Claudin 9 (CLDN9)

CLDN9 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 protein is one of the entry cofactors for hepatitis C virus. Mouse studies revealed that this gene is required for the preservation of sensory cells in the hearing organ and the gene deficiency is associated with deafness. Claudin-6 and claudin-9 expressed in CD81(+) cells also enable the entry of HCV pseudoparticles derived from six of the major genotypes.