Tight junctions in epidermis: from barrier to keratinization.

Tight junctions (TJs) are one type of intercellular junction. TJs prevent diffusion of solutes through the intercellular spaces in simple and stratified epithelia. Mice lacking claudin-1 (an adhesion molecule at TJs) show dehydration from the skin by impaired barrier function of epidermal TJs. Meanwhile, a human hereditary disease with ichthyosis (NISCH syndrome) has been found to be a claudin-1-deficient disease. The two models of lacking-claudin-1 indicate that TJs are related not only to the epidermal barrier but also to keratinization. Research of TJs in epidermis is reviewed in view of the barrier to keratinization.