Actin motors that drive formation and disassembly of epithelial apical junctions.

Tight junctions (TJ) and adherens junctions (AJ) are the most characteristic morphological features of differentiated epithelia which mediate cell-cell adhesions, establishment of the paracellular barrier and development of apico-basal cell polarity. In polarized epithelial cells, TJ and AJ associate with the prominent apical actin cytoskeleton, which is known to stabilize junctional structure and to tighten the epithelial barrier. Furthermore, plasticity of the actin cytoskeleton is thought to be critical for the remodeling of epithelial junctions. Two major molecular motors such as myosin II and actin filament turnover provide driving forces for reorganizations of the actin cytoskeleton. The review focuses on the roles of these actin motors in the establishment, maintenance and disassembly of epithelial TJ and AJ during tissue morphogenesis and in pathology.