Monogenic deficiency in murine intestinal Cdc42 leads to mucosal inflammation that induces crypt dysplasia

CDC42 controls intestinal epithelial (IEC) stem cell (IESC) division. How aberrant CDC42 initiates intestinal inflammation or neoplasia is unclear. We utilized models of inflammatory bowel diseases (IBD), colorectal cancer, aging, and IESC injury to determine the loss of intestinal Cdc42 upon inflammation and neoplasia. Intestinal specimens were collected to determine the levels of CDC42 in IBD or colorectal cancer. Cdc42 floxed mice were crossed with Villin-Cre, Villin-CreER^T2 and/or Lgr5-eGFP-IRES-CreER^T2, or Bmi1-CreER^T2 mice to generate Cdc42 deficient mice. Irradiation, colitis, aging, and intestinal organoid were used to evaluate CDC42 upon mucosal inflammation, IESC/progenitor regenerative capacity, and IEC repair. Our studies revealed that increased CDC42 in colorectal cancer correlated with lower survival; in contrast, lower levels of CDC42 were found in the inflamed IBD colon. Colonic Cdc42 depletion significantly reduced Lgr5⁺ IESCs, increased progenitors' hyperplasia, and induced mucosal inflammation, which led to crypt dysplasia. Colonic Cdc42 depletion markedly enhanced irradiation- or chemical-induced colitis. Depletion or inhibition of Cdc42 reduced colonic Lgr5⁺ IESC regeneration. In conclusion, depletion of Cdc42 reduces the IESC regeneration and IEC repair, leading to prolonged mucosal inflammation. Constitutive monogenic loss of Cdc42 induces mucosal inflammation, which could result in intestinal neoplasia in the context of aging.