Epithelia in multicellular organisms constitute the frontier that separates the individual from the environment. Epithelia are sites of exchange as well as barriers, for the transit of ions and molecules from and into the organism. Epithelial cells achieve this by providing cellular borders that cover external and internal surfaces throughout the body. Complexes between adjacent cells include Gap Junctions, Desmosomes, Adherens Junctions (AJs) and Tight Junctions (TJs). Such junctions are quite essential for the modulation of paracellular permeability in various epithelia. Vertebrate epithelial cells exhibit Tight Junctions that lie apical to Adherens Junctions. Tight Junctions have an organizing role in epithelial polarization and establish an apico-lateral barrier to the diffusion of solutes through the intracellular space (gate function). They also [...]