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 essential for blastocyst formation in preimplantation mouse embryos, and is invloved in and is crucial for the formation and maintenance of the epidermal permeability barrier. This gene is adjacent to another family member Cldn9 on chromosome 17.