Next-generation sequencing reveals a novel pathological mutation in the TMC1 gene causing autosomal recessive non-syndromic hearing loss in an Iranian kindred

Objectives: Hearing loss (HL) is the most common sensory-neural disorder with excessive clinical and genetic heterogeneity, which negatively affects life quality. Autosomal recessive non-syndromic hearing loss (ARNSHL) is the most common form of the disease with no specific genotype-phenotype correlation in most of the cases. Whole exome sequencing (WES) is a powerful tool to overcome the problem of finding mutations in heterogeneous disorders.

Methods: A comprehensive clinical and pedigree examination was performed on a multiplex family from Khuzestan province suffering from hereditary HL. Direct sequencing of GJB2 and genetic linkage analysis of DFNB1A/B was accomplished. WES was utilized to find possible genetic etiology of the disease. Co-segregation analysis of the candidate variant was done. High resolution melting analysis was applied to detect variant status in 50 healthy matched controls.

Results: Clinical investigations suggested ARNSHL in the pedigree. The family was negative for DFNB1A/B. WES revealed a novel nonsense mutation, c.256G > T (p.Glu86*), in TMC1 segregating with the phenotype in the pedigree. The variant was absent in the controls.

Conclusion: Here, we report successful application of WES to identify the molecular pathogenesis of ARNSHL in a large family. The novel nonsense TMC1 variant meets the criteria of being pathogenic according to the ACMG-AMP variant interpretation guideline.