A number of these, including connexin 26 (Cx26)/GJB2, Cx29/Cx31.3/GJC3, Cx30/GJB6, Cx32/GJB1, Cx36/GJD2, Cx43/GJA1, Cx45/GJC1 and Cx47/GJC2 are expressed in the central and/or peripheral nervous system and mutations in a number of these cause central and/or peripheral nervous system disease. The gene discussed is GJB1; the disease is peripheral nervous system disorder.