Cmtm4 deficiency exacerbates colitis by inducing gut dysbiosis and S100A8/9 expression.

The dysfunction of innate immunity components is one of the major drivers for ulcerative colitis (UC), and increasing reports indicate that gut microbiome serves as an intermediate between genetic mutations and UC development. Here, we find that the IL-17 receptor subunit, CMTM4, is reduced in UC patients and DSS-induced colitis. The deletion of CMTM4 (Cmtm4-/- ) in mice leads to a higher susceptibility to DSS-induced colitis in comparison to wildtype, and the gut microbiome significantly changes in the composition. The causal role of gut microbiome is confirmed with co-housing experiment. We further identify that S100a8/9 is significantly up-regulated in Cmtm4-/- colitis, with the block of its receptor RAGE that reverses the phenotype associated with the CMTM4 deficiency. CMTM4 deficiency rather suppresses S100a8/9 expression in vitro via the IL17 pathway, further supporting that the elevation of S100a8/9 in vivo is most likely a result of microbial dysbiosis. Taken together, the results suggest that CMTM4 is involved in the maintenance of the intestinal homeostasis, suppression of S100a8/9, and prevention of the colitis development. Our study further shows CMTM4 as a crucial innate immunity component, confirming its important role in the UC development and providing insights into potential targets for development of future therapies.