Clca1 deficiency exacerbates colitis susceptibility via impairment of mucus barrier integrity and gut microbiota homeostasis.

The intestinal mucus barrier has emerged as a promising therapeutic target for inflammatory bowel disease. Understanding its regulatory mechanisms is critical for elucidating ulcerative colitis (UC) pathogenesis, improving diagnostics, guiding treatments, and preventing relapse. Chloride Channel Accessory 1 (Clca1), a constituent of the mucus layer, remains understudied in colitis. Here, we investigated Clca1's role in mucosal immunity and intestinal homeostasis using experimental colitis models. Clca1-deficient (Clca1-/-) mice displayed compromised mucus layer integrity, reduced neutrophil infiltration, and gut microbiota dysbiosis. Notably, Clca1-/- mice exhibited exacerbated colitis severity following dextran sulfate sodium (DSS) challenge, accompanied by a diminished goblet cell populations. Fecal microbiota transplantation (FMT) studies revealed that gut microbiota critically modulates divergent phenotypic outcomes between genotypes. Our findings establish Clca1 as a multifunctional regulator of mucus barrier integrity through mechanisms involving goblet cell maintenance, neutrophil-mediated immunity, and host-microbiota crosstalk. These results advance the understanding of UC pathogenesis and identify Clca1-associated pathways as potential targets for barrier restoration therapies.