Unique spectrum of GJB2 mutations in Mexico

The aim of this study was to elucidate the involvement of mutations in three relatively common deafness genes in Mexican individuals with non-syndromic hearing loss. We sequenced GJB2 for mutations, screened for two deletions involving GJB6, del(GJB6-D13S1830) and del(GJB6-D13S1854), and for the m.1555A>G mutation in the MTRNR1 gene in 76 (71 simplex and 5 multiplex) unrelated Mexican probands with prelingual non-syndromic hearing loss. Samples were obtained from the Department of Genetics at Instituto Nacional de Rehabilitacion in Mexico City. Eight previously reported pathogenic variants and two polymorphic variants in GJB2 were identified. The two screened GJB6 deletions and the m.1555A>G mutation were not detected. Eight cases (10.6%) were found to have bi-allelic mutations in GJB2 and six (7.9%) were found to have a monoallelic GJB2 mutation. Of the six monoallelic mutations, one (p.R184Q) was a previously reported autosomal dominant variant. The most frequent pathological allele detected in this population was the c.35delG mutation in the GJB2 gene. The p.V27I polymorphic variant was also detected, with an allele frequency of 0.24. All eight probands with GJB2 mutations had symmetric profound deafness, whereas patients without GJB2 mutations had moderate, severe or profound hearing loss. This study shows that GJB2 mutations are an important cause of prelingual deafness in the Mexican population