Regulation of Human Embryonic Stem Cell Proliferation and Differentiation by Wnt

在模式生物中的工作表明，少量的信号转导途径，包括Wnt/b-catenin途径，在整个发育过程中发挥关键作用，以及在成人的组织修复和干细胞动态平衡中发挥关键作用。有趣的是，Wnt/b-catenin途径的组成在不同的细胞环境中是不同的，这取决于信号途径的独特修饰物的表达，或者保守途径成分的不同亚型的表达。我们和其他人有证据(参见初步研究)表明，Wnt/b-catenin信号在经历自我更新的多潜能人类胚胎干细胞(HESCs)中受到抑制，并且信号在分化为早期和晚期中胚层细胞系的过程中都是活跃的。 我们假设Wnt/b-catenin信号的上下文相关修饰物在hESCs的自我更新和分化中起关键作用。 这一建议的最初目标是验证一种假设，即Wnt/b-catenin信号的上下文相关调节器在调节hESCs的自我更新和分化中发挥关键作用。我们相信，对这一目标的追求将揭示Wnt/β-catenin信号调节hESCs自我更新和指定细胞命运的详细机制。 我们的第二个目标是扩大我们对干细胞中信号转导途径作用的研究，包括Hedgehog、Notch和TGFb途径，使用新型的多路复合荧光报告程序来同时监测活细胞中的多条途径。我们相信，同时可视化活细胞中多个信号通路的活动状态的技术的发展将在研究正常和疾病组织中的信号通路方面有许多用途。

Work in model organisms has revealed that a small number of signal transduction pathways, including the Wnt/b-catenin pathway, play key roles throughout development, as well as in tissue repair and stem cell homeostasis in adults. Interestingly, the composition of the Wnt/b-catenin pathway differs in distinct cellular contexts, depending on expression of unique modifiers of the signaling pathway, or expression of different isoforms of conserved pathway components. We and others have evidence (see Preliminary studies) that Wnt/b-catenin signaling is repressed in pluripotent human embryonic stem cells (hESCs) undergoing selfrenewal, and that signaling is active during differentiation into both early and later mesodermal cell lineages. We hypothesize that context-dependent modifiers of Wnt/b-catenin signaling play key roles in the self-renewal and differentiation of hESCs. The initial goal of this proposal is to test the hypothesis that context-dependent modulators of Wnt/b-catenin signaling play key roles in regulating self-renewal and differentiation in hESCs. We believe that pursuit of this goal will reveal detailed mechanisms by which Wnt/beta-catenin signaling regulates self-renewal and specification of cell fate in hESCs. Our second goal is to expand our investigation of the roles of signal transduction pathways in stem cells to include the Hedgehog, Notch, and TGFb pathways, using novel multiplexed fluorescent reporters to enable simultaneous monitoring of multiple pathways in live cells. We believe that the development of the technology to simultaneously visualize the state of activity of multiple signaling pathways in live cells will have numerous uses in studies of signaling pathways in normal and diseased tissues.