Function of Mesendoderm in Closure of the Anterior Neural Tube

描述（由申请人提供）：神经管缺陷（NTD）是由扁平神经板转化为闭合神经管失败引起的，大约每千名新生儿中就有一名发生。当前神经管不能闭合时，会导致一种致命的出生缺陷，称为无脑畸形，大脑和头骨无法发育。我们的长期目标是利用斑马鱼来确定控制前神经管闭合的遗传和细胞机制。我们发现Nodal信号减少的斑马鱼胚胎具有类似于无脑畸形的表型。Nodal信号的作用不在神经管本身内，而是在头部中内胚层内，一种位于前神经管下方的中胚层和内胚层组织。拯救Nodal信号转导突变体中的头部中内胚层有效地纠正了它们的NTD。 头部中内胚层/中胚层在脊椎动物的前神经形成中具有保守的作用，但这种作用知之甚少。这项建议将测试的假设，热中内胚层在斑马鱼是需要在囊胚后期早期原肠胚阶段，以启动组织的神经管前体成极化的神经上皮。我们的目标是：（1）鉴定在发育中的神经上皮中建立粘附连接、紧密连接和不对称蛋白定位的连续生物化学变化，（2）确定这些生物化学变化中的哪些依赖于头部中内胚层，（3）绘制发育中中内胚层何时何地起作用以促进前部神经形成的图谱，和（4）测试候选蛋白在介导中内胚层功能中的重要作用。这些实验将确定头部中内胚层在神经管发育中的新作用。此外，由于驱动神经形成的过程在物种之间很大程度上是保守的，这项研究将增加我们对正常发育的理解，并使我们深入了解人类无脑畸形的潜在原因。 重要的是，本提案中的假设驱动实验旨在由本科生进行。他们依赖于完善的技术，已经掌握了许多本科生在我的实验室。此外，实验被分成特定的部分，每个部分都依赖于一种分子技术。这将使学生能够在他们的时间范围内从开始到出版一个项目。 本科学习。预计该项目将为本科生提供发育遗传学领域的宝贵经验，为他们未来的职业和研究提供基础，同时为我实验室的科学和对神经形成机制的理解做出重要贡献。 公共卫生相关性：神经管闭合失败是人类最常见的出生缺陷之一，但其原因尚不清楚。我们将利用斑马鱼的遗传和胚胎学技术来揭示神经管闭合所需的新机制。由于驱动神经管形成的细胞机制在脊椎动物物种中基本上是保守的，这项工作将为诊断和治疗人类神经管缺陷的新方法提供见解。

DESCRIPTION (provided by applicant): Neural tube defects (NTD), resulting from a failure in the transformation of a flat neural plate into a closed neural tube, occur in approximately one in every thousand births. When the anterior neural tube fails to close, it results in a fatal birth defect called anencephaly in which the brain and skull fail to develop. Our long-term goal is to use zebrafish to define the genetic and cellular mechanisms that control closure of the anterior neural tube. We found that zebrafish embryos with reduced Nodal signaling have a phenotype analogous to anencephaly. The role of Nodal signaling is not within the neural tube itself, but within the head mesendoderm, a combined mesodermal and endodermal tissue that underlies the anterior neural tube. Rescue of head mesendoderm in Nodal signaling mutants effectively corrects their NTD. Head mesendoderm/mesoderm has a conserved role in anterior neurulation in vertebrates, but this role is poorly understood. This proposal will test the hypothesis that hea mesendoderm in zebrafish is required during late blastula to early gastrulation stages to initiate organization of neural tube precursors into a polarized neuroepithelium. Our objectives are to: (1) identify the sequential biochemical changes that establish adherens junctions, tight junctions, and asymmetric protein localization in the developing neuroepithelium, (2) define which of these biochemical changes depend upon head mesendoderm, (3) map when and where during development mesendoderm functions to promote anterior neurulation, and (4) test candidate proteins for essential roles in mediating mesendoderm function. These experiments will identify new roles for head mesendoderm in the development of the neural tube. Further, as the processes that drive neurulation are largely conserved between species, this research will increase our understanding of normal development and give us insight into potential causes of anencephaly in humans. Importantly, the hypothesis-driven experiments in this proposal are designed to be carried out by undergraduate students. They rely on well established techniques that have been mastered many undergraduate students in my laboratory. Further, the experiments are divided into specific sections that each rely on one molecular technique. This will enable students to take a project from beginning to publication within the time frame of their undergraduate studies. It is expected that this project will give undergraduate students valuable experience with the field of developmental genetics that will provide the basis for their future careers and studies while making important contributions to the science in my laboratory and to the understanding of the mechanisms underlying neurulation. PUBLIC HEALTH RELEVANCE: Failures in neural tube closure are some of the most common birth defects in humans, but the causes are not well understood. We will use the genetic and embryological techniques available in zebrafish to uncover new mechanisms required for neural tube closure. As the cellular mechanisms that drive formation of the neural tube are largely conserved among vertebrate species, this work will provide insights into new ways to diagnose and treat neural tube defects in humans.