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Abstract: 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, tRNASer(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, re spectively. The results indicate the necessity of genetic screening for mutations of these causative genes in Chi nese population with nonsyndromic hearing loss. [Copyright &y& Elsevier]

Autosomal dominant non-syndromic hearing loss (ADNSHL) is characterized by postlingual progressive onset. Due to its high genetic heterogeneity, it is difficult to perform a molecular diagnosis for most patients with ADNSHL. In our study, whole-exome sequencing (WES) was used to screen pathogenic gene candidates by analyzing genomic DNA samples from a large Chinese family (JSNY-067), including the proband and her father, who suffered from non-syndromic hearing loss. The pathogenicity of candidate nonsynonymous variants in ADNSHL genes was evaluated by co-segregation analysis in family members by direct PCR and Sanger sequencing. Furthermore, multiple in silico analyses (SIFT, Polyphen2, PROVEAN and MutationTaster) and molecular dynamics simulation were used to assess the potential pathogenicity of the candidate mutations. We identified a novel causative mutation, c.622A>G in MYO6 (DFNA22), that resulted in a p.K208E substitution. This mutation co-segregated with the hearing loss phenotype in extended family members, and was predicted to be pathogenic by SIFT, PolyPhen2, PROVEAN and MutationTaster. Furthermore, molecular dynamics simulation analysis revealed that the p.K208E substitution had a limited influence on the whole protein structure and stability, but that it could affect the locations of the sidechains of nearby hydrophilic residues, which in turn resulted in the sidechains of Asn186 and Glu190 being exposed more frequently at the surface of the protein. WES has thus been shown to be a useful molecular diagnostic tool in screening uncommon gene mutations associated with hereditary hearing loss.

Purpose: Various forms of hearing loss have genetic causes, but many of the responsible genes have not yet been identified. Here, we describe a large seven-generation Chinese family with autosomal dominant nonsyndromic hearing loss that has been excluded as being caused by known deafness gene mutations associated with autosomal dominant nonsyndromic hearing loss with the aim of identifying a novel causative gene involved in deafness., Methods: Whole-exome sequencing was conducted in three affected family members, and cosegregation analysis was performed on other members of the family., Results: Whole-exome sequencing and subsequent segregation analysis identified a heterozygous frameshift mutation (c.153_154delCT, p.Gln53Argfs*100) in the oxysterol binding protein-like 2 (OSBPL2) gene in 25 affected family members. The deletion mutation is predicted to lead to premature truncation of the OSBPL2 protein. Modeling and structure-based analysis support the theory that this gene deletion is functionally deleterious. Our finding was further confirmed by the detection of another missense mutation, a c.583C>A transversion (p.Leu195Met) in exon 7 of OSBPL2, in an additional sporadic case of deafness., Conclusion: Based on this study, OSBPL2 was identified as an excellent novel candidate gene for autosomal dominant nonsyndromic hearing loss; this study is the first to implicate OSBPL2 mutations in autosomal dominant nonsyndromic hearing loss.

Background: Hearing loss is caused by several environmental and genetic factors and the proportion attributed to inherited causes is assumed at 50 ~ 60% . Mutations in GJB2 and mitochondrial DNA (mtDNA) 12S rRNA are the most common molecular etiology for nonsyndromic sensorineural hearing loss (NSHL). The mutation spectra of these genes vary among different ethnic groups., Methods: To add the molecular etiologic information of hearing loss in the Chinese population, a total of 658 unrelated patients with NSHL from Jiangsu Province of China were selected for mutational screening including GJB2 and mtDNA 12S rRNA genes using PCR and DNA sequencing technology. As for controls, 462 normal-hearing individuals were collected., Results: A total of 9 pathogenic mutations in the GJB2 and 7 pathogenic mutations in the 12S rRNA gene were identified. Of all patients, 70 had monoallelic GJB2 coding region mutation in the heterozygous state, 94 carried two confirmed pathogenic mutations including 79 homozygotes and 15 compound heterozygotes. The 235delC appears to be the most common deafness-causing GJB2 mutation (102/658, 15.50% ). No mutations or variants in the GJB2 exon1 and basal promoter region were found. In these patients, 4 subjects carried the m.1494C > T mutation (0.61% ) and 39 subjects harbored the m.1555A > G mutation (5.93% ) in mtDNA 12S rRNA gene. A novel sequence variant at m.1222A > G in the 12S rRNA gene was identified, which could alter the secondary structure of the 12S rRNA., Conclusion: The mutation spectrum and prevalence of GJB2 and mtDNA 12S rRNA genes in Jiangsu population are similar to other areas of China. There are in total 31.46% of the patients with NSHL carry deafness-causing mutation in GJB2 or mtDNA 12S rRNA genes. Mutation in GJB2 gene is the most common factor, mtDNA 12S rRNA also plays an important part in the pathogenesis of hearing loss in Jiangsu Province areas. The m.1222A > G was found to be a new candidate mutation associated with hearing loss. Our results indicated the necessity of genetic screening for mutations of these genes in Jiangsu patients with NSHL.

Objective: To explore the molecular genetic characterization of two Chinese families with aminoglycoside-induced and non-syndromic hearing loss (NSHL)., Design: Clinical evaluations, sequence analysis of mitochondrial DNA (mtDNA) as well as two nuclear genes TRMU and MTO1 encoding mitochondrial proteins., Study Sample: Two Chinese families with aminoglycoside-induced and NSHL., Results: Clinical evaluations revealed incomplete penetrance (28.6% vs. 40.0%) and variable phenotype of hearing losses between two families. When the effect of aminoglycosides was excluded, the penetrances were both 0%. Sequence analysis of mitochondrial genomes showed a homoplasmic 1494C > T mutation in the12S rRNA gene (MT-RNR1) in all maternal relatives, as well as distinct sets of mtDNA polymorphism belonging to Eastern Asian haplogroups D4j and D5a2, respectively. However, none of these mtDNA variants was highly evolutionarily conserved and implicated to have functional significance. No mutations were identified in either TRMU or MTO1 gene., Conclusions: Mitochondrial 1494C> T mutation is the molecular basis responsible for the NSHL of two families, and the use of aminoglycoside antibiotics can worsen the hearing of the mutation carriers. Our results indicate the importance of a systematic screening for the mitochondrial 1494C > T mutation in Chinese subjects in the prevention of aminoglycoside-induced and non-syndromic hearing loss.

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.

Objective: Three genes including the OTOF, the DFNB59 and the DIAPH3 have been implicated previously in human non-syndromic auditory neuropathy. In this study, we aim to investigate whether DIAPH3 gene or the known deafness loci of 25 cloned autosomal dominant deafness (DFNA) genes contribute to the nonsyndromic hearing loss of a Chinese pedigree with dominantly inherited auditory neuropathy (AN)., Method: Nine members of the kernal pedigree in this family were selected. Genomic DNA was isolated from the peripheral leukocytes of the subjects using the Puregene DNA Isolation Kits. Firstly, the 5'UTR of DIAPH3 gene was PCR amplified in all subjects. Then, the DNA fragments spanning the entire coding regions of DIAPH3, GJB2 and GJB3 genes, and 50 exons in other 23 cloned DFNA genes were amplified using specific primers. Each fragment was purified and analyzed by direct sequencing. The resultant sequence data were compared with the standard sequence to identify deafness-associated mutations., Result: PCR amplifications were successfully conducted. We failed to detect the presence either of c. --172G > A mutation in the 5'UTR that have been reported, or any other deafness-associated mutations in the whole DIAPH3 gene, by sequence analysis. We also did not find any known deafness-causing mutations among the 25 cloned DFNA genes., Conclusion: The DIAPH3 gene, and the known deafness loci of 25 cloned DFNA genes seem not contribute to the pathogenesis of this Chinese AN family in this study, which suggesting new gene(s) involvement.

The novel tumor suppressor RASSF1A is frequently inactivated during human tumorigenesis by promoter methylation. In this study, we detected the RASSF1A promoter methylation by methylated-specific PCR and investigated RASSF1A gene expression by semi-quantitative RT-PCR and immunohistochemical staining in 36 cases of breast cancer and their adjacent normal tissues in Chinese women. The promoter methylation of the RASSF1A gene was found to be a frequent event in the breast cancers (61.1%). RASSF1A methylation was not found in the matched adjacent normal tissues. The loss frequency of RASSF1A mRNA was 33.3% and that of the RASSF1A protein was 44.4% in breast cancers. RASSF1A mRNA and protein were all expressed in adjacent normal tissues. The mRNA and protein expression level of RASSF1A was significantly lower in breast cancer than in adjacent normal tissue. However, the promoter methylation of the RASSF1A gene in breast cancers were not correlated with clinical parameters, such as ages, histological types, TNM stages and lymph node metastases. Thus, the promoter methylation of RASSF1A was one reason for the low level of RASSF1A mRNA and protein expression and was a frequent event in primary sporadic breast tumorigenesis in Chinese women.