Role of Wnt/Beta-Catenin Signaling in Liver Development

Wnt/β-连环蛋白信号传导在肝脏发育中的作用

• 批准号: 8397674
• 负责人: Satdarshan Singh Monga
• 金额: $ 38.6万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8397674
• 关键词: Activins; Address; Adult; Albumins; Alcohols; Alleles; Antibodies; Apoptosis; Biliary; Binding; Biology; CCAAT-Enhancer-Binding Proteins; CREB-binding protein; Cell Nucleus; Cell Polarity; Cessation of life; Cyclin D1; Cytomegalovirus; Data; Development; EP300 gene; Embryo; Ensure; Equilibrium; Event; Failure; Funding; Gene Expression; Genes; Germ Lines; Growth; Growth Factor; Growth and Development function; Hepatic; Hepatitis; Hepatocyte; Histology; Individual; Injury; Interleukin-6; Investigation; Knockout Mice; Light; Lipopolysaccharides; Liver; Liver Failure; Liver Regeneration; Liver Stem Cell; Liver diseases; Malignant Neoplasms; Mediating; Modeling; Molecular; Morphogenesis; Mus; Natural regeneration; Nuclear; Nuclear Translocation; Organogenesis; PDGFRB gene; Partial Hepatectomy; Pathway interactions; Play; Process; Proteins; Regulation; Reporting; Resistance; Role; Signal Pathway; Signal Transduction; Specific qualifier value; Staging; Stem cells; TCF Transcription Factor; TCF7L2 gene; TNF gene; Testing; Toxin; Transactivation; Transcriptional Activation; Tumor Necrosis Factor Ligand Superfamily Member 6; Xenopus; Zebrafish; base; beta catenin; bile duct; cofactor; decorin; human CREBBP protein; improved; in vivo; jagged1 protein; liver cell proliferation; liver injury; mRNA Expression; male; outcome forecast; oval cell; response; syndecan 3

SUMMARY Wnt/¿-catenin signaling has come to the forefront in liver biology. Its role in liver development, regeneration & stem cells is beginning to be understood. We identified its role in liver regeneration & showed activation of the Wnt/¿-catenin signaling immediately after partial-hepatectomy (PHx). This was observed as nuclear translocation of ¿-catenin protein ensuring G1 to S transition mediated by factors such as Cyclin-D1. In addition, we identified highest ¿-catenin expression during early stages of hepatic morphogenesis in liver development & showed that its absence led to compromise in hepatoblast expansion & differentiation into bile ducts & failure of hepatocyte maturation. Recently, we have also identified the role of Wnt/¿-catenin in adult liver stem cells or oval cells, where this pathway regulates their emergence & expansion. As we have uncovered several key roles of this pathway, many new questions have arisen! Several of these are of high significance & have taken the form of the current proposal, which is a competing renewal of our previously funded application (1/1/2004-12/31/2008). In the current proposal we want to focus on three aspects of liver biology-development, regeneration & hepatocyte death. We have generated ¿-catenin-conditional null mice (KO1) with Foxa3-Cre driven deletion of ¿-catenin in hepatoblasts during development. This strategy unveiled the importance of ¿-catenin in regulating hepatoblast expansion & differentiation. We propose to identify the molecular basis by which ¿-catenin is regulating these two conceptually opposing events during development & hypothesize (based on stem cell paradigm) that differential interaction of ¿-catenin occurs temporally with cofactors enabling transactivation of distinct genes that regulate the two processes. We will elucidate the basis of failed biliary differentiation in absence of ¿-catenin & examine how lack of ¿-catenin retards hepatocyte maturation. Based on the controversy in the role of Wnt/¿-catenin signaling in hepatic specification in Zebrafish & Xenopus, we will utilize KO1 to address role of ¿-catenin in murine hepatic specification. We have also generated ¿-catenin-conditional-null mice (KO2) using Albumin-Cre & identified lack of proliferation in these mice at 40hrs (peak proliferation in controls) after PHx. We will address the molecular signaling in the absence of ¿-catenin that enables a dramatic rescue of hepatocyte proliferation at 72hrs in KO2 mice. While we are beginning to understand the role of canonical Wnt signaling, the role & extent of noncanonical pathways-Wnt/Ca2+ & planar cell polarity pathways; remain obscure & will be investigated in-depth in liver development & regeneration. Finally, based on enhanced apoptosis in hepatocytes lacking ¿-catenin, we investigated Fas-& TNF¿-mediated injury in the KO2. Interestingly, while KO2 mice were clearly more susceptible to Jo-2 (Fas-ligand) injury than controls, they were resistant to lipopolysaccharide (LPS)-injury. The molecular basis of these findings will be elucidated. Thus, this proposal will be a comprehensive analysis of canonical & noncanonical Wnt signaling in hepatic biology.

概括 Wnt/¿-连环蛋白信号传导已成为肝脏生物学的前沿。它在肝脏发育、再生中的作用 &干细胞开始被理解。我们确定了它在肝再生中的作用并显示出激活作用 部分肝切除术 (PHx) 后立即检测 Wnt/¿-连环蛋白信号传导。这被观察为核 ¿-连环蛋白的易位确保由 Cyclin-D1 等因子介导的 G1 到 S 的转变。在 此外，我们在肝脏形态发生的早期阶段发现了最高的¿-连环蛋白表达 的发展并表明它的缺失导致肝母细胞扩增和分化为妥协 胆管和肝细胞成熟失败。最近，我们还确定了 Wnt/¿-catenin 在 成体肝脏干细胞或卵圆细胞，该途径调节它们的出现和扩张。正如我们所拥有的 揭示了这条通路的几个关键作用，许多新问题也随之出现！其中有几个等级很高 重要性并采取了当前提案的形式，这是我们之前的竞争性更新 资助申请（1/1/2004-12/31/2008）。在当前的提案中，我们希望重点关注以下三个方面： 肝脏生物学——发育、再生和肝细胞死亡。我们已经生成了 ¿-catenin-conditional null 具有 Foxa3-Cre 的小鼠（KO1）在发育过程中导致肝母细胞中 ¿-catenin 缺失。这个策略 揭示了 ¿-连环蛋白在调节肝细胞扩张和分化中的重要性。我们建议 确定 ¿-catenin 调节这两个概念上相反的事件的分子基础 开发并假设（基于干细胞范式）¿-连环蛋白发生不同的相互作用 暂时与辅因子一起实现调节这两个过程的不同基因的反式激活。我们将 阐明在缺乏 ¿-连环蛋白的情况下胆管分化失败的基础并检查缺乏 ¿-连环蛋白是如何造成的 延缓肝细胞成熟。基于Wnt/¿-catenin信号在肝细胞中作用的争议 根据斑马鱼和非洲爪蟾的规范，我们将利用 KO1 来解决 ¿-连环蛋白在小鼠肝脏中的作用 规格。我们还使用白蛋白-Cre 生成了 ¿-catenin-conditional-null 小鼠 (KO2) 并鉴定了 PHx 后 40 小时（对照中的增殖峰值），这些小鼠缺乏增殖。我们将解决 在没有 ¿-连环蛋白的情况下的分子信号传导能够显着挽救肝细胞增殖 KO2 小鼠中 72 小时。当我们开始了解规范 Wnt 信号传导的作用时，其作用和 非规范途径的范围 - Wnt/Ca2+ 和平面细胞极性途径；仍然默默无闻并将 深入研究肝脏发育和再生。最后，基于细胞凋亡的增强 由于肝细胞缺乏 ¿-连环蛋白，我们研究了 KO2 中 Fas 和 TNF 介导的损伤。有趣的是，虽然 KO2 小鼠明显比对照组更容易受到 Jo-2（Fas 配体）损伤，它们对 脂多糖（LPS）损伤。这些发现的分子基础将得到阐明。因此，这个 该提案将对肝脏生物学中的经典和非经典 Wnt 信号传导进行全面分析。