Inherited defect in ST6GalNAc1 reveals roles of sialylation in intestinal homeostasis

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. Integrated analysis of RNA-seq and ATAC-seq data from Wild-type and St6galnac1 intestinal epithelial cells.