Project description:Brg1 has been reported to act as a trans-activator for the Wnt pathway by interacting with beta-catenin. Given this interaction and the crucial role Wnt signalling plays in the intestinal homeostasis, we aimed to investigate the effect of Brg1 loss on gene expression in normal and Wnt activated small intestinal epithelium. We used VillinCreERT2 Cre recombinase and loxP targeted allels of Brg1 and Apc to generate 4 cohorts of conditional knock-out mice: Cre-negative controls (n=4), Brg1 deficient (n=4), Apc deficient (n=3) and double Brg1-Apc deficient (n=4). All mice were induced by 4x80mg/kg daily injections of Tamoxifen. Epithelium enriched (gut scrapes) samples of small intestine (jejunum) were collected at day 4 post induction. Loss of Brg1 expression in the small intestinal epithelium at this time point was confirmed by immunohistochemistry.
Project description:Brg1 has been reported to act as a trans-activator for the Wnt pathway by interacting with beta-catenin. Given this interaction and the crucial role Wnt signalling plays in the intestinal homeostasis, we aimed to investigate the effect of Brg1 loss on gene expression in normal and Wnt activated small intestinal epithelium.
Project description:Chordin-like-2 (CHRDL2) is a secreted BMP antagonist, with overexpression and genomic variants associated with colorectal cancer (CRC) risk. BMP signalling in the normal intestinal epithelium operates in opposition to the WNT signalling pathway, which maintains stem-cells and self-renewal. Elevated WNT signalling leads to expansion of the stem cell compartment and hyperproliferation, defining characteristics of CRC. Here, we explored the impact of CHRDL2 overexpression on CRC cells to investigate whether CHRDL2's inhibition of BMP signalling intensified WNT signalling, and enhanced the cancer stem-cell phenotype. RNA-seq analysis revealed that CHRDL2 increased the expression of stem cell markers and well-established cancer-associated pathways. We suggest that CHRDL2 overexpression can augment the stem-cell potential of CRC and normal intestinal cells.
Project description:In the small intestine (SI), regionalisation enables sequential processing of food and nutrient absorption. To characterise the basis for region-specific mesenchymal-epithelial crosstalks during late small intestinal morphogenesis, we combined transcriptional profiling of epithelial and mesenchymal cell populations isolated from different intestinal regions with ChIP-seq, 3D imaging and functional ex vivo and organoid studies. We find that a mesenchymal PDGFRA-high population located in close proximity to the developing epithelium is enriched for genes involved in signalling and support the epithelium in a region-specific manner via the establishment of a proximal to distal gradient of epithelial Wnt activity. Furthermore, we provide evidence that Wnt signalling in the distal SI directly regulates epithelial expression of Sonic Hedgehog (SHH), which in turn acts on mesenchymal cells driving villi formation. Our results therefore uncover a mechanistic link between Wnt and Hedgehog signalling across different cellular compartments central for anterior-posterior regionalisation and correct organ formation.
Project description:The first step in the development of human colorectal cancer is the aberrant hyperactivation of the Wnt signaling pathway, predominantly caused by inactivating mutations in the adenomatous polyposis coli (Apc) gene encoding an essential tumor suppressor. The gene encoding transcriptional factor msh homeobox 1 (Msx1) displayed robust upregulation upon Apc inactivation in intestinal epithelium isolated in mice harboring the conditional allele of the Apc gene. To identify the gene signature in the small intestine upon Msx1 depletion, small intestinal epithelium from mice harboring conditional alleles of Apc and Msx1 was isolated and the gene expression profile was compared with control mice harboring the conditional allele of Apc only.
Project description:To determine the molecular regulation of ILC3s by Brg1, small intestinal ILC3s (Lin-Thy1highCD45low) from Brg1-deficient and control ILC3s were subjected to assay for transposase-accessible chromatin with high throughput sequencing (ATAC-seq).
Project description:The intestinal epithelium is our first line of defense against infections of the gut and the plasticity in cellular differentiation of the intestinal epithelium is an important part of this response. Here we sequenced the small intestinal epithelium from mice infected with Nippostrongylus brasiliensis to determine how the intestinal epithelium adapts in the context of an infection. By comparing these data to small intestinal organoids treated with cytokines (see related accessions) we determine that the intestinal epithelial response to N. brasiliensis infection correspond to a type II infection driven by IL-13.
Project description:Methylation of H3K79 is associated with chromatin at expressed genes, though it is unclear if this histone modification is required for transcription of all genes. Recent studies suggest that Wnt-responsive genes depend particularly on H3K79 methylation, which is catalyzed by the methyltransferase DOT1L. Human leukemias carrying MLL gene rearrangements show DOT1L-mediated H3K79 methylation and aberrant expression of leukemogenic genes. DOT1L inhibitors reverse these effects but their clinical use is potentially limited by toxicity in Wnt-dependent tissues such as intestinal epithelium. Genome-wide positioning of the H3K79me2 mark in Lgr5+ mouse intestinal stem cells and mature intestinal villus epithelium correlated with mRNA expression levels but not with Wnt-responsive genes per se. Selective Dot1l disruption in Lgr5+ stem cells or in all intestinal epithelial cells eliminated H3K79me2 from the respective compartments, allowing genetic evaluation of DOT1L requirements. Absence of methylated H3K79 did not impair health, intestinal homeostasis or expression of Wnt target genes in crypt epithelium for up to 4 months, despite increased crypt cell apoptosis. Global transcript profiles in Dot1l-null cells were barely altered. Thus, H3K79 methylation is not essential for transcription of Wnt-responsive or other intestinal genes and intestinal toxicity is not imperative when DOT1L is rendered inactive in vivo. Examination of differential gene expression between Dot1l control (Dot1 f/f) and Dot1l mutant (Villin-Cre, Dot1l f/f) villus cells.
Project description:Wnt pathway-driven proliferation and renewal of the intestinal epithelium must be tightly controlled to prevent development of cancer and barrier dysfunction. Although type 1 interferons (IFN) produced in the gut under influence of microbiota are known for their anti-proliferative effects, the role of these cytokines in regulating intestinal epithelial renewal is largely unknown. Here we report a novel role for IFN in the context of intestinal knockout of casein kinase 1α (CK1α), which controls ubiquitination and degradation of both β-catenin and the IFNAR1 chain of the IFN receptor. Ablation of CK1α leads to activation of both β-catenin and IFN pathway and prevents unlimited proliferation of intestinal epithelial cells despite constitutive β-catenin activity. IFN signaling contributes to activation of the p53 pathway and appearance of apoptotic and senescence markers in the CK1α-deficient gut. Concurrent genetic ablation of CK1α and IFNAR1 leads to intestinal hyperplasia, robust attenuation of apoptosis, and rapid and lethal loss of the barrier function. These data indicate that IFN plays an important role in controlling proliferation and function of intestinal epithelium in the context of β-catenin activation. Two conditions were examined, with 2 replicates for each condition, yielding 4 samples in total.
Project description:The aim of this experiment was to determine the contribution that components of the Wnt enhancesome (Bcl9/9l) make to Wnt driven intestinal transcriptional programmes in the context of normal intestinal homeostasis, or intestinal transformation driven by Apc depletion or B-catenin mutation.