Claudin 2 (CLDN2)

Members of the claudin protein family, such as CLDN2, are expressed in an organ-specific manner and regulate the tissue-specific physiologic properties of tight junctions. The deduced protein contains 230 amino acids and shares 93% amino acid identity with mouse Cldn2. Immunostaining of mouse intestine detected higher Cldn2 expression in ileum than in jejunum. the intestine-specific homeodomain proteins CDX1 and CDX2 activated a reporter plasmid driven by the CLDN2 promoter. HNF1-alpha (TCF1) augmented the CDX2-induced activation, but not the CDX1-induced activation. In mice, Hnf1-alpha was required for Cldn2 expression in the villus epithelium of the ileum and within the liver, but not in the kidneys, indicating an organ-specific function of Hnf1-alpha in regulating Cldn2 gene expression.