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源自这些祖细胞的细胞的命运。了解视网膜祖细胞是如何调节的，在这种情况下是由激素调节的，将有助于了解这些重要细胞的基本知识，这些细胞可能有助于开发旨在通过促进内源性修复反应或移植祖细胞来修复受损视网膜的治疗干预措施。在这个应用程序中，重点将是如何TH功能的视网膜祖细胞，以促进同侧投影在青蛙非洲爪蟾。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节的独特分子见解。本应用的具体目的是：1）确定甲状腺激素在控制同侧投射发展中作用的时间和地点; 2）确定甲状腺激素调节的基因Xmamdc 2是否在视交叉的轴突转动中起作用，初步数据显示该基因在同侧投射的神经节细胞中表达并起作用，以及其功能是否与另一类轴突导向分子EphB的已知功能相似或不同; 3）确定假定的转录因子Zic 2是否通过调节EphBs或Xmamdc 2的表达来调节同侧投射，并确定Zic 2或其他甲状腺激素调节基因的作用是否由它们在祖细胞或分化的神经节细胞中的表达介导。为了达到这些目的，同侧投影将通过定量逆行和顺行标记方法进行测定。将用质粒和BAC转基因制造数百只转基因动物，以便在整个神经系统中表达基因产物，仅在眼睛中表达，或特异性地表达到祖细胞或神经节细胞。这些研究将产生新的见解，同侧视网膜丘脑投射的形式，将揭示一种新的机制参与轴突的指导，并将揭示甲状腺激素调节视网膜祖细胞的命运的机制。虽然实验将在非洲爪蟾中进行，但这些发现将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.