NGS-based identification of a MYO7A mutation in a Korean family with DFNB2, a subtype of autosomal recessive non-syndromic hearing loss.

Abstract

Background: Hereditary hearing loss (HHL) exhibits considerable genetic heterogeneity. Among the known causative genes, MYO7A is frequently linked to autosomal recessive non-syndromic hearing loss (ARNSHL), contributing to auditory dysfunction through impaired inner ear cellular mechanics.

Objective: This study aimed to identify the genetic cause of ARNSHL in a Korean family (SR-323) and to assess the pathogenicity of candidate MYO7A variants.

Methods: Whole-exome sequencing (WES) was performed on five family members (two affected individuals and three unaffected relatives). Variant filtering, co-segregation analysis, and Sanger sequencing validation were conducted to identify candidate mutations. Conservation analysis across vertebrate species and in silico pathogenicity predictions were used to evaluate the biological impact of the variants. Additionally, 100 unrelated normal-hearing Korean individuals were screened to determine the frequency of the variant in the general population.

Results: Two MYO7A variants, c.4501G > A (p.Val1501Met) and c.6070 C > T (p.Arg2024Stop), were identified in affected individuals in a compound heterozygous state. Unaffected family members carried only one heterozygous variant. Both amino acid residues were highly conserved across seven vertebrate species. In silico analyses predicted p.Val1501Met to be pathogenic, while c.6070 C > T was previously classified as likely pathogenic. These variants were absent in the normal-hearing cohort, and only individuals with both variants exhibited hearing loss, supporting a compound heterozygous inheritance.

Conclusion: Compound heterozygosity of the MYO7A variants c.4501G > A and c.6070 C > T likely underlies the ARNSHL phenotype in the SR-323 family. These findings expand the known mutational spectrum of MYO7A and highlight the importance of genetic screening in hereditary hearing loss within the Korean population.