GJB4 and GJC3 variants in non-syndromic hearing impairment in Ghana

The contribution of GJB4 and GJC3 gene variants to hearing impairment in Africa has not yet been studied. Here, we investigated the contribution of these genes to autosomal recessive non-syndromic hearing impairment in Ghanaian children. Hearing-impaired children from 141 simplex and 59 multiplex families were enrolled from 11 schools for the deaf in Ghana. The coding regions of GJB4 and GJC3 were amplified, sequenced, and analyzed for the study participants previously found to be negative for GJB2 and GJB6 variants. Seven GJB4 and one GJC3 variants were identified. One out of the seven GJB4 variants was classified as likely pathogenic, while the others were either benign or synonymous. The likely pathogenic variant (p.Asn119Thr/rs190460237) was predicted to be likely associated with hearing impairment. We modeled the wild-type and mutant proteins of this variant (p.Asn119Thr) to evaluate the effect of the mutation on protein structure and ligand-binding properties. The mutant and not the wild type had the potential to bind N-Ethyl-5ʹ-Carboxamido Adenosine (DB03719) which was due to a slight structural change that was observed. No clinically relevant variant was identified in the GJC3 gene. We report for the first time a likely pathogenic GJB4 variant that may be associated with non-syndromic hearing impairment in Ghana; the finding will add to the body of evidence of the contribution of GJB4 to hearing impairment cases around the world. Impact statement: Although connexins are known to be the major genetic factors associated with HI, only a few studies have investigated GJB4 and GJC3 variants among hearing-impaired patients. This study is the first to report GJB4 and GJC3 variants from an African HI cohort. We have demonstrated that GJB4 and GJC3 genes may not contribute significantly to HI in Ghana, hence these genes should not be considered for routine clinical screening in Ghana. However, it is important to study a larger population to determine the association of GJB4 and GJC3 variants with HI.