TJ and AJ proteins may regulate junctional permeability by modulating GTP binding to and/or GTP hydrolysis of Cdc42, Rac, and RhoA, while many previous studies had indicated that the expression and/or localization of TJ (including occludin, JAM-1, ZO-1, claudin-3, and claudin-5) was decreased in the inflammatory colon of patients with IBD. This evidence concerns the gene TJP1 and inflammatory bowel disease.