Modified U1 snRNA and antisense oligonucleotides rescue splice mutations in SLC26A4 that cause hereditary hearing loss.

One of most important factors for messenger RNA (mRNA) transcription is the spliceosomal component U1 small nuclear RNA (snRNA), which recognizes 5' splicing donor sites at specific regions in pre-mRNA. Mutations in these sites disrupt U1 snRNA binding and cause abnormal splicing. In this study, we investigated mutations at splice sites in SLC26A4 (HGNC 8818), one of the major causative genes of hearing loss, which may result in the synthesis of abnormal pendrin, the channel protein encoded by the gene. Seventeen SLC26A4 variants with mutations in the U1 snRNA binding sites were assessed by minigene splicing assays, and 11 were found to result in abnormal splicing. Interestingly, eight of the 11 pathogenic mutations were intronic, suggesting the importance of conserved sequences at the intronic splice site. The application of modified U1 snRNA effectively rescued the abnormal splicing for most of these mutations. Although three were cryptic mutations, they were rescued by cotransfection of modified U1 snRNA and modified antisense oligonucleotides. Our results demonstrate the important role of snRNA in SLC26A4 mutations, suggesting the therapeutic potential of modified U1 snRNA and antisense oligonucleotides for neutralizing the pathogenic effect of the splice-site mutations that may result in hearing loss.

Genetic association of MYH genes with hereditary hearing loss in Korea.

BACKGROUND: Myosin is a key protein involved in regulating the shape and motility of cells. The MYH9 and MYH14 genes, which encode non-muscle myosin heavy chain IIA (NMMHC II-A) and IIC (NMMHC II-C), respectively, are expressed in the inner ear. These myosin genes are known to be associated with autosomal dominant non-syndromic hearing loss (ADNSHL); however, genetic studies in patients with ADNSHL in Korea have rarely been reported. METHODS: We analyzed the MYH9 and MYH14 genes in 75 Korean patients with ADNSHL. RESULTS: We identified 4 possible pathogenic variants: a novel variant p.F1303L and 2 previously reported variants (p.R1730C and p.R1785C) in the MYH9 gene, and a novel variant p.A1868T in the MYH14 gene. All the variants were located in the myosin tail domain, which is essential for the interaction of myosin with actin. These variants were predicted to be possibly pathogenic by functional prediction tools and were absent in 100 unrelated normal controls. CONCLUSION: These results suggest that all the variants identified in this study have a strong potential to affect the structural stability and/or function of non-muscle myosin in the inner ear, which might lead to ADNSHL. This study establishes the link between the genotype and development of ADNSHL and contributes to the establishment of Korean database for hereditary hearing loss.