This gene encodes a member of the claudin family. Claudins are integral membrane proteins and components of tight junction strands. Tight junction strands serve as a physical barrier to prevent solutes and water from passing freely through the paracellular space between epithelial or endothelial cell sheets, and also play critical roles in maintaining cell polarity and signal transductions. The protein encoded by this gene is 75% identical to the mouse homolog. This gene is upstream of the CLDN22 gene, which overlaps the WWC2 gene on the opposite strand in the genome.[provided by RefSeq, Aug 2010]