Project description:The tumor suppressor gene adenomatous polyposis coli (APC) is mutated in most colorectal cancers (CRC) resulting in constitutive Wnt activation. To understand the Wnt-activating mechanism of APC mutation, we applied CRISPR/Cas9 technology to engineer various APC-truncated isogenic lines. We find that the β-catenin inhibitory domain (CID) in APC represents the threshold for pathological levels of Wnt activation and tumor transformation. Mechanistically, CID-deleted APC truncation promotes β-catenin deubiquitination through reverse binding of β-TrCP and USP7 to the destruction complex. USP7 depletion in APC-mutated CRC inhibits Wnt activation by restoring β-catenin ubiquitination, drives differentiation and suppresses xenograft tumor growth. Finally, the Wnt-activating role of USP7 is specific to APC mutations, thus can be used as tumor-specific therapeutic target for most CRCs.
Project description:Wnt/M-NM-2-catenin signaling is involved in various aspects of skeletal muscle development and regeneration. In addition, Wnt3a and M-NM-2-catenin are required for muscle-specific gene transcription in embryonic carcinoma cells and satellite-cell proliferation during adult skeletal muscle regeneration. Downstream targets of canonical Wnt signaling are cyclin D1 and c-myc. However, both target genes are suppressed during differentiation of mouse myoblast cells, C2C12. Underlying molecular mechanisms of M-NM-2-catenin signaling during myogenic differentiation remain unknown. Using C2C12 cells, we examined intracellular signaling and gene transcription during myoblast proliferation and differentiation. We confirmed that several Wnt signaling components, including Wnt9a, Sfrp2 and porcupine, were consistently upregulated in differentiating C2C12 cells. Troponin T-positive myotubes were decreased by Wnt3a overexpression, but not Wnt4. TOP/FOP reporter assays revealed that co-expression with Wnt4 reduced Wnt3a-induced luciferase activity, suggesting that Wnt4 signaling counteracted Wnt3a signaling in myoblasts. FH535, a small-molecule inhibitor of M-NM-2-catenin/Tcf complex formation, reduced basal M-NM-2-catenin in cytoplasm and decreased myoblast proliferation. K252a, a protein kinase inhibitor, increased membrane-bound M-NM-2-catenin and enhanced myoblast fusion. Treatments with K252a or Wnt4 resulted in increased cytoplasmic vesicles containing phosphorylated M-NM-2-catenin (Tyr654) during myogenic differentiation. These results suggest that various Wnt ligands control subcellular M-NM-2-catenin localization, which regulate myoblast proliferation and myotube formation. Wnt signaling via M-NM-2-catenin likely acts as a molecular switch that regulates the transition from cell proliferation to myogenic differentiation. Control cells (day 0) prior to differentiation induction with n=4; differentiated for two days with n=3; differentiated for four days with n=3.
Project description:The Wnt/ß-catenin pathway is orchestrating the development of the blood-brain barrier (BBB), but its downstream mediators have remained elusive. To identify potential effectors, we generated an endothelial cell specific Axin1 over-expressing mouse model, AOEiEC. We found that in AOEiE mice Wnt/ß-catenin signalling was down regulated leading to premature regression and remodelling without directly compromising BBB integrity. Interestingly, by comparing transcriptomes of endothelial cells from control and AOEiEC mice, we identified Adamtsl2 as a novel Wnt/ß-catenin-induced, secreted factor, important for stabilizing the cerebral vasculature during development. Importantly, loss-of-function and gain-of-function experiments revealed that Adamtsl2 alone was sufficient to rescue CNS vascular defects seen upon Wnt-signalling inhibition. Furthermore, using various cell and animal models we demonstrate that Adamtsl2 exerts its function by fine-tuning the TGFβ signalling pathway in CNS vessels. In conclusion, this study implicates Adamtsl2 as a mediator of Wnt/ß-catenin signalling during BBB development by linking it to TGFβ signalling.
Project description:Wnt/β-catenin signaling is involved in various aspects of skeletal muscle development and regeneration. In addition, Wnt3a and β-catenin are required for muscle-specific gene transcription in embryonic carcinoma cells and satellite-cell proliferation during adult skeletal muscle regeneration. Downstream targets of canonical Wnt signaling are cyclin D1 and c-myc. However, both target genes are suppressed during differentiation of mouse myoblast cells, C2C12. Underlying molecular mechanisms of β-catenin signaling during myogenic differentiation remain unknown. Using C2C12 cells, we examined intracellular signaling and gene transcription during myoblast proliferation and differentiation. We confirmed that several Wnt signaling components, including Wnt9a, Sfrp2 and porcupine, were consistently upregulated in differentiating C2C12 cells. Troponin T-positive myotubes were decreased by Wnt3a overexpression, but not Wnt4. TOP/FOP reporter assays revealed that co-expression with Wnt4 reduced Wnt3a-induced luciferase activity, suggesting that Wnt4 signaling counteracted Wnt3a signaling in myoblasts. FH535, a small-molecule inhibitor of β-catenin/Tcf complex formation, reduced basal β-catenin in cytoplasm and decreased myoblast proliferation. K252a, a protein kinase inhibitor, increased membrane-bound β-catenin and enhanced myoblast fusion. Treatments with K252a or Wnt4 resulted in increased cytoplasmic vesicles containing phosphorylated β-catenin (Tyr654) during myogenic differentiation. These results suggest that various Wnt ligands control subcellular β-catenin localization, which regulate myoblast proliferation and myotube formation. Wnt signaling via β-catenin likely acts as a molecular switch that regulates the transition from cell proliferation to myogenic differentiation.
Project description:The forkhead box transcription factor FOXQ1 is aberrantly induced in various cancers, and contributes to tumour growth and metastasis. It has been suggested that the oncogenic potential of FOXQ1 may be explained by its activation of the Wnt/β-catenin signalling pathway.However, the mode of action of FOXQ1 in the Wnt pathway remains to be resolved. Here we report that FOXQ1 is bimodal transcriptional activator of Wnt target gene expression in normal and cancer cells. Using co-immunoprecipitation, proximity proteomics, and reporter assays, we show that FOXQ1 engages the Wnt transcriptional complex to promote gene expressionvia TCF/LEF transcription factors.
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:Expression of the SS18/SYT-SSX fusion protein is believed to underlie the pathogenesis of synovial sarcoma (SS). Recent evidence suggests that deregulation of the Wnt pathway may play an important role in SS but the mechanisms whereby SS18-SSX might affect Wnt signaling remain to be elucidated. Here, we show that SS18/SSX tightly regulates the elevated expression of the key Wnt target AXIN2 in primary SS. SS18-SSX is shown to interact with TCF/LEF, TLE and HDAC but not β -catenin in vivo and to induce Wnt target gene expression by forming a complex containing promoter-bound TCF/LEF and HDAC but lacking β -catenin. Our observations provide a tumor-specific mechanistic basis for Wnt target gene induction in SS that can occur in the absence of Wnt ligand stimulation. SS18SSX expressing C3H cells vs control: no replicates. WNT-stimulated C3H cells vs controls: 3 replicates per condition
Project description:The forkhead box transcription factor FOXQ1 is aberrantly induced in various cancers, and contributes to tumour growth and metastasis. It has been suggested that the oncogenic potential of FOXQ1 may be explained by its activation of the Wnt/β-catenin signalling pathway. However, the mode of action of FOXQ1 in the Wnt pathway remains to be resolved. Here we report that FOXQ1 is bimodal transcriptional regulator of Wnt target gene expression in normal and cancer cells. Using co-immunoprecipitation, proximity proteomics, and reporter assays, we show that FOXQ1 partly engages the Wnt transcriptional complex to promote gene expression via TCF/LEF transcription factors.
Project description:This study aimed to further understand context-specific direct Wnt target gene expression through the use of beta-catenin and FoxH1 ChIP Sequencing data at various developmental stages representing both maternal and zygotic Wnt signalling. Results were further supported through the use of RNA sequencing data from beta-catenin, FoxH1 and nodal gene knock down assays.