Claudin-1 directly interacts with tight junction (TJ) -associated peripheral membrane proteins zonula occludens (ZO) proteins -1/2/3. Defects in the gene encoding claudin-1 are the cause of an autosomal recessive syndrome named ichthyosis-sclerosing cholangitis neonatal (NISCH). Claudinsμ expression is altered in several human cancers. Claudin-1 is frequently up-regulated in colorectal carcinomas (CRCs), resulting in tumor differentiation and progression.
