Project description:Drosophila melanogaster was used to investigate the influence of microbiota-derived intestinal flora and its metabolites on host transcriptional regulation by adding sodium butyrate to a sterile diet for constructing a sterile Drosophila model. In order to further investigate the effects of sodium butyrate on Drosophila melanogaster at the molecular mechanism level, we detected the abundance and composition of midgut microbial colonies based on 16S rRNA gene sequences, and analyzed the overall structure and metabolic activities of host transcriptional networks by combining transcriptome and non-target metabolomics data.
Project description:Proteases constitute the largest enzyme gene family in vertebrates with intracellular and secreted proteases having critical roles in cellular and organ physiology. Intestinal tract contains diverse set of proteases mediating digestion, microbial responses, epithelial and immune signaling. Transit of chyme through the intestinal tract results in significant suppression of proteases. Although endogenous protease inhibitors have been identified, the broader mechanisms underlying protease regulation in the intestinal tract remains unclear. The objective of this study was to determine microbial regulation of proteolytic activity in intestinal tract using phenotype of post-infection irritable bowel syndrome, a condition characterized by high fecal proteolytic activity. Proteases of host pancreatic origin (chymotrypsin like pancreatic elastase 2A, 3B and trypsin 2) drove proteolytic activity. Of the 14 differentially abundant taxa, high proteolytic activity state was characterized by complete absence of the commensal Alistipes putredinis. Germ free mice had very high proteolytic activity (10-fold of specific-pathogen free mice) which dropped significantly upon humanization with microbiota from healthy volunteers. In contrast, high proteolytic activity microbiota failed to inhibit it, a defect that corrected with fecal microbiota transplant as well as addition of A. putredinis. These mice also had increased intestinal permeability similar to that seen in patients. Microbiota β-glucuronidases mediate bilirubin deconjugation and unconjugated bilirubin is an inhibitor of serine proteases. We found that high proteolytic activity patients had lower urobilinogen levels, a product of bilirubin deconjugation. Mice colonized with β-glucuronidase overexpressing E. coli demonstrated significant inhibition of proteolytic activity and treatment with β-glucuronidase inhibitors increased it. The findings establish that specific commensal microbiota mediates effective inhibition of host pancreatic proteases and maintains intestinal barrier function through the production of β-glucuronidases. This suggests an important homeostatic role for commensal intestinal microbiota.
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:Bulk RNAseq from whole adult Drosophila melanogaster guts expressing either mCherry-RNAi (control) or RNAi against ChAT (Choline acteyltransferase) under control of a enteroendocrine-specific driver to assess the role of epithelial acetylcholine production in intestinal barrier function.
Project description:Although much research has been done on the diversity of gut microbiome, little is known about the way it influences intestinal homeostasis under normal and pathogenic conditions. Epigenetic mechanisms have recently been suggested as operating at the interface between the microbiota and the intestinal epithelium cells (IECs). Using genome-wide analyses, we discovered that exposure to microbiota induced both global DNA hypomethylation and localized changes at regulatory elements, which culminates in activation of a set of “early sentinel” response genes that play a role in maintaining gut homeostasis. Furthermore, we demonstrated that exposure to microbiota in acute inflammation results in profound DNA methylation and chromatin accessibility changes at regulatory elements leading to alterations in the gene expression program in colitis and colon cancer. Our studies add a new dimension to our understanding of the cross talk between the microbiota and IECs, and provide the foundation for how microbiota impact epigenetic programming.
Project description:Primary bile acids are produced in the liver whereas secondary bile acids such as lithocholic acid (LCA) are generated by gut bacteria from primary bile acids that escape the ileal absorption. Besides their well-known function as detergents in lipid digestion, bile acids are important signaling molecules mediating effects on the host’s metabolism. As energy metabolism is closely linked to aging and longevity we supplemented fruit flies (Drosophila melanogaster) with 50 µmol/l LCA either for 30 days or throughout their lifetime. LCA supplementation resulted in a significant induction of the mean (+12 days), median (+10 days) and maximum lifespan (+ 11 days) in comparison to untreated control flies. This lifespan extension was accompanied by an induction of spargel (srl), the fly homolog of mammalian PPARG co-activator 1a(PGC1A. In srl mutant flies, LCA failed to induce longevity emphasizing the essential role of srl in the observed lifespan extension. In addition, the administration of antibiotics to wild type flies abrogated LCA-mediated effects on both lifespan and srl expression, suggesting a substantial contribution of the intestinal microbiota to the LCA-induced longevity. In the present study, we show that the secondary bile acid LCA significantly induced the mean, the median and the maximum survival in Drosophila melanogaster. Our data suggest that besides an up-regulation of the PGC1a-homolog srl unidentified alterations in the structure or metabolism of gut microbiota contribute to the longevity effect of LCA.