Thyroid hormone & metamorphic ipsilateral projection

描述(由申请人提供)：拟议研究的广泛、长期目标是了解祖细胞内的基因调控如何影响从这些祖细胞衍生的细胞的命运。了解视网膜祖细胞是如何受到调节的，在这种情况下是由一种激素调控的，这将有助于提供关于这些重要细胞的基本知识，有助于开发旨在通过促进内源性修复反应或通过移植祖细胞来修复受损视网膜的治疗干预措施。在这项应用中，重点将放在TH如何在视网膜前体细胞中发挥作用，以促进非洲爪蛙的同侧投射。利用这种模式生物的多种实验优势，将出现对祖细胞和神经节细胞命运调控的独特分子见解。这一应用的具体目的是：1)确定甲状腺激素在控制同侧投射发育中的作用的时间和地点；2)确定甲状腺激素调节基因Xmadc2是否在同侧投射神经节细胞中表达和功能，以及它的功能是否与另一类轴突引导分子EphBS的已知功能相似或不同；3)确定可能的转录因子Zic2是否通过调节Ephbs或Xmadc2的表达来调节同侧的投射，以及Zic2或其他甲状腺激素调节基因的作用是否通过它们在祖细胞或分化的神经节细胞中的表达来调节。为了达到这些目的，将采用定量逆行和顺行标记法对同侧投射进行分析。数以百计的转基因动物将被制成质粒和BAC转基因动物，以便在整个神经系统中表达基因产物，仅在眼睛中表达，或者特异性地表达到祖细胞或神经节细胞。这些研究将对同侧视网膜丘脑投射如何形成产生新的见解，将揭示参与轴突引导的新机制，并将揭示甲状腺激素调节视网膜前体细胞命运的机制。虽然这些实验将在非洲爪哇进行，但这些发现也适用于其他脊椎动物，包括哺乳动物。

DESCRIPTION (provided by applicant): The broad, long-term objective of the proposed studies is to understand how gene regulation within progenitor cells affects the fate of cells that derive from these progenitors. Understanding how retina progenitors are regulated, in this case by a hormone, will contribute essential knowledge about these important cells that may aid in developing therapeutic interventions that aim to repair the damaged retina either by promoting an endogenous repair response, or by transplanting progenitor cells. In this application, the focus will be on how TH functions in retina progenitors to promote the ipsilateral projection in the frog Xenopus laevis. Capitalizing on multiple experimental advantages of this model organism, unique molecular insight into the regulation of progenitor cell and ganglion cell fate will emerge. The specific aims of this application are to: 1) determine the time and place of thyroid hormone action in controlling the development of the ipsilateral projection; 2) determine both whether a thyroid hormone regulated gene, Xmamdc2, which preliminary data show is expressed and functional in ipsilaterally projecting ganglion cells, functions in the turning of axons at the optic chiasm, and whether its function is similar or different from the known function of another class of axon guidance molecules, the EphBs; 3) determine whether a putative-transcription factor, Zic2, regulates the ipsilateral projection by regulating the expression of EphBs or Xmamdc2, and determine whether the action of Zic2 or other thyroid hormone regulated genes is mediated by their expression in either progenitor cells or differentiated ganglion cells. To meet these aims, the ipsilateral projection will be assayed by quantitative retrograde and anterograde labeling methods. Hundreds of transgenic animals will be made with plasmid and BAC transgenes in order to express gene products in the entire nervous system, only in the eye, or specifically to progenitor cells or ganglion cells. These studies will yield novel insight as to how the ipsilateral retinothalamic projection forms, will reveal a novel mechanism involved in axon guidance, and will uncover the mechanism by which thyroid hormone regulates the fate of retina progenitor cells. Though the experiments will be performed in Xenopus, the findings will be applicable to other vertebrates, including mammals.