Delta and Mesoderm Induction in Eucidaris Embryos

描述(申请人提供)：Delta/Notch信号是大多数动物胚胎中许多不同细胞类型发育的重要诱导途径，包括棘皮动物。利用海胆胚胎，各种技术，包括分子生物学、显微外科和显微镜方法，可以结合起来回答有关发育的重要问题。棘皮动物门也处于与脊椎动物相近的进化位置，为研究后口动物的发育进化提供了独特的模式。这项研究的长期目标是研究棘皮动物门内中胚层发育的进化。衍生海胆的胚胎在植物极有四个微体，具有很强的组织能力。我们最近的研究表明，在衍生的海胆中，Delta的正常作用是诱导中胚层；微米后代表达Delta；仅Delta的表达就足以组织整个胚胎。原始海胆的胚胎具有数量不等的微粒和中胚层，这些胚胎形成的时间比衍生海胆的要晚得多。这些特征表明，中胚层发育存在显著差异，微粒子在发育过程中可能不像衍生海胆那样发挥关键作用。这里提出的研究将确定Delta和其他诱导途径在原始海胆发育中的作用。有四个具体目标。(1)我们将描述Delta的表达模式。我们假设Delta将在稍后的时间表达；Delta可能由微不足道的后代表达，也可能不表达。(2)利用过表达实验和基因敲除实验研究Delta的功能。这些错误表达实验将与显微外科手术相结合，在正常胚胎的背景下检查特定细胞中Delta的功能。(3)利用命运映射技术精确定位中胚层的起源。我们假设有几种类型的中胚层将起源于微粒。(4)我们将研究微体是否对中胚层发育和其他类型的细胞发育是必要和/或充分的。我们还将研究推测的微米诱导的时间。通过关注原始海胆的发育，这项研究将开始深入了解Delta/Notch信号通路和中胚层发育是如何在棘皮动物门中进化的。

DESCRIPTION (provided by applicant): Delta/Notch signaling is an important inductive pathway in the development of many different cell types in the embryos of most animals, including echinoderms. Using sea urchin embryos, a variety of techniques, including methods in molecular biology, microsurgery and microscopy, can be combined to answer important questions about development. The echinoderm phylum is also in a close evolutionary position relative to the vertebrates, and provides a unique model for studying the evolution of deuterostome development. The long-term goal of this research is to examine the evolution of mesoderm development within the echinoderm phylum. The embryos of derived sea urchins have four micromeres at the vegetal pole that have powerful organizing abilities. Our recent studies show that the normal role of Delta in derived sea urchins is to induce mesoderm; the micromere descendants express Delta; and Delta expression alone is sufficient to organize the whole embryo. The embryos of primitive sea urchins have variable numbers of micromeres and mesoderm in these embryos forms much later than in derived sea urchins. These features suggest that there are significant differences in mesoderm development and that the micromeres may not play as critical a role in development as in derived sea urchins. The research proposed here will identify the role of Delta and other inductive pathways involved in the development in the primitive sea urchin. There are four specific aims. (1) We will characterize the expression pattern of Delta. We hypothesize that Delta will be expressed at a later time; Delta may or may not be expressed by micromere descendants. (2) We will use overexpression and knockdown experiments to examine the function of Delta. These misexpression experiments will be combined with microsurgery to examine Delta function in specific cells in the context of an otherwise normal embryo. (3) We will use fate mapping techniques to pinpoint the origin of mesoderm. We hypothesize that that several types of mesoderm will originate from the micromeres. (4) We will examine whether the micromeres are necessary and/or sufficient for mesoderm development and the development of other cell types. We will also examine the timing of putative micromere induction. By focusing on the development of a primitive sea urchin, this research will begin to provide insight on how the Delta/Notch signaling pathway and mesoderm development have evolved within the echinoderm phylum.