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:Suspended animation (e.g. hibernation, diapause) allows organisms to survive extreme environments. But the mechanisms underlying the evolution of suspended animation states are unknown. The African turquoise killifish has evolved diapause as a form of suspended development to survive the complete drought that occurs every summer. Here, we show that gene duplicates – paralogs – exhibit specialized expression in diapause compared to normal development in the African turquoise killifish. Surprisingly, paralogs with specialized expression in diapause are evolutionarily very ancient and are present even in vertebrates that do not exhibit diapause. To determine if evolution of diapause is due to the regulatory landscape rewiring at ancient paralogs, we assessed chromatin accessibility genome-wide in fish species with or without diapause. This analysis revealed an evolutionary recent increase in chromatin accessibility at very ancient paralogs in African turquoise killifish. The increase in chromatin accessibility is linked to the presence of new binding sites for transcription factors, likely due to de novo mutations and transposable element (TE) insertion. Interestingly, accessible chromatin regions in diapause are enriched for lipid metabolism genes, and our lipidomics studies uncover a striking difference in lipid species in African turquoise killifish diapause, which could be critical for long-term survival. Together, our results show that diapause likely originated by repurposing pre-existing gene programs via recent changes in the regulatory landscape. This work raises the possibility that suspended animation programs could be reactivated in other species for long-term preservation via transcription factor remodeling and suggests a mechanism for how complex adaptations evolve in nature.
Project description:Inappropriate cross talk between mammals and their gut microbiota may trigger intestinal inflammation and drive extra-intestinal immune-mediated diseases. Studies with germ-free or gnotobiotic animals represent the gold standard for research on bacterial-host interaction but they are not readily accessible to the wide scientific community. We aimed at refining a protocol that in a robust manner would deplete murine intestinal microbiota and prove to have significant biologic validity. Previously published protocols for depleting mice of their intestinal microbiota by administering broad-spectrum antibiotics in drinking water were difficult to reproduce. We show that twice daily delivery of antibiotics by gavage depleted mice of their cultivable fecal microbiota and reduced the fecal bacterial DNA load by approximately 400 fold while ensuring the animals’ health. Mice subjected to the protocol for 17 days displayed enlarged ceca, reduced Peyer’s patches and small spleens. Antibiotic treatment significantly reduced the expression of antimicrobial factors and altered the expression of 517 genes in total in the colonic epithelium. Genes involved in cell cycle were significantly altered concomitant with reduced epithelial proliferative activity in situ assessed by Ki-67 expression, suggesting that commensal microbiota drives cellular proliferation in colonic epithelium. We present a robust protocol for depleting mice of their cultivatable intestinal microbiota with antibiotics by gavage and show that the biological effect of this depletion is phenotypic characteristics and epithelial gene expression profile similar to those of germ-free mice. Comparison of genome-wide gene expression of colon intestinal epithelial cells from mice subjected to microbiota depletion protocol against to control mice.
Project description:Intestinal Foxp3+ regulatory T cell (Treg) subsets are crucial players for tolerance towards microbiota-derived and food-borne antigens, and compelling evidence suggests that intestinal microbiota modulate their differentiation and maintenance. Selected bacterial species and microbiota-derived metabolites such as short-chain fatty acids (SCFAs) have been reported to foster Treg homeostasis in the intestinal lamina propria. Furthermore, gut-draining mesenteric lymph nodes (mLNs) are particularly efficient sites of de novo Treg induction, and we could previously show that mLN stromal cells contribute to this process. Yet, it is not fully elucidated which direct role microbiota and their metabolites play for the early stages of de novo Treg induction and in shaping the Treg transcriptome already during the initial priming within mLNs. Here, we show that neither dysbiotic microbiota nor dietary SCFA supplementation impact de novo induction of Foxp3+ Tregs within mLNs. Even mice housed under germ-free (GF) conditions displayed equivalent frequencies of de novo induced Foxp3+ Tregs within mLNs. Further dissection of the accessible chromatin and transcriptome revealed that microbiota indeed have a limited impact on fostering the establishment of peripherally induced Tregs and do not contribute to the initialization of the epigenetic landscape for an extensive Treg signature. Viewed as a whole, our data suggest that microbiota are dispensable for the early stages of de novo Treg induction within mLNs, while being required to foster further Treg differentiation and homeostasis at later stages within the intestinal lamina propria.
Project description:Abdominal and pelvic radiotherapy (RT) reduces the renewal capacity of the epithelium. Rectal biopsies obtained from patients receiving pelvic RT have revealed atrophy of surface epithelium, acute cryptitis, crypt abscesses, crypt distortion and atrophy, and stromal inflammation. Modifications in intestinal microbiota, such as an increase in the number of pathogens, may contribute to intestinal injury. The prebiotic effect of a carbohydrate is assessed by its capacity to stimulate the proliferation of healthy bacteria (Bifidobacterium, Lactobacillus) rather than pathogenic bacteria (Clostridium, E. coli).
The hypothesis of the study is that a mixture of inulin and fructooligosaccharide could modulate Lactobacillus and Bifidobacterium and reduce the intestinal injury in patients affected of gynaecological cancer and treated with abdominal radiotherapy.
Project description:Intestinal Foxp3+ regulatory T cell (Treg) subsets are crucial players in tolerance to microbiota-derived and food-borne antigens, and compelling evidence suggests that the intestinal microbiota modulates their generation, functional specialization, and maintenance. Selected bacterial species and microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), have been reported to promote Treg homeostasis in the intestinal lamina propria. Furthermore, gut-draining mesenteric lymph nodes (mLNs) are particularly efficient sites for the generation of peripherally induced Tregs (pTregs). Despite this knowledge, the direct role of the microbiota and their metabolites in the early stages of pTreg induction within mLNs is not fully elucidated. Here, using an adoptive transfer-based pTreg induction system, we demonstrate that neither transfer of a dysbiotic microbiota nor dietary SCFA supplementation modulated the pTreg induction capacity of mLNs. Even mice housed under germ-free (GF) conditions displayed equivalent pTreg induction within mLNs. Further molecular characterization of these de novo induced pTregs from mLNs by dissection of their transcriptomes and accessible chromatin regions revealed that the microbiota indeed has a limited impact and does not contribute to the initialization of the Treg-specific epigenetic landscape. Overall, our data suggest that the microbiota is dispensable for the early stages of pTreg induction within mLNs.
Project description:The TET-family enzymes (TETs) convert methylcytosine to hydroxymethylcytosine, a lately discovered epigenetic modification that can modulate transcription. While recent reports suggest that TETs may play a role in response to oxidative stress, this role remains uncertain. Here we show that Tet1 is sensitive to peroxide and report a global decrease in hydroxymethylcytosine in cells treated with BSO and in the intestinal epithelium of mice lacking the major antioxidant enzymes glutathione peroxidases 1 and 2. Furthermore, genome-wide profiling revealed differentially hydroxymethylated regions in genes involved in responses to oxidative stress. Intriguingly, a considerable proportion of these regions lie in genes encoding microRNAs predicted to target transcripts involved in oxidative stress response. This work thus demonstrates a profound effect of oxidative stress on the hydroxymethylome and opens exciting new avenues of research by highlighting a set of microRNAs that may participate in the prevention or etiology of oxidative-stress-related diseases. Examination of DNA hydroxymethylation landscape in SY5Y cell lines and in intestinal epithelium of mice.
Project description:Inappropriate cross talk between mammals and their gut microbiota may trigger intestinal inflammation and drive extra-intestinal immune-mediated diseases. Studies with germ-free or gnotobiotic animals represent the gold standard for research on bacterial-host interaction but they are not readily accessible to the wide scientific community. We aimed at refining a protocol that in a robust manner would deplete murine intestinal microbiota and prove to have significant biologic validity. Previously published protocols for depleting mice of their intestinal microbiota by administering broad-spectrum antibiotics in drinking water were difficult to reproduce. We show that twice daily delivery of antibiotics by gavage depleted mice of their cultivable fecal microbiota and reduced the fecal bacterial DNA load by approximately 400 fold while ensuring the animals’ health. Mice subjected to the protocol for 17 days displayed enlarged ceca, reduced Peyer’s patches and small spleens. Antibiotic treatment significantly reduced the expression of antimicrobial factors and altered the expression of 517 genes in total in the colonic epithelium. Genes involved in cell cycle were significantly altered concomitant with reduced epithelial proliferative activity in situ assessed by Ki-67 expression, suggesting that commensal microbiota drives cellular proliferation in colonic epithelium. We present a robust protocol for depleting mice of their cultivatable intestinal microbiota with antibiotics by gavage and show that the biological effect of this depletion is phenotypic characteristics and epithelial gene expression profile similar to those of germ-free mice.
Project description:To assess the role of LSD1 in mouse small intestinal epithelium, we grew small intestinal organoids in vitro from mice with an epithelial specific deletion of LSD1 (Villin-Cre+; Lsd1f/f) and from wild type (Villin-Cre-; Lsd1f/f) mice. This experiment uses a new Cre strain with 100% recombination efficiency. Similar to intestinal epithelium from mice with an intestinal epithelium specific LSD1-KO, Paneth cells are not present in LSD1-KO small intestinal organoids. We used these sequencing data to show intrinsic epithelial changes in the intestinal epithelium caused by LSD1 deletion in the absence of microbiota and surrounding in vivo cell types.