Project description:The Wnt/β-catenin signalling pathway is a key regulator of embryonic stem cell self-renewal and differentiation. Constitutive activation of this pathway has been shown to significantly increase mouse embryonic stem cell (mESC) self-renewal and pluripotency marker expression. In this study, we generated a novel β-catenin knock-out model in mESCs by using CRISPR/Cas9 technology to delete putatively functional N-terminally truncated isoforms observed in previous knock-out models. While we showed that aberrant N-terminally truncated isoforms are not functional in mESCS, we observed that canonical Wnt signalling is not active in mESCs, as β-catenin ablation does not alter mESC transcriptional profile in LIF-enriched culture conditions; on the other hand, Wnt signalling activation represses mESC spontaneous differentiation. We also showed that transcriptionally silent β-catenin (ΔC) isoforms can rescue β-catenin knock-out self-renewal defects in mESCs, cooperating with TCF1 and LEF1 in the inhibition of mESC spontaneous differentiation in a Gsk3 dependent manner.
Project description:expression profile of conditional knock out of beta-catenin by K19-CRE at E7.5. Tested a wild type with two alleles of beta-catenin, a heterzyote with one deleted allele and the conditional null in the domain on cytokeratin 19 driven CRE expression
Project description:expression profile of conditional knock out of beta-catenin by K19-CRE at E7.5. Tested a wild type with two alleles of beta-catenin, a heterzyote with one deleted allele and the conditional null in the domain on cytokeratin 19 driven CRE expression Keywords: other
Project description:Canonical Wnt and Nodal signaling are both required for induction of the primitive streak (PS), which guides organization of the early embryo. The Wnt effector β-catenin is thought to function in these early lineage specification decisions via transcriptional activation of Nodal signaling. Here, we demonstrate a broader role for β-catenin in PS formation by analyzing its genome-wide binding in a human embryonic stem cell model of PS induction. β-catenin occupies regulatory regions in numerous PS and neural crest genes, and direct interactions between β-catenin and the Nodal effectors SMAD2/3 are required at these regions for PS gene activation. Furthermore, OCT4 binding in proximity to these sites is likewise required for PS induction, suggesting a collaborative interaction between β-catenin and OCT4. Induction of neural crest genes by β-catenin is repressed by SMAD2/3, ensuring proper lineage specification. This study provides mechanistic insight into how Wnt signaling controls early cell lineage decisions. Examination of β-catenin binding in hESC incubated in media control (RPMI), media containing CHIR or CHIR+SB for 6h and analyzed by ChIP-sequencing
Project description:Heat shock transcription factor 1(HSF1) is an important transcription factor which regulates the expression of a wide array of genes including heat shock proteins and oncogenes. Here, we report that HSF1 as a target of WNT/β-catenin signaling, regulates parts of target genes of WNT/β-catenin signaling. To explore the biological relevance of HSF1 activation to WNT/β-catenin signaling, we profiled gene expression of wild type mouse embryonic fibroblasts (WT MEF) and HSF1 knock out MEF (HSF1 KO MEF) before and after lithium chloride (LiCl) treatment which was a potent GSK3β inhibitor and increased the expression of β-catenin.
Project description:We generated pluripotent stem cells (Mel1 hESC containing a GFP reporter driven by the endogenous insulin promoter) with a functional knock out of PTPN2 by CRISPR/Cas9 genome editing. KO or WT control stem cells were differentiated into beta-like cells (sBC), sorted for GFP, and prepared for deep sequencing.
Project description:It has been shown that hypertrophic chondrocyte (HC) can become osteoblast, contributing to the formation of trabecular bone and endosteum. However, it is unclear what genes regulate the process of differentiation from chondrocyte to osteoblast. Conditional knock-out of β‑catenin in HCs can reduce the trabecular bone amount and there is also some evidence that ablation of β‑catenin in HCs can promote bone marrow adipogenesis. Conditional stabilization of β‑catenin in HCs results in osteopetrosis. In order to investigate the gene regulatory network with different dosage of β‑catenin in HC descendants (i.e. in Loss-of-Function mutant, Gain-of-Function mutant and Wildtype control), we collected HC descendant cells from proximal tibia of mice at postnatal day 5 and performed bulk RNA seq to profile the gene expression pattern in HC descendants.
Project description:The Wnt3a/β-catenin and Activin/Smad2,3 signaling pathways synergize to induce endodermal differentiation of human embryonic stem cells, however the mechanism is not well-understood. Using ChIP-seq and GRO-seq analyses, we report here that hESC enhancers, including Wnt3a/LEF-1 sites, hold enhancer RNAPII complexes (eRNAPII) containing high levels of Ser5P and low Ser7P. In Wnt3a signaling, β-catenin recruits cohesin to the LEF-1:eRNAPII sites to induce enhancer-promoter looping and activate transcription of mesoendodermal (ME) genes. However, paused Ser5P-RNAPII complexes accumulate at these genes, indicating that elongation remains limiting. Subsequent Activin/Smad2,3 signaling increases P-TEFb occupancy, CTD-Ser7P, and productive elongation at ME genes. Additionally, ME genes, including EOMES and MIXL1, are repressed by the Hippo regulator, Yap1, an essential pluripotency factor. GRO-seq experiments indicate that Yap1 blocks nascent transcription and controls NELF occupancy on ME genes. Thus, Wnt3a/β-catenin and Activin/Smad2,3 pathways up-regulate transcription initiation and elongation, respectively, to overcome Yap1 repression during early hESC differentiation