GJB2 and hearing loss disorder: Xu and Nicholson (2013) analyzed the distribution of the reported GJB2 mutations associated with nonsyndromic hearing loss and revealed that TM2 domain of Cx26 shows the highest density of them (67%), followed by TM3 (50%), E2 (43%), TM4 (40%), NT, and CL (36%), TM1 and E1 (33%).