Inherited defect in ST6GalNAc1 reveals roles of sialylation in intestinal homeostasis
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Orbitrap Fusion Lumos
ORGANISM(S): Homo Sapiens (human) Mus Musculus (mouse)
TISSUE(S): Epithelial Cell, Colon
DISEASE(S): Colon Cancer
SUBMITTER: 
Yanlong Ji
LAB HEAD: Kuan-Ting Pan
PROVIDER: PXD028239 | Pride | 2022-03-17
REPOSITORIES: Pride
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Project description:Chronic inflammatory bowel disease (IBD) causes disability, suffering and risk of colon cancer in over 30 million people globally. Here, we investigate 3 kindreds of IBD with mutations in the N-acetylgalactosamide alpha-2,6-sialyltransferase 1/ST6GALNAC1 (ST6) glycosyltransferase gene that is uniquely expressed in the goblet cells (GCs). These mutations cause defective sialic acid (SA) conjugation, elimination of the onco-antigen S-Tn (Sialyl-Tn), and altered glycosylation of the MUC2 protein, a key component of intestinal mucus. Decreased MUC2 sialylation increases susceptibility to bacterial proteolytic degradation and compromises the gastrointestinal (GI) mucus barrier. Mice harboring the patient ST6 mutations recapitulate human colitis and reveal that defective sialylation causes dysbiosis, butyrate overproduction, and impaired GI stem cell proliferation during injury. Thus, this new genetic disease illustrates how sialylation controls host-microbe homeostasis and reveals several new potential approaches to IBD treatment.
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Project description:Background; MUC2 mucin produced by intestinal goblet cells is the major component of the intestinal mucus barrier. MUC2 homo-oligomerizes intracellularly into large secreted polymers which give mucus its viscous properties. The inflammatory bowel disease (IBD) ulcerative colitis is characterized by depleted goblet cells and a reduced mucus layer, whereas goblet cells and the mucus layer are increased in the other major inflammatory bowel disease, Crohnâs disease. Methods and Findings; By murine N-ethyl-N-nitrosourea-mutagenesis we identified two distinct non-complementing missense mutations in Muc2 exons encoding N- and C-terminal homo-oligomerization domains causing an ulcerative colitis-like phenotype. Both strains developed mild spontaneous distal intestinal inflammation, chronic diarrhea, rectal bleeding and prolapse, increased susceptibility to acute and chronic colitis induced by a luminal toxin, aberrant Muc2 biosynthesis, smaller goblet cell thecae (less stored mucin) and a diminished mucus barrier. Enhanced local production of IL-1beta, TNF-alpha and IFN-gamma was seen in the distal colon. The number of leukocytes within mesenteric lymph nodes was increased five-fold and leukocytes cultured in vitro produced both Th1 and Th2 cytokines (IFN-gamma, TNF-alpha and IL-13). Intestinal permeability was increased and the luminal bacterial flora were more heavily coated with immunoglobulin as occurs in IBD. This pathology was accompanied by accumulation of the Muc2 precursor and ultrastructural and biochemical evidence of endoplasmic reticulum (ER) stress in goblet cells, activation of the unfolded protein response, and altered intestinal expression of genes involved in ER stress, inflammation, apoptosis and wound repair. Expression of mutated Muc2 oligomerization domains in vitro demonstrated that aberrant Muc2 oligomerization underlies the ER stress. These models show that mutations in Muc2 oligomerization domains can lead to aberrant assembly of the Muc2 complex leading to ER stress, a depleted mucus barrier and intestinal inflammation. In ulcerative colitis we demonstrate similar accumulation of non-glycosylated MUC2 precursor in goblet cells together with ultrastructural and biochemical evidence of ER stress even in non-inflamed intestinal tissue. Conclusions; The observations that mucin misfolding and ER stress lead directly to intestinal inflammation and that ER stress and goblet cell pathology occur in ulcerative colitis suggest that ER stress-related mucin depletion could be a fundamental component of the pathogenesis of colitis. Experiment Overall Design: 3 individual mice from the Eeyore, Winnie or Wild-type strains were compared as groups. An Affymetrix ID was compared between groups if the ID was Present within two of the three mice within each grouping. IDs were compared by calculating the log2 of Group One average signal divided by Group 2 average signal.
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