Connexin mutations in Brazilian patients with skin disorders with or without hearing loss.

The connexins are a family of proteins whose major function is as part of the gap junctions of cell-to-cell channels. They are expressed in several tissues including brain, skin, and cochlea. Mutations in connexin genes play a major role in non-syndromic sensorineural deafness, but have been also described in individuals with variable dermatological features. In recent years, many genes responsible for hereditary skin diseases have been discovered. These genes may encode different proteins that participate in the terminal differentiation of the epidermis. Therefore alteration or absence of these proteins causes a keratinization disorder. It has been demonstrated that distinct germline mutations within six connexin (Cx) genes GJB2 (Cx26), GJB6 (Cx30), GJB3 (Cx31), GJA1 (Cx43), GJB4 (Cx30.3), and GJB5 (Cx31.1), may cause sensorineural hearing loss and various skin disease phenotypes. The crucial functional importance of each of these connexins in the mentioned ectodermic tissues is reflected by the finding that genetic defects in their genes produce a wide spectrum of genetic disorders comprising sensorineural hearing loss, disorders of cornification of the skin, hair, and nails, and keratitis. Here, we report on different mutations in the connexin genes in individuals with or without hearing loss and different skin disorders illustrating the clinical and genetic heterogeneity of the condition.