GJB2 and hearing loss, autosomal recessive: Mutations in the GJB2 gene (gap junction protein, beta-2, 13q12.11, MIM 121011) encoding transmembrane protein connexin 26 (Cx26) lead to nonsyndromic autosomal recessive deafness 1A (DFNB1A, MIM 220290) which is the most common form of hereditary hearing loss in many populations [1].