Gap junctions are conduits that allow the direct cell-to-cell passage of small cytoplasmic molecules, including ions, metabolic intermediates, and second messengers, and thereby mediate intercellular metabolic and electrical communication. Gap junction channels consist of connexin protein subunits, which are encoded by a multigene family. GJBs (gap-junction proteins or connexins) play crucial functional roles associated with these channels. Defects in GJB3 have been linked to erythrokeratodermia variabilis (EKV) is an autosomal dominant genodermatosis characterized by transient figurate red patches or hyperkeratosis. Mutations in GJB2 have also been associated with genetically derived hearing impairments, including autosomal recessive nonsyndromic deafness.