A Novel Heterozygous Missense Variant (c.667G>T;p.Gly223Cys) in USH1C That Interferes With Cadherin-Related 23 and Harmonin Interaction Causes Autosomal Dominant Nonsyndromic Hearing Loss

BACKGROUND: Pathogenic variants of USH1C, encoding a PDZ-domain-containing protein called harmonin, have been known to cause autosomal recessive syndromic or nonsyndromic hearing loss (NSHL). We identified a causative gene in a large Korean family with NSHL showing a typical pattern of autosomal dominant (AD) inheritance.METHODS: Exome sequencing was performed for five affected and three unaffected individuals in this family. Following identification of a candidate gene variant, segregation analysis and functional studies, including circular dichroism and biolayer interferometry experiments, were performed.RESULTS: A novel USH1C heterozygous missense variant (c.667G>T;p.Gly223Cys) was shown to segregate with the NSHL phenotype in this family. This variant affects an amino acid residue located in the highly conserved carboxylate-binding loop of the harmonin PDZ2 domain and is predicted to disturb the interaction with cadherin-related 23 (cdh23). The affinity of the variant PDZ2 domain for a biotinylated synthetic peptide containing the PDZ-binding motif of cdh23 was approximately 16-fold lower than that of the wild-type PDZ2 domain and that this inaccessibility of the binding site was caused by a conformational change in the variant PDZ2 domain.CONCLUSIONS: A heterozygous variant of USH1C that interferes with the interaction between cdh23 and harmonin causes novel AD-NSHL.

The Detection of Deafness Predisposing Genes Mutation in 375 Nonsyndromic Hearing Loss Patients from Gansu Province / 听力学及言语疾病杂志

Objective To investigate the molecular genetic causes and their characteristics of deafness from patients with nonsyndromic hearing loss in Gansu province.Methods Peripheral blood samples were obtained from a total of 375 patients with nonsyndromic hearing loss to extract genomic DNA.Three genes of GJB2, mitochondrial DNA 12SrRNA, and SLC26A4 were screened for mutations in our study cohort using SNPscan technology.Results Among 375 patients, 23 patients were found to carry the homoplasmic mtDNA12SrRNA A1555G mutation, and 2 patients were detected to carry the homoplasmic mtDNA12SrRNA C1494T mutation.Forty-two cases(11.2%) were caused by GJB2 mutations, including 31cases(8.3%) of homozygous mutations, 11 patients(2.9%) of compound heterozygous mutations, and 25 cases(6.7%) of single homozygous mutations.c.235delC was the most prevalent GJB2 mutation with the allele frequency of 8.8%.Twenty-nine cases (7.7%) were caused by SLC26A4mutations, including 17cases(4.5%) of homozygous mutations, 12 patients(3.2%) of compound heterozygous mutations, and 16 cases(4.3%) of single homozygous mutations.c.919-2A>G and c.2168A>G were the most common SLC26A4 mutation, the allele frequencies were 5.2% and 2.0%, respectively.Conclusion A high incidence of mtDNA12SrRNAA1555G mutation is found in nonsyndromic hearing loss patients from Gansu province, while the incidence of GJB2 and SLC26A4 mutations is similar to the level of the overall Chinese deaf population.These findings demonstrate that a total of 25.6% of deaf patients have inherited hearing impairment caused by GJB2, SLC26A4, and mitochondrialDNA12SrRNA mutations.As a result 36% patients and family member can acquire effective genetic counseling.

Gene screening of neonatal non-syndromic hereditary hearing loss in Guangxi / 重庆医学

Objective To use the matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) technique for detecting the mutation gene of neonatal non-syndromic hereditary hearing impairment gene in Guangxi and to investigate its effectiveness and feasibility in clinical application.Methods A total of 7 100 newborns were performed the hearing preliminary screening and secondary screening by adopting AABR.The genomic DNA was extracted by the heel blood spot.Twenty mutation characteristics of 4 deaf predisposing genes were detected by MALDI-TOF-MS.Results The pass rate of hearing screening in 7 100 newborns was 97.11％ (6 895/7 100),the positive rate of neonatal gene mutation was 3.54％ (251/7 100),in which the GJB2 gene mutation was in 131 cases,the carrying rate was 1.84％,235delC heterozygous mutation was in 108 cases.SLC26A4 gene mutation was in 93 cases,which dominated by 1229C＞T heterozygous mutation and IVS7-2A＞G heterozygous mutation,mtDNA12SRNA gene mutation was in 16 cases and GJB3 gene mutation was in 11 cases.Conclusion Adopting the MALDI-TOF-MS screening technique can increase the detection rate of hot point mutation in common deaf related genes and discover neonatal genetic NSHI from molecular level and provides the corresponding geneticconsulting guidance for early finding and predicting deaf occurrence,and formulating the interventional measures.

Mutation Spectra of Genes in 318 Chinese Han Population with Nonsyndromic Hearing Loss / 中国康复理论与实践

Objective To define the mutation spectra of deafness gene in 318 Chinese Han population with nonsyndromic hearing loss (NSHL). Methods From October, 2015 to April, 2016, anticoagulant venous whole blood of 318 patients with NSHL were collected. The genes including GJB2, SLC26A4, GJB3 and 12Sr RNA were detected with polymerase chain reaction (PCR) and Matrix Assisted Laser De-sorption/Ionization Time-Of-Fight Mass Spectrometry (MALDI-TOF MS). Results Among these patient, 111 cases (34.9%) had GJB2 muta-tions, in which the mutation carrying rate of 235delC was the highest (25.47%), 43 cases (13.5%) had SLC26A4 mutations, 3 cases (0.94%) had GJB3 mutations, and 12 cases (3.77%) had mitochondria 12Sr RNA mutations. Conclusion Definition of mutation spectrum among dif-ferent populations with NSHL is important for development of optimal genetic screening services for congenital hearing impairment.

Progress of common gene mutations and detection methods of non-syndromic inherited hearing impair-ment / 国际儿科学杂志

Deafness is a seriously disabling disease affecting the quality of human life and genetic fac-tors account for a large proportion in the pathogenesis of newborn deafness.With the development of genomics technology,molecular genetics of hearing loss has become a cutting-edge field under investigation in otology. Molecular diagnostic technique plays an important role in exploring the pathogenesis,assisting clinical diagnosis and the prenatal diagnosis.In this review,we introduce the common pathogenic gene mutations and the diagnosis of non-syndromic inherited hearing impairment.

The Mutation Analysis of Common Deafness Genes Using SNPscan Technology in Nonsyndromic Hearing Loss Patients of Minority Ethnicities in Qinghai Province / 听力学及言语疾病杂志

Objective This study aims to investigate the mutation spectrum and frequency of GJB2 , mtDNA12SrRNA,and SLC26A4 genes in Hui people,Tibetan,Tu nationality,and Mongolian patients with non-syndromic hearing loss in Qinghai province.Methods Peripheral blood samples were obtained from a total of 211 minority patients with nonsyndromic hearing loss in Qinghai province to extract genomic DNA.Three genes of GJB2,mitochondrialDNA12SrRNA,and SLC26A4 were screened for mutations in our study cohort using SNPscan technology.Results Among these 211 patients,5 Tu patients and 1 Mongolian patient were found to carry the ho-moplasmic mtDNAA1555G mutation.The GJB2 mutations detection rates were 11.38%,4.55%,5.88%,and 10%in Hui people,Tibetan,Tu nationality,and Mongolian patients,respectively.No statistically significant differences in the GJB2 mutations detection rates were found among all four ethnicities (P>0.05).c.235delC was the most prevalent mutation in both Tu patients and Mongolian patients.The allele frequency was 2.94% and 5%,respec-tively.While for Hui patients,c.299 300delAT was the most prevalent mutation with the allele frequency of 4.47%.The mutations detection rates of SLC26A4 were 6.5%,4.55%and 2.94%in Hui people,Tibetan,and Tu nationality patients,respectively.No statistically significant differences in the SLC26A4 mutations detection rates were found among all three ethnicities (P>0.05).c.235delC was the most prevalent mutation in Hui patients,the allele frequency was 2.44%.While for Tibetan patients,c.1226G>A was the most prevalent mutation with allele frequency of 2.27%.Conclusion A total of 10.9% of deaf patients have inherited hearing impairment caused by GJB2,SLC26A4,and mtDNAA1555G mutations.The mutation spectrum of GJB2 and SLC26A4 genes has the eth-nic specificity in nonsyndromic hearing loss patients of minority ethnicities in Qinghai province.

Mutational analysis of GJB2 gene in a Chinese family with nonsyndromic hearing loss / 重庆医学

Objective To analyze the clinical and genetic features of a Chinese family with nonsyndromic hearing loss ,and to find deafness‐causing mutations in the GJB2 gene .Methods After a detailed history and clinical examination ,genomic DNA was ex‐tracted from peripheral blood for the proband and their family members .Two exons of the GJB2 gene was amplified by polymerase chain reaction ,and the PCR products were subjected to automatic DNA sequencing .Finally ,the mutation analysis was performed by SeqMan software of DNASTAR to compare BLAST .Results All patients in this family had late‐onset and progressive hearing loss and ultimately involved all frequencies .Six SNP polymorphisms were found in this pedigree ,which were previously reported world‐wide ,c .79G > A(p .Val27Ile) ,c .341G > A(p .Glu114Gly) ,were also identified in this family .Four single nucleotide polymorphisms (SNPs) were firstly identified in the GJB2 3′‐UTR ,including g .4159T > C ,g .5142G/T ,g .5227G/A ,g .5352T /C .Two SNPs .Con‐clusion Mutation in exons of GJB2 gene was excluded as a pathogenic cause for nonsyndromic hearing loss in this family .

Application of DNA Microarray and Sanger Sequencing to the Genetic Diagnosis of Nonsyndromic Hearing Loss / 听力学及言语疾病杂志

Objective To study genotypes in nonsyndromic hearing loss (NSHL ) patients from Guangxi Zhuang Autonomous Region hearing speech rehabilitation center using DNA microarray in combination with Sanger sequencing .Methods Deaf patients received routine physical and otorhinolaryngoloical examinations as well as pure tone autiometry .Brainstem auditory evoked potential test was performed in uncooperative children .Blood samples were obtained from a total of 136 patients ,male 81 ,female 55 ,age from one year five month to seventeen ,having nonsyndromic hearing loss .Genomic DNA was extracted and then 9 hot mutation spots in 4 susceptibility genes were detected by DNA microarray .GJB2 and SLC26A was further detected by Sanger sequencing in the patients with negative results and heterozygotes .Results Among the 136 patients with nonsyndromic hearing loss ,20 cases were positive for GJB2 gene ,SLC26A4 gene or mitochondrial 12SrRNA gene mutations .There were 14 .71% (20/136)patients were positive for hot mutation spots in the deafness related genes ,25% (34/136)patients carried muta‐tions of deafness related genes using DNA microarray in combination with Sanger sequencing .Six SLC26A4 rare mutations (c .259G> T ,c .754C> T ,c .1229C> T ,c .1548_1549insC ,c .1705+5A>G and c .2086C> T) were de‐tected by Sanger sequencing .c .235delC was the most common mutation in GJB2 gene .c .919-2A>G ,c .754C> T and c .1229C> T were the common mutations in SLC26A4 gene .The mutation rate of GJB2 and SLC26A4 was 38 . 24% .and 58 .82% ,respectively .Conclusion Prevalent deafness-associated gene mutations in the nine loci studied were less frequently detected in nonsyndromic hearing loss patients from Guangxi Zhuang Autonomous Region hear‐ing speech rehabilitation center .It can improve the detection rate of deafness gene mutations by using gene microar‐ray in combination with Sanger sequencing .GJB2 and SLC26A4 are the common causative genes .