MUC5AC and colitis: Due to the impaired glycosylation and disrupted mucus integrity found when knocking out this protein's corresponding gene, mice with intestinal epithelium-specific deficiency of core 1 derived O-glycans (C1galt1ΔIEC) develop spontaneous colitis in the distal regions of the colon (181) characterized by myeloid cell infiltration, crypt abscess, epithelial ulceration, goblet cell loss, reduced mucin levels, disrupted mucus layer, and increased epithelial–microbial interaction (153, 180).