Diagnostic Value of SLC26A4 Mutation Status in Hereditary Hearing Loss With EVA: A PRISMA-Compliant Meta-Analysis.

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.

IVS8+1 DelG, a Novel Splice Site Mutation Causing DFNA5 Deafness in a Chinese Family.

BACKGROUND: Nonsyndromic hearing loss (NSHL) is highly heterogeneous, in which more than 90 causative genes have currently been identified. DFNA5 is one of the deafness genes that known to cause autosomal dominant NSHL. Until date, only five DFNA5 mutations have been described in eight families worldwide. In this study, we reported the identification of a novel pathogenic mutation causing DFNA5 deafness in a five-generation Chinese family. METHODS: After detailed clinical evaluations of this family, the genomic DNA of three affected individuals was selected for targeted exome sequencing of 101 known deafness genes, as well as mitochondrial DNA and microRNA regions. Co-segregation analysis between the hearing loss and the candidate variant was confirmed in available family members by direct polymerase chain reaction (PCR)-Sanger sequencing. Real-time PCR (RT-PCR) was performed to investigate the potential effect of the pathogenic mutation on messenger RNA splicing. RESULTS: Clinical evaluations revealed a similar deafness phenotype in this family to that of previously reported DFNA5 families with autosomal dominant, late-onset hearing loss. Molecular analysis identified a novel splice site mutation in DFNA5 intron 8 (IVS8+1 delG). The mutation segregated with the hearing loss of the family and was absent in 120 unrelated control DNA samples of Chinese origin. RT-PCR showed skipping of exon 8 in the mutant transcript. CONCLUSIONS: We identified a novel DFNA5 mutation IVS8+1 delG in a Chinese family which led to skipping of exon 8. This is the sixth DFNA5 mutation relates to hearing loss and the second one in DFNA5 intron 8. Our findings provide further support to the hypothesis that the DFNA5-associated hearing loss represents a mechanism of gain-of-function.

Understanding of the molecular evolution of deafness-associated pathogenic mutations of connexin 26.

Connexins (Cxs) were first identified as subunit proteins of the intercellular membrane channels that cluster in the cell communication structures known as gap junctions. Mutations in the gap junction ß2 (GJB2) gene encoding connexin 26 (Cx26) have been linked to sporadic and hereditary hearing loss. In some cases, the mechanisms through which these mutations lead to hearing loss have been partly elucidated using cell culture systems and animal models. The goal of this study was to re-assess the pathogenic roles of the GJB2 mutations by combining comparative evolutionary studies. We used Bayesian phylogenetic analyses to determine the relationships among 35 orthologs and to calculate the ancestral sequences of these orthologs. By aligning sequences from the 35 orthologs and their ancestors and categorizing amino acid sites by degree of conservation, we used comparative evolutionary methods to determine potential functionally important amino acid sites in Cx26 and to identify missense changes that are likely to affect function. We identified six conserved regions in Cx26, five of which are located in the Connexin_CCC, and another is in the connexin super family domain. Finally, we identified 51 missense changes that are likely to disrupt function, and the probability of these changes occurring at hydrophilic amino acid residues was twice that of occurring at hydrophobic residues in the trans-membrane regions of Cx26. Our findings, which were obtained by combining comparative evolutionary methods to predict Cx26 mutant function, are consistent with the pathogenic characteristics of Cx26 mutants. This study provides a new pathway for studying the role of aberrant Cx26 in hereditary hearing loss.

[Comparative analysis of conservation and regulatory network on core transcription factors in mouse inner ear development].

During vertebrate inner ear development, several core genes, such as Six1, Six4, Pax2, Pax8, Foxi1, Dlx5, Gbx2, Irx2/3, and Msx1, are crucial to the regulation of the otic placode induction. In order to get the gene regulatory network during inner ear development, bioinformatics methods were adopted to analyze conservation and regulation of the core transcription factors in mice. Pax2, Pax8, Foxi1, and Dlx5 remained to be the main regulators during inner ear development, which was consistent with the gene regulatory network from literature. Six1 was regulated by many transcription factors, and Gbx2, Irx2/3, and Msx1 played important roles in the regulatory network. The differences in the constructed regulatory network were reasonably analyzed. It was predicted that Msxl regulated the expression of Six1 and Gbx2. In addition, several transcription factors, such as Sox5, Lhx2, Rax, Otx1, Otx2, Pitxl, Pitx2, Nkx2-5, Irx4, Irx6, Dlx2, Hmx1/2/3, Pou4f3, Pax4 and Tlx2, were found to be involved in the regulatory network. Our results provide an improved understanding of the regulatory mechanism during inner ear development.

[Nonsyndromic inherited hearing impairment caused by mtDNA double mutations of A1555G and 961 insC].

OBJECTIVE: To investigate the genotypes of mitochondrial DNA mutations of a large nonsyndromic inherited hearing impairment pedigree. METHODS: The diagnosis was validated by hearing test. Blood samples from the branch pedigree (33 members) and 6 sporadic patients were obtained. DNA was extracted from the leukocytes. The mitochondrial DNA target fragments were amplified by polymerase chain reaction(PCR). The 1555G, 3243G and 7445G mutations were detected by BsmA I, Apa I and Xba I restriction endonuclease digestion respectively. Some PCR products were analyzed by sequencing. RESULTS: Restriction endonuclease digestion identified that 17 patients from the pedigree carried 1555G mutation. All pedigree members, including patients and sporadic patients, did not have 3243G and 7445G mutation. In 6 patients of the pedigree DNA sequence analysis revealed double mutations, an A>G transition at position 1555 and a C insertion at position 961, whereas the unaffected relatives of the pedigree and sporadic patients did not have such mutations. None of them carried 3243G and 7445G mutation. CONCLUSION: Double mutations of A1555G and 961 insC in mitochondrial DNA 12S rRNA gene region may play a pivotal role in the pathogenesis of hearing loss in the large nonsyndromic inherited hearing impairment pedigree.