Recurrent and Novel Pathogenic Variants in Genes Involved with Hearing Loss in the Pakistani Population.

Background: Molecular diagnostic rates for hereditary hearing loss vary by genetic ancestry, highlighting the importance of population-specific studies. In Pakistan, where consanguineous marriages are prevalent, genetic research has identified many autosomal recessive genes, advancing understanding of rare and novel hearing loss mechanisms. This study aimed to identify pathogenic genetic variants in 31 families from Azad Kashmir, Pakistan, presenting non-syndromic hearing loss.

Methods: We conducted exome sequencing and bioinformatics analysis, and targeted gene sequencing on 31 Pakistani families with hearing loss.

Results: We identified ten pathogenic, three likely pathogenic variants, and one variant of uncertain significance, comprising six nonsense, four missense, three frameshift, and one deep intronic variant, across ten hearing loss-associated genes (MYO15A, GJB2, SLC26A4, TMC1, HGF, TMIE, SLC19A2, KCNE1, ILDR, PCDH15 and MYO6) in 25 families. The overall diagnostic rate, including families with pathogenic and likely pathogenic variants, was 77.4%. GJB2 was the most frequently affected gene, identified in seven families. Thirteen out of 14 identified variants were homozygous. Notably, we identified two novel variants: MYO15A (NM_016239.4, DFNB3) c.870C>G, p.(Tyr290*) and MYO6 (NM_016239.4, DFNB37) c.3465del, p.(Pro1156Leufs*9). Additionally, we identified c.10475dupA, p.(Leu3493Alafs*25) in MYO15A (NM_016239.4, DFNB3) and c.617T>A, p.(Leu206*) in SLC26A4 (NM_000441.2, DFNB4), previously documented in ClinVar but unpublished. We also propose SLC19A2 as a candidate gene presenting as non-syndromic hearing loss, despite its association with thiamine-responsive megaloblastic anemia syndrome.

Conclusion: Our work expands the genotypic and phenotypic spectrum of hearing loss by emphasizing the importance of investigating under-represented groups to identify unique genetic variants and clinical characteristics. Such efforts deepen understanding of genetic diversity in under-represented populations to improve diagnosis and treatment strategies.