Molecular basis of digestive system development in Xenopus

项目描述（申请人提供）：本项目的长期目标是阐明控制消化系统胚胎发育的分子机制。这将对我们对人类胃肠道畸形的理解产生广泛而重大的影响，为指导干细胞分化的策略提供信息，并为发育和疾病中的细胞信号传导提供新的基础信息。消化系统的发育是由内胚层和中胚层之间的一系列生长因子信号调控的，这些信号仅被部分理解。肠道发育的基本机制在哺乳动物和其他脊椎动物之间是高度保守的，我们先前利用爪蟾胚胎的实验优势的研究有助于为干细胞诱导人类肠道组织的策略提供信息。尽管最近取得了进展，但我们对前肠和后肠祖细胞如何指定的理解仍然存在根本差距。特别是细胞外环境如何调节GI发育不同阶段的组合信号动力学，以及如何实现对这些信号的转录特异性，这些在很大程度上是未知的，也是本提案的重点。我们的初步研究支持以下假设：分泌卷曲相关蛋白（Secreted frizzzed Related Proteins, Sfrp）通过一种新机制调节细胞外纤维连接蛋白基质，促进BMP信号传导；Sfrp协调BMP和Wnt生长因子之间的信号串扰，使内胚层形成前肠和后肠祖细胞。目的1将描述strps和Tolloid蛋白酶调节纤维连接蛋白基质以调节BMP信号传导的新机制。目的2将确定协调BMP和Wnt信号的机制。目的3将确定BMP和Wnt信号效应因子Smad1和β -连环蛋白的差异活性如何整合到DNA顺式调控元件上，以控制前肠和后肠转录。

DESCRIPTION (provided by applicant): The long-term goal of this project is to elucidate the molecular mechanisms controlling embryonic development of the digestive system. This will have a broad and significant impact on our understanding of human GI malformations, inform strategies to direct the differentiation of stem cells and provide new fundamental information on cell signaling in development and disease. Digestive system development is regulated by a series of growth factor signals between the endoderm and mesoderm, which are only partially understood. The fundamental mechanism of GI development are highly conserved between mammals and other vertebrate species and our previous studies using the experimental advantages of Xenopus embryos has helped inform strategies to induce human intestinal tissue from stem cells. Despite recent advances, fundamental gaps in our understanding of how foregut and hindgut progenitors are specified remain. In particular how the extracellular environment regulates combinatorial signaling dynamics at different stages of GI development, and how transcriptional specificity in response to these signal is achieved are largely unknown and the focus of this proposal. Our preliminary studies support the hypothesis that Secreted Frizzed Related Proteins (Sfrp) regulate the extracellular Fibronectin matrix to promote BMP signaling by a novel mechanism, and that Sfrps coordinate signaling crosstalk between BMP and Wnt growth factors to pattern the endoderm into foregut and hindgut progenitors. Aim 1 will characterize the novel mechanisms by which Sfrps and Tolloid proteases modulate the Fibronectin matrix to regulate BMP signaling. Aim 2 will determine the mechanisms that coordinate BMP and Wnt signaling. Aim 3 will determine how differential activity of the BMP and Wnt signaling effectors Smad1 and beta-catenin are integrated on DNA cis-regulatory elements to control foregut versus hindgut transcription.