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:The small intestinal epithelium is the most rapidly self-renewing tissue of mammals. Proliferative cells are confined to crypts, while differentiated cell types predominantly occupy the villi. We recently demonstrated the existence of a long-lived pool of cycling stem cells defined by Lgr5 expression and intermingled with post-mitotic Paneth cells at crypt bottoms. We have now determined a gene signature for these so called Crypt Base Columnar (CBC) cells. One of the genes within this stem cell signature is the Wnt target Ascl2. Transgenic expression of the Ascl2 transcription factor throughout the intestinal epithelium induces crypt hyperplasia and de novo crypt formation on villi. Induced deletion of the Ascl2 gene in adult small intestine leads to disappearance of the CBC stem cells within days. The combined results from these gain- and loss-of-function experiments imply that Ascl2 controls intestinal stem cell fate. Keywords: expression profiling
Project description:Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell lines HT-29 (47.5-95% of CD133+ population) and LS174T (0.45% of CD133+ population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference. The microRNA (miRNA) microarrays identified 26 two-fold up-regulated miRNAs and 58 two-fold down-regulated miRNAs in shRNA-Ascl2/HT-29 cells and 178 two-fold up-regulated miRNAs and 172 two-fold down-regulated miRNAs in shRNA-Ascl2/LS174T cells. Two-condition experiment: shRNA-Ascl2/HT-29 cells vs. shRNA-Ctr/HT-29 cells, and shRNA-Ascl2/LS174T cells vs. shRNA-Ctr/LS174T cells. Biological replicates: 1 HT-29 cells stably transfected with shRNA-Ascl2/EGFP, 1 LS174T cells stably transfected with shRNA-Ascl2/EGFP, 1 HT-29 cells stably transfected with shRNA-Control/EGFP, and 1 LS174T cells stably transfected with shRNA-Control/EGFP, independently grown and harvested. One replicate per array.
Project description:Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell lines HT-29 (47.5-95% of CD133+ population) and LS174T (0.45% of CD133+ population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference. The microRNA (miRNA) microarrays identified 26 two-fold up-regulated miRNAs and 58 two-fold down-regulated miRNAs in shRNA-Ascl2/HT-29 cells and 178 two-fold up-regulated miRNAs and 172 two-fold down-regulated miRNAs in shRNA-Ascl2/LS174T cells.
Project description:The small intestinal epithelium is the most rapidly self-renewing tissue of mammals. Proliferative cells are confined to crypts, while differentiated cell types predominantly occupy the villi. We recently demonstrated the existence of a long-lived pool of cycling stem cells defined by Lgr5 expression and intermingled with post-mitotic Paneth cells at crypt bottoms. We have now determined a gene signature for these so called Crypt Base Columnar (CBC) cells. One of the genes within this stem cell signature is the Wnt target Ascl2. Transgenic expression of the Ascl2 transcription factor throughout the intestinal epithelium induces crypt hyperplasia and de novo crypt formation on villi. Induced deletion of the Ascl2 gene in adult small intestine leads to disappearance of the CBC stem cells within days. The combined results from these gain- and loss-of-function experiments imply that Ascl2 controls intestinal stem cell fate. Experiment Overall Design: For the stem cell signature we used cell fractions of intestines from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter. RNA was isolated from two FACS sorted cell populations, one expressing GFP at high levels (GFPhi) and the other expressing GFP at low levels (GFPlo). For the analysis of Ascl2 target genes RNA was isolated from intestinal epithelial cells of Ah-Cre/Ascl2floxed/floxed animals and Ah-Cre/Ascl2floxed/wt control animals 3 and 5 days post induction. Differentially labelled cRNA from GFPhi and GFPlo cells from two different sorts (each combining three different mice) were hybridised on 4X44K Agilent Whole Mouse Genome dual colour Microarrays (G4122F) in two dye swap experiments, resulting in four individual arrays. For the Ascl2 target gene analysis we analyzed the 3 and 5 days PI experiments in two dye swap experiments, resulting in four individual arrays.
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 âonâ or âoffâ decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent Examination of Tcf4, B-catenin and Ascl2 DNA occupancy in murine intestinal organoids and human colorectal cancer cell lines *** Original raw files unavailable due to loss during backup ***
Project description:The esophagus is protected from the hostile environment by a stratified epithelium, which renews rapidly. Homeostasis of this epithelium is ensured by a rare population of stem cells in the basal layer: Keratin 15+ (Krt15+) cells. However, little is known about the molecular mechanisms regulating their distinct features, namely self-renewal, potency, and epithelial regeneration. Achaete-Scute Family BHLH Transcription Factor 2 (ASCL2) is strongly upregulated in Krt15+ stem cells and is known to contribute to stem cell maintenance in other tissues. Herein, we investigated the role of ASCL2 in maintaining homeostasis under normal and stress conditions in the esophageal epithelium. ASCL2 overexpression severely dysregulated cell differentiation and cell fate. Proliferation was also reduced due potentially to a blockage in the G1 phase of the cell cycle or an induction of quiescence. Mass spectrometry analysis confirmed alterations in several proteins associated with differentiation and cell cycle. In addition, overexpression of ASCL2 enhanced resistance to radiation and chemotherapeutic drugs. Overall, these results denoted the role of ASCL2 as a key regulator of the proliferation-differentiation equilibrium in the esophageal epithelium.
Project description:Cellular binary fate decisions require the progeny to silence genes associated with the alternative fate. The major subsets of alpha:beta T cells have been extensively studied as a model system for fate decisions. While the transcription factor RUNX3 is required for the initiation of Cd4 silencing in CD8 T cell progenitors, it is not required to maintain the silencing of Cd4 and other helper T lineage genes. The other runt domain containing protein, RUNX1, silences Cd4 in an earlier T cell progenitor, but this silencing is reversed whereas the gene silencing after RUNX3 expression is not reverse. Therefore, we hypothesized that RUNX3 and not RUNX1 recruits other factors that maintains the silencing of helper T lineage genes in CD8 T cells. To this end, we performed a proteomics screen of RUNX1 and RUNX3 to determine candidate silencing factors.
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 “on” or “off” decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent.
Project description:Wnt signals control three functions of intestinal crypts: maintenance of Lgr5 stem cells, proliferation of transit-amplifying daughters and formation of Paneth cells. Here, we study how the Wnt effector β-catenin/Tcf4 cooperates with the Wnt-activated transcription factor Ascl2 to control a stem cell transcription program. DNA elements that are co-occupied and synergistically regulated by Ascl2 and Tcf4 specifically map to stem cell genes. In vitro, Tcf4-/- mini-guts are rescued by Ascl2 expression, while Ascl2-/- organoids are rescued by Wnt signaling. A direct auto-activatory loop leads to an on/off expression pattern of Ascl2 with a threshold that depends on the previous state. Wnt/R-spondin1 activates this loop. This mechanism interprets Wnt levels in crypts and translates this continuous signal into a discrete Ascl2 “on” or “off” decision. In turn Ascl2, together with β-catenin/Tcf, activates stem cell genes. Thus, Ascl2 forms a transcriptional 'stemness switch' that is both Wnt-responsive and Wnt-dependent