NOD2 and Crohn disease: For example, the PGN receptor NOD2 is enriched in ISCs of mice (Nigro et al., 2014) and protects ISCs from irradiation-induced cytotoxicity (Levy et al., 2020), while mutations in NOD2 are linked to Crohn’s disease (Hugot et al., 2001; Ogura et al., 2001).