Gap junction diseases of the skin: novel insights from new mutations

Gap junctions are small membrane pores that facilitate rapid intercellular communication in all vertebrate cells, and are composed of connexins. In humans, 21 different connexin genes are expressed. Each tissue has its own expression pattern. Gap junctions are particularly prominent in the skin and mutations in skin-expressed connexins cause a broad spectrum of ectodermal dysplasias. Intriguingly, it has been found that different dominant mutations in a single skin-expressed connexin, connexin 26, cause a wide variety of syndromes, pointing to great underlying functional complexity that we are now beginning to dissect. Important steps have been taken towards understanding the underlying biology of gap junction disorders of the skin, but how connexin mutations cause skin disease is still essentially unknown.