Colon O-glycosylated mucus in the homeostasis of microbiota and host

Oklahoma Medical Research Foundation, Oklahoma City OK

Investigators

Linked publications & trials

Abstract

Over the past 15 years, our studies have established O-glycans as crucial components of the colonic mucus barrier. Our recent publication demonstrates that the colon mucus is mainly formed from secretion of O-glycosylated Muc2 by goblet cells (GCs) in the proximal colon, where it encapsulates the fecal materials including the microbiota. These findings represent a paradigm shift from the current model of the colon mucus system and provide new insights into host and microbiota symbiosis. However, whether the proximal colon contains a distinct subset of goblet cells (pGCs), and the significance of proximal colon-derived mucus in inflammatory bowel disease is unstudied. To address these questions, in our preliminary studies, we created a new surgical model in mice named cecal- distal colonic anastomosis (CDA) with removal of the proximal colon. Our preliminary data showed CDA mice exhibited impaired mucus layer and developed spontaneous albeit modest inflammation in the distal colon, highlighting the physiological importance of the pGC-derived mucus for whole colon homeostasis. In parallel, we have adopted study of the neo-colon mucosa created by ileal pouch-anal anastomosis (IPAA) in ulcerative colitis patients and its intermittent acquisition of inflammation (pouchitis) as a human “cellular observatory”. Our preliminary data demonstrated the feasibility of mucus characterization, single cell molecular methods, and cohort genetic variation analytic methods in this model, to determine cell biologic and genetic contributions to gut homeostasis. Built on these preliminary data and the importance of the proximal colon-derived mucus we recently discovered, we hypothesize that loss of pGC diversity and plasticity contribute to defective colon homeostasis and inflammation. We propose two Aims to test the hypothesis: Aim 1 is to determine how proximal colon-derived mucus governs the colonic mucus barrier function. We will determine the unique cellular and molecular identity of the pGCs through single- cell RNA sequencing, MERFISH spatial transcriptomics, glycomics, and functional analysis. We’ll also use the CDA model to determine how lack of pGCs affects colon mucus function and the plasticity of the GCs in the distal colon. Aim 2 is to identify human genes involved in GC programming and mucus production and their relation to inflammatory bowel disease phenotypes. The ileal neo-colon created by IPAA in at-risk patients offers a temporal cellular observatory of the initially unaffected ileal neo-colon, as adaption of mucosal GCs heterogeneity and plasticity ensues with perturbations of inflammation and altered microbiome community states. We will conduct biopsy-based single-cell RNA and chromatin analysis of GCs populations in the pouch mucosa as it adapts to inflammatory and microbiome changes. We will also test for gene variants affecting this adaption by IPAA cohort genomic association analysis. Successful completion of the project will 1) establish that pGCs are a unique subset of mucus secretion cells; 2) demonstrate the importance of proximal colon-derived mucus in maintaining homeostasis between microbiota and host mucosa; and 3) provide new insights into the pathogenesis of inflammatory bowel disease such as pouchitis, which may lead to new diagnostic and/or therapeutic options.