Claudins, which consist of four transmembrane domains and two extracellular loops, make up tight junction strands. Claudin expression is often highly restricted to specfic regions of different tissues and may have an important role in transcellular transport through tight junctions. Claudin-8 is a multi-pass membrane protein that belongs to the claudin family. Localized to the caput and the lateral margins of principal cells, claudin-8 plays an important role in tight junction-specific obliteration of the intercellular space.