Whole-Exome Sequencing Reveals Pediatric Rare Syndromic Hearing Loss / 罕见病研究

  Objective  To discuss the significance of genetic diagnosis of children with syndromic hearing loss by using whole-exome sequencing.  Methods  The clinical data of 34 children with sensorineural hearing loss were collected and the whole exons of genome of the children and their parents were sequenced and analyzed.  Results  Genetic causative gene and mutations have been identified in 19 children, including 4 genes (HARS2, USH2A, GATA3, MITF) related to rare syndromic hearing loss. Fifteen children were diagnosed with non-syndromic hearing loss related gene, including 8 cases with GJB2 mutation, 5 cases with SLC26A4 mutation and 2 cases with MYO15A mutation. Mutations of c.435_437del(p.K147del) and c.1403G > C (p.G468A) in gene HARS2, c.11389+1del in gene USH2A, c.1327delA(p.M443Wfs*33) in gene GATA3, c.627C > A(p.C209X) in gene MITF and c.8033_8057delinsG(p.N2678_D2686delinsS) in gene MYO15A were first reported.  Conclusions  Whole-exome sequencing helps the accurate diagnosis of causes of hearing loss, especially for the rare syndromic hearing loss with atypical clinical manifestations. Information from genetic testing may highlight further recommended exams of structure and functions of related organs.

New SNP variants of MARVELD2 (DFNB49) associated with non-syndromic hearing loss in Chinese population / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Non-syndromic hearing loss (NSHL) is a common defect in humans. Variants of MARVELD2 at the DFNB49 locus have been shown to cause bilateral, moderate to profound NSHL. However, the role of MARVELD2 in NSHL susceptibility in the Chinese population has not been studied. Here we conducted a case-control study in an eastern Chinese population to profile the spectrum and frequency of MARVELD2 variants, as well as the association of MARVELD2 gene variants with NSHL. Our results showed that variants identified in the Chinese population are significantly different from those reported in Slovak, Hungarian, and Czech Roma, as well as Pakistani families. We identified 11 variants in a cohort of 283 NSHL cases. Through Sanger sequencing and bioinformatics analysis, we found that c.730G>A variant has detrimental effects in the eastern Chinese population, and may have relatively high correlation with NSHL pathogenicity.

Mutations in GJB2 as Major Causes of Autosomal Recessive Non-Syndromic Hearing Loss: First Report of c.299-300delAT Mutation in Kurdish Population of Iran

BACKGROUND AND OBJECTIVES: Autosomal recessive non-syndromic hearing loss (ARNSHL) with genetic origin is common (1/2000 births). ARNSHL can be associated with mutations in gap junction protein beta 2 (GJB2). To this end, this cohort investigation aimed to find the contribution of GJB2 gene mutations with the genotype-phenotype correlations in 45 ARNSHL cases in the Kurdish population. SUBJECTS AND METHODS: Genomic DNA was extracted from a total of 45 ARNSHL families. The linkage analysis with 3 short tandem repeat markers linked to GJB2 was performed on 45 ARNSHL families. Only 9 of these families were linked to the DFNB1 locus. All the 45 families who took part were sequenced for confirmation linkage analysis (to perform a large project). RESULTS: A total of three different mutations were determined. Two of which [c.35delG and c.-23+1G>A (IVS1+1G>A)] were previously reported but (c.299-300delAT) mutation was novel in the Kurdish population. The homozygous pathogenic mutations of GJB2 gene was observed in nine out of the 45 families (20%), also heterozygous genotype (c.35delG/N)+(c.-23+1G>A/c.-23+1G>A) were observed in 4/45 families (8.8%). The degree of hearing loss (HL) in patients with other mutations was less severe than patients with c.35delG homozygous mutation (p < 0.001). CONCLUSIONS: Our data suggest that GJB2 mutations constitute 20% of the etiology of ARNSHL in Iran; moreover, the c.35delG mutation is the most common HL cause in the Kurdish population. Therefore, these mutations should be included in the molecular testing of HL in this population.

A Mutation Analysis of GJB2 and SLC26A4 Gene in A Chinese Family wi th Non-Syndromi c Deafness / 听力学及言语疾病杂志

Objective To study the molecular pathogenesis of non -syndromic deafness in a Chinese family . Methods Clinical materials and DNA sample were obtained from the non -syndromic family with autosomal reces‐sive deafness .The exons and the flanking splicing sites of GJB2 and SLC26A4 were tested in all family members by PCR and direct sequencing .Results There were four deafness patients in the family ,and three of them had the same clinical phenotypes ,including prelingual profound sensorineural hearing loss and enlarged vestibular ,while the re‐mained one only presented to be prelingual profound sensorineural hearing loss without malformation of temporal bone .One type of GJB2 mutation and 3 different types of SLC26A4 mutations were identified in the family .The proband(Ⅲ -1) ,her sister(Ⅲ -2) ,her mother(Ⅱ -4) and her father(Ⅱ -3) carried different biallelic mutations which were SLC26A4 c .919 -2A > G/p .H723R ,p .Q413R/c .919 -2A > G ,p .Q413R/p .H723R and GJB2 c . 235delC/c .235delC ,respectively .Conclusion Different from most reported deafness families with the same molecu‐lar etiology in each one ,interestingly ,the pathogenies were different among all affected members in this family . They were caused by different biallelic mutations of SLC26A4 or GJB2 .

Prevalence Study of GJB2,SLC26A4 and mtDNA 12S rRNA1555A>G Mutations in Hui Ethnic Group Patients with Non-Syndromic Hearing Loss from Northwest China / 听力学及言语疾病杂志

Objective To investigate the prevalence of GJB2 ,SLC26A4 and mitochondrial DNA 12S rRNA m .1555A>G(mtDNA 1555A>G) mutations in Hui ethic group patients with nonsyndromic hearing loss (NSHL) from Northwest China .Methods A total of 420 peripheral blood samples were collected from unrelated Hui ethic group probands with NSHL in Northwest China .Amplified the target gene by polymerase chain reaction (PCR) af-ter extracting genomic DNA from whole blood .The mtDNA 1555A>G mutation was detected by PCR -Alw26I di-gestion ,then direct sequencing was used to the positive samples of mtDNA 1555A> G ,the coding region of GJB2 gene ,exon 8 and 19 of SLC26A4 gene .Results There were 11(2 .62% ) cases caused by mtDNA 1555A>G homo-zygous mutation in 420 patients with NSHL .There were 41(9 .76% ) cases including homozygote and compound het-erozygote ,caused by GJB2 gene mutation ,which was the most frequent deafness -related gene .The allel frequency of c .235delC accounted for 6 .90% ,as well as the most frequent(51 .33% ) mutational pattern in GJB2 gene .There were 20 patients(4 .76% ) were found carring two allel mutations in SLC26A4 gene .The allel frequency of c .919 -2A>G was 5 .0% ,accounting for a total of 68 .85% in all base alterations of SLC26A4 gene ,which was the major mutant form of SLC26A4 gene .Conclusion GJB2 gene is the most common deafness -gene in Hui ethnic group pa-tients with NSHL from Northwest China ,while c .235delC is the main mutant form ,and c .919-2A>G is the hot-spot mutation of SLC26A4 gene .Through this study we can provide the molecular epidemiology basis for Hui ethnic group patients with NSHL from Northwest China in genetic diagnosis ,genetic counseling and therapy by associated testing of three frequent hearing loss genes .

Analysis of the Mutations in SLC26A4 Gene in Children with Non-syndromic Hearing Loss / 听力学及言语疾病杂志

Objective To study the SLC26A4 mutations in children with non -syndromic hearing loss by ge-netic testing method ,for the purpose of investigating etiology and mutation regularity of hearing loss ,and to provide basic information for the molecular diagnosis of hearing loss .Methods Blood samples and clinical data of 137 spo-radic cases with non -syndromic hearing loss and 126 normal controls were collected .The SLC26A4 gene of the pa-tients and normal controls were amplified by polymerase chain reaction (PCR) ,then subjected to automatic DNA se-quencing .Results Pathologic SLC26A4 mutations were identified in 23 out of 137 patients ,and in 23 out of 119 bi-lateral deafness ,mutate rate were 16 .79% and 19 .33% ,respectively .SLC26A4 mutations were identified in 19 out of 20(95% ) patients with bilateral LVA .A total of 11 mutations were identified in the present study ,including 4 novel mutations (E29K(c .85G>A) ,R79X(c .235C> T) ,C282G(c .844T>G) ,V285I(c .853G>A) )and 7 repor-ted mutations .In the present study ,IVS7-2A>G was the most common mutation ,and was detected in 19 out of 23(82 .61% ) patients with SLC26A4 mutations .Conclusion SLC26A4 mutations ,the common reason for non -syndromic hearing loss ,were closely related with LVA .IVS7-2A>G was the most common mutation in SLC26A4 mutant .