Diverse functions of vertebrate gap junctions

Gap junctions are clusters of intercellular channels between adjacent cells . The channels are formed by the direct apposition of oligomeric transmembr ane proteins, permitting the direct exchange of ions and small molecules (< 1 kDa) between cells without involvement of the extracellular space. Verteb rate gap junction channels are composed of oligomers of connexins, an enlar ging family of proteins consisting of perhaps >20 members. This article rev iews recent advances in understanding the structure of intercellular channe ls and describes the diverse functions attributable to gap junctions as a r esult of insights gained from targeted gene disruptions in mice and genetic diseases in humans.