GJB2 and hearing loss, autosomal recessive: Mutations in gene GJB2 (gap junction protein, beta-2, 13q12.11, MIM 121011) encoding transmembrane protein connexin 26 (Cx26) are the main cause for nonsyndromic autosomal recessive deafness 1A (DFNB1A, MIM 220290) in many populations [4], making GJB2 gene testing essential for the establishment of genetic diagnosis of HL.