背景资料：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. This gene is expressed in germinal center B-cells, placenta and stomach as well as in colon tumor. This gene is down-regulated in intestinal type gastric cancer.