Project description:Wnt signalling maintains the undifferentiated state of intestinal crypt/progenitor cells through the TCF4/Ã-catenin activating transcriptional complex. In colorectal cancer, activating mutations in Wnt pathway components lead to inappropriate activation of the TCF4/Ã-catenin transcriptional program and tumourigenesis in the gut epithelium. The mechanisms by which TCF4/Ã-catenin activate key target genes are not well understood. Using a proteomics approach, we identified Tnik, a member of the Germinal centre kinase family, as a Tcf4 interactor in the proliferative crypts of mouse small intestine. Tnik is recruited to promoters of Wnt target genes in mouse crypts and in Ls174T colorectal cancer cells in a Ã-catenin dependent manner. Depletion of TNIK and expression of TNIK kinase mutants abrogated TCF-LEF transcription, highlighting the essential role of the kinase activity in Wnt target gene activation. siRNA depletion of TNIK followed by expression array analysis demonstrated that TNIK is an essential and exclusive activator of Wnt induced transcriptional program. As an essential component in the TCF4/Ã-catenin activator complex, the kinase TNIK may present an attractive candidate for drug targeting in colorectal cancer. HEK293T cells: Wnt3A vs control medium (CM) induction for 4, 7 and 9 hours; si-TNIK vs si-control after Wnt3A induction at 4 and 7 hours (2 biological replicates for 7 hour time point); dyeswap for each experiment (i.e. 12 arrays in total).
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
Project description:To validate the suitability of two commonly used colorectal cancer cell lines, DLD1 and SW480, as model systems to study colorectal carcinogenesis, we treated these cell lines with beta-catenin siRNA and identified beta-catenin target genes using DNA microarrays. The list of identified target genes was compared to previously published beta-catenin target genes found in the PubMed and the GEO databases. Based on the large number of beta-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study beta-catenin regulated genes and signaling pathways 12 arrays (2 cell lines, 2 treatments, 3 biological replicates)
Project description:Wnt signalling maintains the undifferentiated state of intestinal crypt/progenitor cells through the TCF4/ß-catenin activating transcriptional complex. In colorectal cancer, activating mutations in Wnt pathway components lead to inappropriate activation of the TCF4/ß-catenin transcriptional program and tumourigenesis in the gut epithelium. The mechanisms by which TCF4/ß-catenin activate key target genes are not well understood. Using a proteomics approach, we identified Tnik, a member of the Germinal centre kinase family, as a Tcf4 interactor in the proliferative crypts of mouse small intestine. Tnik is recruited to promoters of Wnt target genes in mouse crypts and in Ls174T colorectal cancer cells in a ß-catenin dependent manner. Depletion of TNIK and expression of TNIK kinase mutants abrogated TCF-LEF transcription, highlighting the essential role of the kinase activity in Wnt target gene activation. siRNA depletion of TNIK followed by expression array analysis demonstrated that TNIK is an essential and exclusive activator of Wnt induced transcriptional program. As an essential component in the TCF4/ß-catenin activator complex, the kinase TNIK may present an attractive candidate for drug targeting in colorectal cancer.
Project description:Microarray-based gene expression data were generated from RNA from Ls174T colorectal carcinoma cell lines in which Wnt-dependent transcriptional activity can be abrogated by inducible overexpression of a dominant-negative form of Tcf4 or siRNA against β-catenin.
Project description:To validate the suitability of two commonly used colorectal cancer cell lines, DLD1 and SW480, as model systems to study colorectal carcinogenesis, we treated these cell lines with β-catenin siRNA and identified β-catenin target genes using DNA microarrays. The list of identified target genes was compared to previously published β-catenin target genes found in the PubMed and the GEO databases. Based on the large number of β-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study β-catenin regulated genes and signaling pathways
Project description:The canonical Wnt pathway plays a central role in stem cell maintenance, differentiation and proliferation in the intestinal epithelium. Constitutive, aberrant activity of the TCF4/β-catenin transcriptional complex is the primary transforming factor in colorectal cancer. Despite significant recent inroads, the full complement of Wnt target genes and the mechanisms of regulation remain incompletely understood. Here we identify a nuclear long non-coding RNA, termed WiNTRLINC1, as a direct target of TCF4/β-catenin in colorectal cancer cells. WiNTRLINC1 positively regulates the expression of its close neighbor ASCL2, a transcription factor that controls intestinal stem cell fate. WiNTRLINC1 interacts with TCF4/β-catenin to mediate the juxtaposition/physical contact of its own promoter with the regulatory regions of ASCL2. ASCL2, in turn, regulates WiNTRLINC1 expression. This feedforward regulatory loop controls stem cell-related gene expression and is highly amplified in colorectal cancer.
Project description:Microarray-based gene expression data were generated from RNA from Ls174T colorectal carcinoma cell lines in which Wnt-dependent transcriptional activity can be abrogated by inducible overexpression of a dominant-negative form of Tcf4 or siRNA against M-NM-2-catenin. shRNA against M-NM-2-catenin, or a dominant-negative Tcf4 transgene, were induced in Ls174T cells for 72 or 24 hours, respectively. Uninduced cells were used as a control. Three replicates per condition.
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.