Genetic Mechanisms of Axis Formation in Vertebrates

描述（由申请方提供）：拟定研究的长期目标是确定脊椎动物发育期间细胞命运特化和原肠胚形成的机制。我们的重点是Nodal TGF β信号通路，它在脊椎动物的原肠胚形成和左右轴决定过程中起着重要作用。特别是，Nodal信号是中胚层和内胚层祖细胞的浓度依赖性诱导剂，并且是原肠胚形成期间细胞内化所需的。拟议的研究解决了三个基本问题：（A）如何在时间和空间中解释节点信号？(B)Nodal信号是如何调节的？(C)哪些基因介导原肠胚形成过程中Nodal信号的作用？为了解决这些问题，提出了以下三个目标。(1)为了确定如何解释Nodal信号，将调节Nodal信号的表达，并将在活胚胎中观察Nodal效应子Smad2的分布。这一目标将检验细胞不断监测Nodal信号并根据信号浓度和暴露时间选择其命运的假设。(2)为了确定microRNA在调节Nodal信号传导中的作用，将改变microRNA功能并分析表型结果。这一目标将检验microRNA通过抑制Nodal信号组分的表达来维持Nodal信号平衡的假设。(3)已经鉴定了参与中胚层和内胚层祖细胞内化和分化的节点调节基因。为了确定Nodal调控基因在原肠胚形成过程中的作用，将结合体内成像和突变体分析。人类的Nodal信号成分异常与前脑异常、左右缺陷和癌症有关。因此，拟议的研究应有助于为理解人类出生缺陷和疾病提供必要的背景。内胚层或中胚层的体外生成对于开发用于再生医学的基于细胞的疗法至关重要。因此，拟议的研究将有助于为诱导干细胞分化为器官祖细胞的策略提供信息。

DESCRIPTION (provided by applicant): The long-range goal of the proposed studies is to identify the mechanisms of cell fate specification and gastrulation during vertebrate development. Our focus is on the Nodal TGFbeta signaling pathway, which plays fundamental roles during gastrulation and left-right axis determination in vertebrates. In particular, Nodal signals are concentration-dependent inducers of mesodermal and endodermal progenitors and required for cell internalization during gastrulation. The proposed research addresses three fundamental questions: (A) How are Nodal signals interpreted in time and space? (B) How is Nodal signaling regulated? (C) Which genes mediate the effects of Nodal signaling during gastrulation? To address these questions, the following three aims are proposed. (1) To determine how Nodal signals are interpreted, the expression of Nodal signals will be modulated and the distribution of the Nodal effector Smad2 will be visualized in live embryos. This aim will test the hypothesis that cells constantly monitor Nodal signals and chose their fate according to both signal concentration and exposure time. (2) To determine the role of microRNAs in the regulation of Nodal signaling, microRNA function will be altered and the phenotypic consequences analyzed. This aim will test the hypothesis that microRNAs maintain Nodal signaling at equilibrium by dampening the expression of Nodal signaling components. (3) Nodal-regulated genes have been identified that are involved in the internalization and differentiation of mesodermal and endodermal progenitors. To determine the role of Nodal-regulated genes during gastrulation, in vivo imaging and mutant analysis will be combined. Abnormalities in Nodal signaling components in humans are associated with forebrain anomalies, left-right defects and cancer. The proposed studies should thus help to provide the necessary context for understanding human birth defects and disease. The in vitro generation of endoderm or mesoderm is crucial to develop cell-based therapies for regenerative medicine. The proposed studies will thus help to inform strategies to induce stem cells to differentiate into organ progenitors.