Inflammatory bowel disease risk loci overlap with DNA regulatory regions in immune cells and intestinal epithelium
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ABSTRACT: Background & Aims: The contribution of genetics to the pathogenesis of inflammatory bowel disease (IBD) has been established by twin studies, targeted sequencing and genome-wide association studies (GWASs). This has yielded a plethora of risk loci with an aim to identify causal variants. Research on the genetic components of IBD has mainly focused on protein coding genes, thereby omitting other functional elements in the human genome i.e. the regulatory regions. Methods: Using acetylated histone 3 lysine 27 (H3K27ac) chromatin immunoprecipitation and sequencing (ChIP-seq), we identified tens of thousands of potential regulatory regions that are active in intestinal epithelium and immune cells, the main cell types involved in IBD. We correlated these regions with susceptibility loci for IBD. Results: We show that 45 out of 163 single nucleotide polymorphisms (SNPs) associated with IBD co-localize with active regulatory elements. In addition, another 47 IBD associated SNPs co-localize with active regulatory element via other SNP in strong linkage disequilibrium. Altogether 92 out of 163 IBD-associated SNPs can be connected with distinct regulatory element. This is 2.5 to 3.5 times more frequent than expected from random sampling. The genomic variation in these SNPs often creates or disrupts known binding motifs - thereby possibly affecting the binding affinity of transcriptional regulators and altering the expression of regulated genes. Conclusions: We show that in addition to protein coding genes, non-coding DNA regulatory regions, active in immune cells and in intestinal epithelium, are involved in IBD. H3K27ac ChIP-seq (ab4729, Abcam) profile of 7 intestinal epithelial samples
Project description:Background & Aims: The contribution of genetics to the pathogenesis of inflammatory bowel disease (IBD) has been established by twin studies, targeted sequencing and genome-wide association studies (GWASs). This has yielded a plethora of risk loci with an aim to identify causal variants. Research on the genetic components of IBD has mainly focused on protein coding genes, thereby omitting other functional elements in the human genome i.e. the regulatory regions. Methods: Using acetylated histone 3 lysine 27 (H3K27ac) chromatin immunoprecipitation and sequencing (ChIP-seq), we identified tens of thousands of potential regulatory regions that are active in intestinal epithelium and immune cells, the main cell types involved in IBD. We correlated these regions with susceptibility loci for IBD. Results: We show that 45 out of 163 single nucleotide polymorphisms (SNPs) associated with IBD co-localize with active regulatory elements. In addition, another 47 IBD associated SNPs co-localize with active regulatory element via other SNP in strong linkage disequilibrium. Altogether 92 out of 163 IBD-associated SNPs can be connected with distinct regulatory element. This is 2.5 to 3.5 times more frequent than expected from random sampling. The genomic variation in these SNPs often creates or disrupts known binding motifs - thereby possibly affecting the binding affinity of transcriptional regulators and altering the expression of regulated genes. Conclusions: We show that in addition to protein coding genes, non-coding DNA regulatory regions, active in immune cells and in intestinal epithelium, are involved in IBD.
Project description:Patient-derived intestinal organoids provide an excellent tool to unravel mechanisms underlying ulcerative colitis (UC). Fresh biopsies, to isolate crypts and culture organoids, were obtained from both inflamed and non-inflamed regions from eight patients with active UC (Mayo endoscopic subscore ≥2), and from eight non-IBD controls.To address the inflammatory character of ex vivo organoids, we compared the transcriptome of biopsies, crypts and organoids derived from inflamed, and non-inflamed regions and aimed to (re-)induce inflammation ex vivo.
Project description:We purified the intestinal epithelial cells from biopsies taken from the ileum and colon of a paediatric cohort of IBD patients and healthy controls
Project description:Our study represents the first detailed analysis of the transcriptional and alternative splicing landscape of intestinal organoids undergoing stress, with biologic replicates, generated by RNA-seq technology. We report significant changes in the expression of genes involved in inflammation, proliferation and transcription, among others. Splicing events commonly regulated by both stresses affected genes regulating splicing and were associated with nonsense-mediated decay (NMD), suggesting that splicing is modulated by an auto-regulatory feedback loop during stress. Murine intestinal organoids were stimulated in triplicate with conditions for either ER stress or nutrient starvation and RNA-seq was conducted to analyze global changes in both gene expression at the transcriptional level and alternative splicing
Project description:Inflammatory bowel disease (IBD) is a common and chronic gut disorder, with two subtypes: Crohn's disease (CD) and ulcerative colitis (UC), which are challenging to diagnose. The molecular pathology IBD is not well understood, and the underlying gene regulatory regions have not been comprehensively investigated. Relatedly, most IBD-associated SNPs are located in non-coding regions, and may effect gene regulation. Here, we profiled genome-wide promoter and enhancer activity in the descending colon of IBD patients. IBD-induced enhancer and promoters are highly enriched for IBD-associated SNPs, and can predict IBD diagnosis with an accuracy of 85% in an external cohort.
Project description:In order to unravel the impact of intestinal smooth muscle tissue on the intestinal epithelium, we isolated clean smooth muscle, cultured it for 24h in DMEM-F12, and collected the supernatant (muscle-SN). This supernatant was used to treat small intestinal organoids (made of intestinal epithelium), compared to normal ENR treatment. After 5 days of muscle-SN exposure, we disrupted the organoids, and directly isolate the RNA. RNA-seq was performed in this sample to assess the genetic changes induced by muscle products.
Project description:We aimed to investigate gene expression changes in intestinal organoids from different mouse genotypes after treatment with interferon-gamma. Wild-type, villinCreER;KrasG12D/+;Trp53fl/flRosa26N1icd/+ (KPN), and villinCreER;Apcfl/fl;KrasG12D/+;Trp53fl/flTgfbrIfl/fl (AKPT) intestinal organoids were plated, and the media was supplemented with 1 ng/mL of recombinant mouse interferon-gamma protein on Day 3. RNA was collected 24h later and processed for RNA sequencing.
Project description:We aimed to investigate gene expression changes in intestinal organoids from different mouse genotypes after treatment with TGF-beta. Wild-type, villinCreER;KrasG12D/+;Trp53fl/flRosa26N1icd/+ (KPN), and villinCreER;Apcfl/fl;KrasG12D/+;Trp53fl/flTgfbrIfl/fl (AKPT) intestinal organoids were plated, and the media was supplemented with 5ng/mL of recombinant mouse TGFß1 protein on Day 3. RNA was collected 24h later and processed for RNA sequencing.
Project description:Background: Genome wide association studies (GWASs) have revealed many susceptibility loci for complex genetic diseases. For most loci the causal genes have not been identified. The identification of candidate genes is currently mainly based genes that localize close to or within the identified loci. We have recently shown that 92 of the 163 Inflammatory Bowel Disease (IBD)-loci co-localize with noncoding DNA regulatory elements (DRE). Mutations in DRE can contribute to the pathogenesis of IBD through dysregulation of gene expression. Consequently, genes that are regulated by these 92 DRE are to be considered as candidate genes. We developed a novel approach for candidate gene identification that is based on DNA regulatory mechanisms.Results: By using circular chromosome conformation capture-sequencing (4C-seq), we have identified genomic regions that physically interact with the 92 DRE that were found at IBD susceptibility loci. Since the activity of regulatory elements is cell type specific, 4C-seq was performed in monocytes, lymphocytes and intestinal epithelial cells. Altogether, we identified 902 novel IBD candidate genes. These genes include genes specific for one of the IBD subtypes and many noteworthy genes like ATG9A and IL10RA. We show that the expression of many novel candidate genes is genotype dependent and that these genes are upregulated during intestinal inflammation in IBD. Pathway analyses further identified HNF4α as a potential key upstream regulator of the IBD candidate genes.Conclusions: In this study, 4C-seq is used to systematically analyze chromatin interactions at IBD susceptibility loci that localize to regulatory DNA We reveal many novel and relevant IBD candidate genes, pathways and regulators. Our approach complements classical candidate gene identification, links novel genes to IBD and can be applied to any existing GWAS data.
Project description:Commensal microbiota contribute to gut homeostasis and influence gene expression. Intestinal organoid culture closely represent intestinal epithelium and retain intestinal stem cells and dynamic recovery capabilities as well as all major cell types of the intestinal epithelium. We established organoid culture using colon crypts isolated from germ-free (GF), and gnotobiotic mice monocolonized either with the E.coli strain O6K13 (O) or Nissle 1917 strain (N). The expression profiles of these organoids were compared to the organoid culture isolated from conventionally reared (CR) mice in order to disclose genes differentially expressed in response to the change in the intestinal microflora composition.