Core 3-derived O-glycans are essential for intestinal mucus barrier function.

O-Glycans are primary components of the intestinal mucins that form the mucus gel layer overlying the gut epithelium. Core 3-derived O-glycans, which are one of the major types of O-glycans, are primarily expressed in colon. To investigate the biological function of core 3-derived O-glycans, we engineered mice lacking core 3 beta1,3-N-acetylglucosaminyltransferase (C3GnT), an enzyme predicted to be important in synthesis of core 3-derived O-glycans. Disruption of the C3GnT gene eliminated core 3-derived O-glycans. C3GnT-deficient mice displayed a discrete, colon-specific reduction in Muc2 protein and increased permeability of the intestinal barrier. Moreover, these mice were highly susceptible to experimental triggers of colitis. These data reveal a requirement for core 3-derived O-glycans in colon mucus barrier function.

Xia L 《-》

Increased susceptibility to colitis and colorectal tumors in mice lacking core 3-derived O-glycans.

An G ，Wei B ，Xia B ，McDaniel JM ，Ju T ，Cummings RD ，Braun J ，Xia L ... -  《-》

Core 1- and 3-derived O-glycans collectively maintain the colonic mucus barrier and protect against spontaneous colitis in mice.

Bergstrom K ，Fu J ，Johansson ME ，Liu X ，Gao N ，Wu Q ，Song J ，McDaniel JM ，McGee S ，Chen W ，Braun J ，Hansson GC ，Xia L ... -  《-》

Defective Intestinal Mucin-Type O-Glycosylation Causes Spontaneous Colitis-Associated Cancer in Mice.

Core 1- and core 3-derived mucin-type O-linked oligosaccharides (O-glycans) are major components of the colonic mucus layer. Defective forms of colonic O-glycans, such as the Thomsen-nouveau (Tn) antigen, frequently are observed in patients with ulcerative colitis and colorectal cancer, but it is not clear if they contribute to their pathogenesis. We investigated whether and how impaired O-glycosylation contributes to the development of colitis-associated colorectal cancer using mice lacking intestinal core 1- and core 3-derived O-glycans. We generated mice that lack core 1- and core 3-derived intestinal O-glycans (DKO mice) and analyzed them, along with mice that singly lack intestinal epithelial core 1 O-glycans (IEC C1galt1(-/-) mice) or core 3 O-glycans (C3Gnt(-/-) mice). Intestinal tissues were collected at different time points and analyzed for levels of mucin and Tn antigen, development of colitis, and tumor formation using imaging, quantitative polymerase chain reaction, immunoblot, and enzyme-linked immunosorbent assay techniques. We also used cellular and genetic approaches, as well as intestinal microbiota depletion, to identify inflammatory mediators and pathways that contribute to disease in DKO and wild-type littermates (controls). Intestinal tissues from DKO mice contained higher levels of Tn antigen and had more severe spontaneous chronic colitis than tissues from IEC C1galt1(-/-) mice, whereas spontaneous colitis was absent in C3GnT(-/-) and control mice. IEC C1galt1(-/-) mice and DKO mice developed spontaneous colorectal tumors, although the onset of tumors in the DKO mice occurred earlier (age, 8-9 months) than that in IEC C1galt1(-/-) mice (15 months old). Antibiotic depletion of the microbiota did not cause loss of Tn antigen but did reduce the development of colitis and cancer formation in DKO mice. Colon tissues from DKO mice, but not control mice, contained active forms of caspase 1 and increased caspase 11, which were reduced after antibiotic administration. Supernatants from colon tissues of DKO mice contained increased levels of interleukin-1β and interleukin-18, compared with those from control mice. Disruption of the caspase 1 and caspase 11 genes in DKO mice (DKO/Casp1/11(-/-) mice) decreased the development of colitis and cancer, characterized by reduced colonic thickening, hyperplasia, inflammatory infiltrate, and tumors compared with DKO mice. Impaired expression of O-glycans causes colonic mucus barrier breach and subsequent microbiota-mediated activation of caspase 1-dependent inflammasomes in colonic epithelial cells of mice. These processes could contribute to colitis-associated colon cancer in humans.

Bergstrom K ，Liu X ，Zhao Y ，Gao N ，Wu Q ，Song K ，Cui Y ，Li Y ，McDaniel JM ，McGee S ，Chen W ，Huycke MM ，Houchen CW ，Zenewicz LA ，West CM ，Chen H ，Braun J ，Fu J ，Xia L ... -  《-》

The mucin Muc2 limits pathogen burdens and epithelial barrier dysfunction during Salmonella enterica serovar Typhimurium colitis.

Zarepour M ，Bhullar K ，Montero M ，Ma C ，Huang T ，Velcich A ，Xia L ，Vallance BA ... -  《-》