T-cell activation Rho GTPase-activating protein (TAGAP) is a GTPase-activating protein, and many single nucleotide polymorphisms (SNPs) near or within the TAGAP gene have been found to be associated with susceptibility to many autoimmune diseases and infectious diseases, including MS, Crohn’s disease, psoriasis, RA, celiac disease, and candidemia17–21. Here, TAGAP is linked to Crohn disease.