Physiologically, the human and murine hearing systems are very similar, justifying the extensive use of mice in experimental models for hearing impairment (HI). About 340 murine HI genes have been reported; however, whether variants in all human-mouse ortholog genes contribute to HI has been rarely investigated. In humans, nearly 120 HI genes have been identified to date, with GJB2 and GJB6 variants accounting for half of congenital HI cases, of genetic origin, in populations of European and Asian ancestries, but not in most African populations. The contribution of variants in other known genes of HI among the populations of African ancestry is poorly studied and displays the lowest pick-up rate. We used whole exome sequencing (WES) to investigate pathogenic and likely pathogenic (PLP) variants in 34 novel human-mouse orthologs HI genes, in 40 individuals from Cameroon and South Africa diagnosed with non-syndromic hearing impairment (NSHI), and compared the data to WES data of 129 ethnically matched controls. In addition, protein modeling for selected PLP gene variants, gene enrichment, and network analyses were performed. A total of 4/38 murine genes, d6wsu163e, zfp719, grp152 and minar2, had no human orthologs. WES identified three rare PLP variants in 3/34 human-mouse orthologs genes in three unrelated Cameroonian patients, namely: OCM2, c.227G>C p.(Arg76Thr) and LRGI1, c.1657G>A p.(Gly533Arg) in a heterozygous state, and a PLP variant MCPH1, c.2311C>G p.(Pro771Ala) in a homozygous state. In silico functional analyses suggest that these human-mouse ortholog genes functionally co-expressed interactions with well-established HI genes: GJB2 and GJB6. The study found one homozygous variant in MCPH1, likely to explain HI in one patient, and suggests that human-mouse ortholog variants could contribute to the understanding of the physiology of hearing in humans. Impact statement Despite, human and murine hearing system being very similar, the contribution of variants in relevant mouse-ortholog genes to hearing impairment (HI) has not been fully investigated. The contribution of variants in the known non-syndromic hearing impairment (NSHI) genes among Africans is poorly studied, suggesting that the novel gene(s) and mutations are yet to be discovered in NSHI in the African populations. Using whole exome sequencing (WES), this study identified rare candidate pathogenic and likely pathogenic (PLP) variants in 3/34 novel human-mouse ortholog genes in 3/40 individuals, with one homozygous variant, MCPH1, c.2311C>G p.(Pro771Ala), likely to explain HI in one patient. In silico functional analyses suggest that these human-mouse ortholog genes could contribute to the understanding of the physiology of hearing in humans and thus the variants identified in those genes deserve additional investigations.
Identification of a novel antimicrobial peptide from amphioxus Branchiostoma japonicum by in silico and functional analyses
