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.

Inherited deafness has been shown to have high genetic heterogeneity. For many decades, linkage analysis and candidate gene approaches have been the main tools to elucidate the genetics of hearing loss. However, this associated study design is costly, time-consuming, and unsuitable for small families. This is mainly due to the inadequate numbers of available affected individuals, locus heterogeneity, and assortative mating. Exome sequencing has now become technically feasible and a cost-effective method for detection of disease variants underlying Mendelian disorders due to the recent advances in next-generation sequencing (NGS) technologies. In the present study, we have combined both the Deafness Gene Mutation Detection Array and exome sequencing to identify deafness causative variants in a large Chinese composite family with deaf by deaf mating. The simultaneous screening of the 9 common deafness mutations using the allele-specific PCR based universal array, resulted in the identification of the 1555A>G in the mitochondrial DNA (mtDNA) 12S rRNA in affected individuals in one branch of the family. We then subjected the mutation-negative cases to exome sequencing and identified novel causative variants in the MYH14 and WFS1 genes. This report confirms the effective use of a NGS technique to detect pathogenic mutations in affected individuals who were not candidates for classical genetic studies.

Age-related hearing loss and noise-induced hearing loss are major causes of human morbidity. Here we used genetics and functional studies to show that a shared cause of these disorders may be loss of function of the ATP-gated P2X(2) receptor (ligand-gated ion channel, purinergic receptor 2) that is expressed in sensory and supporting cells of the cochlea. Genomic analysis of dominantly inherited, progressive sensorineural hearing loss DFNA41 in a six-generation kindred revealed a rare heterozygous allele, P2RX2 c.178G > T (p.V60L), at chr12:133,196,029, which cosegregated with fully penetrant hearing loss in the index family, and also appeared in a second family with the same phenotype. The mutation was absent from more than 7,000 controls. P2RX2 p.V60L abolishes two hallmark features of P2X(2) receptors: ATP-evoked inward current response and ATP-stimulated macropore permeability, measured as loss of ATP-activated FM1-43 fluorescence labeling. Coexpression of mutant and WT P2X(2) receptor subunits significantly reduced ATP-activated membrane permeability. P2RX2-null mice developed severe progressive hearing loss, and their early exposure to continuous moderate noise led to high-frequency hearing loss as young adults. Similarly, among family members heterozygous for P2RX2 p.V60L, noise exposure exacerbated high-frequency hearing loss in young adulthood. Our results suggest that P2X(2) function is required for life-long normal hearing and for protection from exposure to noise.

Background: Mitochondrial mutations have been shown to be responsible for syndromic and nonsyndromic hearing impairment. Aim: To assess the genotypic-phenotypic correlation of mitochondrial DNA mutations in three generations of a single family. Methods: A single family with maternally inherited diabetes and hearing loss was recruited. Genomic DNA was subject to polymerase chain reaction-restriction fragment length polymorphism analysis (ApaI) for A3243G mutation detection and confirmation with direct DNA sequencing. The degree of heteroplasmy for the A3243G mutation in blood DNA samples was quantified. In addition, we reviewed audiological data of A3243G-associated hearing loss cases from the literature to provide details of audiologic features. Results: Six of 11 family members were recruited. All affected members harbored the A3243G mutation. Four of six members had diabetes. Five of five affected members demonstrated hearing loss ranging from mild to severe. The degree of heteroplasmy ranged from 5.51% to 27.74%. Conclusions: Patients with a greater percentage of heteroplasmy have a trend toward more severe phenotypic presentations. Hearing loss is bilateral, sensorineural, and symmetric. The main audiogram shapes found were sloping. Additional studies are necessary to clarify the relationship between degree of heteroplasmy and phenotypic presentation.

Deafness is a heterogeneous trait with many known genetic and environmental causes. Hereditary hearing loss is an extremely common disorder in the general population. Mutations in mitochondrial DNA (mtDNA) are known to be associated with nonsyndromic deafness (NSD) and syndromic deafness. The objective of this article is to investigate the frequency of common mitochondrial mutations (A1555G, G7444A, and A3243G) in an ethnically diverse cohort of probands with NSD from South Florida. These patients were ascertained at the University of Miami. Polymerase chain reaction-restriction fragment length polymorphism analysis and direct sequencing methods were used for mutation screening in a cohort of 217 patients with NSD. The frequency of common mitochondrial mutations is 1.84% (4/217) in this cohort. A1555G and G7444A accounted for four patients with NSD. Our mutation frequencies are comparable with those previously reported in other populations, indicating that mutations in mtDNA are an important cause of NSD in our patient cohort.

Objectives. Determine the diagnostic yield of a shared genetic testing algorithm in adult and pediatric populations with sensorineural hearing loss (SNHL) and recommend effective testing strategies to evaluate for genetic causes of deafness in patients presenting with idiopathic sensorineural hearing loss.Study Design. Hospital-based cohort study.Setting. University of Miami outpatient otology clinics between 2001 and 2010.Subjects. Two hundred twenty-one adult and 163 pediatric patients with nonsyndromic sensorineural hearing loss.Methods. Peripheral blood samples were screened for mutations in GJB2 and GJB6 and mitochondrial DNA mutations 1555A > G, 7444G > A, and 3243A > G. Audiometric data and family history were also collected.Results. GJB2/GJB6-related deafness was diagnosed in 23 of 163 pediatric patients (14%) compared with only 3 of 221 adults (1%). All adults had a family history of hearing loss, and 2 patients noted deafness onset at birth. Nineteen GJB2 mutations were identified with 35delG the most common mutation. The 35delG homozygous state was the most common pathogenic genotype (54%). Mitochondrial DNA (mtDNA) mutations were found in 6 adult probands (3%). No mtDNA mutations were found in pediatric patients.Conclusion. Testing for common GJB2/GJB6 mutations in pediatric patients has considerable value in establishing an etiologic diagnosis for SNHL. Similar testing in adults is of very low yield except perhaps in cases of early-onset SNHL or strong family history. Mitochondrial DNA testing should be considered in adults with idiopathic SNHL.

Objectives/Hypothesis: Audiometric patterns have been shown to indirectly provide information regarding the pathophysiology of presbycusis and be useful in the phenotyping of hereditary deafness. Study Design and Methods: Hospital-based cohort study of adults with presbycusis, comparing the association of audiometric patterns and polymorphisms of antioxidant enzymes that have been linked to presbycusis: GSTT1, GSTM1 and NAT2. All subjects underwent a clinical evaluation and completed questionnaires regarding ototoxicity and noise exposure. Pure-tone threshold audiometry was obtained and subjects' audiograms were classified into specific patterns. DNA was extracted from blood and the polymorphisms of GSTT1, GSTM1, and the NAT2 variants (NAT2* 5A; NAT2* 6A,B) were analyzed by PCR. Results: The audiometric patterns that were more prevalent in our cohort were High-Frequency Steeply Sloping or HFSS (33%), High-Frequency Gently Sloping or HFGS (31%), and Flat (27%), with other patterns being rare. We did not find a statistical significant effect of gender, age, hearing level, and ear side on the audiometric pattern. Subjects with mutant alleles for GSTT1 were more likely to have a HFSS audiogram than subjects with the wild type genotype. Conclusions: In this cohort, there was a similar prevalence for the three audiometric configurations HFSS, HFGS, and Flat, with other configurations being rare. Subjects with mutant alleles for GSTT1 were more likely to have a HFSS audiogram than subjects with the wild type genotype, suggesting that the basal turn of the cochlea is susceptible to GSTT1 regulated oxidative stress. However, further studies of audioprofiles with larger sample sizes may be needed to establish phenotype-genotype correlations in presbycusis. Laryngoscope, 2012

Objective: The purpose of this study was to determine the prevalence of mutations in the GJB2 gene, the GJB6-D13S1830 deletion and the four common mitochondrial mutations (A1555G, A3243G, A7511C and A7445G) in a South African population.Methods: Using single-strand conformation polymorphism and direct sequencing for screening GJB2 mutation; Multiplex PCR Amplification for GJB6-D13S1830 deletion and Restriction Fragment-Length Polymorphism (PCR-RFLP) analysis for the four common mtDNA mutations. We screened 182 hearing impaired students to determine the frequency of these mutations in the population.Results: None of the reported disease causing mutations in GJB2 nor any novel pathogenic mutations in the coding region were detected, in contrast to the findings among Caucasians. The GJB6-D13S1830 deletion and the mitochondrial mutations were not observed in this group.Conclusion: These results suggest that GJB2 may not be a significant deafness gene among sub-Saharan Africans, pointing to other unidentified genes as responsible for nonsyndromic hearing loss in these populations. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Direct evidence of the critical physiological role of connexins (Cxs) has come through the associations of several human diseases with pathogenic mutations in specific Cx genes. Currently, mutations in genes coding for five Cx proteins (Cx26, Cx30, Cx31, Cx32, and Cx43) have been shown to cause sensorineural hearing loss. Cx45 is another gap junction protein, coded by the GJA7 gene. To investigate the possible contribution of GJA7 mutations to deafness, we sequenced the GJA7 gene in 341 unrelated probands with nonsyndromic hearing loss from Turkey, South Africa, United Kingdom, United States, and China. Three nucleotide variants not affecting the amino acid sequence, c.213C>T, c.906C>T, and c.912G>T, and one missense change, c.889C>A (p.D297N), were found. None of the identified changes appeared to be pathogenic. Our data suggest that GJA7 alterations have no or low genetic relevance in nonsyndromic hearing loss in these populations.

Objective To report clinical,genetic,and molecular characteristics of a Chinese family with 6 generations demonstrating hearing loss associated with DFNA41.Methods Fifty five subjects in the family were followed up for 10 years after they were mapped for the DFNA41 gene.Blood samples from some of the members were screened for mutation of 11 candidate causative genes.Results In all affected subjects,audiometry showed symmetrical bilateral sensorineural hearing loss of mild to severe degrees.All male affected members presented sloping high frequency hearing loss at young ages,while all female affected members with low frequency loss with ascending patterns at young ages.As the age increased,hearing loss affected all frequencies in both male and female members and showed a flat pattern.DNA sequencing of coding and exon-intron boundaries of 11 potential inner ear enriched genes in affected subjects did not reveal any disease causing mutation in this DFNA41 family.Conclusion The phenotype of this DFNA41 family appears to be related to the patient's gender and age.Further research on the genotype and phenotype of DFNA41 families will help clone the causative gene.

We report a large Chinese family with X-linked postlingual nonsyndromic hearing impairment in which the critical linkage interval spans a genetic distance of 5.41 cM and a physical distance of 15.1 Mb that overlaps the DFN2 locus. Mutation screening of the PRPS1 gene in this family and in the three previously reported DFN2 families identified four different missense mutations in PRPS1. These mutations result in a loss of phosphoribosyl pyrophosphate (PRPP) synthetase 1 activity, as was shown in silico by structural analysis and was shown in vitro by enzymatic activity assays in erythrocytes and fibroblasts from patients. By in situ hybridization, we demonstrate expression of Prps1 in murine vestibular and cochlea hair cells, with continuous expression in hair cells and postnatal expression in the spiral ganglion. Being the second identified gene associated with X-linked nonsyndromic deafness, PRPS1 will be a good candidate gene for genetic testing for X-linked nonsyndromic hearing loss.

Mutations in the genes coding for connexin 26 (Cx26) and connexin 31 (Cx31) cause non-syndromic deafness. Here, we provide evidence that mutations at these two connexin genes can interact to cause hearing loss in digenic heterozygotes in humans. We have screened 108 GJB2 heterozygous Chinese patients for mutations in GJB3 by sequencing. We have excluded the possibility that mutations in exon 1 of GJB2 and the deletion of GJB6 are the second mutant allele in these Chinese heterozygous probands. Two different GJB3 mutations (N166S and A194T) occurring in compound heterozygosity with the 235delC and 299delAT of GJB2 were identified in three unrelated families (235delC/N166S, 235delC/A194T and 299delAT/A194T). Neither of these mutations in Cx31 was detected in DNA from 200 unrelated Chinese controls. Direct physical interaction of Cx26 with Cx31 is supported by data showing that Cx26 and Cx31 have overlapping expression patterns in the cochlea. In addition, by coimmunoprecipitation of mouse cochlear membrane proteins, we identified the presence of heteromeric Cx26/Cx31 connexons. Furthermore, by cotransfection of mCherry-tagged Cx26 and GFP-tagged Cx31 in human embryonic kidney (HEK)-293 cells, we demonstrated that the two connexins were able to co-assemble in vitro in the same junction plaque. Together, our data indicate that a genetic interaction between these two connexin genes can lead to hearing loss.

Usher syndrome type II (USH2) is an autosomal recessive disorder characterized by moderate to severe hearing impairment and progressive visual loss due to retinitis pigmentosa (RP). To identify novel mutations and determine the frequency of USH2A mutations as a cause of USH2, we have carried out mutation screening of all 72 coding exons and exon–intron splice sites of the USH2A gene. A total of 20 USH2 American probands of European descent were analyzed using single strand conformational polymorphism (SSCP) and direct sequencing methods. Ten different USH2A mutations were identified in 55% of the probands, five of which were novel mutations. The detected mutations include three missense, three frameshifts and four nonsense mutations, with c.2299delG/p.E767fs mutation, accounting for 38.9% of the pathological alleles. Two cases were homozygotes, two cases were compound heterozygotes and one case had complex allele with three variants. In seven probands, only one USH2A mutation was detected and no pathological mutation was found in the remaining eight individuals. Altogether, our data support the fact that c.2299delG/p.E767fs is indeed the most common USH2A mutation found in USH2 patients of European Caucasian background. Thus, if screening for mutations in USH2A is considered, it is reasonable to screen for the c.2299delG mutation first.

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 pheno‐type. 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.

Deafness is an etiologically heterogeneous trait with many known genetic, environmental causes or a combination thereof. The identification of more than 120 independent genes for deafness has provided profound new insights into the pathophysiology of hearing. However, recent findings indicate that a large proportion of both syndromic and non-syndromic forms of deafness in the Chinese population are caused by defects in a small number of genes. Studies of the genetic epidemiology and molecular genetic features revealed that there is a clear relevance of genes causing deafness in Chinese deaf patients as well as a unique spectrum of common and rare deafness gene mutations in the Chinese population. This review is focused on the genetic aspects of non-syndromic and mitochondrial deafness, in which unique molecular genetic features of hearing impairment have been identified in the Chinese population. The current China population is approximately 1.3 billion. It is estimated that 30,000 infants are born with congenital sensorineural hearing loss each year. Better understanding of the genetic causes of deafness in the Chinese population is important for accurate genetics counseling and early diagnosis for timely intervention and treatment options.

Recent progress in gene identification for non-syndromic deafness demonstrates the efficacy of using a large family approach. To assess if clinical and genetic heterogeneity exists in families with non-syndromic hearing impairment we have identified five large Chinese families suitable for investigating clinical and genetic heterogeneity. Five Chinese families spanning 5–6 generations and comprising 48 to 172 members were identified. The auditory phenotype was investigated with pure tone audiometry and DPOAEs. Age at onset of hearing loss was compared between generations by using life-table analysis and the Wilcoxon test in a family. All statistical analyses were performed using the SAS statistical package. Screening for GJB2 and mitochondrial mutations was performed. Two families showing maternal inheritance were found to have the mitDNA A1555G mutation. Subjects with the A1555G mutation exhibit a normal to profound, progressive deafness. Anticipation of the hearing loss was observed in one of these two families. The other three families are segregating for a late onset form of progressive hearing loss with normal vestibular function. DPOAEs from a group of possible gene carriers with normal audiograms in two families have shown a substantial difference from that of controls. Our data show the existence of clinical and genetic heterogeneity in the five large Chinese deaf families. Marked differences in severity of hearing loss, along with a lack of exposure to aminoglycosides and the presence of anticipation in the mitDNA deafness suggest the presence of a modifier. DPOAEs may be a sensitive test for a subclinical change in carriers. Identification of gene(s) for deafness should allow us to better understand the molecular basis of deafness and to improve patient care.

American Journal of Medical Genetics Part AVolume 143A, Issue 4 p. 385-386 Research Letter Paternal uniparental disomy of chromosome 13 causing homozygous 35delG mutation of the GJB2 gene and hearing loss†‡ Denise Yan, Denise Yan Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorXiao Mei Ouyang, Xiao Mei Ouyang Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorSimon I. Angeli, Simon I. Angeli Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorLi Lin Du, Li Lin Du Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorXue Zong Liu, Corresponding Author Xue Zong Liu xliu@med.miami.edu Department of Otolaryngology, University of Miami, Miami, FloridaDepartment of Otolaryngology (D-48), University of Miami, 1666 NW 12th Avenue, Miami, FL 33136.Search for more papers by this author Denise Yan, Denise Yan Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorXiao Mei Ouyang, Xiao Mei Ouyang Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorSimon I. Angeli, Simon I. Angeli Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorLi Lin Du, Li Lin Du Department of Otolaryngology, University of Miami, Miami, FloridaSearch for more papers by this authorXue Zong Liu, Corresponding Author Xue Zong Liu xliu@med.miami.edu Department of Otolaryngology, University of Miami, Miami, FloridaDepartment of Otolaryngology (D-48), University of Miami, 1666 NW 12th Avenue, Miami, FL 33136.Search for more papers by this author First published: 26 January 2007 https://doi.org/10.1002/ajmg.a.31553Citations: 9 † How to cite this article: Yan D, Ouyang XM, Angeli SI, Du LL, Liu XZ. 2007. Paternal uniparental disomy of chromosome 13 causing homozygous 35delG mutation of the GJB2 gene and hearing loss. Am J Med Genet Part A 143A:385–386. ‡ Denise Yan and Xiao Mei Ouyang contributed equally to this work. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume143A, Issue415 February 2007Pages 385-386 RelatedInformation

We report here the clinical, genetic, and molecular characteristics of a large Chinese family exhibiting non-syndromic, late-onset autosomal dominant sensorineural hearing loss. Clinical evaluation revealed variable phenotypes of hearing loss in terms of severity and age-at-onset of disease in these subjects. Genome-wide linkage analysis mapped the disease gene to the DFNA5 locus with a maximum two-point log odds score of 5.39 at [theta] = 0 for marker D7S2457. DNA sequencing of DFNA5 revealed a novel heterozygous IVS8+4 A > G substitution in the splice donor site of intron 8. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed skipping of exon 8 in the mutant transcript. This mutation faithfully cosegregated with hearing loss in the family. In addition, the mutation was absent in 100 unrelated control DNA samples of Chinese origin. The IVS8+4 A > G mutation is predicted to create a shift in the reading frame and introduce a stop codon at position 372, thereby resulting in a prematurely truncated DFNA5 protein. Up to date, a total of four mutations in DFNA5 have been reported to lead to hearing impairment, all of them result in skipping of exon 8 at the mRNA level. Our findings provide further support for the hypothesis that DFNA5-associated hearing loss is caused by a very specific gain-of-function mutation.