Project description:A striking example of the intricate interplay between diet, microbiota, and host is the effect of inulin, a dietary fiber, on the intestinal epithelium. Ingestion of inulin triggers a wide range of epithelial effects in the colon, such as enhanced proliferation, increased production of mucus and antimicrobial peptides, as well as systemic effects on host metabolism and immune function that are dependent on microbiota-derived molecules. In this study, we investigated the impact of inulin on two critical aspects of diet-microbiota-host interactions: intestinal hypoxia and the modulation of hypoxia-inducible factor (HIF)-1 signaling in intestinal epithelial cells (IECs) in mice colon. To achieve this, we employed a multilayered and multi-omics approach, including dietary interventions, in vitro analysis using intestinal organoids, and both genetic and pharmacological interventions. We found that inulin intake enhances intestinal hypoxia, resulting in the stabilization of HIF-1 in IECs, an effect that is both microbiota- and host-dependent. Our study revealed that HIF-1 plays a key role in regulating IEC proliferation and intestinal stem cell (ISC) function. These changes are associated with HIF-1-dependent metabolic alterations in IECs. Our findings uncover a novel mechanism by which HIF-1 acts in the colon: it acts as a molecular brake, modulating cell proliferation in a microbiota-dependent manner and through metabolic reprogramming, highlighting the complexity of the diet-microbiota-host interactions in the gut.
Project description:We profiled transcriptome and accessible chromatin landscapes in intestinal epithelial cells (IECs) from mice reared in the presence or absence of microbiota. We show that regional differences in gene transcription along the intestinal tract were accompanied by major alterations in chromatin organization. Surprisingly, we discovered that microbiota modify host gene transcription in IECs without significantly impacting the accessible chromatin landscape. Instead, microbiota regulation of host gene transcription might be achieved by differential expression of specific TFs and enrichment of their binding sites in nucleosome depleted CRRs near target genes. Our results suggest that the chromatin landscape in IECs is pre-programmed by the host in a region-specific manner to permit responses to microbiota through binding of open CRRs by specific TFs. mRNA and accessible chromatin (DNase-seq) profiles from colonic and ileal IECs were compared between conventionally-raised (CR), germ-free (GF), and conventionalized (CV) C57BL/6 mice.
Project description:We profiled transcriptome and accessible chromatin landscapes in intestinal epithelial cells (IECs) from mice reared in the presence or absence of microbiota. We show that regional differences in gene transcription along the intestinal tract were accompanied by major alterations in chromatin organization. Surprisingly, we discovered that microbiota modify host gene transcription in IECs without significantly impacting the accessible chromatin landscape. Instead, microbiota regulation of host gene transcription might be achieved by differential expression of specific TFs and enrichment of their binding sites in nucleosome depleted CRRs near target genes. Our results suggest that the chromatin landscape in IECs is pre-programmed by the host in a region-specific manner to permit responses to microbiota through binding of open CRRs by specific TFs.
Project description:Remodeling of the gut microbiota is implicated in various metabolic and inflammatory diseases of the gastrointestinal tract. We hypothesized that the gut microbiota affects the DNA methylation profile of intestinal epithelial cells (IECs) which could, in turn, alter intestinal function. Here, we used mass spectrometry and methylated DNA capture to respectively investigate global and genome-wide DNA methylation of intestinal epithelial cells from germ-free (GF) and conventionally raised mice (CONV-R). In colonic IECs from GF mice, DNA was markedly hypermethylated. This was associated with a dramatic loss of Ten-Eleven-Translocation activity, a lower DNA methyltransferase activity and lower circulating levels of the one carbon metabolites cobalamin and folate. At the gene level, we found an enrichment for differentially methylated regions at proximity of genes regulating cytotoxicity of Natural Killer cells (FDR < 8.9E-6), notably members of the natural killer group 2 member D ligand superfamily Raet. Our results suggest that altered activity of methylation-modifying enzymes in GF mice influences the IEC epigenome at genes involved in the crosstalk between intestinal and immune cells. Epigenetic reprogramming of IECs by the gut microbiota may modulate intestinal function in diseases associated with altered gut microbiota.
Project description:Posttranslational modifications (PTMs) on histone proteins are a key source of regulation on chromatin through impacting genome organization and important cellular processes, including gene expression. These PTMs often arise from small metabolites and are thus impacted by cellular metabolism and environmental cues. One such class of metabolically regulated PTMs are histone acylations, which include histone acetylation, along with butyrylation, crotonylation, and propionylation. We asked whether histone acylations of intestinal epithelial cells (IECs) are regulated through the availability of short chain fatty acids (SCFAs), which are generated by the commensal microbiota in the intestinal lumen. We identified specific sites of butyrylation and propionylation on lysine 9 and 27 on histone H3. We demonstrate that these acylations are regulated by the microbiota, whereas histone butyrylation is additionally regulated by the metabolite tributyrin. Furthermore, we also identify tributyrin-regulated gene programs that correlate with histone butyrylation and demonstrate that histone butyrylation (H3K27bu) is associated with active gene regulatory elements and levels of gene expression. Together, our observations demonstrate a physiological setting in which previously uncharacterized histone acylations are dynamically regulated and associated with gene expression.
Project description:Intestinal epithelial cells (IEC) express large amounts of major histocompatibility complex II (MHCII) molecules. Despite this long-appreciated observation, the function of epithelial MHCII-mediated signaling on gut homeostasis remains enigmatic. As IECs serve as the primary cellular barrier between intestinal microbes and underlying host immune cells, we reasoned that IEC-intrinsic antigen presentation may play a role in tolerogenic responses towards the microbiota. Mice with an IEC-intrinsic defect in MHCII expression (IECΔMHCII) develop elevated T cell-dependent IgA responses, but a reduction in microbiota responsive regulatory T cells (Tregs). Despite elevated IgA levels in IECΔMHCII mice, immunoglobulin repertoires exhibit less selection and IgA has reduced reactivity to the microbiota, which is associated with increased inter-individual variability in microbiota composition. Consistent with reductions in microbiota-responsive Tregs, IECΔMHCII mice develop worsened colitis. A striking difference observed in the absence of IEC-MHCII is that while transcription of MHCII is similar, underlying mononuclear phagocytes had reduced surface MHCII. Macrophages were found to be capable of acquiring MHCII molecules from IECs, and macrophages isolated from IECΔMHCII mice had decreased capacity to stimulate Treg development. Thus, epithelial-myeloid interactions govern development of adaptive responses to microbial antigens within the gastrointestinal tract.