The intestinal lumen, especially that of the distal colon, is occupied by a large and diverse commensal microbiota. On the other hand, the intestinal mucosa contains the largest compartment of the immune system in the body, and these mucosal immune cells must be physically shielded from the dense luminal bacteria. Disruption of the homeostasis between commensal bacteria and mucosal immune cells is recognized as a critical step in the pathogenesis of inflammatory bowl disease (IBD), especially ulcerative colitis (UC). Normally, the luminal bacteria is separated from epithelium and immune cells in the colon by the mucus layer, which consists primarily of mucins that are heavily modified by O-linked oligosaccharides (O-glycans). Over 80% of mucin mass consists of the two types of complex O-glycans, called core 1- and core 3-derived O-glycans. Our published papers in the previous funding period show that mice lacking these complex O-glycans develop spontaneous colitis resembling UC, which indicates O-glycans as crucial components of the mucus barrier. However, how O-glycans maintain mucus barrier function and contribute to the pathogenesis of UC remains to be addressed. In this renewal proposal, we hypothesize that O-glycosylation maintains mucus barrier function by regulating mucin stability, by concentrating and presenting epithelial-derived antimicrobial proteins, and by complementing dietary glycans to prevent microbial dysbiosis. We will test these hypotheses by determining: 1) How mucin O-glycosylation maintains mucus layer homeostasis and barrier function. Sialic acid is a common capping sugar on O-glycans. Some microbiota are known to produce sialidase. In this Aim, we will first test the role of O-glycan sialylation in protecting mucus stability using in vitro mucin degradation assays and a novel mouse line with deficiency of sialylation in intestinal epithelial cells. Then, we will test the role of sialylated O-glycans in the mucus function by concentrating and positioning antimicrobial proteins. 2) How defective O-glycosylation alters mucus/microbiota homeostasis and promotes colitis. In a previous study, we discovered that somatic clonal mutations in the Cosmc gene regulate core 1-O glycosylation in colon epithelial cells of a subset of UC patients, suggesting a partial deficiency of core 1 O-glycans contributes to colitis pathogenesis. First, we will test a hypothesis that combination of a partial loss of core 1 O-glycans, similar to those seen in UC patients, with a polysaccharide-deficient diet, leads to a colitogenic microbiota, which subsequently causes defective mucus barrier and colitis. Second, we will test whether administration of exogenous sialylated oligosaccharides improves mucus barrier function and ameliorates colitis in this model. The mucus layer is an important part of the intestinal barrier, but its biological function is insufficiently studied. The proposed research will determine the contributions of O-glycans, the primary components of the intestinal mucus layer, to intestinal barrier function and pathogenesis of colitis.

Public Health Relevance

Ulcerative colitis (UC) is a chronic inflammation of the large intestine with an unknown cause or cure that can last years to decades, which leads to physical as well as psychological discomfort and even disability. Altered expression of large sugar molecules called O-glycans in the large intestine is seen in UC patients, although whether this alteration causes the disease is unknown. The proposed project is poised to provide novel insights into the role of intestinal mucin-type O-glycans in intestinal mucus barrier function and in pathogenesis of the common human disease, which may lead to a novel therapy for patients with UC.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK085691-08
Application #
9690672
Study Section
Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
Program Officer
Perrin, Peter J
Project Start
2010-08-01
Project End
2021-04-30
Budget Start
2019-05-01
Budget End
2020-04-30
Support Year
8
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Oklahoma Medical Research Foundation
Department
Type
DUNS #
077333797
City
Oklahoma City
State
OK
Country
United States
Zip Code
73104
Chugh, Seema; Barkeer, Srikanth; Rachagani, Satyanarayana et al. (2018) Disruption of C1galt1 Gene Promotes Development and Metastasis of Pancreatic Adenocarcinomas in Mice. Gastroenterology 155:1608-1624
Jacobs, Jonathan P; Lin, Lin; Goudarzi, Maryam et al. (2017) Microbial, metabolomic, and immunologic dynamics in a relapsing genetic mouse model of colitis induced by T-synthase deficiency. Gut Microbes 8:1-16
Song, Kai; Fu, Jianxin; Song, Jianhua et al. (2017) Loss of mucin-type O-glycans impairs the integrity of the glomerular filtration barrier in the mouse kidney. J Biol Chem 292:16491-16497
Chandrakesan, Parthasarathy; Yao, Jiannan; Qu, Dongfeng et al. (2017) Dclk1, a tumor stem cell marker, regulates pro-survival signaling and self-renewal of intestinal tumor cells. Mol Cancer 16:30
Bergstrom, K; Fu, J; Johansson, M E V et al. (2017) Core 1- and 3-derived O-glycans collectively maintain the colonic mucus barrier and protect against spontaneous colitis in mice. Mucosal Immunol 10:91-103
Gao, Nan; Bergstrom, Kirk; Fu, Jianxin et al. (2016) Loss of intestinal O-glycans promotes spontaneous duodenal tumors. Am J Physiol Gastrointest Liver Physiol 311:G74-83
Bergstrom, Kirk; Liu, Xiaowei; Zhao, Yiming et al. (2016) Defective Intestinal Mucin-Type O-Glycosylation Causes Spontaneous Colitis-Associated Cancer in Mice. Gastroenterology 151:152-164.e11
Chang, Baojun; Tessneer, Kandice L; McManus, John et al. (2015) Epsin is required for Dishevelled stability and Wnt signalling activation in colon cancer development. Nat Commun 6:6380
Jacobs, Jonathan; Braun, Jonathan (2014) Host genes and their effect on the intestinal microbiome garden. Genome Med 6:119
Sommer, Felix; Adam, Nina; Johansson, Malin E V et al. (2014) Altered mucus glycosylation in core 1 O-glycan-deficient mice affects microbiota composition and intestinal architecture. PLoS One 9:e85254

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