Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcriptome analysis of Brg1 deficient small intestinal epithelium in the context of normal and aberrant Wnt signalling

ABSTRACT: 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.

ORGANISM(S): Mus musculus

SUBMITTER: Aliaksei Holik

PROVIDER: E-GEOD-46129 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Wnt signaling maintains the undifferentiated state of intestinal crypt progenitor cells by inducing the formation of nuclear TCF4/beta-catenin complexes. In colorectal cancer, activating mutations in Wnt pathway components cause inappropriate activation of TCF4/beta-catenin -driven transcription. Despite the passage of a decade after the discovery of TCF4 and beta-catenin as the molecular effectors of the Wnt signal, few transcriptional activators essential and unique to the regulation of this transcription program have been found. Methodology/Principal Findings: Using proteomics, we identified the leukemia-associated Mllt10/Af10 and the methyltransferase Dot1l, as Tcf4/beta-catenin interactors in mouse small intestinal crypts. Mllt10/Af10-Dot1l, essential for transcription elongation, are recruited to Wnt target genes in a beta-catenin -dependent manner, resulting in H3K79 methylation over their coding regions in vivo in proliferative crypts of mouse small intestine, in colorectal cancer and Wnt-inducible HEK293T cells. Depletion of MLLT10/AF10 in colorectal cancer and Wnt-inducible HEK293T cells followed by expression array analysis identifies MLLT10/AF10 and DOT1L as essential activators dedicated to Wnt target gene regulation. In contrast, previously published b-catenin coactivators p300 and beta-catenin displayed a more pleiotropic target gene expression profile controlling Wnt and other pathways. tcf4, mllt10/af10 and dot1l are co-expressed in Wnt-driven tissues in zebrafish and essential for Wnt-reporter activity. Intestinal differentiation defects in apc-mutant zebrafish can be rescued by depletion of Mllt10 and Dot1l, establishing these genes as activators downstream of Apc in Wnt target gene activation in vivo. Morpholino-depletion of mllt10/af10-dot1l in zebrafish results in defects in intestinal homeostasis and a significant reduction in the in vivo expression of direct Wnt target genes and in the number of proliferative intestinal epithelial cells. Conclusions/Significance: We conclude that Mllt10/Af10-Dot1l are essential, dedicated activators of Wnt-dependent transcription, critical for maintenance of intestinal proliferation and homeostasis. The methyltransferase Dot1l may present an attractive candidate for drug targeting in colorectal cancer. 6 samples for Ls174T cells: si-b-catenin against si-control and dyeswap of it, si-control, si-MLLT10, si-BRG1 and si-P300 are hybridized against common reference RNA; 6 samples of HEK293T cells: Wnt3A or control medium (CM) induction for 9 hours, si-MLLT10, si-DOT1L, si-BRG1 and si-P300 upon 9 hour Wnt3A induction are all hybridized against common reference RNA

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Transcriptome analysis of Brg1 deficient small intestinal epithelium in the context of normal and aberrant Wnt signalling

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