subjects with hearing test results received at least one of three genetic testings including: mutations in coding region of GJB2 and SLC26A4 with sequencing analysis and mitochondrial DNA C1494T/A1555G with microarray detection. Of 1448 subjects, 1333 have bilateral sensorineural hearing loss, 65 have unilateral hearing loss and 50 have normal hearing threshold even though they have high frequency hearing loss or family history. The informed consent of each subject was achieved. RESULT: Mutation positive rate of GJB2, SLC26A4 and mtDNA C1494T/ A1555G of 1448 subjects were 19.23%, 27.55%, 0.1% and 1.72% respectively. The positive rate of GJB2 and SLC26A4 mutations in bilateral hearing loss group (20.22%, 29.17%) was statistically significantly higher than unilateral group (0, 0) (P < 0.01). In bilateral hearing loss group, the positive rate of GJB2 mutations was highest in the profound group (24.67%), and then severe (22.33%), moderate (14.33%) and mild group (6.58%) (P < 0.01). The positive rate of SLC26A4 mutations was highest in the severe group (48.67%), and then profound (28.42%), moderate (21.16%) and mild (8.93%) (P < 0.01). CONCLUSION: The positive rate of GJB2 and SLC26A4 mutations is high in the groups with bilateral profound and severe sensorineural hearing loss, whose genetic testing should be put emphasis on. However, the genetic testing should be performed in patients with mild to moderate hearing impairment as well if necessary.
Genotyping with a 198 mutation arrayed primer extension array for hereditary hearing loss: assessment of its diagnostic value for medical practice. Juan Rodriguez-Paris;Lynn Pique;Tahl Colen;Joseph Roberson;Phyllis Gardner;Iris Schrijver. 2010. PLoS One. 5. PMID: 20668687

Molecular diagnostic testing of individuals with congenital sensorineural hearing loss typically begins with DNA sequencing of the GJB2 gene. If the cause of the hearing loss is not identified in GJB2, additional testing can be ordered. However, the step-wise analysis of several genes often results in a protracted diagnostic process. The more comprehensive Hereditary Hearing Loss Arrayed Primer Extension microarray enables analysis of 198 mutations across eight genes (GJB2, GJB6, GJB3, GJA1, SLC26A4, SLC26A5, MTRNR1 and MTTS1) in a single test. To evaluate the added diagnostic value of this microarray for our ethnically diverse patient population, we tested 144 individuals with congenital sensorineural hearing loss who were negative for biallelic GJB2 or GJB6 mutations. The array successfully detected all GJB2 changes previously identified in the study group, confirming excellent assay performance. Additional mutations were identified in the SLC26A4, SLC26A5 and MTRNR1 genes of 12/144 individuals (8.3%), four of whom (2.8%) had genotypes consistent with pathogenicity. These results suggest that the current format of this microarray falls short of adding diagnostic value beyond the customary testing of GJB2, perhaps reflecting the array's limitations on the number of mutations included for each gene, but more likely resulting from unknown genetic contributors to this phenotype. We conclude that mutations in other hearing loss associated genes should be incorporated in the array as knowledge of the etiology of hearing loss evolves. Such future modification of the flexible configuration of the Hereditary Hearing Loss Arrayed Primer Extension microarray would improve its impact as a diagnostic tool.
The SLC26 gene family of multifunctional anion exchangers. David B Mount;Michael F Romero. 2003. Pflugers Arch. 447. PMID: 12759755

The ten-member SLC26 gene family encodes anion exchangers capable of transporting a wide variety of monovalent and divalent anions. The physiological role(s) of individual paralogs is evidently due to variation in both anion specificity and expression pattern. Three members of the gene family are involved in genetic disease; SLC26A2 in chondrodysplasias, SLC26A3 in chloride-losing diarrhea, and SLC26A4 in Pendred syndrome and hereditary deafness (DFNB4). The analysis of Slc26a4-null mice has significantly enhanced the understanding of the roles of this gene in both health and disease. Targeted deletion of Slc26a5 has in turn revealed that this paralog is essential for electromotor activity of cochlear outer hair cells and thus for cochlear amplification. Anions transported by the SLC26 family, with variable specificity, include the chloride, sulfate, bicarbonate, formate, oxalate and hydroxyl ions. The functional versatility of SLC26A6 identifies it as the primary candidate for the apical Cl(-)-formate/oxalate and Cl(-)-base exchanger of brush border membranes in the renal proximal tubule, with a central role in the reabsorption of Na(+)-Cl(-) from the glomerular ultrafiltrate. At least three of the SLC26 exchangers mediate electrogenic Cl(-)-HCO(3)(-) and Cl(-)-OH(-) exchange; the stoichiometry of Cl(-)-HCO(3)(-) exchange appears to differ between SLC26 paralogs, such that SLC26A3 transports >/=2 Cl(-) ions per HCO(3)(-) ion, whereas SLC26A6 transports >/=2 HCO(3)(-) ions per Cl(-) ion. SLC26 Cl(-)-HCO(3)(-) and Cl(-)-OH(-) exchange is activated by the cystic fibrosis transmembrane regulator (CFTR), implicating defective regulation of these exchangers in the reduced HCO(3)(-) transport seen in cystic fibrosis and related disorders; CFTR-independent activation of these exchangers is thus an important and novel goal for the future therapy of cystic fibrosis.
Application of SNPscan in Genetic Screening for Common Hearing Loss Genes. Zixuan Gao;Yu Lu;Jia Ke;Tao Li;Ping Hu;Yu Song;Chiyu Xu;Jie Wang;Jing Cheng;Lei Zhang;Hong Duan;Huijun Yuan;Furong Ma. 2016. PLoS One. 11. PMID: 27792752

The current study reports the successful application of a fast and efficient genetic screening system for common hearing loss (HL) genes based on SNPscan genotyping technology. Genetic analysis of 115 variants in common genes related to HL, GJB2, SLC26A4 and MT-RNR, was performed on 695 subjects with non-syndromic hearing loss (NSHL) from the Northern China. The results found that 38.7% (269/695) of cases carried bi-allelic pathogenic variants in GJB2 and SLC26A4 and 0.7% (5/695) of cases carried homoplasmic MT-RNR1 variants. The variant allele frequency of GJB2, SLC26A4 and MT-RNR1 was 19.8% (275/1390), 21.9% (304/1390), and 0.86% (6/695), respectively. This approach can explain ~40% of NSHL cases and thus is a useful tool for establishing primary molecular diagnosis of NSHL in clinical genetics.
A reverse dot blot assay for the screening of twenty mutations in four genes associated with NSHL in a Chinese population. Siping Li;Qi Peng;Shengyun Liao;Wenrui Li;Qiang Ma;Xiaomei Lu. 2017. PLoS One. 12. PMID: 28505178

BACKGROUND: Congenital deafness is one of the most distressing disorders affecting humanity and exhibits a high incidence worldwide. Most cases of congenital deafness in the Chinese population are caused by defects in a limited number of genes. A convenient and reliable method for detecting common deafness-related gene mutations in the Chinese population is required. METHODS: We developed a PCR-reverse dot blot (RDB) assay for screening 20 hotspot mutations of GJB2, GJB3, SLC26A4, and MT-RNR1, which are common non-syndromic hearing loss (NSHL)-associated genes in the Chinese population. The PCR-RDB assay consists of multiplex PCR amplifications of 10 fragments in the target sequence of the four above-mentioned genes in wild-type and mutant genomic DNA samples followed by hybridization to a test strip containing allele-specific oligonucleotide probes. We applied our method to a set of 225 neonates with deafness gene mutations and 30 normal neonates. RESULTS: The test was validated through direct sequencing in a blinded study with 100% concordance. CONCLUSIONS: The results demonstrated that our reverse dot blot assay is a reliable and effective genetic screening method for identifying carriers and individuals with NSHL among the Chinese population.
Targeted Next-Generation Sequencing Successfully Detects Causative Genes in Chinese Patients with Hereditary Hearing Loss. Siqi Chen;Cheng Dong;Qi Wang;Zhen Zhong;Yu Qi;Xiaomei Ke;Yuhe Liu. 2016. Genet Test Mol Biomarkers. 20. PMID: 27610647

AIMS: We attempted to identify the genetic epidemiology of hereditary hearing loss among the Chinese Han population using next-generation sequencing (NGS). MATERIALS AND METHODS: The entire length of the genes GJB2, SLC26A4, and GJB3, as well as exons of 57 additional candidate genes were sequenced from 116 individuals suffering from hearing loss. RESULTS: Thirty potentially causative mutations from these 60 genes were identified as the likely etiologies of hearing loss in 67 of the cases. In our study, SLC26A4 and GJB2 were the most frequently affected genes among the Chinese Han population with hearing loss. Collectively, they account for 52.8% of the cases, followed by MTRNR1, PCDH15, and TECTA. These data also illustrate that NGS can be used to identify rare alleles responsible for hereditary hearing loss: 22 of the 30 (73.3%) genes identified with mutations are rarely mutated in hereditary hearing loss and only account for 21.5% (42/195) of the total mutation frequency, explaining no more than 2% for each gene. These rarely mutated genes would be missed by conventional diagnostic sequencing approaches. CONCLUSIONS: NGS can be used effectively to identify both the common and rare genes causing hereditary hearing loss.
Genetic frequencies related to severe or profound sensorineural hearing loss in Inner Mongolia Autonomous Region. Yongzhi Liu;Liying Ao;Haitao Ding;Dongli Zhang. 2016. Genet Mol Biol. 39. PMID: 27727359

The aim was to study the frequencies of common deafness-related mutations and their contribution to hearing loss in different regions of Inner Mongolia. A total of 738 deaf children were recruited from five different ethnic groups of Inner Mongolia, including Han Chinese (n=486), Mongolian (n=216), Manchurian (n=24), Hui (n=6) and Daur (n=6). Nine common mutations in four genes (GJB2, SLC26A4, GJB3 and mitochondrial MT-RNR1 gene) were detected by allele-specific PCR and universal array. At least one mutated allele was detected in 282 patients. Pathogenic mutations were detected in 168 patients: 114 were homozygotes and 54 were compound heterozygotes. The 114 patients were carriers of only one mutated allele. The frequency of GJB2 variants in Han Chinese (21.0%) was higher than that in Mongolians (16.7%), but not significantly different. On the other hand, the frequency of SLC26A4 variants in Han Chinese (14.8%) was lower than that in Mongolians (19.4%), but also not significantly different. The frequency of patients with pathogenic mutations was different in Ulanqab (21.4%), Xilingol (40.0%), Chifeng (40.0%), Hulunbeier (30.0%), Hohhot (26.3%), and in Baotou (0%). In conclusion, the frequency of mutated alleles in deafness-related genes did not differ between Han Chinese and Mongolians. However, differences in the distribution of common deafness-related mutations were found among the investigated areas of Inner Mongolia.
Compound heterozygous mutations of SLC26A4 in 4 Chinese families with enlarged vestibular aqueduct. Gendong Yao;Shouxia Li;Dingli Chen;Huijun Wang;Jin Zhang;Zhixing Feng;Lili Guo;Zhiming Yang;Sujun Yang;Caixia Sun;Xiaofang Zhang;Duan Ma. 2013. Int J Pediatr Otorhinolaryngol. 77. PMID: 23385134

OBJECTIVE: Enlarged vestibular aqueduct is the most common inner ear malformation in individuals with sensorineural hearing loss. Mutations in SLC26A4 can cause non-syndromic EVA. To date, more than 170 SLC26A4 mutations have been described. The aim of the present study was to detect and report genetic causes of four unrelated Chinese families with hearing loss. METHODS: We evaluated 4 families presenting bilateral enlarged vestibular aqueducts and describe the clinical and molecular characteristics of 5 patients. RESULTS: The SLC26A4 gene was sequenced in 23 members of these 4 Chinese families with EVA, and the patients were found to carry 4 compound heterozygous mutations, p.G197R and p.S391R, IVS7-2A>G, p.I188T and c.1746 del G, p.V659L and p.T410M, and p.T94I and p.G197R, none of which have been reported previously. CONCLUSIONS: These results emphasize the necessity of considering the complete DNA sequencing of the SLC26A4 gene in molecular diagnosis of deafness, especially when phenotypes such as congenital, invariable, and progressive hearing loss with EVA are present.
[Screening of common deafness gene mutations in 17 000 Chinese newborns from Chengdu based on microarray analysis]. Kangmo Lyu;Yehua Xiong;Hao Yu;Ling Zou;Longrong Ran;Deshun Liu;Qin Yin;Yingwen Xu;Xue Fang;Zuling Song;Lijia Huang;Dayong Tan;Zhiwei Zhang. 2014. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 31. PMID: 25297577

OBJECTIVE: To achieve early diagnosis for inheritable hearing loss and determine carrier rate of deafness causing gene mutations in order to provide information for premarital, prenatal and postnatal genetic counseling. METHODS: A total of 17 000 dried heel blood spots of normal newborns in Chengdu were collected with informed consent obtained from their parents. Genomic DNA was extracted from dried blood spots using Qiagen DNA extraction kits. Microarrays with 9 common mutation loci of 4 deafness-associated genes in Chinese population were used. Nine hot mutations including GJB2 (35delG, 176del16, 235delC and 299delAT), GJB3 (538C> T), SLC26A4 (IVS 7-2A> G, 2168A> G), and mitochondrial DNA 12S rRNA (1555A> G, 1494C> T) were detected by PCR amplification and microarray hybridization. Mutations detected by microarray were verified by Sanger DNA sequencing. RESULTS: Of the 17 000 new-borns, 542 neonates had mutations of the 4 genes. Heterozygous mutations of GJB2, at 235delC, 299delAT, and 176del16 were identified in 254, 55, and 15 newborns, respectively. Two newborns had homozygous mutation of GJB2, 235delC. Heterozygous mutations at 538C> T of GJB3, 2168A> G and IVS 7-2A> G of SLC26A4 were found in 23, 17 and 128 newborns, respectively. For mutation analysis of mitochondrial DNA 12S rRNA, 1494C> T and 1555A> G were homogeneous mutations in 4 and 42 neonates, respectively. In addition, 6 complexity mutations were detected, which demonstrated that one newborn had heterozygous mutations at GJB2 235delC and SLC26A4, IVS7-2A> G, one had heterozygous mutation GJB2 235delC and 12S rRNA homogeneous mutation, 1555 A> G, one heterozygous mutations at GJB2, 299delAT, and GJB3, 538C> T, one at GJB2, 299delAT and 12S rRNA, 1555 A> G, two at GJB2, 299delAT, and SLC26A4, IVS7-2A> G. All mutations as above were confirmed by DNA sequencing. CONCLUSION: The total mutation carrier rate of the 4 deafness genes is 3.19% in healthy newborns at Chengdu. Mutations of GJB2 and SLAC26A4 are major ones (86.5% of total). The mutation rate of mitochondrial DNA 12S rRNA is 2.71‰, which may have deafness induced by aminoglycoside antibiotics. Newborn screening for mutation of genes related to hereditary deafness plays an important role in the early detection and proper management for neonatal deafness as well as genetic counseling for premarital, prenatal and postnatal diagnosis.
Prevalence of mutations in GJB2, SLC26A4, and mtDNA in children with severe or profound sensorineural hearing loss in southwestern China. Jie Qing;Yuan Zhou;Ruosha Lai;Peng Hu;Yan Ding;Weijing Wu;Zian Xiao;Phi T Ho;Yuyuan Liu;Jia Liu;Lilin Du;Denise Yan;Bradley J Goldstein;Xuezhong Liu;Dinghua Xie. 2014. Genet Test Mol Biomarkers. 19. PMID: 25493717

AIM: To study the distribution characteristics of common mutations in the GJB2, SLC26A4, and mtDNA genes in children with severe or profound sensorineural hearing loss (SNHL) in southwestern China. MATERIALS AND METHODS: A total of 1,164 individuals were recruited to screen for the common GJB2, SLC26A4, and mtDNA mutations by microarrays. Subsequencing for the coding region of the GJB2 gene in the samples without the GJB2 hotspot mutations as well as subsequencing for the exon 1 of the TRMU gene in those samples with the mtDNA hotspot mutations was performed by Sanger sequencing. All mutations were analyzed in association with medical imaging. RESULTS: In this study, 28.43% of all subjects carried mutations. The mutation frequencies in the GJB2, SLC26A4, and mtDNA genes were 17.27%, 7.04%, and 4.12%, respectively. No TRMU mutation was found in the study. The frequency of the mtDNA mutations in the multiethnic minorities was six times that in the Han (11.23% vs. 1.91%; p approaches 0.000) and in the urban group was one-third of that in the suburban group(1.49% vs. 4.47%; p=0.047). The frequency of the GJB2 mutations in urban and suburban groups was 23.38% and 15.99%, respectively (p=0.012). The enlarged vestibular aqueduct (EVA) was the most common inner ear malformation and ∼79.10% of EVA cases were associated with the SLC26A4 mutations. CONCLUSIONS: More than one-fourth of children with severe or profound SNHL carried the common deafness mutations. The proportions of ethnic minorities and urban subjects could impact the frequency of the GJB2 and mtDNA mutations. The SLC26A4 hotspot mutations are prevalent and correlate strongly with EVA.
Novel heterozygous mutation c.662_663insG compound with IVS7-2A>G mutation in SLC26A4 gene in a Chinese family with Pendred syndrome. Kaitian Chen;Wei Zhou;Ling Zong;Min Liu;Jintao Du;Hongyan Jiang. 2012. Int J Pediatr Otorhinolaryngol. 76. PMID: 22906308

OBJECTIVE: Pendred syndrome is one of the most common hereditary determined diseases in patients with syndromic sensorineural hearing impairment. Mutations in the SLC26A4 gene are a major cause of Pendred syndrome. However, Pendred syndrome is quite rare in China. This investigation aims to identify genetic cause of a Chinese family with Pendred syndrome. METHODS: Clinical and molecular evaluations were conducted in a Chinese family with Pendred syndrome. RESULTS: A novel SLC26A4 c.662_663insG mutation was detected in compound heterozygosity with IVS7-2A>G. No FOXI1, KCNJ10 or GJB2 pathogenic mutation was found. The novel mutation c.662_663insG (p.G221) locates in SLC26A4 gene exon 6, and cause frameshift mutation on pendrin protein transmembrane domain five. CONCLUSION: The compound heterozygosity of the novel c.662_663insG and IVS7-2A>G mutations in the SLC26A4 gene was considered to be the cause of Pendred syndrome in the proband. This study also supplemented the mutation spectrum of Pendred syndrome.
Common molecular etiologies are rare in nonsyndromic Tibetan Chinese patients with hearing impairment. Yongyi Yuan;Xun Zhang;Shasha Huang;Lujie Zuo;Guozheng Zhang;Yueshuai Song;Guojian Wang;Hongtian Wang;Deliang Huang;Dongyi Han;Pu Dai. 2012. PLoS One. 7. PMID: 22389666

BACKGROUND: Thirty thousand infants are born every year with congenital hearing impairment in mainland China. Racial and regional factors are important in clinical diagnosis of genetic deafness. However, molecular etiology of hearing impairment in the Tibetan Chinese population living in the Tibetan Plateau has not been investigated. To provide appropriate genetic testing and counseling to Tibetan families, we investigated molecular etiology of nonsyndromic deafness in this population. METHODS: A total of 114 unrelated deaf Tibetan children from the Tibet Autonomous Region were enrolled. Five prominent deafness-related genes, GJB2, SLC26A4, GJB6, POU3F4, and mtDNA 12S rRNA, were analyzed. Inner ear development was evaluated by temporal CT. A total of 106 Tibetan hearing normal individuals were included as genetic controls. For radiological comparison, 120 patients, mainly of Han ethnicity, with sensorineural hearing loss were analyzed by temporal CT. RESULTS: None of the Tibetan patients carried diallelic GJB2 or SLC26A4 mutations. Two patients with a history of aminoglycoside usage carried homogeneous mtDNA 12S rRNA A1555G mutation. Two controls were homozygous for 12S rRNA A1555G. There were no mutations in GJB6 or POU3F4. A diagnosis of inner ear malformation was made in 20.18% of the Tibetan patients and 21.67% of the Han deaf group. Enlarged vestibular aqueduct, the most common inner ear deformity, was not found in theTibetan patients, but was seen in 18.33% of the Han patients. Common molecular etiologies, GJB2 and SLC26A4 mutations, were rare in the Tibetan Chinese deaf population. CONCLUSION: The mutation spectrum of hearing loss differs significantly between Chinese Tibetan patients and Han patients. The incidence of inner ear malformation in Tibetans is almost as high as that in Han deaf patients, but the types of malformation vary greatly. Hypoxia and special environment in plateau may be one cause of developmental inner ear deformity in this population.
Identification of two heterozygous deafness mutations in SLC26A4 (PDS) in a Chinese family with two siblings. Jie Chen;Qinjun Wei;Jun Yao;Xiaoyun Qian;Yanhong Dai;Ye Yang;Xin Cao;Xia Gao. 2012. Int J Audiol. 52. PMID: 23151031

OBJECTIVE: To detect genetic cause of two Chinese siblings (patient 1 and 2) with Pendred syndrome. DESIGN: Patients and their parents underwent clinical and genetic evaluations. To identify genetic mutations, sequencing of SLC26A4 was carried out. STUDY SAMPLE: Two siblings and their parents. RESULTS: Clinical evaluations showed that patient 1 suffered from bilateral postlingual progressive sensorineural hearing loss with enlarged vestibular aqueduct and slight diffuse multinodular goiter with euthyroid, and patient 2 suffered from bilateral prelingual progressive sensorineural hearing loss with enlarged vestibular aqueduct and no goiter with euthyroid. Furthermore, the sequence analysis of SLC26A4 indicated that either of the two siblings presented a compound heterozygote for the c.919A>G mutation in the splice site of intron 7 and for the c.1548insC mutation in exon 14. Their mother was a heterozygous carrier of the splice site mutation in intron 7, and their father was a heterozygous carrier of the insertion mutation in exon 14. CONCLUSIONS: Mutation analysis identified a compound heterozygous mutation (c.919A>G/c.1548insC) in SLC26A4 in two Chinese siblings with Pendred syndrome. Also, c.1548insC was first reported in the Chinese population. Although the two siblings from the same family carried the same genotype, they presented different phenotypes.
Reduction of Cellular Expression Levels Is a Common Feature of Functionally Affected Pendrin (SLC26A4) Protein Variants. Vanessa C S de Moraes;Emanuele Bernardinelli;Nathalia Zocal;Jhonathan A Fernandez;Charity Nofziger;Arthur M Castilho;Edi L Sartorato;Markus Paulmichl;Silvia Dossena. 2016. Mol Med. 22. PMID: 26752218

Sequence alterations in the pendrin gene (SLC26A4) leading to functionally affected protein variants are frequently involved in the pathogenesis of syndromic and nonsyndromic deafness. Considering the high number of SLC26A4 sequence alterations reported to date, discriminating between functionally affected and unaffected pendrin protein variants is essential in contributing to determine the genetic cause of deafness in a given patient. In addition, identifying molecular features common to the functionally affected protein variants can be extremely useful to design future molecule-directed therapeutic approaches. Here we show the functional and molecular characterization of six previously uncharacterized pendrin protein variants found in a cohort of 58 Brazilian deaf patients. Two variants (p.T193I and p.L445W) were undetectable in the plasma membrane, completely retained in the endoplasmic reticulum and showed no transport function; four (p.P142L, p.G149R, p.C282Y and p.Q413R) showed reduced function and significant, although heterogeneous, expression levels in the plasma membrane. Importantly, total expression levels of all of the functionally affected protein variants were significantly reduced with respect to the wild-type and a fully functional variant (p.R776C), regardless of their subcellular localization. Interestingly, reduction of expression may also reduce the transport activity of variants with an intrinsic gain of function (p.Q413R). As reduction of overall cellular abundance was identified as a common molecular feature of pendrin variants with affected function, the identification of strategies to prevent reduction in expression levels may represent a crucial step of potential future therapeutic interventions aimed at restoring the transport activity of dysfunctional pendrin variants.
SLC26A4 c.919-2A>G varies among Chinese ethnic groups as a cause of hearing loss. Pu Dai;Qi Li;Deliang Huang;Yongyi Yuan;Dongyang Kang;David T Miller;Hong Shao;Qingwen Zhu;Jia He;Fei Yu;Xin Liu;Bing Han;Huijun Yuan;Orah S Platt;Dongyi Han;Bai-Lin Wu. 2008. Genet Med. 10. PMID: 18641518

PURPOSE: Mutations in the SLC26A4 gene are second only to GJB2 mutations as a currently identifiable genetic cause of sensorineural hearing loss. In most areas of China, genetic testing for sensorineural hearing loss is unavailable because of limited knowledge of the mutation spectrum. Although SLC26A4 c.919-2A>G (IVS7-2A>G) is a common mutation among some Asian populations, the mutation prevalence among various ethnic groups within China has not been studied. METHODS: DNA specimens from 3271 subjects with moderate to profound sensorineural hearing loss from 27 regions of China were genotyped for the c.919-2A>G mutation by polymerase chain reaction/restriction-fragment-length polymorphism. Normal hearing controls from Han (n = 185) and Uigur (n = 152) populations were also tested. RESULTS: Overall, 408 subjects with sensorineural hearing loss (12.5%) carried at least one c.919-2A>G allele, with 158 (4.8%) homozygotes and 250 (7.6%) heterozygotes. Within the subpopulations examined, the rate varies from 0% to 12.2% for c.919-2A>G homozygotes and from 0% to 17.6% for heterozygotes. Based on this cohort, Chinese subjects with sensorineural hearing loss seem to have a relatively higher c.919-2A>G frequency than that of other Asian populations. CONCLUSION: These results demonstrate that a simple and efficient genetic test for the c.919-2A>G mutation alone would identify the molecular cause in up to 8-12% of individuals with sensorineural hearing loss in a few eastern and central regions of China. Those who are negative for the c.919-2A>G mutation would be candidates for further mutational analysis of SLC26A4 or other deafness-related genes. This would greatly improve genetic diagnosis and counseling for a huge number of Chinese individuals and family members with sensorineural hearing loss in China, and many more ethnic Chinese in other countries, which might be up to one million.
Diagnostic outcomes of exome sequencing in patients with syndromic or non-syndromic hearing loss. Tina Likar;Mensuda Hasanhodžić;Nataša Teran;Aleš Maver;Borut Peterlin;Karin Writzl. 2018. PLoS One. 13. PMID: 29293505

Hereditary hearing loss (HL) is a common sensory disorder, with an incidence of 1-2 per 1000 newborns, and has a genetic etiology in over 50% of cases. It occurs either as part of a syndrome or in isolation and is genetically very heterogeneous which poses a challenge for clinical and molecular diagnosis. We used exome sequencing to seek a genetic cause in a group of 56 subjects (49 probands) with HL: 32 with non-syndromic non-GJB2 HL and 17 with syndromic HL. Following clinical examination and clinical exome sequencing, an etiological diagnosis was established in 15 probands (15/49; 30%); eight (8/17;47%) from the syndromic group and seven (7/32; 21%) from the non-syndromic non-GJB2 subgroup. Fourteen different (half of them novel) non-GJB2 variants causing HL were found in 10 genes (CHD7, HDAC8, MITF, NEFL, OTOF, SF3B4, SLC26A4, TECTA, TMPRSS3, USH2A) among 13 probands, confirming the genetic heterogeneity of hereditary HL. Different genetic causes for HL were found in a single family while three probands with apparent syndromic HL were found to have HL as a separate clinical feature, distinct from the complex phenotype. Clinical exome sequencing proved to be an effective tool used to comprehensively address the genetic heterogeneity of HL, to detect clinically unrecognized HL syndromes, and to decipher complex phenotypes in which HL is a separate feature and not part of a syndrome.
Genetic testing for deafness--GJB2 and SLC26A4 as causes of deafness. Richard J H Smith;Nathaniel H Robin. 2002. J Commun Disord. 35. PMID: 12160355

UNLABELLED: Recent advances in the molecular biology of hearing and deafness are being transferred from the research laboratory to the clinical arena. This transfer of knowledge will enhance patient care by making the diagnosis of hereditary deafness easier; however physicians and audiologists must clearly identify that subset of the deaf and hearing populations best served by this knowledge. It is also essential for physicians and audiologists to understand the limitations of genetic testing for deafness, and it is imperative that these limitations be appropriately explained to patients and their families. LEARNING OUTCOMES: The reader will be introduced to the concept of genetic testing for deafness. Two genes that make appreciable contributions to the autosomal recessive non-syndromic deafness (ARNSD) genetic load will be reviewed, GJB2 and SLC26A4. In addition, the unique aspects of genetic counseling for deafness and recurrence chance estimates are explained.
Molecular epidemiology and functional assessment of novel allelic variants of SLC26A4 in non-syndromic hearing loss patients with enlarged vestibular aqueduct in China. Yongyi Yuan;Weiwei Guo;Jie Tang;Guozheng Zhang;Guojian Wang;Mingyu Han;Xun Zhang;Shiming Yang;David Z Z He;Pu Dai. 2012. PLoS One. 7. PMID: 23185506

BACKGROUND: Mutations in SLC26A4, which encodes pendrin, are a common cause of deafness. SLC26A4 mutations are responsible for Pendred syndrome and non-syndromic enlarged vestibular aqueduct (EVA). The mutation spectrum of SLC26A4 varies widely among ethnic groups. To investigate the incidence of EVA in Chinese population and to provide appropriate genetic testing and counseling to patients with SLC26A4 variants, we conducted a large-scale molecular epidemiological survey of SLC26A4. METHODS: A total of 2352 unrelated non-syndromic hearing loss patients from 27 different regions of China were included. Hot spot regions of SLC26A4, exons 8, 10 and 19 were sequenced. For patients with one allelic variant in the hot spot regions, the other exons were sequenced one by one until two mutant alleles had been identified. Patients with SLC26A4 variants were then examined by temporal bone computed tomography scan for radiological diagnosis of EVA. Ten SLC26A4 variants were cloned for functional study. Confocal microscopy and radioisotope techniques were used to examine the membrane expression of pendrin and transporter function. RESULTS: Of the 86 types of variants found, 47 have never been reported. The ratio of EVA in the Chinese deaf population was at least 11%, and that in patients of Han ethnicity reached at least 13%. The mutational spectrum and mutation detection rate of SLC26A4 are distinct among both ethnicities and regions of Mainland China. Most of the variants caused retention of pendrin in the intracellular region. All the mutant pendrins showed significantly reduced transport capability. CONCLUSION: An overall description of the molecular epidemiological findings of SLC26A4 in China is provided. The functional assessment procedure can be applied to identification of pathogenicity of variants. These findings are valuable for genetic diagnosis, genetic counseling, prenatal testing and pre-implantation diagnosis in EVA families.
A New Genetic Diagnostic for Enlarged Vestibular Aqueduct Based on Next-Generation Sequencing. Yalan Liu;Lili Wang;Yong Feng;Chufeng He;Deyuan Liu;Xinzhang Cai;Lu Jiang;Hongsheng Chen;Chang Liu;Hong Wu;Lingyun Mei. 2016. PLoS One. 11. PMID: 27997596

Enlarged vestibular aqueduct (EVA) is one of the most common congenital inner ear malformations and accounts for 1-12% of sensorineural deafness in children and adolescents. Multiple genetic defects contribute to EVA; therefore, early molecular diagnosis is critical for EVA patients to ensure that the most effective treatment strategies are employed. This study explored a new genetic diagnosis method for EVA and applied it to clinic diagnoses of EVA patients. Using next-generation sequencing technology, we set up a multiple polymerase chain reaction enrichment system for target regions of EVA pathogenic genes (SLC26A4, FOXI1, and KCNJ10). Forty-six EVA samples were sequenced by this system. Variants were detected in 87.0% (40/46) of cases, including three novel variants (SLC26A4 c.923_929del, c.1002-8C>G, and FOXI1 c.519C>A). Biallelic potential pathogenic variants were detected in 27/46 patient samples, leading to a purported diagnostic rate of 59%. All results were verified by Sanger sequencing. Our target region capture system was validated to amplify and measure SLC26A4, FOXI1, and KCNJ10 in one reaction system. The result supplemented the mutation spectrum of EVA. Thus, this strategy is an economic, rapid, accurate, and reliable method with many useful applications in the clinical diagnosis of EVA patients.
Identification of a novel mutation in SLC26A4 gene in a Chinese family with enlarged vestibular aqueduct syndrome. Fengguo Zhang;Xiaohui Bai;Yun Xiao;Xue Zhang;Guodong Zhang;Jianfeng Li;Lei Xu;Haibo Wang. 2016. Int J Pediatr Otorhinolaryngol. 85. PMID: 27240500

OBJECTIVE: To investigate the genetic causes of hearing loss in a two generation Chinese family with enlarged vestibular aqueduct syndrome (EVAS). METHODS: Clinical and genetic evaluations were conducted in a deaf proband and her normal-hearing parents. Sanger sequencing analysis of all the 21 exons, the exon-intron boundaries and the promoter in SLC26A4 gene was performed to detect the pathogenic mutations. PCR-restricted fragment length polymorphism (PCR-RFLP) was used to further identify the mutation. Phylogenetic analysis was carried out with multiple sequence alignment using BioEdit software. Three-dimensional (3D) modeling of the human wild-type and mutant SLC26A4 (NP_000432.1) was carried out using I-TASSER (http://zhanglab.ccmb.med.umich.edu/). RESULTS: Clinical examinations showed that the proband suffered from typical features of sensorineural hearing loss with enlarged vestibular aqueduct. A novel nonsense mutation c.2118C>A (p.C706X) in exon 19 was identified in compound heterozygosity with the splice-site mutation c.919-2A>G in the proband by using Sanger sequencing. The mother was a heterozygous carrier of c.919-2A>G in intron 7, while the father was a heterozygous carrier of c.2118C>A. The mutation c.2118C>A was not found in 200 unrelated controls using Sanger sequencing. PCR-RFLP showed the PCR product of the proband was not digested at 2110 by Fau I because of the c.2118C>A mutation. 3D-structure modeling indicated that the mutation c.2118C>A resulted in a truncate Pendrin protein. Protein alignment indicated high conservation of p.C706 residue in healthy Homo, Nomascus, Pan, Macaca, Canis, Sus, Mus, Rattus, Cricetulus and Xenopus. CONCLUSIONS: This study revealed a novel heterozygous mutation c.2118C>A (p.C706X) compound with c.919-2A>G in SLC26A4 gene in a patient with EVAS.
[Analysis of deafness-related gene mutations in 23 nonsyndromic hearing impairment families in Guangxi Zhuang Autonomous Region]. M Shi;F Liu;L Xu;M Liu;F Z Tang;J P Liang;Q T Lu;S H Zhai;J Huang;R C Chen. 2017. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 31. PMID: 29871242

Objective:To investigate the genetic characteristics of the mutations responsible for nonsyndromic hearing loss in Guangxi Zhuang Autonomous Region, and analyze the deafness-related gene mutations in nonsyndromic hearing impairment families in this region.Method:In 23 nonsyndromic hearing impairment families,66 patients or their families were enrolled as family history group and 167 patients or their families without family histiory as control group, respectively. Deafness gene mutations were determined with deafness-related gene mutations detection kits. The mutation rates among the deafness probands, the hearing impairment patients and their audibility relatives were analyzied. Whole length sequences of the deafness-related gene were detected if there was mutation by the kits, to explore Guangxi region-specific mutation-sites.Result:Common deafness-related gene mutation rate in family history group(31.82%) was higher than that in control group(11.38%), including those that in GJB2 homozygous(21.21%), SLC26A4 homozygous (9.09%), both were higher than the control group (GJB2 homozygous 5.99%, SLC26A4 homozygous 3.59%) . The rate of common deafness-related gene mutations in the deafness probands was 34.78%, in the hearing impairment patients was 30.56%, in their audibility relatives was 29.63%, all of which were higher than those in the control group. We found three rarely seen mutations, SLC26A4 IVS11+47T>C, 1548insC and GJB2 109 A>G, by detecting the whole-length sequences of the deafness-related gene.Conclusion:The results indicated that GJB2 and SLC26A4 were the most frequent mutant genes in Guangxi region. Analysis of the individual family were helpful to linkage the mutations and the deafness.
Newborn hearing concurrent genetic screening for hearing impairment-a clinical practice in 58,397 neonates in Tianjin, China. Junqing Zhang;Peng Wang;Bing Han;Yibing Ding;Lei Pan;Jing Zou;Haisheng Liu;Xinzhi Pang;Enqing Liu;Hongyue Wang;Hongyan Liu;Xudong Zhang;Xiu Cheng;Dafei Feng;Qian Li;Dayong Wang;Liang Zong;Yuting Yi;Ning Tian;Feng Mu;Geng Tian;Yaqiu Chen;Gongshu Liu;Fuxia Zhang;Xin Yi;Ling Yang;Qiuju Wang. 2013. Int J Pediatr Otorhinolaryngol. 77. PMID: 24100002

OBJECTIVE: Newborn hearing screening (NHS) is used worldwide due to its feasibility and cost-efficiency. However, neonates with late-onset and progressive hearing impairment will be missed by NHS. Genetic factors account for an estimated 60% of congenital profound hearing loss. Our previous cohort studies were carried out in an innovative mode, i.e. hearing concurrent genetic screening, in newborns to improve the abilities or early diagnosis and intervention for the hearing defects. In this study, we performed the first clinical practice of this mode in Tianjin city. METHODS: A large cohort of 58,397 neonates, born between December 2011 and December 2012, in 44 hospitals in Tianjin, were screened for 20 hot spot hearing loss associated mutations from GJB2, GJB3, SLC26A4 and MTRNR1(12S rRNA). The data of genetic screening results was comprehensively analyzed with newborn hearing screening (NHS) results. RESULTS: We developed an accurate, high throughput genetic screening method and applied it to a total of 58,397 newborns in Tianjin. 3225 (5.52%) infants were detected to carry at least one mutation allele in GJB2, GJB3, SLC26A4 or MTRNR1. 34 (0.58‰) infants were positive for hearing loss caused by GJB2 or SLC26A4 mutations (homozygote or compound heterozygote). 54(0.93‰) infants are heterozygous of various genes. 109(1.87‰) infants had the pathological mitochondrial DNA mutation. CONCLUSION: Accurate, comprehensive hearing loss associated genetic screening can facilitate genetic counseling and provides valuable prognostic information to affected infants. This united screening mode of this study was a promising clinical practice.
[Combined hearing and deafness gene mutation screening of 11,046 Chinese newborns]. Xuejing Sun;Zuoming Xi;Jing Zhang;Baoyan Liu;Xinli Xing;Xin Huang;Qing Zhao. 2015. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 32. PMID: 26663044

OBJECTIVE: To evaluate the efficacy of combined newborn hearing screening and deafness-related mutation screening. METHODS: Eleven thousand and forty-six newborn babies were screened with otoacoustic emission, automatic auditory brainstem response and genetic testing using a standard protocol. Common mutations of three deafness-related genes have included GJB2 (c.235delC, c.299-300delAT), mtDNA 12srRNA (c.1494C>T, c.1555A>G) and SLC26A4 (c.2168A>G, c.IVS7-2A>G). RESULTS: The detection rate for hearing loss in the first-step screening was 0.81% (90/11,046). 513 individuals were found to carry one or two mutant alleles, which gave a carrier rate of 4.64% (513/11,046). Five hundred and eighty-four newborns were positive for hearing screening and genetic screening. Among these, 19 have failed both tests, 71 have failed hearing screening, and 494 have failed genetic screening. The combined hearing and genetic screening has given a positive rate of 5.29%. CONCLUSION: Neither hearing screening nor genetic screening is sufficient to identify individuals susceptible to auditory disorders. Combined used of these methods can improve the rate of detection.
[Analysis and prenatal diagnosis of deafness-related gene mutations in patients with nonsyndromic hearing loss]. Huanzheng Li;Yunying Chen;Yijian Mao;Yi Ding;Xueqin Xu;Shaohua Tang. 2014. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 31. PMID: 25297579

OBJECTIVE: To analyze deaf-related genes in patients with nonsyndromic hearing loss (NSHL) and set up a prenatal diagnosis system for such patients. METHODS: Nine NSHL families were collected. Potential mutations of GJB2 (35delG, 176del16, 235delC, 299delAT), SLC26A4 (2168A> G, IVS7-2A> G), GJB3 (538C> T) and mtDNA (1494C> T, 12S rRNA 1555A> G) were detected by direct sequencing. Maternal blood contamination was excluded prior to the testing. RESULTS: Sixteen patients from 4 families were detected with GJB2 mutations, 8 patients from 2 families were found with SLC26A4 mutations, and 4 patients from 2 families were found with mutations in mtDNA. For 2 patients from one remaining family, no mutations were found with above genes. CONCLUSION: A diagnostic system for NSHL has been established, which may provide a basis for prenatal diagnosis and genetic counseling to NSHL families.
Pendred syndrome, DFNB4, and PDS/SLC26A4 identification of eight novel mutations and possible genotype-phenotype correlations. C Campbell;R A Cucci;S Prasad;G E Green;J B Edeal;C E Galer;L P Karniski;V C Sheffield;R J Smith. 2001. Hum Mutat. 17. PMID: 11317356

Mutations in PDS (SLC26A4) cause both Pendred syndrome and DFNB4, two autosomal recessive disorders that share hearing loss as a common feature. The hearing loss is associated with temporal bone abnormalities, ranging from isolated enlargement of the vestibular aqueduct (dilated vestibular aqueduct, DVA) to Mondini dysplasia, a complex malformation in which the normal cochlear spiral of 2(1/2) turns is replaced by a hypoplastic coil of 1(1/2) turns. In Pendred syndrome, thyromegaly also develops, although affected persons usually remain euthyroid. We identified PDS mutations in the proband of 14 of 47 simplex families (30%) and nine of 11 multiplex families (82%) (P=0.0023). In all cases, mutations segregated with the disease state in multiplex families. Included in the 15 different PDS allele variants we found were eight novel mutations. The two most common mutations, T416P and IVS8+1G>A, were present in 22% and 30% of families, respectively. The finding of PDS mutations in five of six multiplex families with DVA (83%) and four of five multiplex families with Mondini dysplasia (80%) implies that mutations in this gene are the major genetic cause of these temporal anomalies. Comparative analysis of phenotypic and genotypic data supports the hypothesis that the type of temporal bone anomaly may depend on the specific PDS allele variant present.
SIX1 mutation associated with enlargement of the vestibular aqueduct in a patient with branchio-oto syndrome. Taku Ito;Yoshihiro Noguchi;Takatoshi Yashima;Ken Kitamura. 2006. Laryngoscope. 116. PMID: 16652090

OBJECTIVES: : The objectives of this study were to identify SIX1 gene mutations in a patient with branchio-oto syndrome (BO) and to clarify the relationship between SIX1 mutation and enlargement of the vestibular aqueduct (EVA). METHODS: : A genetic study and retrospective chart review for a patient in whom EYA1 mutation had already been excluded was conducted. We studied a Japanese patient who had autosomal-dominant mixed hearing loss, a unilateral ear pit and unilateral EVA, and who was previously diagnosed as having BO. We searched for SIX1 and SLC26A4 mutations using polymerase chain reaction and direct gene sequencing. RESULTS: : The patient carried a heterozygous A-->G mutation at nucleotide 386 within exon 1 of SIX1 that resulted in substitution of a cysteine for a tyrosine at codon 129 (Y129C) of the gene product. Y129C is a previously identified SIX1 mutation and was not detected in any of our 164 control chromosomes. No SLC26A4 mutations were identified. CONCLUSION: : Y129C mutation in SIX1 may cause EVA as well as BO.
A Novel Mutation in SLC26A4 Causes Nonsyndromic Autosomal Recessive Hearing Impairment. Axel Wolf;Alexandra Frohne;Matthew Allen;Thomas Parzefall;Martin Koenighofer;Markus M Schreiner;Christian Schoefer;Klemens Frei;Trevor Lucas. 2016. Otol Neurotol. 38. PMID: 27861301

BACKGROUND: Heterozygous mutations in GJB2 (MIM: 121011) encoding the gap junction protein connexin 26 are overrepresented in patient groups suffering from nonsyndromic sensorineural hearing impairment (HI) implying the involvement of additional genetic factors. Mutations in SLC26A4 (MIM: 605646), encoding the protein pendrin can cause both Pendred syndrome and autosomal recessive, nonsyndromic HI locus 4 type sensorineural HI (MIM: 600791). OBJECTIVES: Aim of this study was to investigate the role of SLC26A4 coding mutations in a nonsyndromic hearing impairment (NSHI) patient group bearing heterozygous GJB2 35delG mutations. DESIGN: We analyzed the 20 coding exons of SLC26A4 in a group of patients (n = 15) bearing heterozygous 35delG mutations and exclusively suffering from congenital HI. RESULTS: In a case of bilateral congenital hearing loss we identified a rare, novel SLC26A4 exon 2 splice donor mutation (c.164+1delG) predicted to truncate pendrin in the first cytoplasmic domain, as a compound heterozygote with the pathogenic missense mutation c.1061T>C (p.354F>S; rs111033243). CONCLUSIONS: Screening for SLC26A4 mutations may identify the genetic causes of hearing loss in patients bearing heterozygous mutations in GJB2. HYPOTHESIS: SLC26A4 coding mutations are genetic causes for nonsyndromic HI in patients bearing heterozygous GJB2 35delG mutations.
A novel mutation in the SLC26A4 gene in a Chinese family with non-syndromic hearing loss and enlarged vestibular aqueduct. Yuan Liang;Qi Peng;Kangwei Wang;Pengyuan Zhu;Chunqiu Wu;Chunbao Rao;Jiang Chang;Siping Li;Xiaomei Lu. 2018. Int J Pediatr Otorhinolaryngol. 107. PMID: 29501320

OBJECTIVES: To identity the genetic causes of hearing loss in a Han Chinese family with enlarged vestibular aqueduct syndrome. METHODS: Multiplex PCR technology combined with Ion Torrent™ next-generation sequencing technology was used to search for pathogenic mutations. A group of 1500 ethnically-matched normal hearing subjects screened for mutations in deafness-related genes using the same method in previously studied were included as a control. RESULTS: The proband and his little sister suffered from typical features of sensorineural hearing loss with enlarged vestibular aqueduct (EVA). Both subjects harbored two compound heterozygous mutations in the SLC26A4 gene. A novel mutation named c.2110 G > C (p.Glu704Gln) in exon 19 and another previously reported mutation c.1673 A > T (p.Asn558Ile) were identified. These mutations were carried in the heterozygous state by the parents and therefore co-segregated with the genetic disease. The c.2110 G > C (p.Glu704Gln) mutation was absent in 1500 healthy newborns. Protein alignment indicated high evolutionary conservation of the p.E704 residue, and this mutation was predicted by online tools to be damaging and deleterious. CONCLUSION: This study demonstrates that the novel mutation c.2110 G > C (p.Glu704Gln) in compound heterozygosity with c.1673 A > T (p.Asn558Ile) in the SLC26A4 gene corresponds to the EVA in this family. Our study will provide a foundation for elucidating the SLC26A4-related mechanisms of hearing loss.
Unresolved questions regarding human hereditary deafness. A U Rehman;T B Friedman;A J Griffith. 2016. Oral Dis. 23. PMID: 27259978

Human hearing loss is a common neurosensory disorder about which many basic research and clinically relevant questions are unresolved. This review on hereditary deafness focuses on three examples considered at first glance to be uncomplicated, however, upon inspection, are enigmatic and ripe for future research efforts. The three examples of clinical and genetic complexities are drawn from studies of (i) Pendred syndrome/DFNB4 (PDS, OMIM 274600), (ii) Perrault syndrome (deafness and infertility) due to mutations of CLPP (PRTLS3, OMIM 614129), and (iii) the unexplained extensive clinical variability associated with TBC1D24 mutations. At present, it is unknown how different mutations of TBC1D24 cause non-syndromic deafness (DFNB86, OMIM 614617), epilepsy (OMIM 605021), epilepsy with deafness, or DOORS syndrome (OMIM 220500) that is characterized by deafness, onychodystrophy (alteration of toenail or fingernail morphology), osteodystrophy (defective development of bone), mental retardation, and seizures. A comprehensive understanding of the multifaceted roles of each gene associated with human deafness is expected to provide future opportunities for restoration as well as preservation of normal hearing.
A sensitive and convenient method for clinical detection of non-syndromic hearing loss-associated common mutations. Er-Feng Yuan;Wei Xia;Jing-Tao Huang;Ling Hu;Xing Liao;Xiang Dai;Song-Mei Liu. 2017. Gene. 628. PMID: 28734895

BACKGROUND: The majority of non-syndromic hearing loss (NSHL) patients result from causative mutations in GJB2, SLC26A4 and mitochondrial 12S rRNA genes. Accurate detection of these genetic mutations is increasingly recognized for its clinical significance to reduce incidence and guide individual treatment of NSHL. Current methods for clinical practice are labor intensive, expensive or of low sensitivity. METHODS: Genomic DNA from 7 newborns not passing the hearing screening and 94 newborns passing the hearing screening were analyzed for the common mutations using high resolution melting analysis (HRMA) and Sanger sequencing. RESULTS: Our newly developed HRMA allowed the hot-spot mutations of GJB2 c.176_191del16 and c.235delC, SLC26A4 IVS7-2A>G and mitochondrial 12S rRNA 1494C>T and 1555A>G to be detected by melting profiles based on small amplicons. HRMA can distinguish different content mutant DNA from wildtype DNA, with a detection limit of 5%. Moreover, the results were highly concordant between HRMA and Sanger sequencing. CONCLUSIONS: These results indicate that HRMA could be used as a routine clinical method for prenatal diagnosis and newborn genetic screening due to its accuracy, sensitivity, and rapid, low-cost and less laborious workflows.
[Application of MALDI-TOF-MS in gene testing for non-syndromic hearing loss]. Yun Zeng;Dan Jiang;Da-fei Feng;Dong-dong Jin;Xiao-hui Wu;Yan-li Ding;Jing Zou. 2014. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 48. PMID: 24506996

OBJECTIVE: To investigate the feasibility of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) , according to the genetic test of non-syndromic hearing loss (NSHL), and check using the direct sequencing. METHODS: Peripheral blood was collected from 454 NSHL patients. DNA samples were extracted and 20 loci of the four common disease-causing genes were analysed by MALDI-TOF-MS, including GJB2 (35delG, 167delT, 176_191del16, 235delC, 299_300delAT ), GJB3 (538C→T, 547G→A), SLC26A4 (281C→T, 589G→A, IVS7-2A→G, 1174A→T, 1226G→A, 1229C→T, IVS15+5G→A, 1975G→C, 2027T→A, 2162C→T, 2168A→G), and mitochondrial 12S rRNA (1494C→T, 1555A→G). Direct sequencing was also used to analyse the aforementioned 20 loci in order to validate the accuracy of MALDI-TOF-MS. RESULTS: Among the 454 patients, 166 cases (36.56%) of disease-causing mutations were detected, which included 69 cases (21.15%) of GJB2 gene mutation, four cases (0.88%) of GJB3 gene mutation, 64 cases (14.10%) of SLC26A4 gene mutation, and three cases (0.66%) of mitochondrial 12S rRNA gene mutation. Moreover, the results obtained from direct sequencing and MALDI-TOF-MS were consistent, and the results showed that the two methods were consistent. CONCLUSIONS: The MALDI-TOF-MS detection method was designed based on the hearing loss-related mutation hotspots seen in the Chinese population, and it has a high detection rate for NSHL related mutations. In comparison to the conventional detection methods, MALDI-TOF-MS has the following advantages: more detection sites, greater coverage, accurate, high throughput and low cost. Therefore, this method is capable of satisfying the needs of clinical detection for hearing impairment and it is suitable for large-scale implementation.
Phenotypic analyses and mutation screening of the SLC26A4 and FOXI1 genes in 101 Taiwanese families with bilateral nonsyndromic enlarged vestibular aqueduct (DFNB4) or Pendred syndrome. Chen-Chi Wu;Ying-Chang Lu;Pei-Jer Chen;Po-Lin Yeh;Yi-Nin Su;Wuh-Liang Hwu;Chuan-Jen Hsu. 2009. Audiol Neurootol. 15. PMID: 19648736

Recessive mutations in the SLC26A4 gene are responsible for nonsyndromic enlarged vestibular aqueduct (EVA) and Pendred syndrome. However, in some affected families, only 1 or 0 mutated allele can be identified, as well as no clear correlation between SLC26A4 genotypes and clinical phenotypes, hampering the accuracy of genetic counseling. To elucidate the genetic composition of nonsyndromic EVA and Pendred syndrome, we screened related genomic fragments, including the SLC26A4 coding regions, the SLC26A4 promoter and the FOXI1 transcription factor gene, in 101 Taiwanese families, and analyzed their phenotypic and genotypic results. Mutation screening in the SLC26A4 coding regions by direct sequencing and quantitative polymerase chain reaction detected 2 mutations in 63 (62%) families, 1 mutation in 24 (24%) families and no mutation in 14 (14%) families. The radiological findings, the presence of goiters and the audiological results were not different among probands (i.e. index cases of the families) with different SLC26A4 genotypes. Specifically, probands heterozygous for SLC26A4 mutations demonstrated clinical features indistinguishable from those of probands with 2 mutated alleles, implicating that there might be undetected mutations. However, except for a variant (c.-2554G>A of SLC26A4) with possible pathological consequences, no definite mutation was detected after extensive screening in the SLC26A4 promoter and FOXI1. In other words, in most Taiwanese families nonsyndromic EVA or Pendred syndrome might not result from aberrance in the transcriptional control of SLC26A4 by FOXI1. Meanwhile, exploration of undetected mutations in the SLC26A4 noncoding regions revealed 9 divergent haplotypes among the 21 no-mutation-detected SLC26A4 alleles of the c.919-2A>G heterozygotes, indicating that there might be no common and predominant mutations in the SLC26A4 introns.
[Value of pre-gestational deafness-related mutation screening for the prevention and intervention of congenital deafness]. Xuejing Sun;Xinli Xing;Qingqing He;Lin Zhou;Jing Zhang;Qing Zhao;Huili Hou;Zuoming Xi. 2017. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 34. PMID: 28981942

OBJECTIVE: To assess the value of pre-gestational deafness-related mutation screening for the prevention and intervention of congenital deafness. METHODS: In this study, 2168 couples with normal hearing were screened for common mutations associated with congenital deafness using real-time fluorescence quantitative PCR. The mutations have included GJB2 c.235delC and c.299_300delAT, SLC26A4 c.2168A>G and c.IVS7-2A>G, and mtDNA 12SrRNA c.1494C>T and c.1555A>G. For couples who have both carried heterozygous mutations of the same gene, genetic counseling and prenatal diagnosis were provided. RESULTS: Among of the 4 336 individuals, 178 (4.06%) were found to carry a mutation. Mutation rate for c.235delC and c.299_300delAT of GJB2 gene, c.IVS7-2 A>G and c.2168 A>G of SLC26A4 gene, c.1555 A>G and c.1494 C>T of DNA 12S rRNA gene were 0.91%, 0.20%, 0.68%, 0.11%, 0.1% and 0.01%, respectively. For six couples who have both carried mutations of the same gene, all fetuses showed a normal karyotype, while DNA sequencing indicated that two fetuses have carried homozygous c.235delC mutation of the GJB2 gene, one carried a heterozygous c.235delC mutation of the GJB2 gene, one carried heterozygous mutation of GJB2 gene (c.299_300delAT), and two have carried a heterozygous mutation of c.IVS7-2A>G of the SLC26A4 gene. CONCLUSION: Pre-gestational screening for deafness gene mutation can facilitate avoidance the birth of affected children and has a great clinical value for the prevention and intervention of birth defect.
Preimplantation genetic diagnosis (embryo screening) for enlarged vestibular aqueduct due to SLC26A4 mutation. Chen-Chi Wu;Shin-Yu Lin;Yi-Nin Su;Mei-Ya Fang;Shee-Uan Chen;Chuan-Jen Hsu. 2010. Audiol Neurootol. 15. PMID: 20160438

Preimplantation genetic diagnosis (PGD) is used to analyze embryos genetically before their transfer into the uterus. For families with genetic diseases, PGD offers a chance to have an unaffected child, without facing termination of pregnancy. Although PGD has been performed for many monogenic disorders, such as cystic fibrosis and beta-thalassemia, the application of PGD to hereditary hearing impairment has not been explored. In the present study, we reported the development and application of PGD protocols to address enlarged vestibular aqueduct (EVA), which is a common type of hereditary hearing impairment associated with mutations in the SLC26A4 gene. The family requesting PGD had a history of EVA, segregating the SLC26A4 c.919-2A-->G mutation. In short, the PGD process was composed of two steps: the development of a single-cell testing protocol and clinical PGD cycles (i.e., selection and implantation of unaffected embryos using the single-cell testing protocol). First, protocols for genetic testing in a single cell were established for the c.919-2A-->G mutation using GenomiPhi technology and primer extension mini-sequencing. These protocols were validated on single lymphocytes collected from both parents and their affected child. Two clinical PGD cycles were then performed for the parents, with the second cycle successfully leading to a singleton pregnancy. The baby was homozygous for the wild-type SLC26A4 allele and revealed a normal audiological phenotype after birth. To our knowledge, this is the first report in the literature describing successful PGD in families with genetic hearing impairment. In our opinion, the application of PGD in the field of hereditary hearing impairment involves fewer ethical controversies than other novel applications of PGD and traditional indications for PGD for other monogenic diseases. Therefore, the approach demonstrated in the present study can also be used in a large number of families with other types of hereditary hearing impairment.
Genetic causes of nonsyndromic hearing loss in Iran in comparison with other populations. Nejat Mahdieh;Bahareh Rabbani;Susan Wiley;Mohammad Taghi Akbari;Sirous Zeinali. 2010. J Hum Genet. 55. PMID: 20739942

Hearing loss (HL) is the most prevalent sensory defect affecting 1 in 500 neonates. Genetic factors are involved in half of the cases. The extreme heterogeneity of HL makes it difficult to analyze and determine the accurate genetic causes of the impairment. Up to now, 10 genes, namely, GJB2, GJB6, SLC26A4, TECTA, PJVK, Col11A2, Myo15A, TMC1, RDX and microRNA (miR-183), have been studied in an Iranian population. The prevalence of HL in Iran was estimated to be 2-3 times higher than that in other parts of the world. Here, the most common bases of congenital nonsyndromic hearing loss (NSHL) are discussed. We reviewed GJB2, GJB6 (large deletion), TECTA, SLC26A4 and PEJVK mutations, and studied their frequencies and distributions in different ethnic groups in 1934, 500, 121, 80 and 34 unrelated families throughout Iran, respectively. GJB2 mutation was the most common factor causing NSHL, with a mean frequency of 18.17% in the Iranian population. The importance of Iran's geographical location in the migration pathway from west to east through the silk route was also highlighted. SLC26A4 and TECTA mutations were the second and third main reasons of HL and accounted for up to 10 and 4% of prelingual HL in Iran, respectively. Mutations in GJB2, SLC26, TECTA and PJVK genes have an important role in HL in Iran and a screening test should be generated for better intervention and diagnosis programs.
Novel mutations of SLC26A4 in Chinese patients with nonsyndromic hearing loss. Gendong Yao;Dingli Chen;Huijun Wang;Shouxia Li;Jin Zhang;Zhixing Feng;Lili Guo;Zhiming Yang;Sujun Yang;Caixia Sun;Xiaofang Zhang;Duan Ma. 2013. Acta Otolaryngol. 133. PMID: 23638949

CONCLUSIONS: This study demonstrated high prevalence of GJB2, SLC26A4, and mtDNA A1555G mutations in Chinese patients with nonsyndromic hearing loss and discovered eight novel mutations in SLC26A4. Most of these novel mutations were predicted pathogenic variants. OBJECTIVES: Nonsyndromic hearing loss is the most common neurosensory deafness where the majority of patients have highly diversified genetic defects. This study aimed to define the genetic profile of deafness in a Chinese population with potential to discover novel mutations. METHODS: A total of 227 segregating deaf students and 200 individuals with normal hearing were enrolled. With the Sanger sequencing chemistry, direct sequencing was performed on entire coding regions of GJB2, GJB3, SLC26A4, and mtDNA m.C1494T and m.A1555G. RESULTS: Direct sequencing analysis revealed that 53 (23.35%) of 227 patients carried at least 1 mutant allele in GJB2, 40 (17.62%) patients in SLC26A4, 5 (2.20%) patients in mtDNA A1555G, and 1 (0.44%) patient in mtDNA C1494T mutations. Four patients carried three unclassified mutations in GJB3 genes. Overall 38 mutant variants were detected in this cohort of patients, including 8 novel mutations in SLC26A4. The eight novel variants were six missense substitutions (p.V163L, p.G222S, p.A456D, p.N457I, p.C466Y, p.F667L), one nonsense mutation (p.W472X), and one frameshift (p.Asn612Ilefs×23).
The Role of RANTES Promoter Polymorphism in Functional Dyspepsia. Tomomitsu Tahara;Tomoyuki Shibata;Hiromi Yamashita;Ichiro Hirata;Tomiyasu Arisawa. 2009. J Clin Biochem Nutr. 45. PMID: 19794934

Altered inflammatory immune responses have been shown to be associated with functional gastro intestinal disorder. We aimed to clarify the effect of functional promoter polymorphism of RANTES, which is a potent chemoattractant peptide for memory T lymphocytes and eosinophils, on the risk of functional dyspepsia in a Japanese population. RANTES promoter C-28G polymorphism was genotyped in 246 subjects including 134 FD patients according to Roma III criteria and 112 non-symptomatic healthy controls. Although frequency of RANTES promoter polymorphisms in overall dyspeptic patients and non-symptomatic healthy controls did not show any significant differences, a significant association was found between G carrier and reduced risk of PDS according to Roma III criteria (age, sex, H. pylori infection adjusted OR = 0.23, 95% CI = 0.06-0.80). We also found that the same genotype held a lower risk of PDS in H. pylori positive PDS subjects (age, sex adjusted OR = 0.11, 95% CI = 0.01-0.94). Our data suggest that RANTES promoter -28G carriers is associate with a reduced risk of PDS especially in H. pylori positive subjects.
Genetic diagnosis and cochlear implantation for patients with nonsyndromic hearing loss and enlarged vestibular aqueduct. R Lai;P Hu;F Zhu;G Zhu;R Vivero;A Peng;W Wu;Z Xiao;X Liu;D Xie. 2012. J Laryngol Otol. 126. PMID: 22289209

OBJECTIVE: To review the genotype and cochlear implantation outcome of patients with nonsyndromic hearing loss and enlarged vestibular aqueduct. METHODS: Twenty-one Chinese children with nonsyndromic hearing loss and enlarged vestibular aqueduct underwent genetic examination. A DNA microarray was used to screen for the IVS7-2A>G and H723R mutations. Any DNA samples with one or none of the two mutant alleles were sequenced to detect other mutations in the SLC26A4 and FOXI1 genes. RESULTS: Twelve SLC26A4 mutations were detected, including three novel mutations. The most common mutations detected were IVS7-2A>G and H723R. Twelve patients received cochlear implants, and subsequently demonstrated excellent speech perception. CONCLUSION: Three novel mutations were detected in Chinese patients with nonsyndromic hearing loss and enlarged vestibular aqueduct. The SLC26A4 mutation spectrum in the Chinese population is similar to that in other East Asian populations. Cochlear implantation is a safe and effective treatment in patients with enlarged vestibular aqueduct.
Molecular screening of patients with nonsyndromic hearing loss from Nanjing city of China. Yajie Lu;Dachun Dai;Zhibin Chen;Xin Cao;Xingkuan Bu;Qinjun Wei;Guangqian Xing. 2011. J Biomed Res. 25. PMID: 23554706

Hearing loss is the most frequent sensory disorder involving a multitude of factors, and at least 50% of cases are due to genetic etiology. To further characterize the molecular etiology of hearing loss in the Chinese population, we recruited a total of 135 unrelated patients with nonsyndromic sensorineural hearing loss (NSHL) for mutational screening of GJB2, GJB3, GJB6, SLC26A4, SLC26A5 IVS2-2A>G and mitochondrial 12SrRNA, tRNA(Ser(UCN)) by PCR amplification and direct DNA sequencing. The carrier frequencies of deafness-causing mutations in these patients were 35.55% in GJB2, 3.70% in GJB6, 15.56% in SLC26A4 and 8.14% in mitochondrial 12SrRNA, respectively. The results indicate the necessity of genetic screening for mutations of these causative genes in Chinese population with nonsyndromic hearing loss.
KCNJ10 may not be a contributor to nonsyndromic enlargement of vestibular aqueduct (NSEVA) in Chinese subjects. Jiandong Zhao;Yongyi Yuan;Shasha Huang;Bangqing Huang;Jing Cheng;Dongyang Kang;Guojian Wang;Dongyi Han;Pu Dai. 2014. PLoS One. 9. PMID: 25372295

BACKGROUND: Nonsyndromic enlargement of vestibular aqueduct (NSEVA) is an autosomal recessive hearing loss disorder that is associated with mutations in SLC26A4. However, not all patients with NSEVA carry biallelic mutations in SLC26A4. A recent study proposed that single mutations in both SLC26A4 and KCNJ10 lead to digenic NSEVA. We examined whether KCNJ10 excert a role in the pathogenesis of NSEVA in Chinese patients. METHODS: SLC26A4 was sequenced in 1056 Chinese patients with NSEVA. KCNJ10 was screened in 131 patients who lacked mutations in either one or both alleles of SLC26A4. Additionally, KCNJ10 was screened in 840 controls, including 563 patients diagnosed with NSEVA who carried biallelic SLC26A4 mutations, 48 patients with nonsyndromic hearing loss due to inner ear malformations that did not involve enlargement of the vestibular aqueduct (EVA), 96 patients with conductive hearing loss due to various causes, and 133 normal-hearing individuals with no family history of hereditary hearing loss. RESULTS: 925 NSEVA patients were found carrying two-allele pathogenic SLC26A4 mutations. The most frequently detected KCNJ10 mutation was c.812G>A (p.R271H). Compared with the normal-hearing control subjects, the occurrence rate of c.812G>A in NSEVA patients with lacking mutations in one or both alleles of SLC26A4 had no significant difference(1.53% vs. 5.30%, χ(2) = 2.798, p = 0.172), which suggested that it is probably a nonpathogenic benign variant. KCNJ10 c.1042C>T (p.R348C), the reported EVA-related mutation, was not found in patients with NSEVA who lacked mutations in either one or both alleles of SLC26A4. Furthermore, the normal-hearing parents of patients with NSEVA having two SLC26A4 mutations carried the KCNJ10 c.1042C>T or c.812G>A mutation and a SLC26A4 pathogenic mutation. CONCLUSION: SLC26A4 is the major genetic cause in Chinese NSEVA patients, accounting for 87.59%. KCNJ10 may not be a contributor to NSEVA in Chinese population. Other genetic or environmental factors are possibly play a role in the etiology of Chinese EVA patients with zero or monoallelic SLC26A4 mutation.
Pendred syndrome in a large consanguineous Brazilian family caused by a homozygous mutation in the SLC26A4 gene. Adriana Lofrano-Porto;Gustavo B Barra;Paula P Nascimento;Patrícia G G Costa;Erica C Garcia;Rodrigo F Vaz;Ana R T Batista;Ana C R de Freitas;Bruno L B Cherulli;Fayez Bahmad;Larissa G Figueiredo;Francisco A R Neves;Luiz Augusto Casulari. 2009. Arq Bras Endocrinol Metabol. 52. PMID: 19169484

Pendred Syndrome (PS) is an autossomal recessive disorder characterized by sensorineural deafness, goiter and iodide organification defect. The hearing loss is associated with inner ear abnormalities, ranging from an isolated enlarged vestibular aqueduct (EVA) to a typical coclear dysplasia. Mutations in the gene that encodes pendrin (SLC26A4), a chloride/iodide transporter, have been shown to be associated with PS. We describe the clinical and molecular characteristics of a large consanguineous family harboring a mutation in the SLC26A4 gene. The proband was a 26-year-old deaf Brazilian woman who presented a bulky multinodular goiter and hypothyroidism since puberty. Five other siblings were deaf: one brother had a similar phenotype, three siblings also had goiters but normal thyroid function tests, and one brother had only a subtle thyroid enlargement. Other 4 siblings had no thyroid or hearing disorder. Parents were first degree cousins and had normal hearing. The mother was healthy, except for subclinical hypothyroidism; the father was deceased. A perchlorate test in the proband showed a discharge of 21% of the incorporated iodide 2h after the administration of 1g of KClO4. Audiological examinations showed profound hearing loss in all deaf subjects; CT and MRI of the temporal bones showed EVA in all of them. Genomic DNA was isolated from whole blood, from the 6 affected and 4 unaffected siblings, the mother and control. The coding region of the PDS gene (exons 2-21), including exon/intron boundaries, were amplified by PCR and sequenced. A single base-pair (T) deletion at position 1197 of exon 10 was detected in homozygous state in the 6 deaf siblings. The mother and 2 unaffected siblings were heterozygous for this mutation, which has been described by Everett et al. The 1197delT mutation is predicted to result in a frameshift and a truncated protein. The existence of PS phenocopies and intrafamilial phenotypic variability are well documented. The definite diagnosis requires molecular analysis. Our study illustrates the value and challenges of mutational analysis in selected patients with PS.
Application of SNaPshot multiplex assays for simultaneous multigene mutation screening in patients with idiopathic sensorineural hearing impairment. Chen-Chi Wu;Ying-Chang Lu;Pei-Jer Chen;Alyssa Yan-Zhen Liu;Wuh-Liang Hwu;Chuan-Jen Hsu. 2009. Laryngoscope. 119. PMID: 19718752

OBJECTIVES/HYPOTHESIS: To develop a cost-effective and robust genetic diagnostic tool for patients with idiopathic nonsyndromic sensorineural hearing impairment. STUDY DESIGN: Development of a diagnostic tool and validation in a prospective cohort. METHODS: Twenty common sequence variants in GJB2, SLC26A4, and the mitochondrial 12S rRNA gene were selected based on our previous epidemiological study. These variants were analyzed using the SNaPshot technique. The efficacies of the SNaPshot multiplex assays were determined by using a prospective cohort composed of 214 unrelated Taiwanese patients with idiopathic sensorineural hearing impairment. The results of the assays were compared to the results obtained by direct sequencing. RESULTS: We developed a diagnostic technique consisting of two consecutive panels of SNaPshot multiplex assays, with each panel screening 10 common sequence variants. Theoretically, this design can detect more than 98% of the known deafness-associated sequence variants in Taiwanese individuals. A total of 126 (58.9%) patients were diagnosed as having at least one sequence variant using the SNaPshot multiplex assays. In total, the SNaPshot assays yielded an accuracy of more than 99%. CONCLUSIONS: The strengths of SNaPshot multiplex assays include high accuracy, high sensitivity, high flexibility (the examination panel can be easily expanded for additional mutations), low cost (less than US $10 per patient), and easy implementation for any institute with a DNA sequencer. Although only 20 to 30 mutations can be examined in two to three runs of the SNaPshot assay, this technology may be suitable for first-pass screening of deafness-associated mutations in populations with a relatively homogeneous ethnic background.
Etiologic and Audiologic Characteristics of Patients With Pediatric-Onset Unilateral and Asymmetric Sensorineural Hearing Loss. Pei-Hsuan Lin;Chuan-Jen Hsu;Yi-Hsin Lin;Yin-Hung Lin;Hui-Yu Lee;Chen-Chi Wu;Tien-Chen Liu. 2017. JAMA Otolaryngol Head Neck Surg. 143. PMID: 28687817

Importance: Pediatric-onset unilateral and asymmetric sensorineural hearing loss (SNHL) is a common condition, but in most patients, the cause remains unclear; thus, determination of the hearing outlook is difficult. Objective: To analyze the etiologic and audiologic characteristics of pediatric-onset unilateral and asymmetric SNHL. Design, Setting, and Participants: In this retrospective cohort study performed from January 1, 2008, through December 31, 2016, patients at a tertiary referral center who were diagnosed with pediatric-onset unilateral or asymmetric SNHL were divided into 3 groups according to their hearing levels: unilateral hearing loss with scaled-out levels (UHL-SO), unilateral hearing loss with residual hearing (UHL-RH), and asymmetric hearing loss (AHL). Main Outcomes and Measures: Basic demographic data, family and medical histories, audiologic results, imaging findings, and genetic results were ascertained and compared among patients of the 3 groups. Results: A total of 133 patients (mean [SD] age, 9.1 [10.9] years; 63 [47.4%] male and 70 [52.6%] female), including 50 with UHL-SO, 42 with UHL-RH, and 41 with AHL, were enrolled for analyses. Of 50 patients with UHL-SO, 49 (98.0%) had stable hearing levels with time, whereas 10 of 42 patients with UHL-RH (23.8%) and 18 of 41 patients with AHL (43.9%) revealed progressive or fluctuating hearing loss. Inner ear malformations detected with temporal bone high-resolution computed tomography, particularly cochlear aperture stenosis, were detected at higher rates in patients with UHL-SO (9 of 31 [29.0%]) and UHL-RH (6 of 24 [25.0%]) than in those with AHL (1 of 30 [3.3%]). In contrast, screening for mutations in 3 common deafness genes-GJB2, SLC26A4, and MTRNR1-achieved definite diagnosis in a higher percentage of patients with AHL (10 of 37 [27.0%]) than patients with UHL-SO (0 of 33) and UHL-RH (1 of 25 [4.0%]). Conclusions and Relevance: The UHL-SO and UHL-RH conditions share a common or similar etiopathogenesis different from that of AHL. Imaging studies and genetic testing might be prioritized during the respective general etiologic workups for patients with UHL and AHL. Regular hearing checkups are warranted for patients with UHL and AHL because a certain proportion of patients might sustain progression in SNHL.
Mutation Spectrum of Common Deafness-Causing Genes in Patients with Non-Syndromic Deafness in the Xiamen Area, China. Yi Jiang;Shasha Huang;Tao Deng;Lihua Wu;Juan Chen;Dongyang Kang;Xiufeng Xu;Ruiyu Li;Dongyi Han;Pu Dai. 2015. PLoS One. 10. PMID: 26252218

In China, approximately 30,000 babies are born with hearing impairment each year. However, the molecular factors causing congenital hearing impairment in the Xiamen area of Fujian province have not been evaluated. To provide accurate genetic testing and counseling in the Xiamen area, we investigated the molecular etiology of non-syndromic deafness in a deaf population from Xiamen. Unrelated students with hearing impairment (n = 155) who attended Xiamen Special Education School in Fujian Province were recruited for this study. Three common deafness-related genes, GJB2, SLC26A4, and mtDNA12SrRNA, were analyzed using all-exon sequencing. GJB2 mutations were detected in 27.1% (42/155) of the entire cohort. The non-syndromic hearing loss (NSHL) hotspot mutations c.109G>A (p.V37I) and c.235delC were found in this population, whereas the Caucasian hotspot mutation c.35delG was not. The allelic frequency of the c.109G>A mutation was 9.03% (28/310), slightly higher than that of c.235delC (8.39%, 26/310), which is the most common GJB2 mutation in most areas of China. The allelic frequency of the c.109G>A mutation was significantly higher in this Xiamen's deaf population than that in previously reported cohorts (P = 0.00). The SLC26A4 mutations were found in 16.77% (26/155) of this cohort. The most common pathogenic allele was c.IVS7-2A>G (6.13%, 19/310), and the second most common was the c.1079C>T (p.A360V) mutation (1.94%, 6/310) which has rarely been reported as a hotspot mutation in other studies. The mutation rate of mtDNA12SrRNA in this group was 3.87% (6/155), all being the m.A1555G mutation. These findings show the specificity of the common deaf gene-mutation spectrum in this area. According to this study, there were specific hotspot mutations in Xiamen deaf patients. Comprehensive sequencing analysis of the three common deaf genes can help portray the mutation spectrum and develop optimal testing strategies for deaf patients in this area.
Targeted next-generation sequencing in Uyghur families with non-syndromic sensorineural hearing loss. Ying Chen;Zhentao Wang;Zhaoyan Wang;Dongye Chen;Yongchuan Chai;Xiuhong Pang;Lianhua Sun;Xiaowen Wang;Tao Yang;Hao Wu. 2015. PLoS One. 10. PMID: 26011067

The mutation spectrum of deafness genes may vary in different ethnical groups. In this study, we investigated the genetic etiology of nonsyndromic deafness in four consanguineous and two multiplex Uyghur families in which mutations in common deafness genes GJB2, SLC26A4 and MT-RNR1 were excluded. Targeted next-generation sequencing of 97 deafness genes was performed in the probands of each family. Novel pathogenic mutations were identified in four probands including the p.L416R/p.A438T compound heterozygous mutations in TMC1, the homozygous p.V1880E mutation in MYO7A, c.1238delT frameshifting deletion in PCDH15 and c.9690+1G>A splice site mutation in MYO15A. Co-segregation of the mutations and the deafness were confirmed within each family by Sanger sequencing. No pathogenic mutations were identified in one multiplex family and one consanguineous family. Our study provided a useful piece of information for the genetic etiology of deafness in Uyghurs.
A Family of H723R Mutation for SLC26A4 Associated with Enlarged Vestibular Aqueduct Syndrome. Sunghee Kim;Dae Gun Song;Jae Woong Bae;Soo-Young Choi;Un-Kyung Kim;Young Jun Choi;Kyu Yup Lee;Sang Heun Lee;Jung Rae Lee. 2009. Clin Exp Otorhinolaryngol. 2. PMID: 19565036

Recessive mutations of the SLC26A4 (PDS) gene on chromosome 7q31 can cause sensorineural deafness with goiter (Pendred syndrome, OMIM 274600) or NSRD with goiter (at the DFNB4 locus, OMIM 600791). H723R (2168A>G) is the most commonly reported SLC26A4 mutations in Korean and Japanese and known as founder mutation. We recently experienced one patient with enlarged vestibular aqueduct syndrome. The genetic study showed H723R homozygous in the proband and H723R heterozygous mutation in his family members. The identification of a disease-causing mutation can be used to establish a genotypic diagnosis and provide important information to both families and their physicians.
Genetic analysis through OtoSeq of Pakistani families segregating prelingual hearing loss. Mohsin Shahzad;Theru A Sivakumaran;Tanveer A Qaiser;Julie M Schultz;Zawar Hussain;Megan Flanagan;Munir A Bhinder;Diane Kissell;John H Greinwald;Shaheen N Khan;Thomas B Friedman;Kejian Zhang;Saima Riazuddin;Sheikh Riazuddin;Zubair M Ahmed. 2013. Otolaryngol Head Neck Surg. 149. PMID: 23770805

OBJECTIVE: To identify the genetic cause of prelingual sensorineural hearing loss in Pakistani families using a next-generation sequencing (NGS)-based mutation screening test named OtoSeq. STUDY DESIGN: Prospective study. SETTING: Research laboratory. SUBJECTS AND METHODS: We used 3 fluorescently labeled short tandem repeat (STR) markers for each of the known autosomal recessive nonsyndromic (DFNB) and Usher syndrome (USH) locus to perform a linkage analysis of 243 multigenerational Pakistani families segregating prelingual hearing loss. After genotyping, we focused on 34 families with potential linkage to MYO7A, CDH23, and SLC26A4. We screened affected individuals from a subset of these families using the OtoSeq platform to identify underlying genetic variants. Sanger sequencing was performed to confirm and study the segregation of mutations in other family members. For novel mutations, normal hearing individuals from ethnically matched backgrounds were also tested. RESULTS: Hearing loss was found to co-segregate with locus-specific STR markers for MYO7A in 32 families, CDH23 in 1 family, and SLC26A4 in 1 family. Using the OtoSeq platform, a microdroplet PCR-based enrichment followed by NGS, we identified mutations in 28 of the 34 families including 11 novel mutations. Sanger sequencing of these mutations showed 100% concordance with NGS data and co-segregation of the mutant alleles with the hearing loss phenotype in the respective families. CONCLUSION: Using NGS-based platforms like OtoSeq in families segregating hearing loss will contribute to the identification of common and population-specific mutations, early diagnosis, genetic counseling, and molecular epidemiology.
[Diagnostic function of SLC26A4 hot spot mutations screening to enlarged vestibular aqueduct syndrome]. Qi Li;Ruping Fang;Yiwen You;Yong Wang;Pu Dai. 2010. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 24. PMID: 21174747

OBJECTIVE: To investigate the frequencies of SLC26A4 hot spot mutations by genetic testing method in non-syndromic hearing loss children. The feasibility of genetic screening method in finding enlarged vestibular aqueduct syndrome was confirmed by temporal bone CT scan. METHOD: Ninety-two children with moderate-profound hearing loss were enrolled and DNA were extracted from peripheral blood. SLC26A4 IVS7-2A > G and H723R mutations were analyzed by direct sequencing. The individual with homozygous, compound heterozygous or heterozygous SLC26A4 mutations was given further temporal CT scan. RESULT: The sequencing results revealed 11 (12.0%) cases carrying SLC26A4 mutations, including 5 cases of bi-allelic mutation and 6 cases of single allelic mutation. CONCLUSION: The SLC26A4 mutations has a high carrying rate in non-syndromic hearing loss children. The screening for the SLC26A4 gene mutations is useful in the diagnosis of EVAS.
Genotyping data and novel haplotype diversity of STR markers in the SLC26A4 gene region in five ethnic groups of the Iranian population. Marjan Mojtabavi Naeini;Hamzeh Mesrian Tanha;Morteza Hashemzadeh Chaleshtori;Sadeq Vallian. 2014. Genet Test Mol Biomarkers. 18. PMID: 25390158

BACKGROUND AND AIMS: SLC26A4 gene mutations are the second currently identifiable genetic cause of autosomal recessive nonsyndromic hearing loss after GJB2 mutations. Because of the extensive size of the SLC26A4 gene and the variety of mutations, indirect diagnosis using linkage analysis has been suggested. Therefore, in this investigation three potential short tandem repeat (STR) markers related to this region including D7S2420, D7S496, and D7S2459 were selected for further analysis. METHODS: The characteristics and haplotype frequency of the markers were examined for the first time in five ethnic groups of the Iranian population including Fars, Azari, Turkmen, Gilaki, and Arab using the polymerase chain reaction followed by fluorescent capillary electrophoresis. RESULTS were analyzed by GeneMarker HID Human STR Identity, GenePop, Microsatellite tools, PowerMarker 3.25, and Arlequin 3.5 software. RESULTS: Analysis of the allelic frequency revealed the presence of 11, 10, and 8 alleles for D7S2420, D7S496, and D7S2459 markers, respectively, in the Iranian population. The detailed analysis of each ethnic group was reported. Calculated polymorphism information content values were above 0.7 in the Iranian population. Pairwise linkage disequilibrium (LD) revealed a significant LD in pairing markers of D7S2420-D7S496 and in D7S496-D7S2459. Estimation of the haplotype frequency showed the presence of 20, 13, 15, 15, and 20 informative haplotypes in Fars, Azari, Turkmen, Gilaki, and Arabian ethnics, respectively. CONCLUSION: Together, the investigated markers could be suggested as powerful tools for linkage analysis of SLC26A4 gene mutations in the Iranian population.
The role of transcription factors of neurosensory cells in non-syndromic sensorineural hearing loss with or without inner ear malformation. Yuan Zhou;Jie Qing;Yunpeng Dong;Jin Nie;Jingkun Li;Chunmei Wang;Yuyuan Liu;Tao Peng;Maoli Duan;Xuezhong Liu;Dinghua Xie. 2015. Acta Otolaryngol. 136. PMID: 26634621

CONCLUSIONS: Previous studies have stated the roles and correlation of the four TFs (Sox2, Atoh1, Neurog1, and Neurod1) in the development of neurosensory cells. but whether they are inherited pathogenic factors to cause non-syndromic sensorineural hearing loss is unknown so far. This is the first time for screening the Sox2, Atoh1, Neurog1, and Neurod1 genes in children with NSHL. The c.133A > G in Neurod1 gene is a polymorphism, which is not associated with NSHL. Although these genes are the recognized TFs for modulating the development and transformation of NSCs, they may not be the inherited pathogenic factors to cause congenital severe or profound NSHL directly. OBJECTIVE: To investigate the effect of the transcription factors (TFs) for the development of neurosensory cells (NSCs) and to explore the genetic etiology of congenital profound non-syndromic sensorineural hearing loss (NSHL). METHODS: Children with NSHL, from multi-national and regional group, and control group were recruited to screen for the most common mutations for non-syndromic deafness among East Asian (mtDNA 12S rRNA: 1555A > G, 1494C > T; SLC26A4: IVS7-2 A > G, 2168 C > T). And mutational analysis of the coding regions in Sox2, Atoh1 and Neurog1, Neurod1 genes were performed. RESULTS: Only the c.133A > G (p. Ala45Thr) in the Neurod1 gene was detected in this study. The allele frequencies of this variant were 88.00% and 84.88% in the inner ear malformation group and the normal inner ear group, respectively, while 90.85% of children in the control group carried c.133A > G. This variant existed in every group commonly and had no significant difference among them. No variant in the other two TFs was detected in this cohort.
Identification of novel functional null allele of SLC26A4 associated with enlarged vestibular aqueduct and its possible implication. Jeong Hun Jang;Jinsei Jung;Ah Reum Kim;Young Mi Cho;Min Young Kim;Sang Yeon Lee;Jae Young Choi;Jun Ho Lee;Byung Yoon Choi. 2014. Audiol Neurootol. 19. PMID: 25358692

Mutations in the SLC26A4 gene, which encodes pendrin, cause congenital hearing loss as a manifestation of Pendred syndrome (PS) with an iodide organification defect or nonsyndromic enlarged vestibular aqueduct (NSEVA, DFNB4). There have been reports of differences between PS and NSEVA, including their auditory phenotypes and molecular genetic bases. For appropriate genetic diagnosis and counseling, it is important to functionally characterize SLC26A4 variants. In this study, we identified and evaluated a novel null mutation of SLC26A4 and report our method of assessing the pathogenic potential of mutations in SLC26A4, one of the most frequent causative genes of deafness in humans. A 3-year-old female with progressive sensorineural hearing loss and her parents were recruited. They underwent clinical, audiological, radiological and genetic evaluations, which revealed that the female patient had an enlarged vestibular aqueduct and an incomplete partition type II anomaly in the cochlea bilaterally. Sanger sequencing of the SLC26A4 gene was also performed. For a confirmatory genetic diagnosis, we first characterized the anion/base exchange ability of mutant pendrin products in HEK 293 cells and, if necessary, evaluated whether the mutant pendrin traffics to the plasma membrane in COS-7 cells. We also expressed a null function mutant, p.H723R, and a previously documented polymorphism, p.P542R, as controls. The pure tone average was 66 dB HL in the right ear and 75 dB HL in the left ear. Sequencing of SLC26A4 revealed a known pathogenic mutation (p.H723R) and a novel missense variant (p.V510D) as a compound heterozygote. When we expressed the p.V510D mutant pendrin in mammalian cells, the rate constants for Cl-/HCO3- exchange were 10.96±4.79% compared with those of wild-type pendrin. This figure was comparable to that of p.H723R, indicating p.V510D to be another pathogenic mutation with a null function. The p.V510D pendrin product was shown to be entrapped in the endoplasmic reticulum (ER) at 24-30 h after transfection, and not trafficked to the plasma membrane in COS-7 cells, suggesting retention in the ER and abnormal trafficking as the pathogenic mechanism. This was similar to p.H723R, which is a null function founder mutant in this population but is a candidate variant for future drug therapy to rescue the abnormal cell trafficking. Impaired cellular trafficking due to ER retention and abolished exchange activity of the newly detected p.V510D indicates the pathogenic potential of this variant. These missense variants may be good candidate variants for drug therapy if the intrinsic exchange activity is not damaged by the change.
Prestin, a cochlear motor protein, is defective in non-syndromic hearing loss. Xue Zhong Liu;Xiao Mei Ouyang;Xia Juan Xia;Jing Zheng;Arti Pandya;Fang Li;Li Lin Du;Katherine O Welch;Christine Petit;Richard J H Smith;Bradley T Webb;Denise Yan;Kathleen S Arnos;David Corey;Peter Dallos;Walter E Nance;Zheng Yi Chen. 2003. Hum Mol Genet. 12. PMID: 12719379

Prestin, a membrane protein that is highly and almost exclusively expressed in the outer hair cells (OHCs) of the cochlea, is a motor protein which senses membrane potential and drives rapid length changes in OHCs. Surprisingly, prestin is a member of a gene family, solute carrier (SLC) family 26, that encodes anion transporters and related proteins. Of nine known human genes in this family, three (SLC26A2, SLC26A3 and SLC26A4) are associated with different human hereditary diseases. The restricted expression of prestin in OHCs, and its proposed function as a mechanical amplifier, make it a strong candidate gene for human deafness. Here we report the cloning and characterization of four splicing isoforms for the human prestin gene (SLC26A5a, b, c and d). SLC26A5a is the predominant form of prestin whereas the others showed limited distribution associated with certain developmental stages. Based on the functional importance of prestin we screened for possible mutations involving the prestin gene in a group of deaf probands. We have identified a 5'-UTR splice acceptor mutation (IVS2-2A>G) in exon 3 of the prestin gene, which is responsible for recessive non-syndromic deafness in two unrelated families. In addition, a high frequency of heterozygosity for the same mutation was observed in these subjects, suggesting the possibility of semi-dominant influence of the mutation in causing hearing loss. Finally, the observation of this mutation only in the Caucasian probands indicated an association with a specific ethnic background. This study thereby reveals an essential function of prestin in human auditory processing.
Screening and analysis of mutation hot-spots in deafness-associated genes among adolescents with hearing loss. Hong Jiang;Qizhen Liu;Lihong Chen. 2015. Mol Med Rep. 12. PMID: 26499821

The present study aimed to screen the hot-spot deafness gene mutations of adolescents with non‑syndromic hearing loss in Yongchuan, Chongqing (CQ-YC ANSHL), aiming to preliminarily understand the region's spectrum and occurrence frequency of deafness gene mutation hot‑spots. A total of 60 CQ‑YC ANSHL were selected from the Special Education School of Yongchuan, Chongqing and the nine most common mutations of four deafness genes among the Chinese population were detected and associated with the patients' medical history as well as family history of deafness. Deafness gene mutations were detected in 22 cases, among which the detection rates of GJB2, mitochondrial 12S ribosomal ribonucleic acid and SLC26A4 mutations were 23.73% (14/59), 10.17% (6/59) and 5.08% (3/59), respectively, while no GJB3 mutation was detected. The carrying rate of deafness gene mutations in CQ‑YC ANSHL was high; therefore, based on the deafness gene diagnosis, the combination of medication guidance, pre‑natal diagnosis and clinical interventions may be able to effectively reduce the incidence of deafness in this region.
Genetic Linkage Analysis of 15 DFNB Loci in a Group of Iranian Families with Autosomal Recessive Hearing Loss. Ma Tabatabaiefar;F Alasti;M Montazer Zohour;L Shariati;E Farrokhi;Dd Farhud;Gv Camp;Mr Noori-Daloii;M Hashemzadeh Chaleshtori. 2011. Iran J Public Health. 40. PMID: 23113071

BACKGROUND: Hearing loss (HL) is the most frequent sensory birth defect in humans. Autosomal recessive non-syndromic HL (ARNSHL) is the most common type of hereditary HL. It is extremely heterogeneous and over 70 loci (known as DFNB) have been identified. This study was launched to determine the relative contribution of more frequent loci in a cohort of ARNSHL families. METHODS: Thirty-seven Iranian families including 36 ARNSHL families and 1 family with Pendred syndrome each with ≥ 4 affected individuals, from seven provinces of Iran, were ascertained. DFNB1 contribution was initially studied by DNA sequencing of GJB2 and linkage analysis using the relative STR markers. The excluded families were then subjected to homozygosity mapping for fifteen ARNSHL loci. RESULTS: Sixteen families were found to be linked to seven different known loci, including DFNB1 (6 families), DFNB4 (3 families +1 family with Pendred syndrome), DFNB63 (2 families), DFNB2 (1 family), DFNB7/11 (1 family), DFNB9 (1 family) and DFNB21 (1 family). DNA sequencing of the corresponding genes is in progress to identify the pathogenic mutations. CONCLUSION: The genetic causes were clarified in 43.2% of the studied families, giving an overview of the causes of ARNSHL in Iran. DFNB4 is ranked second after DFNB1 in the studied cohort. More genetic and epigenetic investigations will have to be done to reveal the causes in the remaining families.
Genetic characteristics of the couple with non-syndromic sensorineural hearing loss and fertility guidance. Ri-Ming Liu;Hong-Jie Liu;Jiang-Lin Cong;Ai-Ling Sun;Jiang-Dong Du;Cheng-Ming Sun. 2016. Int J Clin Exp Med. 8. PMID: 26885137

PURPOSE: We aim to report a genetic testing and fertility guidance for the deaf through analyzing pedigree and molecular genetic characteristics of the couple who have non-syndromic sensorineural hearing loss (NSHL). METHODS: One of hospitalized congenial deaf couple and family members were included in this study. The wife was twin pregnant woman and her gestational age was 31(+5) pregnant weeks. The DNA was extracted from peripheral blood and umbilical vein blood, respectively. Mutation screening of common deafness genes was performed in pregnant women and other family members. Nine common mutations in four major deafness genes, GJB2 (35delG, 176del16, 235delC, 299delAT), GjB3 (C538T), SLC26A4 (IVS7-2A>G, A2168G) and Mitochondrial 12S rRNA (A1555G, C1494T), were detected simultaneously with a microarray based method. SLC26A4 whole genome sequencing was carried out for the results of the DNA microarray. According to the test results, the couple chose abortion termination of pregnancy twins, and after one year obtained singleton pregnancy by artificial insemination by donor (AID). In week 16 of pregnancy, amniocentesis had been done to collect fetal somatic cell and extract DNA, and then the above tests had been repeated. RESULTS: The couple had SLC26A4 combined heterozygous mutation. Both parents had SLC26A4 single heterozygous mutation. Twin fetuses had SLC26A4 combined heterozygous mutation. The probability of naturally being pregnant and bearing deaf children for the pregnant women was 100%. Fetus obtained by AID had SLC26A4 single heterozygous mutation. After the birth of the baby, her hearing has been normal. CONCLUSIONS: To reduce children with congenital deafness, screening high mutation sites by microarray, combined with pedigree analysis and gene sequencing is effective, and should be used as a routine inspection item for the deaf before marriage and pregnancy. On the basis of genetic testing for the couple with hearing loss, human assisted reproductive technology is a viable option to avoid the birth of infant with hereditary deafness.
Pendred syndrome (goitre and sensorineural hearing loss) maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4. B Coyle;R Coffey;J A Armour;E Gausden;Z Hochberg;A Grossman;K Britton;M Pembrey;W Reardon;R Trembath. 1996. Nat Genet. 12. PMID: 8630497

Inherited causes account for about 50% of individuals presenting with childhood (prelingual) hearing loss, of which 70% are due to mutation in numerous single genes which impair auditory function alone (non-syndromic). The remainder are associated with other developmental anomalies termed syndromic deafness. Genes responsible for syndromic forms of hearing loss include the COL4A5 gene in Alport syndrome and the PAX3 and MITF genes in Waardenburg syndrome. Pendred syndrome is an autosomal recessive disorder associated with developmental abnormalities of the cochlea, sensorineural hearing loss and diffuse thyroid enlargement (goitre). Pendred syndrome is the most common syndromal form of deafness, yet the primary defect remains unknown. We have established a panel of 12 families with two or more affected individuals and used them to search for the location of the Pendred gene by linkage analysis. We excluded localization to four previously mapped nonsyndromic deafness loci but obtained conclusive evidence for linkage of the Pendred syndrome gene to microsatellite markers on chromosome 7q31 (D7S495 Zmax 7.32, Qmax = 0). This region contains a gene, DFNBL, for autosomal recessive non-syndromic sensorineural hearing loss. Multipoint analysis indicates that DFNB4 and Pendred syndrome co-localize to the same 5.5 centiMorgan (cM) interval flanked by D7S501 and D7S523. These data raise the possibility that Pendred syndrome is either allelic with DFNB4 or may represent an inherited contiguous gene disorder, not clinically manifest in the heterozygote.
A novel compound heterozygous mutation of SLC26A4 in two Chinese families with nonsyndromic hearing loss and enlarged vestibular aqueducts. Guang-Jie Zhu;Lu-Sen Shi;Han Zhou;Ye Yang;Jie Chen;Xia Gao. 2017. Mol Med Rep. 16. PMID: 28990112

Enlarged vestibular aqueduct (EVA)‑associated hearing loss is frequently detected in individuals carrying the SLC26A4 mutation in the Chinese population. The present study aimed to identify the causative SLC26A4 coding mutations in a patient group with nonsyndromic hearing loss (NSHL) and EVA. Genomic DNA was extracted from blood samples obtained from 52 NSHL patients with EVA and from 60 normal controls. The mutation analysis for 20 coding exons of SLC26A4 was performed by direct sequencing. The results of the mutational analysis showed that there were two probands from two separate families suffering from bilateral sensorineural hearing loss with EVA, carrying the same novel compound heterozygous mutation of SLC26A4 (c.1644_1645insA and c.2168A>G). Other members of the two families had heterozygous mono‑allelic mutations with normal hearing. However, neither of these mutations were detected in the 60 normal controls. These results are the first, to the best of our knowledge, to link the compound heterozygote mutation, c.1644_1645insA and c.2168A>G, in the SLC26A4 gene to NSHL patients with EVA. The two mutations identified in the present study were located in the anti‑sigma factor antagonist domain, the core region for plasma membrane targeting of anion transporters, which suggested that the reduced or complete loss of SLC26A4 function was the direct cause of hearing loss in the two patients. These results provide a foundation for further elucidating the genetic factors responsible for EVA‑associated NSHL.
[Analysis common gene mutation spots of 127 non-syndromic deafness natients in Guangxi Drovince]. Shuixia Liu;Liang Xu;Bowen Chen;Min Liu;Shenghong Qu;Jianping Liang;Fengzhu Tang;Min Shi;Lu Peng;Yan Jing;Fengti Li;Youqiong Liang. 2016. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 29. PMID: 26911057

OBJECTIVE: To investigate the mutation characteristics of common deafness gene from 127 non-syndromic hearing loss patients in Guangxi province. METHOD: Deafness-related gene mutations detection kit was used to detect 15 mutation sites in four deafness-associated genes, and a total of 127 hearing impaired patients were tested. The samples that could not be diagnosed with DNA microarray were subjected to PCR and sequenced to detect other mutations. RESULT: Among the 127 patients with non-syndromic deafness, the total mutation rate is 8.66% (11/127), including GJB2 235delC homozygous in 3 cases (2.36%), 235delC single heterozygous mutation in 2 cases (1.57%), GJB2 235delC and 109 A > G mutations in 2 cases (1.57%); SLC26A4 1229C > T homozygous in 1 case (0.79%), IVS7-2A > G, IVS11 + 47T > C and 15448insC mutaion in 2 cases (1.57%); mitochondrial 12S rRNA gene mutations were not detected. The result indicates that GJB2 and SLC26A4 were the main genes in this study, and the mutation rate is significantly lower than the national average level. Three new mutations (SLC26A4 IVS11 + 47T > C,1548insC and GJB2 109A > G) were found. There may be rare mutations among sites or genes associated with deafness in Guangxi.
Causes of hearing impairment in the Norwegian paediatric cochlear implant program. Geir Siem;Toril Fagerheim;Christoffer Jonsrud;Claude Laurent;Erik Teig;Sten Harris;Trond P Leren;Andreas Früh;Ketil Heimdal. 2010. Int J Audiol. 49. PMID: 20553101

Severe to profound hearing impairment (HI) is estimated to affect around 1/2000 young children. Advances in genetics have made it possible to identify several genes related to HI. This information can cast light upon prognostic factors regarding the outcome in cochlear implantation, and provide information both for scientific and genetic counselling purposes. From 1992 to 2005, 273 children from 254 families (probands) were offered cochlear implants in Norway. An evaluation of the causes of HI, especially regarding the genes GJB2, GJB6, SLC26A4, KCNQ1, KCNE1, and the mutation A1555G in mitochondrial DNA was performed in 85% of the families. The number of probands with unknown cause of HI was thus reduced from 120 to 68 (43% reduction). Ninety-eight (46%) of the probands had an identified genetic etiology of their HI. A relatively high prevalence of Jervell and Lange-Nielsen syndrome was found. The main causes of severe and profound HI were similar to those found in other European countries. GJB2 mutations are a common cause of prelingual HI in Norwegian cochlear implanted children.
Prevalence of mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes in 103 children with sensorineural hearing loss in Shaoxing, China. Hong Yu;Dan Liu;Jingqun Yang;Zhiqiang Wu. 2018. Ear Nose Throat J. 97. PMID: 30036422

Mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes are known to be a common cause of hearing loss. However, the frequency of hot-spot mutations and genotype-phenotype correlations in patients with sensorineural hearing loss (SNHL) has been less frequently reported. We conducted a study of 103 children-56 boys and 47 girls, aged 5 months to 9 years (mean: 4.1 yr)-with SNHL who underwent genetic screening for 20 hot-spot mutations of the GJB2, SLC26A4, GJB3, and MT-RNR1 genes. Mutations were detected by multiple-PCR-based MALDI-TOF MS assay. At least one mutated allele was detected in 48 patients (46.6%), and 30 patients (29.1%) carried pathogenic mutations. Among all the detected mutations, the most common were GJB2 c.235delC and SLC26A4 c.919-2A>G, with allele frequencies of 23.8 and 6.8%, respectively. At least one mutant allele of SLC26A4 was detected in the 13 patients who had an enlarged vestibular aqueduct (EVA). Almost half of the children with SNHL carried a common deafness-related mutation, and nearly one-third carried a pathogenic mutation. The mutations in SLC26A4 were prevalent and correlated strongly with EVA.
Clinical application of genetic testing for deafness. Richard J H Smith. 2004. Am J Med Genet A. 130A. PMID: 15368487

Advances in the molecular biology of hearing and deafness have identified many genes essential for normal auditory function. Allele variants of these genes cause nonsyndromic deafness, making mutation screening a valuable test to unequivocally diagnose many different forms of inherited deafness. In this study, genetic testing of GJB2, SLC26A4 and WFS1 is reviewed.
Molecular Analysis of Twelve Pakistani Families with Nonsyndromic or Syndromic Hearing Loss. Rongrong Wang;Shirui Han;Amjad Khan;Xue Zhang. 2017. Genet Test Mol Biomarkers. 21. PMID: 28281779

AIM: To investigate the causative genetic mutations in 12 Pakistani families with nonsyndromic or syndromic hearing loss. METHODS: Mutations in the most common causative gene for hearing loss, GJB2, were evaluated by Sanger sequencing. Targeted next-generation sequencing or whole-exome sequencing was used to analyze the genomic DNA samples from 11 probands with hearing loss. Sanger sequencing was performed to verify all identified variants. RESULTS: We found pathogenic, or likely to be pathogenic, mutations in all 12 families, including six known mutations in GJB2, SLC26A4, LHFPL5, and USH2A and eight novel mutations in ESPN, MYO7A, LRTOMT, PCDH15, USH2A, or EPS8L2. Notably, four compound heterozygous mutations in the MYO7A and USH2A genes were detected in two consanguineous families. In addition, the novel frameshift mutation in EPS8L2 was first documented in Pakistan. CONCLUSIONS: Our study increases the spectrum of mutations associated with hearing loss in the Pakistani population. In addition, our study highlights the fact that compound heterozygous mutations, although rare, can occur in consanguineous families.
Analysis of the thyroid phenotype in 42 patients with Pendred syndrome and nonsyndromic enlargement of the vestibular aqueduct. Miriam Ladsous;Virginie Vlaeminck-Guillem;Viviane Dumur;Christophe Vincent;Frédérique Dubrulle;Claire-Marie Dhaenens;Jean-Louis Wémeau. 2013. Thyroid. 24. PMID: 24224479

BACKGROUND: Pendred syndrome (PS), a recessive disorder caused by mutations in the SLC26A4 (PDS) gene, is associated with deafness and goiter. SLC26A4 mutations have also been identified in patients exhibiting isolated sensorineural hearing loss without apparent thyroid abnormality (nonsyndromic enlargement of the vestibular aqueduct; nonsyndromic EVA). Our aim was to describe systematically the thyroidal phenotypes and the SLC26A4 genotypes of patients presenting with PS or nonsyndromic EVA. METHODS: Nineteen patients with PS and 23 patients with nonsyndromic EVA, aged 5-53 years, were included. They underwent thyroid evaluation (physical examination, biological thyroid function tests, measurement of thyroglobulin level, thyroid ultrasonography, and thyroid (123)I scintigraphy with perchlorate discharge test), otological evaluation, and SLC26A4 mutation screening. RESULTS: In 19 patients with PS, goiter was identified in 15 (79%) and hypothyroidism in 15 (79%); hypothyroidism was subclinical in four patients and congenital in six patients. The perchlorate discharge test (PDT) was positive in 10/16 (63%). Morphological evaluation of the inner ear using MRI and/or CT showed bilateral EVA in 15/15 PS patients. Mutation screening revealed two SLC26A4 mutant alleles in all 19 PS patients that were homozygous in two families and compound heterozygous in 12 families. In the 23 patients with nonsyndromic EVA, systematic thyroid evaluation found no abnormalities except for slightly increased thyroglobulin levels in two patients. SLC26A4 mutations were identified in 9/23 (39%). Mutations were biallelic in two (compound heterozygous) and monoallelic in seven patients. CONCLUSION: The thyroid phenotype is widely variable in PS. SLC26A4 mutation screening is needed in patients exhibiting PS or nonsyndromic EVA. PS is associated with biallelic SLC26A4 mutations and nonsyndromic EVA with no, monoallelic, or biallelic SLC26A4 mutations. Systematic thyroid evaluation is recommended in patients with nonsyndromic EVA associated with one or two SLC26A4 mutations. We propose using a combination of three parameters to define and diagnose PS: (i) sensorineural deafness with bilateral EVA; (ii) thyroid abnormality comprising goiter and/or hypothyroidism and/or a positive PDT; (iii) biallelic SLC26A4 mutations.
High phenotypic intrafamilial variability in patients with Pendred syndrome and a novel duplication in the SLC26A4 gene: clinical characterization and functional studies of the mutated SLC26A4 protein. Laura Fugazzola;Valentina Cirello;Silvia Dossena;Simona Rodighiero;Marina Muzza;Pierangela Castorina;Faustina Lalatta;Umberto Ambrosetti;Paolo Beck-Peccoz;Guido Bottà;Markus Paulmichl. 2007. Eur J Endocrinol. 157. PMID: 17766716

OBJECTIVE: Pendred syndrome (PS) is characterized by the association of sensorineural hearing loss (SNHL) and a partial iodide organification defect at the thyroid level. It is caused by mutations in the SLC26A4 gene. The encoded transmembrane protein, called pendrin, has been found to be able to transport chloride and other anions. DESIGN: The aim of the present study was to characterize a family with PS, which shows a strong intrafamilial phenotypic variability, including kidney atrophy in one member. The age of disease-onset was significantly different in all three affected siblings, ranging from 2 to 21 years for thyroid alterations and from 1.5 to 11 years for SNHL. METHODS: Clinical and genetic studies were carried out in affected siblings. The functional activity of the novel duplication found was studied by a fluorimetric method in a human renal cell line (HEK293 Phoenix) in which the protein was overexpressed. RESULTS: All three siblings were found to be compound heterozygotes for the missense mutation (1226G>A, R409H) and for a novel 11 bp duplication (1561_1571CTTGGAATGGC, S523fsX548). The latter mutation creates a frame shift leading to the loss of the entire carboxy-terminus domain. Functional studies of this mutant demonstrated impaired transport of chloride and iodide when expressed in HEK 293 Phoenix cells, when compared with wild type pendrin. CONCLUSIONS: A novel 11 bp duplication was found in a family with Pendred syndrome, showing a high intrafamilial phenotypic variability. An impaired transmembrane anionic transport of the mutated SLC26A4 protein was demonstrated in functional studies using a heterologous cell system.
Mutation analysis of SLC26A4 (Pendrin) gene in a Brazilian sample of hearing-impaired subjects. Renata Watanabe Nonose;Karina Lezirovitz;Maria Teresa Balester de Mello Auricchio;Ana Carla Batissoco;Guilherme Lopes Yamamoto;Regina Célia Mingroni-Netto. 2018. BMC Med Genet. 19. PMID: 29739340

BACKGROUND: Mutations in the SLC26A4 gene are associated with Pendred syndrome and autosomal recessive non-syndromic deafness (DFNB4). Both disorders have similar audiologic characteristics: bilateral hearing loss, often severe or profound, which may be associated with abnormalities of the inner ear, such as dilatation of the vestibular aqueduct or Mondini dysplasia. But, in Pendred syndrome (OMIM #274600), with autosomal recessive inheritance, besides congenital sensorineural deafness, goiter or thyroid dysfunctions are frequently present. The aim of this study was to determine whether mutations in SLC26A4 are a frequent cause of hereditary deafness in Brazilian patients. METHODS: Microsatellite haplotypes linked to SLC26A4 were investigated in 68 families presenting autosomal recessive non-syndromic deafness. In the probands of the 16 families presenting segregation consistent with linkage to SLC26A4, Sanger sequencing of the 20 coding exons was performed. In an additional sample of 15 individuals with suspected Pendred syndrome, because of the presence of hypothyroidism or cochleovestibular malformations, the SLC26A4 gene coding region was also sequenced. RESULTS: In two of the 16 families with indication of linkage to SLC26A4, the probands were found to be compound heterozygotes for probably pathogenic different mutations: three novel (c.1003 T > G (p. F335 V), c.1553G > A (p.W518X), c.2235 + 2 T > C (IVS19 + 2 T > C), and one already described, c.84C > A (p.S28R). Two of the 15 individuals with suspected Pendred syndrome because of hypothyreoidism or cochleovestibular malformations were monoallelic for likely pathogenic mutations: a splice mutation (IVS7 + 2 T > C) and the previously described c.1246A > C (p.T416P). Pathogenic copy number variations were excluded in the monoallelic cases and in those with normal results after Sanger sequencing. Additional mutations in the SLC26A4 gene or other definite molecular cause for deafness were not identified in the monoallelic patients, after exome sequencing. CONCLUSIONS: Biallelic pathogenic mutations in SLC26A4 explained ~ 3% of cases selected because of autosomal recessive deafness. Monoallelic mutations were present in ~ 13% of isolated cases of deafness with cochleovestibular malformations or suspected Pendred syndrome. These data reinforce the importance of mutation screening of SLC26A4 in Brazilian subjects and highlight the elevated frequency of monoallelic patients.
Identification of TMPRSS3 as a Significant Contributor to Autosomal Recessive Hearing Loss in the Chinese Population. Xue Gao;Sha-Sha Huang;Yong-Yi Yuan;Jin-Cao Xu;Ping Gu;Dan Bai;Dong-Yang Kang;Ming-Yu Han;Guo-Jian Wang;Mei-Guang Zhang;Jia Li;Pu Dai. 2017. Neural Plast. 2017. PMID: 28695016

Hereditary hearing loss is characterized by a high degree of genetic heterogeneity. Mutations in the TMPRSS3 (transmembrane protease, serine 3) gene cause prelingual (DFNB10) or postlingual (DFNB8) deafness. In our previous study, three pathogenic mutations in TMPRSS3 were identified in one Chinese family. To evaluate the importance of TMPRSS3 mutations in recessive deafness among the Chinese, we screened 150 autosomal recessive nonsyndromic hearing loss (ARNSHL) families and identified 6 that carried seven causative TMPRSS3 mutations, including five novel mutations (c.809T>A, c.1151T>G, c.1204G>A, c.1244T>C, and c.1250G>A) and two previously reported mutations (c.323-6G>A and c.916G>A). Each of the five novel mutations was classified as severe, by both age of onset and severity of hearing loss. Together with our previous study, six families were found to share one pathogenic mutation (c.916G>A, p.Ala306Thr). To determine whether this mutation arose from a common ancestor, we analyzed six short tandem repeat (STR) markers spanning the TMPRSS3 gene. In four families, we observed linkage disequilibrium between p.Ala306Thr and STR markers. Our results indicate that mutations in TMPRSS3 account for about 4.6% (7/151) of Chinese ARNSHL cases lacking mutations in SLC26A4 or GJB2 and that the recurrent TMPRSS3 mutation p.Ala306Thr is likely to be a founder mutation.
[Analysis of the hereditary etiology of 336 patients with non-syndromic sensorineural hearing loss from Ningxia Hui Autonomous Region of China]. Yan-li Wang;Yi-ming Zhu;Xiao-wen Liu;Bai-cheng Xu;Yu-fen Guo;Qiu-ju Wang. 2012. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 47. PMID: 23141447

OBJECTIVE: To investigate the molecular genetic causes and their characteristics of deafness in Ningxia province, we established screening of three common hereditary deafness genes in 336 deaf and hard-of-hearing patients in this district. METHODS: Peripheral blood samples were obtained from a total of 336 patients with non-syndromic sensorineural hearing loss in parts of special education schools in Ningxia province to extract genomic DNA. The mitochondrial DNA 12S rRNA m.1555A > G mutation was screened by PCR Alw26I digestion and sequence analysis PCR and direct sequencing were used to analyze the coding region of GJB2 and exons 8 and 19 of SLC26A4. Statistical analysis was performed by using SPSS 11.0 software. Frequencies of different GJB2 or SLC26A4 mutations were compared between Han and Hui people. RESULTS: Among these 336 patients, seven cases (2.08%, 7/336) were found to carry mtDNA 12S rRNA m.1555A > G homozygous mutation, 45 cases (13.39%) were caused by GJB2 mutations and 28 cases (8.33%) had two mutated alleles (homozygote and compound heterozygote) of SLC26A4. In detail, 16.67% (56/336) patients carried GJB2 mutations including 11 single mutant carriers. The allele frequency of c.235delC and c.299_300delAT were 9.52% (64/672) and 2.68% (18/672), respectively, making up 81.19% (82/101) of all pathogenic mutated alleles for GJB2. The single mutant allele carriers of SLC26A4 is 32, and two types (c.919-2A > G and c.2168A > G) accounted for 95.29% (24/27) mutations, totally. We also found that statistically significant differences in c.919-2A > G and c.2168A > G frequencies between Han and Hui people (c.919-2A > G, χ(2) = 8.229, P = 0.004; c.2168A > G, χ(2) = 5.277, P = 0.022). However, there was no statistically significant difference in GJB2 mutation between Han and Hui people. CONCLUSIONS: GJB2 mutation was a primary cause for non-syndromic sensorineural hearing loss in Ningxia province, and c.235delC was the most common mutant forms of GJB2. c.919-2A > G and c.2168A > G were common mutant forms of SLC26A4, their frequencies were also statistically significant differences between Han and Hui people.
Newborn genetic screening for hearing impairment: a population-based longitudinal study. Chen-Chi Wu;Ching-Hui Tsai;Chia-Cheng Hung;Yin-Hung Lin;Yi-Hsin Lin;Fang-Li Huang;Po-Nien Tsao;Yi-Ning Su;Yungling Leo Lee;Wu-Shiun Hsieh;Chuan-Jen Hsu. 2016. Genet Med. 19. PMID: 27308839

PURPOSE: The feasibility of genetic screening for deafness-causing mutations in newborns has been reported in several studies. The aim of this study was to investigate the long-term results in those who screened positive for deafness mutations; these results are crucial to determine the cost-effectiveness to justify population-wide genetic screening. METHODS: We performed simultaneous hearing screening and genetic screening targeting four common deafness mutations (p.V37I and c.235delC of GJB2, c.919-2A>G of SLC26A4, and the mitochondrial m.1555A>G) in 5173 newborns at a tertiary hospital between 2009 and 2015. Serial audiometric results up to 6 years old were then analyzed in children with conclusive genotypes. RESULTS: Newborn genetic screening identified 82 (1.6%) babies with conclusive genotypes, comprising 62 (1.2%) with GJB2 p.V37I/p.V37I, 16 (0.3%) with GJB2 p.V37I/c.235delC, and 4 (0.1%) with m.1555A>G. Of these, 46 (56.1%) passed hearing screening at birth. Long-term follow-up demonstrated progressive hearing loss in children with the GJB2 p.V37I/p.V37I and p.V37I/c.235delC genotypes; this hearing loss deteriorated by approximately 1 decibel hearing level (dBHL) per year. CONCLUSIONS: We delineated the longitudinal auditory features of the highly prevalent GJB2 p.V37I mutation on a general population basis and confirmed the utility of newborn genetic screening in identifying infants with late-onset or progressive hearing impairment undetectable by newborn hearing screening.Genet Med 19 1, 6-12.
[Detection of trisomy 21 by quantitative fluorescent PCR in clinical samples undergoing prenatal diagnosis for hereditary hearing loss]. Yan-ping Lu;Jing Cheng;Bing Han;Long-xia Wang;Pu Dai;Hui-jun Yuan;Ya-li Li. 2011. Zhonghua Fu Chan Ke Za Zhi. 46. PMID: 21781583

OBJECTIVE: To establish the genetic test technique of trisomy 21 concurrently conducts with prenatal diagnosis for hereditary hearing loss. METHODS: Fifty-four pregnant women who underwent prenatal diagnosis for hearing loss of their fetuses in Chinese People's Liberation Army General Hospital from March 2009 to May 2010 were enrolled in this study. All probands from the deaf families have confirmed the causative mutation for hearing loss in Genetic Testing Center in Chinese People's Liberation Army General Hospital. The mean age of 54 pregnant women is 31 years at pregnancy of 18 - 26 weeks, 5 cases > pregnancy of 23 weeks, 9 cases ≥ 35 years. All subjects did not conduct the serologic tests for trisomy 21 before. Fifteen to twenty ml amniotic fluid was drawn from 49 cases at pregnancy of 18 - 23 weeks and 5 cases > pregnancy of 23 weeks. One to two ml umbilical blood was drawn from 5 cases > pregnancy of 23 weeks. For 9 cases ≥ 35 years, amniotic fluid cell culture and karyotyping analysis were conducted concurrently. A multiple quantitative fluorescent (QF) PCR and six microsatellite markers were applied to diagnosis trisomy 21. The samples with peaks of 1:1:1 or 2:1 at two microsatellite markers can be diagnosed as trisomy 21. RESULTS: (1) Fifty-four fetuses were successfully conducted prenatal genetic diagnosis for hearing loss (included GJB2 and SLC26A4). Ten fetuses copied the exactly same genotypes as the probands. The other 44 cases fetuses did not copy the same genotypes as the probands and won't develop hearing loss. The hearing test showed normal hearing for the neonates. (2) All the 54 fetuses were excluded of trisomy 21 by QF-PCR and were verified after birth. Five fetuses with advanced maternal age were performed karyotyping analysis and showed normal. The diagnostic results of QF-PCR can be obtained in 1-3 days without misdiagnosed. CONCLUSIONS: QF-PCR is an efficient, rapid and accurate technique for detection of trisomy 21 without increasing sample amount. It can be used for fetuses who were undertaken hearing loss gene test or other prenatal gene test.
Newborn Screening of Genetic Mutations in Common Deafness Genes With Bloodspot-Based Gene Chip Array. Xuehu He;Xiuzhong Li;Yaqi Guo;Yue Zhao;Hui Dong;Jie Dong;Li Zhong;Zhiyun Shi;Yuying Zhang;Mario Soliman;Chunhua Song;Zhijun Zhao. 2017. Am J Audiol. 27. PMID: 29234782

Purpose: This study screens for deafness gene mutations in newborns in the Northwest China population. Method: The 9 sites of 4 common deafness genes (GJB2, GJB3, SLC26A4, and mt 12S rRNA) were detected by bloodspot-based gene chip array in 2,500 newborns. Results: We detected mutations of the 4 genes in 101 (4.04%) newborns; particularly, 0.20% detected the double mutations. In the Hui population, 4.58% of the newborns tested positive for mutations, whereas 4.01% of Han newborns tested positive for mutations. The detective rates are as follows: 1.44% for GJB2 235delC, 1.08% for SLC26A4 IVS7-2A>G, 0.48% for GJB2 299_300delAT, 0.28% for SLC26A4 2168A>G, 0.2% for mt 12S rRNA 1555A>G, and 0.16% for GJB3 538C>T. The 31.25% (5/16) of infants with GJB2 235delC, 50% (3/6) with GJB2 299_300delAT, and 25% (3/12) with SLC26A4 IVS7-2A>G showed abnormal hearing when tested; only 1 double mutation case received the hearing test, and this infant showed abnormality in both ears on the hearing test. Conclusions: High mutation rates in the common deafness genes were detected in newborns in Northwest China. Our study is helpful in understanding the deafness genomic epidemiology and also provides evidence for prenatal and postnatal care as well as policy making on population health in the region.
Functional differences of the PDS gene product are associated with phenotypic variation in patients with Pendred syndrome and non-syndromic hearing loss (DFNB4). D A Scott;R Wang;T M Kreman;M Andrews;J M McDonald;J R Bishop;R J Smith;L P Karniski;V C Sheffield. 2000. Hum Mol Genet. 9. PMID: 10861298

The PDS gene encodes a transmembrane protein, known as pendrin, which functions as a transporter of iodide and chloride. Mutations in this gene are responsible for Pendred syndrome and autosomal recessive non-syndromic hearing loss at the DFNB4 locus on chromosome 7q31. A screen of 20 individuals from the midwestern USA with non-syndromic hearing loss and dilated vestibular aqueducts identified three people (15%) with PDS mutations. To determine whether PDS mutations in individuals with Pendred syndrome differ functionally from PDS mutations in individuals with non-syndromic hearing loss, we compared three common Pendred syndrome allele variants (L236P, T416P and E384G), with three PDS mutations reported only in individuals with non-syndromic hearing loss (V480D, V653A and I490L/G497S). The mutations associated with Pendred syndrome have complete loss of pendrin-induced chloride and iodide transport, while alleles unique to people with DFNB4 are able to transport both iodide and chloride, albeit at a much lower level than wild-type pendrin. We hypothesize that this residual level of anion transport is sufficient to eliminate or postpone the onset of goiter in individuals with DFNB4. We propose a model for pendrin function in the thyroid in which pendrin transports iodide across the apical membrane of the thyrocyte into the colloid space.
Analysis of the SLC26A4 gene in patients with Pendred syndrome in Taiwan. Chien-Chung Lai;Chih-Yang Chiu;An-Suey Shiao;Yi-Chu Tso;Yi-Chi Wu;Tzong-Yang Tu;Tjin-Shing Jap. 2007. Metabolism. 56. PMID: 17697873

Pendred syndrome (PS) is an autosomal recessive disease that is characterized by congenital sensorineural hearing loss, goiter, and a partial iodine organification defect. In this study, we characterized the thyroid status and identified mutations in the SLC26A4 gene in Chinese subjects with PS. We evaluated 7 unrelated Chinese subjects who had PS. Biochemical analysis, formal audiogram, ultrasonography of the thyroid gland, perchlorate discharge test, computerized tomography scan of the vestibular aqueducts, and DNA sequence analysis of SLC26A4 were performed. Levels of thyroid hormones were essentially normal in all patients: 2 patients had goiters and/or elevated serum thyroglobulin levels, whereas 2 other patients had positive thyroid antibodies and a positive perchlorate discharge test. We identified SLC26A4 gene mutations in 6 of 7 probands and their affected relatives. The affected subjects in family I was compound heterozygous for 2 missense mutations: a mutation in exon 9 (1079C>T) that resulted in the replacement of alanine by valine at codon 360 (A360V) and a mutation in exon 19 (2168A>G) that resulted in the replacement of histidine by arginine at codon 723 (H723R). The affected subjects in families II and III all were homozygous for a mutation in intron 7. The probands IV and V were compound heterozygotes for the mutation in intron 7 and in exon 19, and the proband VI was compound heterozygous for the intron 7 mutation and a missense mutation in exon 12 (1343C>T) that resulted in the replacement of serine by leucine at codon 448 (S448L). One novel mutation was identified (A360V). We identified biallelic mutations in the SLC26A4 gene in 6 of 7 probands with PS in Taiwan, including a novel missense mutation. The mild thyroid dysfunction in these patients suggests that PS should be considered in all patients with congenital or early-onset hearing impairment.
Hereditary hearing loss and deafness genes in Japan. Taku Ito;Yoshihiro Noguchi;Takatoshi Yashima;Kazuchika Ohno;Ken Kitamura. 2010. J Med Dent Sci. 57. PMID: 20437760

Hearing loss (HL) is the most common sensory impairment occurring at birth in developed countries. Epidemiological data show that more than one child in 1000 is born with HL, while more than 50% of prelingual HL cases are found to be hereditary. Approximately 70% of hereditary HL is nonsyndromic and subdivided to autosomal dominant (20%), autosomal recessive (75%), X-linked HL (1%), and maternally-inherited HL associated with the mitochondrial DNA mutation. More than 10 deafness genes have been reported to be responsible for nonsyndromic hereditary HL in Japan. Among them, the most prevalent causative genes, GJB2 and the mitochondrial DNA 12SrRNA are introduced. In addition, this study also refers to the specific genes responsible for the unique audiogram, mainly WFS1. Finally, the genes related to the enlargement of vestibular aqueduct of inner ear abnormality, SLC26A4, EYA1 and SIX1 are discussed. The clinical and genetic findings associated with these disorders including the results of a recent study are reviewed.
A distinct spectrum of SLC26A4 mutations in patients with enlarged vestibular aqueduct in China. Q-J Wang;Y-L Zhao;S-Q Rao;Y-F Guo;H Yuan;L Zong;J Guan;B-C Xu;D-Y Wang;M-K Han;L Lan;S-Q Zhai;Y Shen. 2007. Clin Genet. 72. PMID: 17718863

There is a worldwide interest in studying SLC26A4 mutations that are responsible for enlarged vestibular aqueduct (EVA) in different ethnic background and populations. The spectrum of SLC26A4 mutations in Chinese population is yet to be fully characterized. In this study, all the 21 exons of SLC26A4 were screened in 107 Chinese patients with hearing loss associated with EVA or both EVA and Mondini dysplasia (MD), taken from six multiplex and 95 simplex families. The two types of control populations consisted of 84 normal-hearing subjects and 46 sensorineural hearing loss subjects without inner ear malformations. Biallelic mutations were found in 12 patients from multiplex families and 84 patients (88.4%) from the simplex families. In addition, monoallelic variant was detected in nine patients in the remaining 11 simplex families. Overall, up to 97.9% patients were found having at least one possible pathogenic variant in SLC26A4, with most having biallelic variants consistent with recessive inheritance of this disorder. A total of 40 mutations including 25 novel mutations were identified in the Chinese patients but were not detected in all the controls except for one normal subject. For the Chinese mutation spectrum of SLC26A4 gene, IVS 7-2A>G mutation was the most common form accounting for 57.63% (102/177) of all the mutant alleles.
Compound heterozygous MYO7A mutations segregating Usher syndrome type 2 in a Han family. Ling Zong;Kaitian Chen;Xuan Wu;Min Liu;Hongyan Jiang. 2016. Int J Pediatr Otorhinolaryngol. 90. PMID: 27729122

OBJECTIVE: Identification of rare deafness genes for inherited congenital sensorineural hearing impairment remains difficult, because a large variety of genes are implicated. In this study we applied targeted capture and next-generation sequencing to uncover the underlying gene in a three-generation Han family segregating recessive inherited hearing loss and retinitis pigmentosa. METHODS: After excluding mutations in common deafness genes GJB2, SLC26A4 and the mitochondrial gene, genomic DNA of the proband of a Han family was subjected to targeted next-generation sequencing. The candidate mutations were confirmed by Sanger sequencing and subsequently analyzed with in silico tools. RESULTS: An unreported splice site mutation c.3924+1G > C compound with c.6028G > A in the MYO7A gene were detected to cosegregate with the phenotype in this pedigree. Both mutations, located in the evolutionarily conserved FERM domain in myosin VIIA, were predicted to be pathogenic. In this family, profound sensorineural hearing impairment and retinitis pigmentosa without vestibular disorder, constituted the typical Usher syndrome type 2. CONCLUSION: Identification of novel mutation in compound heterozygosity in MYO7A gene revealed the genetic origin of Usher syndrome type 2 in this Han family.
Fluctuant, progressive hearing loss associated with Menière like vertigo in three patients with the Pendred syndrome. C Stinckens;P L Huygen;F B Joosten;G Van Camp;B Otten;C W Cremers. 2001. Int J Pediatr Otorhinolaryngol. 61. PMID: 11700190

OBJECTIVE: To evaluate vestibular and long-term audiometric findings in patients with Pendred syndrome. STUDY DESIGN: Retrospective analysis of long-term clinical data. SETTING: University hospital department. PATIENTS: Three patients with Pendred syndrome caused by a mutation in the SLC26A4 gene. METHODS: Perchlorate discharge test, mutation analysis of the SLC26A4 gene, MR imaging of temporal bones, vestibular function test (in two cases) and serial audiometry. A saturation hyperbola with onset age was fitted to the audiometric threshold-on-age data using a nonlinear regression method. The residues remaining after regression were analyzed in a correlation analysis to detect significant ipsilateral or contralateral cofluctuation. RESULTS: All three patients had a mutation in the SLC26A4 gene and bilateral enlarged vestibular aqueduct; two of them had a positive perchlorate discharge test but in one of two siblings this test was negative. Hearing loss was significantly progressive with significant ipsilateral and contralateral cofluctuation in all evaluable cases, combined with episodes of Menière like vertigo in two cases. The episodes of vertigo are as seen in Menière disease. One case had unilateral caloric areflexia and one had bilateral vestibular hyporeflexia, proven to be progressive in a repeat examination. CONCLUSIONS: Patients with Pendred syndrome may exhibit progressive and fluctuant hearing loss with episodes of vertigo.
Identification and genotype/phenotype correlation of mutations in a large German cohort with hearing loss. Christopher Beck;Jose Carmelo Pérez-Álvarez;Alexander Sigruener;Frank Haubner;Till Seidler;Charalampos Aslanidis;Jürgen Strutz;Gerd Schmitz. 2014. Eur Arch Otorhinolaryngol. 272. PMID: 25214170

The prevalence of hearing impairment is estimated as approximately 1 on 1,000 newborn children. To assess a higher mutation detection rate in individuals with hearing loss a three-step mutation screening program consisting of GJB2 in first line, then GJB1, GJB3 and GJB6 (second step) and if tested negative or heterozygote, testing of GJA1, GJB4, SLC26A4 and PJVK (third) was performed. Audiograms were derived from all patients to characterize audiological features of GJB2 mutations especially. In 59 patients (31.3%) of the 188 probands, the hearing impairment was due to GJB2 mutations, 45 (23.9%) of these being homozygous for 35delG mutation and 14 (7.4%) compound heterozygous for GJB2 mutations in the coding region of exon 2 whereas no significant sequence variation was found in exon 1. In 22 (11.7%) additional patients a single recessive mutation in GJB2, GJB3, GJB6 and SLC26A4 without a second mutation on the other allele was identified, making genetic counseling difficult. Our study showed significant difference in hearing loss degree in the patients with GJB2-mutations. Forty-five (45.5%) GJB2-cases were identified in 99 individuals diagnosed with severe to profound hearing loss, 14 (17.7%) GJB2-cases were identified in 79 individuals with moderate deafness whereas no clear GJB2 mutation was found in 10 patients with mild hearing loss (p < 0.001). Revealing a high variability of hearing levels in identical genotypes (even intrafamilial), a significant genotype-phenotype correlation could not be established. Based on the identified mutations spectrum and frequencies, speaking mostly of GJB2, a step by step screening for mutations can be devised and in addition may lead to a better stratification of patients for specific therapeutical approaches.
Molecular analysis of SLC26A4 gene in patients with nonsyndromic hearing loss and EVA: identification of two novel mutations in Brazilian patients. Vanessa Cristine Sousa de Moraes;Nathalia Zocal Pereira dos Santos;Priscila Zonzini Ramos;Maria Carolina Costa Melo Svidnicki;Arthur Menino Castilho;Edi Lúcia Sartorato. 2013. Int J Pediatr Otorhinolaryngol. 77. PMID: 23273637

UNLABELLED: The SLC26A4 gene has been described as the second gene involved in most cases of sensorineural non-syndromic hearing loss, since the first is the GJB2 gene. Recessive mutations in the SLC26A4 gene encoding pendrin, an anion transporter, are responsible for non-syndromic hearing loss associated with an enlarged vestibular aqueduct (EVA) and Pendred syndrome, which causes early hearing loss and affects the thyroid gland. Typically, the hearing loss is profound and prelingual. However, in some individuals, hearing impairment may develop later in childhood and then progress. Over 200 different SLC26A4 mutations have been reported, with each ethnic population having its own distinctive mutant allele series including a few prevalent founder mutations. OBJECTIVE: Perform the screening of the 20 coding exons of SLC26A4 gene in Brazilian deaf individuals with EVA. PATIENTS AND METHODS: Among the 23 unrelated non-syndromic hearing loss Brazilian patients with EVA, in whom no deafness-causing mutations of the GJB2 gene, the direct sequencing was performed to screen the 20 exons and their flanking regions of the SLC26A4 gene. RESULTS: The sequencing results revealed 9 cases (39%) carrying 13 different SLC26A4 mutations, including 11 known mutations (279delT, V138F, T193I, IVS8+1G>A, T410M, Q413R, R409H, L445W, IVS15+5G>A, V609G, and R776C) and 2 novel mutation (G149R and P142L). CONCLUSION: The SLC26A4 mutations have a high carrying rate in non-syndromic hearing loss Brazilian patients. The identification of a disease-causing mutation can be used to establish a genotypic diagnosis and provide important information to the patients and their families.
Resistance to hypertension and high Cl- excretion in humans with SLC26A4 mutations. B G Kim;T-H Yoo;J-E Yoo;Y J Seo;J Jung;J Y Choi. 2016. Clin Genet. 91. PMID: 27090054

Pendrin is a membrane transporter encoded by solute carrier family26A4 (SLC26A4). Mutations in this gene are known to cause hearing loss, and recent data from animal studies indicate a link between pendrin expression and hypertension; although, this association in humans is unclear. To clarify this issue, we investigated the influence of pendrin on blood pressure by analyzing demographic and biochemical data - including blood pressure and urinary electrolyte excretion - in patients with bi-allelic SLC26A4 mutations. Systolic and diastolic blood pressure and the left ventricular hypertrophy index were lower in subjects with pendrin mutations than in controls. In addition, fractional excretion of Na+ and Cl- was increased and serum renin, angiotensin I and II levels were higher in subjects with pendrin mutations as compared to controls. Thus, patients with impaired pendrin function are likely to be resistant to high blood pressure due to enhanced urinary Na+ /Cl- excretion. These results suggest that pendrin may regulate blood pressure through increased urinary salt excretion.
[Molecular diagnosis of deafness]. Shin-ichi Usami. 2011. Nihon Rinsho. 69. PMID: 21387690

Despite advances in discovery of deafness genes, clinical application still entails difficulties because of the genetic heterogeneity of deafness. In order to establish strategy for clinical application, we reviewed the genes responsible for hearing loss patients in Japan (Usami S et al; Acta Otolaryngol 128: 446-454, 2008), and discussed diagnostic strategy for mutation screening based on a mutation/gene database (Abe S et al; Genet Test 11: 333-340, 2007). Our series of mutation screenings has revealed that mutations in GJB2, SLC26A4, and CDH23, and the 1555A>G mutation in the mitochondrial 12S rRNA, were the major causes of hearing loss in Japanese patients. Interestingly, spectrums of GJB2, SLC26A4, and CDH23 mutations found in the Japanese population were quite different from those reported in populations with European ancestry. Our simultaneous screening of the multiple deafness mutations was based on the mutation spectrum of a corresponding population. The multicenter trial for this assay using an Invader panel revealed that approximately 40% of congenital hearing loss subjects could be diagnosed. This assay will enable us to detect deafness mutations in an efficient and practical manner in the clinical platform.
SLC26A4 mutation testing for hearing loss associated with enlargement of the vestibular aqueduct. Taku Ito;Julie Muskett;Parna Chattaraj;Byung Yoon Choi;Kyu Yup Lee;Christopher K Zalewski;Kelly A King;Xiangming Li;Philine Wangemann;Thomas Shawker;Carmen C Brewer;Seth L Alper;Andrew J Griffith. 2013. World J Otorhinolaryngol. 3. PMID: 25960948

Pendred syndrome (PS) is characterized by autosomal recessive inheritance of goiter associated with a defect of iodide organification, hearing loss, enlargement of the vestibular aqueduct (EVA), and mutations of the SLC26A4 gene. However, not all EVA patients have PS or SLC26A4 mutations. Two mutant alleles of SLC26A4 are detected in ¼ of North American or European EVA populations, one mutant allele is detected in another ¼ of patient populations, and no mutations are detected in the other ½. The presence of two mutant alleles of SLC26A4 is associated with abnormal iodide organification, increased thyroid gland volume, increased severity of hearing loss, and bilateral EVA. The presence of a single mutant allele of SLC26A4 is associated with normal iodide organification, normal thyroid gland volume, less severe hearing loss and either bilateral or unilateral EVA. When other underlying correlations are accounted for, the presence of a cochlear malformation or the size of EVA does not have an effect on hearing thresholds. This is consistent with observations of an Slc26a4 mutant mouse model of EVA in which hearing loss is independent of endolymphatic hydrops or inner ear malformations. Segregation analyses of EVA in families suggest that the patients carrying one mutant allele of SLC26A4 have a second, undetected mutant allele of SLC26A4, and the probability of a sibling having EVA is consistent with its segregation as an autosomal recessive trait. Patients without any mutations are an etiologically heterogeneous group in which siblings have a lower probability of having EVA. SLC26A4 mutation testing can provide prognostic information to guide clinical surveillance and management, as well as the probability of EVA affecting a sibling.
[Investigation of clinical features and detection of 79 known deafness genes in a large Chinese family with dominant non-syndromic hearing loss]. Xiaojiang Lin;Dongye Chen;Hao Wu;Tao Yang;Dan Zhang;Yongchuan Chai. 2014. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 49. PMID: 25351123

OBJECTIVE: To investigate the clinical and genetic characteristics of a large family with late-onset, progressive autosomal dominant non-syndromic hearing loss. METHODS: Collections of detail history hereditary features, physical and audiological examination were performed. After mutation screening of GJB2, SLC26A4, MTRNR1 (12SrRNA) genes by Sanger sequencing, the proband was investigated by targeted next-generation sequencing of 79 deafness genes. RESULTS: This family included seven generations and 73 members. Eleven persons with hearing loss and 11 normal-hearing persons participated in this study. All affected members but one exhibited late-onset, progressive non-syndromic sensorineural hearing loss; the ages of onset were between 9 and 30 years. Mutation screening by sanger-sequencing and targeted next-generation sequencing excluded the possibility of pathogenic mutations within known deafness gene. CONCLUSIONS: A Chinese family with late-onset progressive non-syndromic sensorineural hearing loss was investigated clinically and genetically. By candidate gene approach and targeted next-generation sequencing, this family was preliminary proved to be caused by unknown deafness gene.
Genetic etiology study of the non-syndromic deafness in Chinese Hans by targeted next-generation sequencing. Tao Yang;Xiaoming Wei;Yongchuan Chai;Lei Li;Hao Wu. 2013. Orphanet J Rare Dis. 8. PMID: 23767834

BACKGROUND: Although over 60 non-syndromic deafness genes have been identified to date, the etiologic contribution of most deafness genes remained elusive. In this study, we addressed this issue by targeted next-generation sequencing of a large cohort of non-syndromic deaf probands. METHODS: Probands with mutations in commonly screened deafness genes GJB2, SLC26A4 and MT-RNR1 were pre-excluded by Sanger sequencing. The remaining 125 deaf probands proceeded through targeted exon capturing of 79 known deafness genes and Illumina HiSeq2000 sequencing. RESULTS: Bi-allelic mutations in 15 less commonly screened deafness genes were identified in 28 deaf probands, with mutations in MYO15A, GPR98, TMC1, USH2A and PCDH15 being relatively more frequent (≥3 probands each). Dominant mutations in MYO6, TECTA, POU4F3 and COCH were identified in 4 deaf families. A mitochondrial MTTS1 mutation was identified in one maternally inherited deaf family. No pathogenic mutations were identified in three dominant deaf families and two consanguineous families. CONCLUSIONS: Mutations in the less commonly screened deafness genes were heterogeneous and contributed to a significant percentage (17.4%) of causes for non-syndromic deafness. Targeted next-generation sequencing provided a comprehensive and efficient diagnosis for known deafness genes. Complementary to linkage analysis or whole-exome sequencing of deaf families, pre-exclusion of known deafness genes by this strategy may facilitate the discovery of novel deafness genes.
[Analysis of the SLC26A4 mutation from 230 deafness patients in Guangxi region]. M Liu;L Xu;F Z Tang;M Shi;S H Qu;J P Liang;Q T Lu;R C Chen;J Huang;Y Y Huang. None. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 30. PMID: 29871136

Objective:To investigate the mutation characteristics of SLC26A4 gene from 230 hearing loss patients in Guangxi region.Method:Two hundred thirty patients with hearing loss were enrolled in the study. Eight mutation sites in SLC26A4 gene were tested; the types of gene mutation and the inner ear CT features of the mutationpositive patients were analyzed.Result:Among 230 deafness patients,the total mutation rate of SLC26A4 gene is 2.61%(6/230). The types of gene mutation include SLC26A4 IVS7-2A> G heterozygous in 2 case(0.87%).1226G> A homozygous in 1 cases(0.43%),IVS7-2A>G,IVS11+47T>C and 1548insC mutations in 2 cases(0.87%).Conclusion:The mutation rate of SLC26A4 gene in Guangxi region is lower than the national average level. The main mutation type in Guangxi region is SLC26A4 IVS7 2A>G. In this study, two gene mutations (SLC26A4 IVS11+47T> C and 1548insC) are firstly found, suggesting that some rare mutation types of SLC26A4 may exist in patients living in Guangxi region.
Contribution of SLC26A4 to the molecular diagnosis of nonsyndromic prelingual sensorineural hearing loss in a Brazilian cohort. Simone da Costa E Silva Carvalho;Carlos Henrique Paiva Grangeiro;Clarissa Gondim Picanço-Albuquerque;Thaís Oliveira Dos Anjos;Greice Andreotti De Molfetta;Wilson Araujo Silva;Victor Evangelista de Faria Ferraz. 2018. BMC Res Notes. 11. PMID: 30068397

OBJECTIVE: Hereditary hearing loss (HL) is the most common sensorineural disorder in humans. Besides mutations in GJB2 and GJB6 genes, pathogenic variants in the SLC26A4 gene have been reported as a cause of hereditary HL due to its role in the physiology of the inner ear. In this research we wanted to investigate the prevalence of mutations in SLC26A4 in Brazilian patients with nonsyndromic prelingual sensorineural HL. We applied the high-resolution melting technique to screen 88 DNA samples from unrelated deaf individuals that were previously screened for GJB2, GJB6 and MT-RNR1 mutations. RESULTS: The frequency of mutations in the SLC26A4 gene was 28.4%. Two novel mutations were found: p.Ile254Val and p.Asn382Lys. The mutation c.-66C>G (rs17154282) in the promoter region of SLC26A4, was the most frequent mutation found and was significantly associated with nonsyndromic prelingual sensorineural HL. After mutations in the GJB2, GJB6 and mitochondrial genes, SLC26A4 mutations are considered the next most common cause of hereditary HL in Brazilian as well as in other populations, which corroborates with our data. Furthermore, we suggest the inclusion of the SCL26A4 gene in the investigation of hereditary HL since there was an increase in the frequency of the mutations found, up to 22.7%.
[Prenatal diagnosis for hereditary deaf families assisted by genetic testing]. Bing Han;Pu Dai;Qing-wei Qi;Long-xia Wang;Yi Wang;Xu-ming Bian;Qiu-ju Wang;Xin Zhang;Dong-yang Kang;Guo-jian Wang;Dong-yi Han. 2007. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 42. PMID: 18051563

OBJECTIVE: To provide prenatal diagnosis for deaf families, which the first child was confirmed to be hereditary deafness caused by gap junction beta-2 (GJB2) or SLC26A4 (PDS) mutation, to avoid another deaf birth in these families. METHODS: Eight deaf families joined in this study. Each family had one child with severe to profound hearing loss while parents had normal hearing except a deaf father from family 8; mothers had been pregnant for 6-28 weeks. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) A1555G mutation were firstly performed in probands and their parents whose DNA was extracted from peripheral blood, and then prenatal testing was carried out in the fetus whose DNA was extracted from different fetus materials depending on the time of gestation. RESULTS: The probands from family 1-4 were found to carry homozygous or compound GJB2 mutations while their parents carried corresponding heterozygous GJB2 mutations. The probands from family 5-8 and the deaf father from family 8 were found to carry compound SLC26A4 mutations while their parents and the mother from family 8 carried a single SLC26A4 mutation. Prenatal testing showed that the fetuses from family 1, 5, 8 only carried the paternal mutation and the fetuses from family 2, 3, 6 didn't carry any GJB2 or SLC26A4 mutations. The new born babies from these six families all had normal hearing revealed by new born hearing screening. However, the fetuses from family 4,7 carried the same mutations with probands in each family. The parents from family 4, 7 decide to terminate pregnancy. CONCLUSION: Prenatal diagnosis assisted by genetic testing can provide efficient information about hearing condition of their offsprings.
A quantitative cSMART assay for noninvasive prenatal screening of autosomal recessive nonsyndromic hearing loss caused by GJB2 and SLC26A4 mutations. Mingyu Han;Zhifeng Li;Wenlu Wang;Shasha Huang;Yanping Lu;Zhiying Gao;Longxia Wang;Dongyang Kang;Linwei Li;Yiqian Liu;Mengnan Xu;David S Cram;Pu Dai. 2017. Genet Med. 19. PMID: 28541280

PurposeThe aim of this study was to assess the performance of a noninvasive prenatal screening (NIPS) assay for accurate fetal genotyping of pregnancies at genetic risk for autosomal recessive nonsyndromic hearing loss (ARNSHL).MethodsA total of 80 pregnant couples carrying known mutations in either the GJB2 or SLC26A4 genes associated with a risk for ARNSHL were recruited to the study. Fetal amniocyte samples were genotyped by invasive prenatal screening (IPS), whereas the cell-free fetal DNA present in maternal plasma samples was genotyped using a novel NIPS method based on circulating single-molecule amplification and resequencing technology (cSMART).ResultsIPS of the 80 at-risk pregnancies identified 20 normal homozygote, 42 heterozygote, 5 affected homozygote, and 13 affected compound heterozygote fetuses. Benchmarking against IPS, 73 of 80 fetuses (91.3%) were correctly genotyped by the cSMART NIPS assay. A low fetal DNA fraction (<6%) was identified as the main contributing factor in five of seven discordant NIPS results. At fetal DNA fractions >6%, the sensitivity and specificity of the cSMART assay for correctly diagnosing ARNSHL were 100 and 96.5%, respectively.ConclusionBased on key performance indicators, the cSMART NIPS assay has clinical potential as an alternative to traditional IPS of ARNSHL.
Application of gene detection technique in the antenatal diagnosis of hereditary hearing loss. Y Fang;M-S Gu;F Suo;C-X Wang;X-H Liu;F-M Liu. 2017. Eur Rev Med Pharmacol Sci. 21. PMID: 28429364

OBJECTIVE: Gene chip and gene sequencing techniques were used to detect the main pathogenic genes in pregnant women with hereditary hearing loss. PATIENTS AND METHODS: From May 2015 to May 2016, 1080 pregnant in Xuzhou Maternal and Child Health Hospital were enrolled in this study. Women age range was 18 to 40 years. 4 genes and 9 mutation sites, including 4 sites (35delG, 176, 235delC and 299) in GJB2 gene, 2 sites (2168A>G and IVS-7-2A>G) in SLC26A4 (PDS) gene, 2 sites (1494C>T and 1555A>G) in 12s rRNA gene and 1 site (538C>T) in GJB3 gene, were detected using the GeeDom® 9-item hereditary hearing loss gene detection kit. Deafness genes in the husband of the pregnant woman with GJB2 and SLC26A4 positive gene mutations were verified using Sanger sequencing. Fetuses with the same deafness genes as their parents were diagnosed before delivery using amniocentesis. RESULTS: 48 patients (4.45 %) were detected positive for hereditary hearing loss. Most of them (28 cases) were identified with GJB2 gene mutation (1 case with 176 site mutation, 22 cases with 235delC site mutation and 5 cases with 299 site mutation). We had 15 cases of the SLC26A4 gene mutation (3 cases of 2168A>G site mutation and 12 cases of IVS-7-2A>G site mutation), 2 cases of 538C>T site mutation of GJB3 gene and 3 cases of 1555A>G site mutation of 12s rRNA gene. CONCLUSIONS: The gene detection technique has a great health-economic significance in screening the main pathogenic genes involved in the hereditary hearing loss.
Genetics of Hearing Loss--Nonsyndromic. Kay W Chang. 2015. Otolaryngol Clin North Am. 48. PMID: 26275501

Eighty percent of nonsyndromic hearing losses are caused by autosomal-recessive (AR) inheritance, while most of the other 20% are caused by autosomal-dominant (AD) inheritance. Although AR nonsyndromic SNHL is most commonly caused by GJB2 and SLC26A4, there is no single gene that accounts for any significant proportion of AD SNHL. High-throughput sequencing techniques, also called next-generation sequencing (NGS) or massively parallel sequencing (MPS), may allow for routine definitive diagnosis of all possible genetic causes for hearing loss in the not-too-distant future.
[Analysis of genotypes and audiological characteristics of children with SLC26A4 gene pathogenic mutations]. X L Zhao;L H Huang;X Y Wang;Yt DU;Xl Wang;X H Cheng;L P Zhao;Y Li. None. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 32. PMID: 29921053

Objective:To explore the correlation of SLC26A4 genotype and audiology.Method:The subjects were 70 children aged 0 to 7 years old, who were admitted to otological outpatient department.All subjects received nine crystal hereditary deafness gene chip and confirmed by (or)SLC26A4 gene full coding region detection.The patients were diagnosed as homozygous or compound heterozygous mutations.At the same time,acoustic immittance,auditory brainstem response, auditory steady state response and pediatric behavior audiometry, newborn hearing screening and other audiological tests were displayed. According to the genotype, the subjects were divided into two groups: group A (SLC26A4 gene homozygous mutation) in 40 cases, group B (SLC26A4 gene compound heterozygous mutation) in 30 cases. The frequency of SLC26A4 gene mutation, the two groups of genotypes and hearing screening results,the degree of hearing loss and audiometric configurations were analyzed statistically. Result: In 70 patients, the top 4 of the 70 patients with high frequency of mutations were IVS7-2A> G(76.43%), 2168A> G(15.00%), 1226G> A(2.86%) and 2000T> C(2.16%), respectively. 34.29% of newborns passed hearing screening with single or double ears, among which group A and group B were 32.50% and 36.67%,respectively. There was no statistically significant difference between two groups in hearing screening. The degree of hearing loss in group A(56.25%) and group B(48.33%) were mainly profound and there was no significant difference between them. The audiometric configurations: group A(60.00%) was mainly high frequency loss type, while group B(55.00%) was mainly flat type. The difference between them was statistically significant.Conclusion:The mutation sites of SLC26A4 gene were mainly IVS7-2A> G, and the degree of hearing loss was mostly profound. To the audiometric configurations,SLC26A4 gene homozygous mutant were mainly high frequency loss type, while SLC26A4 gene compound heterozygous mutant were mainly flat type. 34.29% children passed universal newborn hearing screening with one ear at least, which indicates SLC26A4 gene mutations can result in late-onset hearing loss, so those patients should be attached great importance..
Molecular characterization of autosomal recessive non syndromic hearing loss in selected families from District Mardan, Pakistan. Shahid Hussain;Jabar Zaman Khattak;Mohammad Ismail;Qaisar Mansoor;Mohammad Haroon Khan. None. Pak J Pharm Sci. 31. PMID: 29348084

Deafness is the most common sensory disorder, which affects 1/1000 neonates globally. Genetic factors are major contributors for hearing impairment. This study was conducted to explore the linkage of DFNB loci and their mutations with NSHL in selected Pakistani families. We included 10 families with history of deafness from district Mardan, Pakistan. Blood sample (5ml) along with personal and clinical information was collected from the available family members including both diseased and un-affected individuals. Genomic DNA was amplified using loci specific STR markers to investigate the linkage of DFNB loci. Family found linked with DFNB4 locus was screened for SLC26A4 mutations. One out of the ten explored families was found linked with DFNB4 locus which was further investigated for SLC26A4 gene mutation through direct DNA sequencing. Two novel mutations were observed in the studied family, one at splice donor site (164+2T>G) and the other at position 164+5C>G only in the affected members of the linked family. DFNB4 locus was found linked in the present study which harbors SLC26A4 gene. The novel mutation of SLC26A4 gene at the splice donor site results in skipping of the first coding exon and thus can lead to loss of expression of SLC26A4 product in the inner ear.
Diagnostic Value of SLC26A4 Mutation Status in Hereditary Hearing Loss With EVA: A PRISMA-Compliant Meta-Analysis. Ya-Jie Lu;Jun Yao;Qin-Jun Wei;Guang-Qian Xing;Xin Cao. 2015. Medicine (Baltimore). 94. PMID: 26683941

Many SLC26A4 mutations have been identified in patients with nonsyndromic enlarged vestibular aqueduct (EVA). However, the roles of SLC26A4 genotypes and phenotypes in hereditary deafness remain unexplained. This study aims to perform a meta-analysis based on the PRISMA statement to evaluate the diagnostic value of SLC26A4 mutant alleles and their correlations with multiethnic hearing phenotypes in EVA patients. The systematic literature search of the PubMed, Wiley Online Library, EMBASE, Web of Science, and Science Direct databases was conducted in English for articles published before July 15, 2015. Two investigators independently reviewed retrieved literature and evaluated eligibility. Discrepancy was resolved by discussion and a third investigator. Quality of included studies was evaluated using Newcastle-Ottawa Quality Assessment Scale. Data were synthesized using random-effect or fixed-effect models. The effect sizes were estimated by measuring odds ratios (ORs) with 95% confidence interval (CI). Twenty-five eligible studies involved 2294 cases with EVA data. A total of 272 SLC26A4 variations were found in deafness with EVA and 26 mutations of SCL26A4 had higher frequency. The overall OR was 646.71 (95% CI: 383.30-1091.15, P = 0.000). A total of 22 mutants were considered statistically significant in all ethnicities (ORs >1, P < 0.05). In particular, 8 mutants were specificity of EVA phenotypes in mutations of SLC26A4 for Asia deafness populations (ORs >1, P < 0.05), 4 mutants for Europe and North America (ORs >1, P < 0.05), and the IVS7-2A>G mutations in SLC26A4 were found to have the highest frequency in deafness individuals with EVA phenotype (62.42%). Moreover, subgroups for studies limited to cases with EVA phenotype, 11 mutants relevant risks (RRs) were P < 0.05, especially for IVS7-2A>G bi-allelic mutants assayed in a deafness population (RR = 0.880, P = 0.000). Diagnostic accuracy of SLC26A4 mutation results also identified the significant association of IVS7-2A>G (AUC = 0.99, 95% CI: 0.97-0.99) and p.H723R (AUC = 0.99, 95% CI: 0.98-1.00) detecting deafness with EVA. To conclude, the IVS7-2A>G and H723R in SLC26A4 present a significant predicting value and discriminatory ability for clinical use on diagnosis of EVA within a deafness population.
Analysis of p.V37I compound heterozygous mutations in the GJB2 gene in Chinese infants and young children. Yating Du;Lihui Huang;Xiaohua Cheng;Liping Zhao;Yu Ruan;Tingting Ni. 2016. Biosci Trends. 10. PMID: 27350192

The p.V37I (c.109G>A) mutation in the GJB2 gene is the common frequent cause of congenital deafness; however, its pathogenicity is debated. The present study investigated the prevalence of p.V37I in Chinese infants and young children and associated clinical characteristics. The subjects of the present study were screened for mutations in GJB2 (235delC, 299delAT, 176dell6, 35delG), SLC26A4 (IVS7-2A>G, 2168A>G), GJB3 (538C>T), and in the mitochondrial 12S rRNA gene (1555A>G, 1494C>T). Subjects with p.V37I underwent an audiological evaluation. GJB2 exon sequencing revealed that 20 subjects had p.V37I compound heterozygous mutations, one of whom had a family history; the mutations included c.235delC/p.V37I (n = 12), c.299AT/p.V37I (n = 7), and c.176del16/p.V37I (n = 1). Of the 20 subjects, 12 were referred for Universal Newborn Hearing Screening (UNHS). Nine of the 20 subjects had mild hearing loss in the better ear and 5 had moderate hearing loss in the better ear while 4 had normal hearing. Among subjects with the c.235delC/p.V37I mutation, 5 had mild hearing loss and 2 had moderate hearing loss while 3 had normal hearing. Among subjects with the c.299AT/p.V37I mutation, 3 had mld hearing loss and 3 had moderate hearing loss while 1 had normal hearing. One subject with the c.176del16/p.V37I mutation had mild hearing loss. Few studies have reported on the clinical characteristics of Chinese infants with p.V37I compound heterozygous mutations identified via screening for deafness genes and GJB2 sequencing. The c.235delC/p.V37I mutation was the most prevalent mutation found in subjects. The degree of hearing loss associated with p.V37I compound heterozygous mutations was mainly mild to moderate.
[Evaluation of deaf-mute patients with sensitive deafness gene screening in Shandong province]. Yu-bin Ji;Dong-yi Han;Da-yong Wang;Yu Zhou;Cui Zhao;Hui Wang;Lan Lan;Qiu-ju Wang. 2010. Zhonghua Yi Xue Za Zhi. 89. PMID: 20137612

OBJECTIVE: To discuss how to determine the number of samples in epidemiological study about deafness genes and reveal the characteristics of GJB2, SLC26A4 and mitochondrial DNA A1555G mutations in deaf-mute patients in schools for deaf-mutes in Shandong Province. METHODS: A total of 485 subjects were collected from the different schools for deaf-mutes in Shandong province. Amplified target fragments included GJB2 coding sequence, mtDNA12SrRNA and exon 8, 10, 17, 19 of SLC26A4 gene. The amplicons of mtDNA 12S rRNA were subjected to restriction enzyme Alw26I. The amplicons of patients whose enzyme reaction highly indicating A1555G mutation, amplicons of GJB2 and those exons PCR products of SLC26A4 were directly sequenced. RESULTS: The study revealed that 36.29% patients had two mutated alleles (homozygote & compound heterozygote) of GJB2 (24.12%) and SLC26A4 (6.60%) and mtDNA12SrRNA A1555G (5.57%). The 235delC and IVS7-2A > G were still the mutational hot spot in GJB2 and SLC26A4 respectively. CONCLUSION: The method of determining the number of sample is very important in the epidemiological study. There were about 24 thousand deaf-mute patients who were caused by three sensitive deafness genes mutations in Shandong province. Screening the sensitive deafness genes in newborn is imminent.
Molecular analysis of hearing loss associated with enlarged vestibular aqueduct in the mainland Chinese: a unique SLC26A4 mutation spectrum. Hao Hu;Lingqian Wu;Yong Feng;Qian Pan;Zhigao Long;Juan Li;Heping Dai;Kun Xia;Desheng Liang;Norio Niikawa;Jiahui Xia. 2007. J Hum Genet. 52. PMID: 17443271

It has been shown that mutations in the SLC26A4 gene are involved in syndromic deafness characterized by congenital sensorineural hearing impairment and goitre (Pendred's syndrome), as well as in congenital isolated deafness (DFNB4), both of which are associated with enlarged vestibular aqueduct (EVA). The prevalence of SLC26A4 mutations in Pendred's syndrome is clearly established in many ethnic groups, but the data from Mainland Chinese patients with deafness and EVA remain poor. In this report, 15 patients from 13 unrelated Chinese families with deafness and EVA were analyzed for SLC26A4 using direct sequencing. A total of 15 pathogenic mutations were observed in 11 unrelated families, 4 of which were novel. One mutation, IVS7-2A>G, was most common, accounting for 22.3% (5/22) of all the mutant alleles, and H723R was infrequent. To date, a total of 23 mutations have been reported among the Chinese, 13 of which were unique. In conclusion, EVA could be a radiological marker for SLC26A4 analysis among Mainland Chinese hearing-loss patients, and the SLC26A4 mutation spectrum in the Chinese was different from other reported populations.
[Analysis of deafness-related gene mutations in 100 non-syndromic hearing loss patients in Henan province]. Aili Yang;Manying Geng;Hui Zhang;Xiaoyan Guo;Jianfen Tang;Fugen Han. 2016. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 29. PMID: 26911058

OBJECTIVE: To preliminarily determine the gene mutation frequency and the hotspots in Henan province, we analysed the deafness-related gene mutation in patients with non-syndromic hearing loss (NSHL). METHOD: Genomic DNA samples of 100 patients with NSHL in Henan province were extracted from peripheral blood after clinical history inquiry and clinical examination, Four common deafness genes GJB2, SLC26A4, mitochondrial 12SrRNA, and GJB3 were detected by Sanger sequencing method,and then data analysis were conducted. RESULT: Among 100 patients with NSHL. the gene mutation frequency was 44%. In these patients, 29 cases had GJB2 mutations, 13 cases had SLC26A4 gene mutations, and 3 cases had mitochondrial 12SrRNA mutations. CONCLUSION: Among the patients with NSHL in Henan province, the most frequent mutation causing hereditary deafness was mutation in GJB2, followed by SLC26A4,and it will provide a theoretical basis to determine the etiology of deafness in Henan Province.
Pathogenic substitution of IVS15 + 5G > A in SLC26A4 in patients of Okinawa Islands with enlarged vestibular aqueduct syndrome or Pendred syndrome. Akira Ganaha;Tadashi Kaname;Kumiko Yanagi;Kenji Naritomi;Tetsuya Tono;Shin-ichi Usami;Mikio Suzuki. 2013. BMC Med Genet. 14. PMID: 23705809

BACKGROUND: Pendred syndrome (PS) and nonsyndromic hearing loss associated with enlarged vestibular aqueduct (EVA) are caused by SLC26A4 mutations. The Okinawa Islands are the southwestern-most islands of the Japanese archipelago. And ancestral differences have been reported between people from Okinawa Island and those from the main islands of Japan. To confirm the ethnic variation of the spectrum of SLC26A4 mutations, we investigated the frequencies of SLC26A4 mutations and clinical manifestations of patients with EVA or PS living in the Okinawa Islands. METHODS: We examined 22 patients with EVA or PS from 21 unrelated families in Okinawa Islands. The patient's clinical history, findings of physical and otoscopic examinations, hearing test, and computed tomography (CT) scan of the temporal bones were recorded. To detect mutations, all 21 exons and the exon-intron junctions of SLC26A4 were sequenced for all subjects. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) for SLC26A4 and calculations using the comparative CT (2(-ΔΔCT)) method were used to determine the pathogenicity associated with gene substitutions. RESULTS: SLC26A4 mutations were identified in 21 of the 22 patients. We found a compound heterozygous mutation for IVS15 + 5G > A/H723R in nine patients (41%), a homozygous substitution of IVS15 + 5G > A in six patients (27%), and homozygous mutation for H723R in five patients (23%). The most prevalent types of SLC26A4 alleles were IVS15 + 5G > A and H723R, which both accounted for 15/22 (68%) of the patients. There were no significant correlations between the types of SLC26A4 mutation and clinical manifestations. Based on qRT-PCR results, expression of SLC26A4 was not identified in patients with the homozygous substitution of IVS15 + 5G > A. CONCLUSIONS: The substitution of IVS15 + 5G > A in SLC26A4 was the most common mutation in uniquely found in patients with PS and EVA in Okinawa Islands. This suggested that the spectrum of SLC26A4 mutation differed from main islands of Japan and other East Asian countries. The substitution of IVS15 + 5G > A leads to a loss of SLC26A expression and results in a phenotype of PS and EVA.
Genes important for otoneurological diagnostic purposes - current status and future prospects. K Pawlak-Osiñska;K Linkowska;T Grzybowski. 2018. Acta Otorhinolaryngol Ital. 38. PMID: 29984802

SUMMARY: This review focuses on the current knowledge of the genes responsible for non-syndromic hearing loss that can be useful for otoneurological diagnostic purposes. From among a large number of genes that have been associated with non-syndromic hearing impairment, we selected several best-known genes, including the COCH gene, GJB2, GJB6 and SLC26A4, and we describe their role and effects of mutations and prevalence of mutations in various populations. Next, we focus on genes associated with tinnitus. Important areas for further research include assessment of genes potentially involved in pathophysiology of tinnitus and vertigo, which have traditionally been considered as being of otological aetiology, while advances in neuroimaging techniques have increasingly shifted studies toward neurological correlations.
[Autosomal dominant hearing loss resulting from mutation in the GJB2 gene:nonsyndromic presentation in a Chinese family]. X Dai;J Li;X J Hu;J Tong;W Q Cai. 2016. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 30. PMID: 29798269

Objective:To investigate the genotype, phenotype and genetic features. The mutations in GJB2, GJB3, GJB6, SLC26A4 genes, 12SrRNA and tRNASer(UCN) were tested in a Chinese family with autosomal dominant nonsyndromic hearing loss. Method:Blood samples and clinical data of the proband and her partial family members were collected. DNA was extracted from the blood samples. The GJB2, GJB3, GJB6, SLC26A4 genes, 12SrRNA and tRNASer(UCN) mutations were analyzed by polymerase chain reaction(PCR) and direct sequencing. Result:Heterozygous mutation of GJB2 R75Q was identified in the proband and her mother. No mutation of other testing genes was detected. Conclusion:The R75Q mutation of the GJB2 gene cause autosomal dominant nonsyndromic deafness in the proband and her mother. Children can inherit the R75Q mutation from their parents, so the results of gene testing will be helpful for further guidance of procreation.
Forty-six genes causing nonsyndromic hearing impairment: which ones should be analyzed in DNA diagnostics? Nele Hilgert;Richard J H Smith;Guy Van Camp. 2008. Mutat Res. 681. PMID: 18804553

Hearing impairment is the most common sensory disorder, present in 1 of every 500 newborns. With 46 genes implicated in nonsyndromic hearing loss, it is also an extremely heterogeneous trait. Here, we categorize for the first time all mutations reported in nonsyndromic deafness genes, both worldwide and more specifically in Caucasians. The most frequent genes implicated in autosomal recessive nonsyndromic hearing loss are GJB2, which is responsible for more than half of cases, followed by SLC26A4, MYO15A, OTOF, CDH23 and TMC1. None of the genes associated with autosomal dominant nonsyndromic hearing loss accounts for a preponderance of cases, although mutations are somewhat more frequently reported in WFS1, KCNQ4, COCH and GJB2. Only a minority of these genes is currently included in genetic diagnostics, the selection criteria typically reflecting: (1) high frequency as a cause of deafness (i.e. GJB2); (2) association with another recognisable feature (i.e. SLC26A4 and enlarged vestibular aqueduct); or (3) a recognisable audioprofile (i.e. WFS1). New and powerful DNA sequencing technologies have been developed over the past few years, but have not yet found their way into DNA diagnostics. Implementing these technologies is likely to happen within the next 5 years, and will cause a breakthrough in terms of power and cost efficiency. It will become possible to analyze most - if not all - deafness genes, as opposed to one or a few genes currently. This ability will greatly improve DNA diagnostics, provide epidemiological data on gene-based mutation frequencies, and reveal novel genotype-phenotype correlations.
[Identification of a novel mutation of SLC26A4 gene with enlarged vestibular aqueduct syndrome]. J Chen;L S Shi;H Zhou;G J Zhu;D B Ma;J Y Li;X Gao. None. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 31. PMID: 29871349

Objective:To explore the mutation spectrum of SLC26A4 in Chinese patients with enlarged vestibular aqueduct syndrome.Method:Genomic DNA samples were extracted from peripheral blood of the cochlear implant recipients associated with enlarged vestibular aqueduct syndrome. The SLC26A4 mutations were analyzed by direct sequencing.Result:A novel missense mutation(347G>A) of SLC26A4 gene was found in a male patient,which led to a substitution of codon 116 from glycine to asparagic acid. This mutation was not observed among 60 normal controls.Conclusion:The 347G>A of SLC26A4 gene was a novel pathologic mutation,contributing to the mutation spectrum of SLC26A4 of enlarged vestibular aqueduct syndrome.
[Analysis the relationship between SLC26A4 mutation and current diagnosis of inner ear malformation in children with sensorineural hearing loss]. Baochun Sun;Chengyong Zhou;Zhiyao Dai. 2015. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 28. PMID: 25752102

OBJECTIVE: Explore the relationship between the pathogenic mutations of SLC26A4 gene and inner ear malformation, and analyze the feasibility of genetic testing to help current diagnosis in part of children with sensorineural hearing loss. METHOD: 2094 cases of children were detected by SLC26A4 with the method of DNA sequence. CT phenotypes of those children were classified according to the method proposed by Sennaroglu. We analyzed the relationship between the pathogenic mutations of gene and the CT phenotypes. RESULT: (1) 685 cases of inner ear malformations were found in 2094 cases of children with sensorineural hearing loss by CT examination (371 cases of cochlea malformation were consisted of the follow types of malformation. Michel deformity was 6 cases, cochlea aplasia was 8 cases, common cavity deformity was 12 cases, incomplete partition type I was 27 cases, cochlea hypoplasia was 30 cases and Mondini malformation was 288 cases); Vestibular aqueduct was 265 cases; Vestibular/semicircular canal/internal auditory canal were 49 cases, normal was 1409 cases. (2) The DNA sequence results revealed that 465 cases carried pathogenic mutations (Bi-allelic mutations) of SLC26A4 gene, among which 135 cases were homozygous, 330 cases were compound heterozygous. (3) Pathogenic mutations of SLC26A4 gene detected 100% (465/465) in the group related to vestibular aqueduct malformation. CONCLUSION: The results suggest that pathogenic mutation of SLC26A4 gene is closely related to the CT phenotype of vestibular aqueduct malformation. Detecting of pathogenic mutations for hearing loss is binging the possibility to identify children with inner malformations at an early stage. As a consequence, it will improve the current diagnosis and therapeutical option.
Identification of SLC26A4 mutations in patients with hearing loss and enlarged vestibular aqueduct using high-resolution melting curve analysis. Stephen Mercer;Patricia Mutton;Hans-Henrik M Dahl. 2011. Genet Test Mol Biomarkers. 15. PMID: 21366435

Mutations in the SLC26A4 gene can cause both Pendred syndrome and nonsyndromic enlargement of the vestibular aqueduct, two conditions associated with sensorineural hearing loss. We analyzed the SLC26A4 gene in 44 hearing-impaired patients by nested polymerase chain reaction followed by high-resolution melt analysis. We also used this approach to scan for mutations in KCNJ10 and FOXI1, two genes reported to play a role in the pathogenesis of Pendred syndrome and enlarged vestibular aqueduct. Seven patients with known SLC26A4 mutations were included as controls. All previously identified mutations were detected by high-resolution melt analysis. Of the patients with no known mutations, we detected two SLC26A4 mutations in 5 probands (12%), one mutation in 9 probands (21%), and no mutations in 29 probands (67%). We identified two novel SLC26A4 mutations, p.T485M and p.F718S, and found no evidence of a digenic contribution of KCNJ10 and FOXI1 mutations.
SLC26A4 variations among Graves' hyper-functioning thyroid gland. Hassen Hadj-Kacem;Rihab Kallel;Salima Belguith-Maalej;Mouna Mnif;Ilhem Charfeddine;Abdelmounem Ghorbel;Mohamed Abid;Hammadi Ayadi;Saber Masmoudi. 2010. Dis Markers. 29. PMID: 21045265

Deleterious mutations of SLC26A4 cause Pendred syndrome (PS), an autosomal recessive disorder comprising goitre and deafness with enlarged vestibular aqueducts (EVA), and nonsyndromic hearing loss (NSHL). However, the SLC26A4 hyperactivity was recently associated with the emergence of autoimmune thyroid diseases (AITD) and asthma among human and mouse model. Here, by direct sequencing, we investigate the sequences of the 20 coding exons (2 to 21) of SLC26A4 and their flanking intron-exon junctions among patients affected with Graves' disease (GD) hyperthyroidism. Ten mono-allelic variants were identified, seven of which are intronic and previously unreported. Two, c.898A>C (p.I300L) and c.1061T>C (p.F354S), of the three exonic variants are non synonymous. The p.F354S variant is already described to be involved in PS or NSHL inheritances. The exploration by PCR-RFLP of p.I300L and p.F354S variants among 132 GD patients, 105 Hashimoto thyroiditis (HT), 206 Healthy subjects and 102 families with NSHL have shown the presence of both variants. The p.F354S variation was identified both among patients (1~HT and 3 GD) and healthy subjects (n=5). Whereas, the p.I300L variant was identified only in GD patients (n=3). Our studies provide evidence of the importance of systematic analysis of SLC26A4 gene sequences on models other than deafness. This approach allows the identification of new variants and the review of the pathogenic effects of certain mono-allelic variants reported responsible for PS and NSHL development.
DNA Diagnostics of Hereditary Hearing Loss: A Targeted Resequencing Approach Combined with a Mutation Classification System. Manou Sommen;Isabelle Schrauwen;Geert Vandeweyer;Nele Boeckx;Jason J Corneveaux;Jenneke van den Ende;An Boudewyns;Els De Leenheer;Sandra Janssens;Kathleen Claes;Margriet Verstreken;Nicola Strenzke;Friederike Predöhl;Wim Wuyts;Geert Mortier;Maria Bitner-Glindzicz;Tobias Moser;Paul Coucke;Matthew J Huentelman;Guy Van Camp. 2016. Hum Mutat. 37. PMID: 27068579

Although there are nearly 100 different causative genes identified for nonsyndromic hearing loss (NSHL), Sanger sequencing-based DNA diagnostics usually only analyses three, namely, GJB2, SLC26A4, and OTOF. As this is seen as inadequate, there is a need for high-throughput diagnostic methods to detect disease-causing variations, including single-nucleotide variations (SNVs), insertions/deletions (Indels), and copy-number variations (CNVs). In this study, a targeted resequencing panel for hearing loss was developed including 79 genes for NSHL and selected forms of syndromic hearing loss. One-hundred thirty one presumed autosomal-recessive NSHL (arNSHL) patients of Western-European ethnicity were analyzed for SNVs, Indels, and CNVs. In addition, we established a straightforward variant classification system to deal with the large number of variants encountered. We estimate that combining prescreening of GJB2 with our panel leads to a diagnosis in 25%-30% of patients. Our data show that after GJB2, the most commonly mutated genes in a Western-European population are TMC1, MYO15A, and MYO7A (3.1%). CNV analysis resulted in the identification of causative variants in two patients in OTOA and STRC. One of the major challenges for diagnostic gene panels is assigning pathogenicity for variants. A collaborative database collecting all identified variants from multiple centers could be a valuable resource for hearing loss diagnostics.
Extremely discrepant mutation spectrum of SLC26A4 between Chinese patients with isolated Mondini deformity and enlarged vestibular aqueduct. Shasha Huang;Dongyi Han;Yongyi Yuan;Guojian Wang;Dongyang Kang;Xin Zhang;Xiaofei Yan;Xiaoxiao Meng;Min Dong;Pu Dai. 2011. J Transl Med. 9. PMID: 21961810

BACKGROUND: Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity). The relationship between mutations in SLC26A4 and Mondini deformity without enlarged vestibular aqueduct has not been studied in any Chinese deaf population. The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity) in a Chinese population. METHODS: In total, 144 patients with sensorineural hearing loss were included and subjected to high-resolution temporal bone CT. Among them, 28 patients with isolated Mondini dysplasia (MD group), 50 patients with enlarged vestibular aqueduct with Mondini dysplasia (EVA with MD group), 50 patients with enlarged vestibular aqueduct without Mondini dysplasia (EVA group), and 16 patients with other types of inner ear malformations (IEM group) were identified. The coding exons of SLC26A4 were analyzed in all subjects. RESULTS: DNA sequence analysis of SLC26A4 was performed in all 144 patients. In the different groups, the detection rate of the SLC26A4 mutation differed. In the isolated MD group, only one single allelic mutation in SLC26A4 was found in one patient (1/28, 3.6%). In the EVA with MD group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. Also, in the EVA group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. These percentages were identical to those in the EVA plus MD group. Only two patients carried monoallelic mutations of the SLC26A4 gene in the IEM group (2/16, 12.5%). There were significant differences in the frequency of SLC26A4 mutation among the groups (P<0.001). The detection rate of SLC26A4 mutation in the isolated MD group was significantly lower than in the EVA group (with or without MD; P<0.001), and there was no significant difference in the detection rate of SLC26A4 between the MD group and IEM group (P>0.5). CONCLUSION: Although mutations in the SLC26A4 gene were frequently found in Chinese EVA patients with and without MD, there was no evidence to show a relationship between isolated MD and the SLC26A4 gene in the Chinese population examined. Hearing impairment in patients with isolated MD may be caused by factors other than mutations in the SLC26A4 gene.
Mutations in the SLC26A4 (pendrin) gene in patients with sensorineural deafness and enlarged vestibular aqueduct. F Bogazzi;D Russo;F Raggi;F Ultimieri;S Berrettini;F Forli;L Grasso;C Ceccarelli;S Mariotti;A Pinchera;L Bartalena;E Martino. 2004. J Endocrinol Invest. 27. PMID: 15279074

Pendred syndrome and the enlarged vestibular aqueduct (EVA) are considered phenotypic variations of the same entity due to mutations in the SLC26A4 (pendrin) gene. Pendred syndrome consists in sensorineural deafness, goiter and impaired thyroid hormone synthesis while in EVA thyroid function seems to be preserved. The aim of this study was to evaluate thyroid function and morphology and to look for mutations in the SLC26A4 gene in patients presented with EVA. Among 57 consecutive patients with sensorineural deafness 15 with EVA, as assessed by magnetic resonance imaging (MRI), were identified and studied. A complete evaluation of thyroid function including thyroid echography and perchlorate discharge test was carried out in all patients with EVA; all exons of the SLC26A4 gene were amplified from peripheral leukocytes and directly sequenced, using specific intronic primers. Out of 15 patients with EVA, goiter was present in 8 (53%), hypothyroidism in 7 (47%), increased serum thyroglobulin levels in 8 (53%) and a positive perchlorate discharge test in 10 (67%). Nine alleles of the SLC26A4 gene were mutated: 2 novel mutations (L465W and G497R) and 4 already known mutations (T410M, R409H, T505N and IVS1001+1G>A) were found. Four subjects were compound heterozygous and 1 heterozygous (G497R/wt). All patients harbouring mutations in the SLC26A4 gene had goiter and a positive perchlorate discharge test: 3 were slightly hypothyroid and 2 euthyroid. The remaining 10 patients had no mutations in the SLC26A4 gene: 4 of them were hypothyroid, 2 with goiter and positive perchlorate discharge test, 2 without goiter and with negative perchlorate discharge test. Two patients without mutations were euthyroid with positive perchlorate discharge test. Patients with mutations in the SLC26A4 gene had larger thyroid volume (p<0.002), higher serum thyroglobulin (Tg) levels (p<0.002) and greater radioiodine discharge after perchlorate (p=0.09) than patients without mutations. The results of the present study lend support to the concept that all patients with mutated SLC26A4 gene have abnormalities of thyroid function tests.
Hearing loss associated with enlargement of the vestibular aqueduct: mechanistic insights from clinical phenotypes, genotypes, and mouse models. Andrew J Griffith;Philine Wangemann. 2011. Hear Res. 281. PMID: 21669267

Enlargement of the vestibular aqueduct (EVA) is one of the most common inner ear malformations associated with sensorineural hearing loss in children. The delayed onset and progressive nature of this phenotype offer a window of opportunity to prevent or retard progression of hearing loss. EVA is not the direct cause of hearing loss in these patients, but rather is a radiologic marker for some underlying pathogenetic defect. Mutations of the SLC26A4 gene are a common cause of EVA. Studies of an Slc26a4 knockout mouse demonstrate that acidification and enlargement of the scala media are early events in the pathogenesis of deafness. The enlargement is driven by fluid secretion in the vestibular labyrinth and a failure of fluid absorption in the embryonic endolymphatic sac. Elucidating the mechanism of hearing loss may offer clues to potential therapeutic strategies.
Novel compound heterozygous mutations in SLC26A4 gene in a Chinese Han family with enlarged vestibular aqueduct. Mingming Wang;Fengguo Zhang;Lei Xu;Yun Xiao;Jianfeng Li;Zhaomin Fan;Qian Sun;Xiaohui Bai;Haibo Wang. 2016. Int J Pediatr Otorhinolaryngol. 90. PMID: 27729126

OBJECTIVE: To identify the disease-related SLC26A4 mutants in a Chinese Han pedigree associated with Enlarged vestibular aqueduct (EVA). METHODS: EVA diagnosis was based on the family history, clinical examinations, systematically audiometric evaluations, high-resolution computed tomography (HRCT) of the temporal bone, and magnetic resonance imaging (MRI) of inner ear. Sanger sequencing and mutation analysis of the SLC26A4 gene were performed in all members of this family to identify the disease-related SLC26A4 mutants. Mutations in the SLC26A4 gene were compared with 200 ethnically matched control persons to exclude common polymorphism. RESULTS: All members in this family were negative for systemic and thyroid diseases. There were three subjects (I-2, II-2 and II-3) with bilateral sensorineural deafness since childhood. Temporal bone HRCT scans and inner ear MRI showed bilateral enlarged vestibular aqueduct with Mondini malformation in II-2 and II-3. A novel SLC26A4 splice-site mutation c.1001 + 5G > C was identified in compound heterozygosity with the mutation c.919-2A > G in the proband and in II-2. This novel compound heterozygote of two splice site mutations was not found in 200 normal hearing Chinese Han controls. CONCLUSIONS: A novel splice site mutation of c.1001 + 5G > C was identified, and the novel compound heterozygote of two splice site mutations, c.1001 + 5G > C and c.919-2A > G, in the SLC26A4 gene has been linked to hearing impairment in EVA patients.
SLC26A4 genotypes and phenotypes associated with enlargement of the vestibular aqueduct. Taku Ito;Byung Yoon Choi;Kelly A King;Christopher K Zalewski;Julie Muskett;Parna Chattaraj;Thomas Shawker;James C Reynolds;John A Butman;Carmen C Brewer;Philine Wangemann;Seth L Alper;Andrew J Griffith. 2011. Cell Physiol Biochem. 28. PMID: 22116369

Enlargement of the vestibular aqueduct (EVA) is the most common inner ear anomaly detected in ears of children with sensorineural hearing loss. Pendred syndrome (PS) is an autosomal recessive disorder characterized by bilateral sensorineural hearing loss with EVA and an iodine organification defect that can lead to thyroid goiter. Pendred syndrome is caused by mutations of the SLC26A4 gene. SLC26A4 mutations may also be identified in some patients with nonsyndromic EVA (NSEVA). The presence of two mutant alleles of SLC26A4 is correlated with bilateral EVA and Pendred syndrome, whereas unilateral EVA and NSEVA are correlated with one (M1) or zero (M0) mutant alleles of SLC26A4. Thyroid gland enlargement (goiter) appears to be primarily dependent on the presence of two mutant alleles of SLC26A4 in pediatric patients, but not in older patients. In M1 families, EVA may be associated with a second, undetected SLC26A4 mutation or epigenetic modifications. In M0 families, there is probably etiologic heterogeneity that includes causes other than, or in addition to, monogenic inheritance.
A novel variant of SLC26A4 and first report of the c.716T>A variant in Iranian pedigrees with non-syndromic sensorineural hearing loss. Fatemeh Azadegan-Dehkordi;Reza Ahmadi;Tayyeb Bahrami;Nasrin Yazdanpanahi;Effat Farrokhi;Mohammad Amin Tabatabaiefar;Morteza Hashemzadeh-Chaleshtori. 2018. Am J Otolaryngol. . PMID: 30077349

The autosomal recessive non-syndromic hearing loss (ARNSHL) can be associated with variants in solute carrier family 26, member 4 (SLC26A4) gene and is the second most common cause of ARNSHL worldwide. Therefore, this study aims to determine the contribution of the SLC26A4 genotype in the hearing loss (HL) of 40 ARNSHL pedigrees in Iran. A cohort of the 40 Iranian pedigrees with ARNSHL, having no mutation in the GJB2 gene, was selected. The linkage analysis with five short tandem repeat (STR) markers linked to SLC26A4 was performed for the 40 ARNSHL pedigrees. Then, two out of the 40 pedigrees with ARNSHL that linked to DFNB4 locus were further screened to determine the variants in all exons of SLC26A4 gene by direct DNA sequencing. The 21 exons of SCL26A4 were analyzed for the two pedigrees. A known variant (c.716T>A homozygote), it is the first reported incidence in Iran, a novel variant (c.493A>C homozygote) were detected in the two pedigrees and pathogenesis of c.493A>C confirmed in this study with review 100 hearing ethnically matched controls by PCR-RFLP analysis. The present study suggests that the SLC26A4 gene plays a crucial role in the HL occurring in Iranian pedigrees. Also, the results probably support the specificity and unique spectrum of SLC26A4 variants among Iranian HL patients. Molecular study of SLC26A4 gene may lead to elucidation of the profile of the population-specific variants which has importance in diagnostics of HL.
[Epidemiological analysis of GJB2,SLC26A4,mtRNA,GJB3 in nonsyndromic hearing loss in Kashi in Xinjiang]. J Sun;Y Chen;H Zhang;H Wen. None. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 31. PMID: 29871328

Objective:To investigate the epidemiological analysis of the GJB2,SLC26A4,mtRNA and GJB3 gene in nonsyndromic hearing loss in Kashi in Xinjiang.Method:In this study, we analyzed the mutations of GJB2, SLC26A4, mitochondrial mtRNA and GJB3 gene mutations in 629 cases of patients with nonsyndromic hearing loss in Kashi in Xinjiang by using the gene kit. Result:The proportion of GJB2 gene mutation was 60.29%(41/68), the SLC26A4 and mtRNA were 8.82%(6/68)and 30.88%(21/68)respectively. Conclusion:GJB2 gene, SLC26A4, mtRNA gene are common cause of nonsyndromic hearing loss in Xinjiang.
Mutation analysis of SLC26A4 for Pendred syndrome and nonsyndromic hearing loss by high-resolution melting. Neng Chen;Lisbeth Tranebjærg;Nanna Dahl Rendtorff;Iris Schrijver. 2011. J Mol Diagn. 13. PMID: 21704276

Pendred syndrome and DFNB4 (autosomal recessive nonsyndromic congenital deafness, locus 4) are associated with autosomal recessive congenital sensorineural hearing loss and mutations in the SLC26A4 gene. Extensive allelic heterogeneity, however, necessitates analysis of all exons and splice sites to identify mutations for individual patients. Although Sanger sequencing is the gold standard for mutation detection, screening methods supplemented with targeted sequencing can provide a cost-effective alternative. One such method, denaturing high-performance liquid chromatography, was developed for clinical mutation detection in SLC26A4. However, this method inherently cannot distinguish homozygous changes from wild-type sequences. High-resolution melting (HRM), on the other hand, can detect heterozygous and homozygous changes cost-effectively, without any post-PCR modifications. We developed a closed-tube HRM mutation detection method specific for SLC26A4 that can be used in the clinical diagnostic setting. Twenty-eight primer pairs were designed to cover all 21 SLC26A4 exons and splice junction sequences. Using the resulting amplicons, initial HRM analysis detected all 45 variants previously identified by sequencing. Subsequently, a 384-well plate format was designed for up to three patient samples per run. Blinded HRM testing on these plates of patient samples collected over 1 year in a clinical diagnostic laboratory accurately detected all variants identified by sequencing. In conclusion, HRM with targeted sequencing is a reliable, simple, and cost-effective method for SLC26A4 mutation screening and detection.
[Molecular etiology analysis among students with profound hearing loss in a special education school in Yangzhou]. Xin Peng;Xia Li;Li Xu;Bing Guan;Junzhong Zhang;Aimin Yu. 2012. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 26. PMID: 23002639

OBJECTIVE: To study molecular epidemiological basis of non-syndromic hearing loss in Yangzhou area. METHOD: The selected objects were 90 severe non-syndrome deafness students in special education schools in Yangzhou city, Jiangsu province. The deafness gene chip diagnostic kit was used for screening the nine hot spots mutations in four common deafness-related genes in Medical Testing Center of Northern Jiangsu People's Hospital. These nine hot spots gene mutations included GJB2 (35 delG, 176 del16, 235 delC and 299 delAT) GJB3 (538C > T), SLC26A4 (IVS7-2A > G, 2168A > G) and mtDNA 12S rRNA (A > G,1494C > T) mutation detection by line. RESULT: In 90 patients, 64 patients were found to carry deafness mutations by using gene chip diagnostic kit (the rate of mutation was 71.7%) GJB2 gene mutation in 40 cases (44.4%)which included 235 delC homozygous in 20 (22.2%) cases, 235 delC single heterozygous mutation in 4 cases (4.4%)and 235 delC and 299 delAT compound heterozygous mutations in 2 case (2.2%) separately. 299 delAT single heterozygous mutation in 2 case (2.2%), 299 delAT simple mutation in 2 case (2.2%). 176 del16 heterozygous mutations in 2 case, 176 del16 homozygous mutation in 2 case (2.2%). 176 del16 heterozygous mutations, and 235 del C heterozygous mutation in 6 cases (6.7%). SLC26A4 gene mutations in 22 cases (24.4%),which included IVS7-2A > G homozygous in 2 (2.22%) cases, IVS7-2A > G and 2168A > G compound heterozygous mutations in 2 cases (2.2%), IVS7-2A > G single heterozygous mutation in 18 cases (20.2%), and mtDNA 12S rRNA A > G mutation in 2 cases (2.2%), GJB3 mutations were not detected. CONCLUSION: The deafness gene diagnostic techniques is worth applying for screening and diagnosis.
A 7666-bp genomic deletion is frequent in Chinese Han deaf patients with non-syndromic enlarged vestibular aqueduct but without bi-allelic SLC26A4 mutations. Xiuhong Pang;Yongchuan Chai;Longxia He;Penghui Chen;Xiaowen Wang;Lei Li;Huan Jia;Hao Wu;Tao Yang. 2015. Int J Pediatr Otorhinolaryngol. 79. PMID: 26549381

OBJECTIVES: To investigate the genetic cause of the patients with non-syndromic enlarged vestibular aqueduct (EVA) but without bi-allelic SLC26A4 mutations. METHODS: Presence of a homozygous genomic deletion was detected in a Chinese Han deaf patient (D1467-1) who failed to amplify the first three exons of SLC26A4. The breakpoints of the deletion were fine-mapped and revealed by PCR amplification and sequencing. This deletion was subsequently screened in 22 Chinese Han EVA probands with mono-allelic SLC26A4 mutations. The possible founder effect of the newly identified genomic deletion was evaluated by haplotype analysis. RESULTS: A homozygous c.-2071_307+3801del7666 deletion of SLC26A4 was identified in patient D1467-1. This novel genomic deletion was subsequently identified in 18% (4/22) of the Chinese Han EVA probands with mono-allelic SLC26A4 mutations. Haplotype analysis showed that this genomic deletion is likely a founder mutation in Chinese Hans. CONCLUSION: Our results suggested that the cryptic c.-2071_307+3801del7666 deletion of SLC26A4 is relatively frequent in Chinese Han non-syndromic EVA patients without bi-allelic SLC26A4 mutations. Screening of this genomic deletion should be incorporated into the routine DNA testing of SLC26A4 in Chinese Hans.
[Establishment of the multiplex quantitative ligase chain reaction for detecting mutations of deafness genes]. Xiao-lin Yang;Zheng-min Xu. 2010. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 27. PMID: 20931531

OBJECTIVE: To establish a low-cost, convenient and accurate multiplex quantitative ligase chain reaction (MQ-LCR) technique to detect the five common mutations in Chinese patients with deafness. METHODS: Primers and probes for 5 common mutations of deafness genes, i.e., GJB2 gene 235delC and 299-300delAT, mtDNA A1555G, SLC26A4 gene IVS7-2 A>G and 2168A>G, were designed and synthesized. The technique for those mutations was established, and the reliability of the technique was tested in 98 patients with impaired hearing and 30 children with normal hearing, who were randomly selected from the ENT in Children's Hospital of Fudan University. The subjects were detected by MQ-LCR and direct DNA sequencing of PCR products, following a double-blind approach. Finally the results from the two methods were compared. RESULTS: The results revealed 48 cases carried two mutations, 31 cases carried heterozygous mutations in the 98 deaf children, and 3 had heterozygous mutation in 30 normal controls. These results were consistent with that from DNA sequencing. No false positive and false negative result was obtained. CONCLUSION: The MQ-LCR technique established in this study is of low-cost, convenience, accuracy, high sensitivity and high specificity. It is suitable for large-scale detection and preventive diagnosis of mutations in deafness.
Clinical characteristics and genotype-phenotype correlation of hearing loss patients with SLC26A4 mutations. Hiroaki Suzuki;Aki Oshima;Koji Tsukamoto;Satoko Abe;Kozo Kumakawa;Kyoko Nagai;Hitoshi Satoh;Yukihiko Kanda;Satoshi Iwasaki;Shin-ichi Usami. 2007. Acta Otolaryngol. 127. PMID: 17851929

CONCLUSIONS: The present study confirmed the clinical characteristics of patients with SLC26A4 mutations: congenital, fluctuating, and progressive hearing loss usually associated with vertigo and/or goiter during long-term follow-up. This clarification should help to facilitate appropriate genetic counseling and proper medical management for patients with these mutations, but there was no particular genotype-phenotype correlation among them, suggesting that other factors may contribute to such variability. OBJECTIVES: Due to the wide range of phenotypes caused by SLC26A4 mutations, there is controversy with regard to genotype-phenotype correlation. The present study was performed: (1) to determine phenotypic range in patients with biallelic SLC26A4 mutations, and (2) to evaluate whether possible genotype-phenotype correlation exists. SUBJECTS AND METHODS: Phenotypes in 39 hearing loss patients with SLC26A4 mutations were summarized and genotype-phenotype correlation was analyzed. RESULTS: Hearing level varied in the individuals from mild to profound severity. Most of the patients had fluctuating and progressive hearing loss that may have been of prelingual onset. Twenty-four (70.6%) patients had episodes of vertigo, and 10 (27.8%) patients had goiter, which had appeared at age 12 or older. In contrast to such phenotypic variabilities, no apparent correlation was found between these phenotypes and their genotypes.
Detection of hereditary hearing loss gene by DNA microarray. G-Y Han;Z Xu;Q-S Li;H-Y Shen;W Zhang;J Liang. 2017. Eur Rev Med Pharmacol Sci. 21. PMID: 28925492

OBJECTIVE: Screening genes in patients suffering clinically sporadic deafness, using DNA microarray, and evaluating the application value of the clinical detection. PATIENTS AND METHODS: DNA extracted from patients' venous blood was amplified by PCR, and hybridization was carried out in a myriad class clean room. Nine mutation sites of four deaf genes commonly seen in Chinese people were tested. RESULTS: Among 24 patients, 7 cases with mutations were detected, with a positive rate of 29.17%. These include 4 cases with GJB2 gene mutation (16.67%), of which 1 case with 176 del 16 site heterozygous mutation; 1 with 235 del C site homozygous mutation; 2 with 299 del AT site heterozygous mutation; 1 with SLC26A4 gene IVS7-2A>G site heterozygous mutation (4.17%), 2 with mitochondrion 12SrRNA gene1555A>G site homogeneous mutation (8.33%). No GJB3 gene mutation was detected. CONCLUSIONS: Gene chip technology of hereditary hearing loss can detect related mutation sites of hearing loss rapidly and with high-throughput, which meets the demands of clinical deaf gene detection.
SLC26A4 gene copy number variations in Chinese patients with non-syndromic enlarged vestibular aqueduct. Jiandong Zhao;Yongyi Yuan;Jing Chen;Shasha Huang;Guojian Wang;Dongyi Han;Pu Dai. 2012. J Transl Med. 10. PMID: 22551242

BACKGROUND: Many patients with enlarged vestibular aqueduct (EVA) have either only one allelic mutant of the SLC26A4 gene or lack any detectable mutation. In this study, multiplex ligation-dependent probe amplification (MLPA) was used to screen for copy number variations (CNVs) of SLC26A4 and to reveal the pathogenic mechanisms of non-syndromic EVA (NSEVA). METHODS: Between January 2003 and March 2010, 923 Chinese patients (481 males, 442 females) with NSEVA were recruited. Among these, 68 patients (7.4%) were found to carry only one mutant allele of SLC26A4 and 39 patients (4.2%) lacked any detectable mutation in SLC26A4; these 107 patients without double mutant alleles were assigned to the patient group. Possible copy number variations in SLC26A4 were detected by SALSA MLPA. RESULTS: Using GeneMapper, no significant difference was observed between the groups, as compared with the standard probe provided in the assay. The results of the capillary electrophoresis showed no significant difference between the patients and controls. CONCLUSION: Our results suggest that CNVs and the exon deletion in SLC26A4 are not important factors in NSEVA. However, it would be premature to conclude that CNVs have no role in EVA. Genome-wide studies to explore CNVs within non-coding regions of the SLC26A4 gene and neighboring regions are warranted, to elucidate their roles in NSEVA etiology.
Mutation screening of the SLC26A4 gene in a cohort of 192 Chinese patients with congenital hypothyroidism. Chunyun Fu;Haiyang Zheng;Shujie Zhang;Yun Chen;Jiasun Su;Jin Wang;Bobo Xie;Xuyun Hu;Xin Fan;Jingsi Luo;Chuan Li;Rongyu Chen;Yiping Shen;Shaoke Chen. 2016. Arch Endocrinol Metab. 60. PMID: 26886089

OBJECTIVE: Pendred syndrome (PS) is an autosomal recessive disorder characterised by sensorineural hearing loss and thyroid dyshormonogenesis. It is caused by biallelic mutations in the SLC26A4 gene encoding for pendrin. Hypothyroidism in PS can be present from birth and therefore diagnosed by neonatal screening. The aim of this study was to examine the SLC26A4 mutation spectrum and prevalence among congenital hypothyroidism (CH) patients in the Guangxi Zhuang Autonomous Region of China and to establish how frequently PS causes hearing impairment in our patients with CH. SUBJECTS AND METHODS: Blood samples were collected from 192 CH patients in Guangxi Zhuang Autonomous Region, China, and genomic DNA was extracted from peripheral blood leukocytes. All exons of the SLC26A4 gene together with their exon-intron boundaries were screened by next-generation sequencing. Patients with SLC26A4 mutations underwent a complete audiological evaluation including otoscopic examination, audiometry and morphological evaluation of the inner ear. RESULTS: Next generation sequencing analysis of SLC26A4 in 192 CH patients revealed five different heterozygous variations in eight individuals (8/192, 4%). The prevalence of SLC26A4 mutations was 4% among studied Chinese CH. Three of the eight were diagnosed as enlargement of the vestibular aqueduct (EVA), no PS were found in our 192 CH patients. The mutations included one novel missense variant p.P469S, as well as four known missense variants, namely p.V233L, p.M147I, p.V609G and p.D661E. Of the eight patients identified with SLC26A4 variations in our study, seven patients showed normal size/location of thyroid gland, and one patients showed a decreased size one. CONCLUSIONS: The prevalence of SLC26A4 pathogenic variants was 4% among studied Chinese patients with CH. Our study expanded the SLC26A4 mutation spectrum, provided the best estimation of SLC26A4 mutation rate for Chinese CH patients and indicated the rarity of PS as a cause of CH.
A case of palmoplantar lichen planus in a patient with congenital sensorineural deafness. A Ogawa;K Shimizu;A Yoshizaki;S Sato;Y Kanda;H Kumagami;H Takahashi;S Usami. 2012. Clin Exp Dermatol. 38. PMID: 22924538

We report a case of palmoplantar lichen planus in a 7-year-old Japanese girl with congenital deafness, who presented with erythematous eruptions and hyperkeratosis, with peeling and fissures on her soles, palms and digits. On histological examination of a skin biopsy from the lesion on her wrist, lichen planus was identified. Using computed tomography of the inner ears, bilateral cochlear dysplasia was found. The patient's DNA was sequenced; no sequence variants were detected in the GJB2 gene encoding connexin-26, but she had a missense mutation in SLC26A4 (solute carrier family 26, member 4). Mutations in SLC26A4 are known causes of hearing loss, but this is a novel mutation, which has not been reported previously. In addition, there have been no reports of cutaneous symptoms in previously reported patients with mutations in SLC26A4. To our knowledge, therefore, this is the first report of palmoplantar lichen planus associated with sensorineural deafness accompanied by a mutation in the SLC26A4 gene.
Identification of two novel mutations, c.232T>C and c.2006A>T, in SLC26A4 in a Chinese family associated with enlarged vestibular aqueduct. Yu-Fen Guo;Yan-Li Wang;Bai-Cheng Xu;Xiao-Wen Liu;Yi-Ming Zhu;Fei-Fan Zhao;Yu-Bin Ji;Ying Zhou;Jian-Qiang Li;Qian Li;Da-Yong Wang;Qiu-Ju Wang. 2010. Int J Pediatr Otorhinolaryngol. 74. PMID: 20483489

It is known that enlarged vestibular aqueduct syndrome is closely related to the SLC26A4 mutation. Up to date, more than 200 of SLC26A4 mutations have been described, and novel mutations are being continually identified in different countries and ethnic groups. In this study, two novel variations were identified in a Chinese family associated with enlarged vestibular aqueduct. The two novel substitutions, c.232T>C and c.2006A>T, were detected in exon 3 and exon 17 of the pendrin encoding gene, respectively. The T/C transversion at 232 nucleotide caused p.Y78H mutation while the A/T transversion at 2006 nucleotide caused p.D669V mutation.
Transcriptional control of SLC26A4 is involved in Pendred syndrome and nonsyndromic enlargement of vestibular aqueduct (DFNB4). Tao Yang;Hilmar Vidarsson;Sandra Rodrigo-Blomqvist;Sally S Rosengren;Sven Enerback;Richard J H Smith. 2007. Am J Hum Genet. 80. PMID: 17503324

Although recessive mutations in the anion transporter gene SLC26A4 are known to be responsible for Pendred syndrome (PS) and nonsyndromic hearing loss associated with enlarged vestibular aqueduct (EVA), also known as "DFNB4," a large percentage of patients with this phenotype lack mutations in the SLC26A4 coding region in one or both alleles. We have identified and characterized a key transcriptional regulatory element in the SLC26A4 promoter that binds FOXI1, a transcriptional activator of SLC26A4. In nine patients with PS or nonsyndromic EVA, a novel c.-103T-->C mutation in this regulatory element interferes with FOXI1 binding and completely abolishes FOXI1-mediated transcriptional activation. We have also identified six patients with mutations in FOXI1 that compromise its ability to activate SLC26A4 transcription. In one family, the EVA phenotype segregates in a double-heterozygous mode in the affected individual who carries single mutations in both SLC26A4 and FOXI1. This finding is consistent with our observation that EVA occurs in the Slc26a4(+/-); Foxi1(+/-) double-heterozygous mouse mutant. These results support a novel dosage-dependent model for the molecular pathogenesis of PS and nonsyndromic EVA that involves SLC26A4 and its transcriptional regulatory machinery.
Molecular epidemiological analysis of mitochondrial DNA12SrRNA A1555G, GJB2, and SLC26A4 mutations in sporadic outpatients with nonsyndromic sensorineural hearing loss in China. Yu-bin Ji;Dong-Yi Han;Lan Lan;Da-Yong Wang;Liang Zong;Fei-Fan Zhao;Qiong Liu;Cindy Benedict-Alderfer;Qing-yin Zheng;Qiu-Ju Wang. 2010. Acta Otolaryngol. 131. PMID: 21162657

CONCLUSION: GJB2 mutation was frequent in sporadic outpatients and its mutation frequency was significant higher in the prelingual group than in the postlingual group, whereas the mutation of mtDNA A1555G and SLC26A4 was very rare in Chinese sporadic outpatients with nonsyndromic sensorineural hearing loss (NSHL). Standard and comprehensive inclusion and grouping criteria are necessary for epidemiological studies of deafness-related gene mutations. OBJECTIVES: This study aimed to examine the mutations of the three common deafness genes GJB2, SLC26A4, and mtDNA A1555G in Chinese sporadic outpatients with NSHL and to discuss the factors that influence the detection accuracy of mutation frequencies. METHODS: A total of 473 sporadic NSHL patients without any type of inner ear malformation, including both prelingual and postlingual groups were enrolled in this study. Three genes of mtDNA A1555G, GJB2, and SLC26A4 were screened for mutation in our study cohort. A chi-square test was performed to compare mutation frequencies between prelingual and postlingual groups. RESULTS: The mutation frequencies of MtDNA A1555G, GJB2, and SLC26A4 were 1.63%, 13.63%, and 0%, respectively, in our study cohort. The mutational hot spot of GJB2 was c.235delC, whose allele frequency was 12.68% in sporadic outpatients. Mutation frequency of GJB2 in the prelingual group was significantly higher than in the postlingual group (p < 0.05).
Use of SLC26A4 mutation testing for unilateral enlargement of the vestibular aqueduct. Parna Chattaraj;Fabian R Reimold;Julie A Muskett;Boris E Shmukler;Wade W Chien;Anne C Madeo;Shannon P Pryor;Christopher K Zalewski;John A Butman;Carmen C Brewer;Margaret A Kenna;Seth L Alper;Andrew J Griffith. 2013. JAMA Otolaryngol Head Neck Surg. 139. PMID: 24051746

IMPORTANCE: Approximately one-half of all subjects with unilateral or bilateral hearing loss with enlargement of the vestibular aqueduct (EVA) will have SLC26A4 gene mutations. The number (0, 1, or 2) of mutant alleles of SLC26A4 detected in an individual subject with EVA is each associated with a distinct combination of diagnostic and prognostic information as well as probability of recurrence of EVA in siblings. OBJECTIVE: To evaluate the results of SLC26A4 mutation testing in subjects with unilateral EVA. (The study objective was formulated before data were collected.) DESIGN: Prospective cross-sectional study of cohort ascertained between 1998 and 2012. SETTING: National Institutes of Health Clinical Center, a federal biomedical research facility. PARTICIPANTS: Twenty-four subjects (10 males, 14 females) with unilateral EVA, defined as a midpoint diameter greater than 1.5 mm, who were referred or self-referred to participate in a study about the clinical and molecular analysis of EVA. Twenty-one (87.5%) of 24 subjects were white. Mean age was 10.3 years (age range, 5-39 years). INTERVENTION: SLC26A4 mutation analysis. MAIN OUTCOMES AND MEASURES: Audiometric results, the presence or absence of EVA, and the number of mutant alleles of SLC26A4. RESULTS: Approximately 8.3% of the subjects with unilateral EVA had 2 mutant SLC26A4 alleles, 16.7% had 1 mutant allele, and 75.0% had 0 mutant alleles. CONCLUSIONS AND RELEVANCE: Unilateral EVA can be associated with all possible SLC26A4 genotype results. The distinct combination of prognoses and recurrence probability associated with each genotype supports the clinical use of testing for SLC26A4 mutations in subjects with unilateral EVA.
Molecular etiology of hearing impairment in Inner Mongolia: mutations in SLC26A4 gene and relevant phenotype analysis. Pu Dai;Yongyi Yuan;Deliang Huang;Xiuhui Zhu;Fei Yu;Dongyang Kang;Huijun Yuan;Bailin Wu;Dongyi Han;Lee-Jun C Wong. 2008. J Transl Med. 6. PMID: 19040761

BACKGROUND: The molecular etiology of hearing impairment in Chinese has not been thoroughly investigated. Study of GJB2 gene revealed that 30.4% of the patients with hearing loss in Inner Mongolia carried GJB2 mutations. The SLC26A4 gene mutations and relevant phenotype are analyzed in this study. METHODS: One hundred and thirty-five deaf patients were included. The coding exons of SLC26A4 gene were sequence analyzed in 111 patients, not including 22 patients carrying bi-allelic GJB2 mutations or one patient carrying a known GJB2 dominant mutation as well as one patient with mtDNA 1555A>G mutation. All patients with SLC26A4 mutations or variants were subjected to high resolution temporal bone CT scan and those with confirmed enlarged vestibular aqueduct and/or other inner ear malformation were then given further ultrasound scan of thyroid and thyroid hormone assays. RESULTS: Twenty-six patients (19.26%, 26/135) were found carrying SLC26A4 mutation. Among them, 17 patients with bi-allelic SLC26A4 mutations were all confirmed to have EVA or other inner ear malformation by CT scan. Nine patients were heterozygous for one SLC26A4 mutation, including 3 confirmed to be EVA or EVA and Mondini dysplasia by CT scan. The most common mutation, IVS7-2A>G, accounted for 58.14% (25/43) of all SLC26A4 mutant alleles. The shape and function of thyroid were confirmed to be normal by thyroid ultrasound scan and thyroid hormone assays in 19 of the 20 patients with EVA or other inner ear malformation except one who had cystoid change in the right side of thyroid. No Pendred syndrome was diagnosed. CONCLUSION: In Inner Mongolia, China, mutations in SLC26A4 gene account for about 12.6% (17/135) of the patients with hearing loss. Together with GJB2 (23/135), SLC26A4 are the two most commonly mutated genes causing deafness in this region. Pendred syndrome is not detected in this deaf population. We established a new strategy that detects SLC26A4 mutations prior to the temporal bone CT scan to find EVA and inner ear malformation patients. This model has a unique advantage in epidemiologic study of large deaf population.
[Mutation analysis of 16 mutation spots related to children patients with non-syndromic sensorineural hearing loss]. Rongjun Man;Zeng Zhang;Rongzhong Lu;Xiao Wang;Shiping Sun;Dan Wang;Xiaosong Xu;Weiguo Wang;Huizhong Wang. 2015. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 29. PMID: 26121829

OBJECTIVE: To explore the clinical signification of screening 16 target deafness mutations in GJB2, GJB3, SLC26A4, WFS1 and mitochondrial DNA 12S rRNA in 135 children patients with non-syndromic sensorineural hearing loss (NSHL) in Zibo City, Shandong province. METHOD: Peripheral blood samples of 135 subjects in the study diagnosed as NSHL were collected; Polymerase chain reaction (PCR) and direct sequencing were used to analyze the 16 mutation spots. RESULT: Sixty-two cases of 135 patients (45.9%, 62/135) were found out to be carries of at least one pathogenic gene mutation. Among them, 24 cases (17.8%, 24/135) had two mutated alleles (homozygote and compound heterozygote), and 38 cases (28.1%, 38/135) were single mutant carriers. Among all the children patients, 30 cases (22. 2%, 30/135) had SLC26A4 mutations, and 19 cases (14.1%, 19/135) had GJB2 mutations. In the study 86 Mutant alleles were detected, and the allele frequency of SLC26A4 c. 766_2A > G and GJB2 c. 235delC was 11.11% (30/270) and 8.5% (23/270) respectively. The allele frequency of SLC26A4 c. 2168A > G and WFS1 c. 2158A > G is 2.6% (7/270). CONCLUSION: SLC26A4 mutation is the primary cause of the patients with NSHL in this study, and GJB2 mutation is the secondary. The most common mutant form is c. 766_2A of SLC26A4, and the second is c. 235delC of GJB2. GJB3 and WFS1 mutations were detected, whereas mtDNA mutations were not found out in this study.
[Mutational screening of the SLC26A4 gene in patients with nonsyndromic hearing loss by denaturing high-performance liquid chromatography]. Juan Zhao;Ling-qian Wu;Yong Feng;Qian Pan;Kai Zhao;Hong-yan Li;De-sheng Liang. 2009. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 26. PMID: 19199245

OBJECTIVE: To study the SLC26A4 gene mutations in patients with nonsyndromic hearing loss (NSHL) and provide the clinical guidance of gene diagnosis. METHODS: PCR and denaturing high-performance liquid chromatography (DHPLC) were used to screen the 21 exons and their flanking regions of the SLC26A4 gene. Samples with abnormal DHPLC wave patterns were sequenced to identify the variations. RESULTS: Among the 30 unrelated NSHL patients in whom no deafness-causing mutations of the GJB2 gene were identified, 10 types of variations were detected, including 7 known mutations, 2 novel mutations (F572L and D87Y), and 1 known polymorphism (Ivs11+47T>C). The Ivs7-2A>G is the most common type of variation, accounting for 40% of all the mutations. CONCLUSION: SLC26A4 mutation is a major cause of NSHL, just next to the GJB2 mutations. For NSHL patients without deafness-causing GJB2 mutations, the SLC26A4 mutation rate was 23.3%, and the Ivs7-2A>G was the most common mutation.
Carrier re-sequencing reveals rare but benign variants in recessive deafness genes. Longxia He;Xiuhong Pang;Penghui Chen;Xiaowen Wang;Tao Yang;Hao Wu. 2017. Sci Rep. 7. PMID: 28900111

For recessive Mendelian disorders, determining the pathogenicity of rare, non-synonymous variants in known causative genes can be challenging without expanded pedigrees and/or functional analysis. In this study, we proposed to establish a database of rare but benign variants in recessive deafness genes by systematic carrier re-sequencing. As a pilot study, 30 heterozygous carriers of pathogenic variants for deafness were identified from unaffected family members of 18 deaf probands. The entire coding regions of the corresponding genes were re-sequenced in those carriers by targeted next-generation sequencing or Sanger sequencing. A total of 32 non-synonymous variants were identified in the normal-hearing carriers in trans with the pathogenic variant and therefore were classified as benign. Among them were five rare (minor allele frequencies less than 0.005) variants that had previously undefined, disputable or even misclassified function: p.A434T (c.1300 G > A) in SLC26A4, p.R266Q (c.797 G > A) in LOXHD1, p.K96Q (c.286 A > C) in MYO15A, p.T123N (c.368 C > A) in GJB2 and p.V1299I (c.797 G > A) in CDH23. Our results suggested that large scale carrier re-sequencing may be warranted to establish a database of rare but benign variants in causative genes in order to reduce false positive genetic diagnosis of recessive Mendelian disorders.
Novel mutation located in EC7 domain of protocadherin-15 uncovered by targeted massively parallel sequencing in a family segregating non-syndromic deafness DFNB23. Yuan Zhan;Min Liu;DeHua Chen;KaiTian Chen;HongYan Jiang. 2015. Int J Pediatr Otorhinolaryngol. 79. PMID: 25930172

OBJECTIVE: Hereditary hearing loss is a clinically and genetically heterogeneous disorder associated with mutations of a large number of diverse genes. In this study we applied targeted capture and massively parallel sequencing to identify the disease-causing gene of a Chinese family segregating recessive inherited deafness. METHODS: After excluding mutations in common deafness genes GJB2, SLC26A4, mitochondrial m.1555A>G, genomic DNA of the proband of family GDSW24 was subjected to targeted next-generation sequencing. Subsequently, a candidate homozygous mutation was confirmed by Sanger sequencing. RESULTS: A novel PCDH15 c.2367_2369delTGT/p.V788-homozygous mutation was detected. In this family, no obvious vestibular disorder was found. The in-frame mutation c.2367_2369delTGT is located in the evolutionarily conserved EC7 domain of Protocadherin-15 and was predicted to be pathogenic. CONCLUSION: The novel homozygous mutation in a family segregating non-syndromic hearing loss family supports previous reported observations that PCDH15 does not only causes Usher syndrome type 1F, but also DFNB23.
[Sequencing analysis of whole SLC26A4 gene in severe to profound sensorineural hearing loss patients with IVS7-2A to G mutation of the gene]. Qi Li;De-liang Huang;Qing-wen Zhu;Yong-yi Yuan;Ru-ping Fang;Pu Dai. 2010. Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 27. PMID: 21154317

OBJECTIVE: To investigate the whole sequence of the SLC26A4 gene in moderate to profound sensorineural hearing loss (SNHL) patients with IVS7-2A to G mutation of the gene in China. METHODS: Whole SLC26A4 gene sequence was analyzed by direct sequencing in 80 SLC26A4 gene IVS7-2A to G mutation carriers for the occurrence of a second mutation in the gene. RESULTS: Forty-seven out of the 80 patients were found to have a second heterozygous mutation, whereas a single IVS7-2A to G mutation could be responsible for SNHL in the remaining 33 patients. Three novel mutations, 5+ 2T to A, 14-2A to G and 1825del G, were identified. The five most common mutations include H723R (20%), T410M(5%), C.1705+ 5G to A (15+ 5G to A)(5%), L676Q(5%), and N392Y (3.75%). Exon 17 harbored the most types of compound heterozygosity with the IVS7-2A to G mutation. CONCLUSION: A Chinese specific SLC26A4 diversity was found, and comparable SLC26A4 contributing to deafness. This study suggested that if a heterozygous SLC26A4 mutation is found in a patient with deafness, other exons of the SLC26A4 gene should be analyzed. Furthermore, double heterozygosity of the SLC26A4 gene may also account for some of the disease phenotype.
Atypical patterns of segregation of familial enlargement of the vestibular aqueduct. Julie A Muskett;Parna Chattaraj;John F Heneghan;Fabian R Reimold;Boris E Shmukler;Carmen C Brewer;Kelly A King;Christopher K Zalewski;Thomas H Shawker;John A Butman;Margaret A Kenna;Wade W Chien;Seth L Alper;Andrew J Griffith. 2015. Laryngoscope. 126. PMID: 26485571

OBJECTIVES/HYPOTHESIS: Hearing loss and enlarged vestibular aqueduct (EVA) can be inherited as an autosomal recessive trait caused by mutant alleles of the SLC26A4 gene. In some other families, EVA does not segregate in a typical autosomal recessive pattern. The goal of this study was to characterize the SLC26A4 genotypes and phenotypes of extended families with atypical segregation of EVA. STUDY DESIGN: Prospective study of cohort of families ascertained between 1998 and 2014 at the National Institutes of Health Clinical Center. METHODS: Study subjects were members of eight families segregating EVA in at least two members who were not related as siblings. Evaluations included pure-tone audiometry, temporal bone imaging, SLC26A4 nucleotide sequence analysis, SLC26A4-linked marker genotype and haplotype analysis, and pedigree analysis. RESULTS: One family had members with EVA caused by different etiologies, and two families had pseudodominant inheritance of recessive mutations of SLC26A4. In five families, the etiology remained unknown and could include inheritance of mutant alleles at another genetic locus, nongenetic influences, or a combination of these factors. CONCLUSIONS: Familial EVA can demonstrate a variety of atypical segregation patterns. Pseudodominant inheritance of SLC26A4 mutations or recessive alleles of other hearing loss genes may be more likely to occur in families in which deaf individuals have intermarried. The etiologic basis of atypical segregation of EVA without detectable SLC26A4 mutations remains unknown. Future studies of these families may reveal novel genes for EVA. LEVEL OF EVIDENCE: NA Laryngoscope, 126:E240-E247, 2016.
Further characterisation of the recently described SLC26A4 c.918+2T>C mutation and reporting of a novel variant predicted to be damaging. A C Gonçalves;R Santos;A O'Neill;P Escada;G Fialho;H Caria. 2016. Acta Otorhinolaryngol Ital. 36. PMID: 27214836

Pendred syndrome (PS) is the second most common type of autosomal recessive syndromic hearing loss (HL). It is characterised by sensorineural HL and goiter with occasional hypothyroidism. These features are generally accompanied by malformations of the inner ear, as enlarged vestibular aqueduct (EVA). In about 50% of probands, mutations in the SLC26A4 gene are the cause of the disease. Here we report the case of a Portuguese female, aged 47, presenting with severe to profound HL and hypothyroidism. Her mother and sister, both deceased, had suffered from HL and goiter. By MRI and CT, an enlarged vestibular aqueduct and endolymphatic sac were observed. Molecular study of the patient included screening for GJB2 coding mutations and GJB6 common deletions followed by screening of all SLC26A4 exons, as well as intronic regions 8 and 14. Mutation c.918+2T>C was found for the first time in homozygosity in the intronic region 7 of the SLC26A4 gene. Whilst sequencing the control samples, a novel mutation c.821C>G was found in heterozygosity in the exon 7 of SLC26A4 gene and was predicted to be damaging. This study thus led to the finding of two novel SLC26A4 genotypes and provides new insight on the phenotypic features associated with PS.
Molecular etiology of hearing impairment associated with nonsyndromic enlarged vestibular aqueduct in East China. Yongchuan Chai;Zhiwu Huang;Zheng Tao;Xiaohua Li;Lei Li;Yun Li;Hao Wu;Tao Yang. 2013. Am J Med Genet A. 161A. PMID: 23918157

Recessive mutations in SLC26A4 and in rarer cases double heterozygous mutations of FOXI1/SLC26A4 and KCNJ10/SLC26A4 lead to hearing impairment associated with enlarged vestibular aqueduct (EVA), the most common inner ear malformation. In our large cohort study, we addressed several important questions to the molecular etiology of this disorder. The overall prevalence of SLC26A4 mutations in nonsyndromic childhood sensorineural hearing loss (11.2%, 37/330) were determined by sequencing of SLC26A4 in 330 hearing impaired children who did not undergo inner ear radiologic imaging prior to their genetic test. The penetrance of EVA in bi-allelic SLC26A4 mutation carriers (100%, 37/37) was determined by follow-up computed tomography scanning. Combined with the study of 140 additional probands diagnosed with nonsyndromic EVA, we characterized the mutation spectrum of SLC26A4 in East China, which consisted of 19 novel SLC26A4 mutations and differed from those reported in other regions of China.
[An investigation of SLC26A4 gene mutation in nonsydromic hearing impairment in Hunan province of China]. Lu Jiang;Yong Feng;Hongsheng Chen;Chufeng He;Lingyun Mei. 2010. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 24. PMID: 20842945

OBJECTIVE: To determinate the occurring frequency and mutational hot spot in Hunan province. METHOD: Blood samples was obtained from 96 patients with nonsydromic hearing impairment in Hunan province. PCR and DHPLC techniques were used to screening for all the 21exon of SLC26A4. PCR samples which were abnormal for DHPLC screening were analyzed with direct sequencing. Sequencing results were analyzed in DNASTAR software. RESULT: Fifteen of 96 patients were found to have SLC26A4 gene mutations, detection rate was 15 6 , for 3 examples were homozygous mutations, ten samples were complex heterozygous mutations and 2 were heterozygous mutations. Totally, sixteen base variations were found, including 10 types of known gene mutation were identified (S90L, S252P, IVS7-2A>G, T410M, N392Y, IVS10-12T>A, S448X, G497S, S517fs, H723R. Four types of novel gene mutation (S8X, A227P,C565fs, Y728H), one type of same sense mutation (c. 2182 T>C)and 1 type of polypeptide IVS11+47 T>C). IVS7-2A>G was the most common gene mutation , which 9 samples were identified with, and it's detection rate was 9.38% and 5.73% for all the mutant alleles. IVS11+47 T>C was the most common polypeptide, which 20 samples were detected. CONCLUSION: IVS7-2A>G was the most common gene mutation type for nonsyndromic hearing impairment in Hunan province; 4 novel mutations which were detected in the study enriched SLC26A4 gene mutation spectrum of Chinese.
[Research progress on the etiology of delayed-onset hearing loss in children]. X Y Wang;L H Huang;Y T Du. 2017. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi.