Function of Mesendoderm in Closure of the Anterior Neural Tube

描述（由申请人提供）：神经管缺陷（NTD）是由于平坦的神经管板未能转变为封闭的神经管而导致的，大约每千名新生儿中就会发生一例。当前神经管无法闭合时，就会导致一种致命的先天缺陷，即大脑和颅骨无法发育。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。我们发现斑马鱼胚胎与减少的节点信号具有类似于无脑畸形的表型。节点信号的作用不在神经管本身，而是在头部中胚层，前神经管下面的中胚层和内胚层的结合组织。节点信号突变体头部中胚层的抢救有效地纠正了它们的NTD。头部中胚层/中胚层在脊椎动物的前神经发育中具有保守的作用，但人们对其作用知之甚少。这一提议将验证斑马鱼在囊胚晚期到原肠胚早期需要中胚层来启动神经管前体组织成极化神经上皮的假设。我们的目标是：(1)确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化变化，(2)确定这些生化变化中哪些依赖于头部中胚层，(3)绘制中胚层在发育过程中何时何地促进前神经的功能，以及(4)测试候选蛋白在介导中胚层功能中的重要作用。这些实验将确定头部中胚层在神经管发育中的新作用。此外，由于驱动神经发育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是为本科生设计的。它们依赖于我实验室中许多本科生已经掌握的成熟技术。此外，实验被分成特定的部分，每个部分依赖于一种分子技术。这将使学生能够在他们的时间框架内从开始到出版一个项目

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.