The Diverse Genetic Landscape of Hearing Impairment in South African Families

To elucidate the genetic etiology of hearing impairment (HI) in South Africa, 45 nonsyndromic HI (NSHI) and syndromic HI (SHI) families with ≥ 2 affected members were analyzed. Exome and sanger sequencing were used to identify causal genes. For NSHI, 14 of 24 families segregated variants in NSHI genes, that is, CDH23, GJB2, MITF, MYO7A, MYO15A, PCDH15, POU3F4, REST, SLC26A4, TMPRSS3, and WFS1. For the 21 SHI families, 14 have Waardenburg syndrome, two Branchio-Oto-Renal syndromes, and one each with Bartter, Chudley-McCullough, Deafness-Albinism, MYH9-related disorder, and Pendred syndromes. The cause of SHI was determined for 14 families, with EDN3, EDNRB, GPSM2, MITF, MYH9, SLC12A1, and SLC26A4 underlying the syndrome in a single family, EYA1 in two families, and PAX3 in five families. For the NSHI and SHI genes, 52.9% and 35.7% of the variants, respectively, have not been reported in disease etiology. Additionally, two Waardenburg families segregated variants in NSHI genes, BDP1 and MYO6, but these findings need to be validated. This study enhances the understanding of the genetic landscape of HI in South Africa, revealing a high level of locus and allelic heterogeneity. Studying diverse populations provides new insights into HI etiology that, in turn, can improve genetic diagnosis and personalized management.