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: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.
Project description:The APC (Adenomatous Polyposis Coli) gene encodes a large multidomain protein that plays an integral role in the Wnt/beta-catenin signaling pathway. The loss-of-function mutation in APC is considered the earliest genetic alteration in the course of adenoma-carcinoma sequence of colorectal cancer progression, and the resulting constitutive activation of Wnt/beta-catenin signaling is required for the maintenance of advanced colorectal cancer. In order to identify genes affected by loss of Apc function, we performed transcription profiling of mouse small intestinal tissues comparing polyps with normal mucosa of Apc+/Delta716 mice. We isolated total RNA from intestinal polyps and normal intestinal mucosa from 3 individual Apc+/Delta716 mice. Total RNA samples were then employed to perform microarray analysis (Agilent Whole Mouse Genome Microarray Ver. 2.0, 4x44K).
Project description:We previously showed that nucleoredoxin (NRX) suppresses Wnt/β-catenin signaling through its binding to Dishevelled (Dvl) (Nat Cell Biol 8, 501-508 (2006)). To clarify the in vivo role of NRX in mammals, we here generate NRX gene-knockout mice (NRX-/- mice) by homologous recombination. NRX-/- mice die around birth. Therefore, we performed microarray analyses with NRX+/+ and NRX-/- embryos of E9.5 and E11.5 stages. Surprisingly, in the genes commonly upregulated at both stages, we could not observe Wnt/β-catenin targets. Rather, several target genes for Wnt/β-catenin pathway, such as Frizzled2 and Occludin, are downregulated in NRX-/- whole embryos. Frizzled2 is a gene reportedly expressed in developmental heart. Indeed, by RT-PCR analyses we confirmed that the expression of Frizzled2, as well as other Wnt/β-catenin target genes, was downregulated in embryonic heart of NRX-/- mice. We also found that the amount of unphosphorylated (i.e. activated) form of β-catenin was downregulated in NRX-/- embryonic heart. These results reveal that NRX plays another role which was unidentified in culture cell studies; it is required for the maintenance of Wnt/β-catenin signaling activity.
Project description:Canonical Wnt signaling plays critical roles in development and tissue renewal by regulating β-catenin target genes. Recent evidence showed that β-catenin-independent Wnt signaling is also required for faithful execution of mitosis. This mitotic Wnt signaling functions through Wnt-dependent stabilization of proteins (Wnt/STOP), as well as through components of the LRP6 signalosome. However, the targets and specific functions of mitotic Wnt signaling still remain uncharacterized. Using phosphoproteomics, we identified that Wnt signaling regulates the microtubule depolymerase KIF2A during mitosis. We found that Dishevelled recruits KIF2A via its N-terminal and motor domains, which is further promoted upon LRP6 signalosome formation during mitosis. We show that Wnt signaling modulates KIF2A interaction with PLK1, which is critical for KIF2A localization and the assembly of a bipolar mitotic spindle. Accordingly, Wnt signaling promotes chromosome congression during metaphase by monitoring KIF2A protein levels at the spindle poles both in somatic cells and in pluripotent stem cells. Our findings highlight a novel function of Wnt signaling during cell division, which could have important implications for genome maintenance, notably in stem cells.
Project description:The Wnt/β-catenin signaling pathway is a critical regulator of development and stem cell maintenance. Mounting evidence suggests that the context-specific outcome of Wnt signaling is determined by the collaborative action of multiple transcription factors, including members of the highly conserved forkhead box (FOX) protein family. The contribution of FOX transcription factors to Wnt signaling has not been investigated in a systemic manner. Here, by combining β-catenin reporter assays with Wnt pathway-focused qPCR arrays and proximity proteomics of selected FOX family members, we determine that most FOX proteins are involved in the regulation of Wnt pathway activity and the expression of Wnt ligands and target genes. We conclude that FOX proteins are common regulators of the Wnt/β-catenin pathway that may control the outcome of Wnt signaling in a tissue-specific manner.
Project description:The β-catenin mutation is frequently observed in hepatoblastoma (HB), but the underlying mechanism by which Wnt/β-catenin signaling induces HB tumor formation is unknown. We found that expression of growth regulation by estrogen in breast cancer 1 (GREB1) depends on Wnt/β-catenin signaling in HB patients. GREB1 was localized to the nucleus where it bound Smad2/3 in a competitive manner with p300 and inhibited TGFβ signaling, thereby promoting HepG2 HB cell proliferation. Forced expression of β-catenin, YAP, and c-Met induced HB-like mouse liver tumor (BYM mice), with an increase in GREB1 expression and HB markers. Depletion of GREB1 strongly suppressed marker gene expression and HB-like liver tumorigenesis, and instead enhanced TGFβ signaling in BYM mice. Furthermore, antisense oligonucleotides for GREB1 suppressed the formation of HepG2 cell-induced tumors and HB-like tumors in vivo. We propose that GREB1 is a novel target molecule of Wnt/β-catenin signaling and required for HB progression.
Project description:Canonical Wnt signaling output is mediated by β-catenin, which interacts with LEF/TCF transcription factors and recruits a general transcriptional activation complex to its C-terminus. Its N-terminus binds BCL9/9L proteins, which bind co-activators that in mammals contribute to fine-tuning the transcriptional output. We found that a BCL9/9L-dependent gene expression signature was strongly associated with patient outcome in colorectal cancer and that stem cell and mesenchymal genes determine its prognostic value. Abrogating BCL9/9L-β-catenin signaling in independent mouse colorectal cancer models resulted in virtual loss of these traits, and oncogenic intestinal organoids lacking BCL9/9L proteins proved no longer tumorigenic. Our findings suggest that the BCL9/9L arm of Wnt-β-catenin signaling sustains a stemness-to-differentiation equilibrium in colorectal cancer, which critically affects disease outcome. Mutational activation of the Wnt pathway is a key oncogenic event in colorectal cancer. Targeting the pathway downstream of activating mutations is challenging, and the therapeutic window is limited by intestinal toxicity. Contrasting with phenotypes caused by inactivating key Wnt pathway components, ablation of BCL9/9L proteins in adult mice indicated that they were dispensable for intestinal homeostasis, consistent with their role in tuning transcription. Cancer stem cells are increasingly recognized as responsible for tumor recurrence. The correlation between stemness traits in colorectal cancer models and BCL9/9L-β-catenin signaling suggests that high Wnt signaling output is required for their maintenance. Our findings suggest that pruning Wnt-β-catenin signaling might be well tolerated and prove sufficient for trimming stemness traits and improving disease outcome.