Project description:Given that [beta]-catenin is a well-known transcriptional coactivator, and its transcriptional downstream genes may mediate [beta]-catenin’s action on hepatocarcinogenesis. Here, we performed ChIP-seq to study genome-wide distribution of [beta]-catenin in [beta]-catenin[delta](ex3)/+ livers in quest of the putative genes.
Project description:β-catenin signaling can be both a physiological and an oncogenic pathway in the liver. It controls compartmentalized gene expression, allowing the liver to ensure its essential metabolic function. It is activated by mutations in 20 to 40% of hepatocellular carcinomas with specific metabolic features. We decipher the molecular determinants of β-catenin-dependent zonal transcription using mice with β-catenin-activated or -inactivated hepatocytes, characterizing in vivo their chromatin occupancy by Tcf4 and β-catenin, their transcriptome and their metabolome. We find that Tcf4 DNA-bindings depend on β-catenin. Tcf4/β-catenin binds Wnt-responsive elements preferentially around β-catenin-induced genes. In contrast, genes repressed by β-catenin bind Tcf4 on Hnf4-responsive elements. β-catenin, Tcf4 and Hnf4α interact, dictating β-catenin transcription which is antagonistic to that elicited by Hnf4α. Finally, we find the drug/bile metabolism pathway to be the one most heavily targeted by β-catenin, partly through xenobiotic nuclear receptors. We conclude that β-catenin patterns the zonal liver together with Tcf4, Hnf4α and xenobiotic nuclear receptors. This network represses lipid metabolism, and exacerbates glutamine, drug and bile metabolism, mirroring hepatocellular carcinomas with β-catenin mutational activation. In vivo liver samples in 4 conditions: Betacat activated (WCE, Tcf4 chipseq, Betacat chipseq, mRNAseq with 2 replicates), Betacat null (WCE, Tcf4 chipseq, mRNAseq with 2 replicates), Betacat control (mRNAseq with 2 replicates), Wild type (mRNAseq with 2 replicates)
Project description:Plakoglobin (PG; γ-Catenin, JUP) is a protein with controversial function. First described as a component of intercellular junctions, it has remained unresolved whether this near-ubiquitously expressed protein acts as a genuine transcriptional regulator in adult tissue like its closest relative β-catenin. Here we have mapped the global gene targets of PG by ChIP-chip in differentiating skin keratinocytes. Applying a peak algorithm, over 5’000 high-confidence PG target promoters were identified and 2’000 for β-catenin with an overlap of 38%. Bioinformatics analyses most significantly associated PG target genes with the Wnt signaling pathway as well as relevant pathways for keratinocyte differentiation. Using a combination of wild-type, PG, β-catenin and PG/β-catenin double null keratinocytes, PG was functionally validated as a LEF/TCF-dependent transcriptional regulator. These data challenge the current understanding of Wnt signaling, one of the most important pathways in tissue homeostasis, by identifying PG as a potent LEF/TCF-dependent transcriptional regulator which functionally overlaps with β-catenin.
Project description:To investigate mechanisms by which activated β-catenin signaling promotes liver tumor formation and to identify potential therapeutics for these cancers, we generated transgenic zebrafish expressing hepatocyte-specific activated β-catenin (Tg(fabp10a:pt-β-cat) zebrafish. As adults, these animals show increased liver size, decreased survival, and histologic abnormalities similar to human HCC. To further characterize our model, we used microarray analysis to compare gene expression in Tg(fabp10a:pt-β-cat) zebrafish livers to that of non-transgenic control sibling livers. This experiment includes 2 biological replicates. Each replicate represents one Tg(fabp10a:pt-beta-catenin) zebrafish compared to non-transgenic control sibling.
Project description:Study of beta-catenin activation in liver regeneration using comparaison between ko-mice for beta-catenin gene with control mice before and after hepatectomy.
Project description:β-catenin signaling can be both a physiological and an oncogenic pathway in the liver. It controls compartmentalized gene expression, allowing the liver to ensure its essential metabolic function. It is activated by mutations in 20 to 40% of hepatocellular carcinomas with specific metabolic features. We decipher the molecular determinants of β-catenin-dependent zonal transcription using mice with β-catenin-activated or -inactivated hepatocytes, characterizing in vivo their chromatin occupancy by Tcf4 and β-catenin, their transcriptome and their metabolome. We find that Tcf4 DNA-bindings depend on β-catenin. Tcf4/β-catenin binds Wnt-responsive elements preferentially around β-catenin-induced genes. In contrast, genes repressed by β-catenin bind Tcf4 on Hnf4-responsive elements. β-catenin, Tcf4 and Hnf4α interact, dictating β-catenin transcription which is antagonistic to that elicited by Hnf4α. Finally, we find the drug/bile metabolism pathway to be the one most heavily targeted by β-catenin, partly through xenobiotic nuclear receptors. We conclude that β-catenin patterns the zonal liver together with Tcf4, Hnf4α and xenobiotic nuclear receptors. This network represses lipid metabolism, and exacerbates glutamine, drug and bile metabolism, mirroring hepatocellular carcinomas with β-catenin mutational activation.
Project description:Hepatoblastoma (HB), the most common type of pediatric liver cancer, is associated with aberrant wnt/β-catenin activation and Myc amplification/overexpression. Mice expressing both alleles developed HBs and HCCs with incomplete penetrance by 5-6 weeks of age with fetal and mixed fetal/embryonal HBs, the most prevalent histologic HB subtypes seen in children being the predominant tumor types. To address the roles of mutant wnt/β-catenin activation and Myc over-expression in the pathogenesis of HB, c-Myc and mutant dominant-stable β-catenin were co-targeted to immature cells of the developing mouse liver.