Development of Synaptic Pathways in Retina

描述（由申请人提供）：活动依赖性突触重塑是CNS正常发育和退行性疾病的基本特征。对中枢神经系统神经元回路活动依赖性重构的理解的一个关键障碍是缺乏突触活动如何调节神经元结构的知识。近年来的研究表明，免疫系统相关蛋白在中枢神经系统的正常发育和多种中枢神经系统疾病的发病机制中，由神经元表达并调节活性依赖性突触可塑性。因此，研究免疫分子在视网膜突触重塑中的作用，将为深入了解退行性视网膜疾病发病机制的分子和突触机制提供基础。本研究的长期目标是确定突触活性和T细胞受体（TCR）控制下调节RGC树突重塑的机制。我们最近发现TCR的一个关键成分CD 3？，以RGC表示。CD 3基因缺失？显著损害RGC轴突和树突的正常发育。野生型小鼠谷氨酸受体（GluR）介导的突触活性的药理学阻断表型模仿了在CD 3？-/-小鼠，但没有额外的影响，在CD 3？突变体，这表明CD 3？可能在GluR介导的RGCs树突重塑中起关键作用。因为CD 3的主要功能？在免疫细胞中的作用是通过重组细胞骨架来调节细胞形态，我们建议进一步研究CD 3？通过细胞骨架重组直接调节RGC树突。此外，我们将确定是否GluR介导的突触活动所需的CD 3？介导的调节RGC树突重塑。本研究的第一个目的是确定是否CD 3？直接和选择性地调节RGC树突重塑检查RGC树突与获得的功能CD 3？通过AAV 2病毒诱导RGCs表达CD 3？在CD 3中？-/-视网膜第二个目标将调查如何CD 3？相互作用与RGC突触活动在发展过程中确定是否CD 3？调节RGC树突重塑而不具有或具有GluR介导的突触活性。第三个目的是确定是否CD 3？通过Fyn/ZAP 70介导的信号通路调节RGC树突状重塑，研究Fyn和ZAP 70的突变/敲低是否像CD 3那样损害RGC树突状重塑？缺失，以及Fyn和ZAP 70是否与CD 3相互作用？介导的活性调节RGC树突重塑。 这些研究的结果将不仅提供重要的见解，免疫分子如何调节视网膜突触回路的发展，但也解决了突触活动的变化如何导致神经元形态的变化，在活动依赖性突触可塑性的基本问题。 公共卫生相关性：了解中枢神经系统（CNS）的神经元网络是如何在正常发育过程中形成的，并在病理条件下重塑，将提供生物学基础的治疗策略的发展，以保护和重建的结构和功能的中枢神经系统在神经元疾病。本研究将探讨突触活动和免疫分子如何调控视网膜神经节细胞树突的发育。本研究中提出的实验的完成不仅将为CNS中活性依赖性突触可塑性的机制开辟新的研究领域，而且还将刺激未来对免疫分子在各种神经元疾病的发病机制和治疗中的作用的研究。

DESCRIPTION (provided by applicant): Activity-dependent synaptic remodeling is a fundamental feature for both normal development and degenerative diseases of CNS. A critical barrier to fully understand activity-dependent remodeling of neuronal circuitry of CNS is the lack of the knowledge of how neuronal structure is regulated by synaptic activity. Recent studies have demonstrated that proteins typically associated with the immune system are expressed by neurons and regulate activity-dependent synaptic plasticity in the normal development of CNS and pathogenesis of many CNS diseases. Therefore, studies to identify the function of immune molecules in the synaptic remodeling of retina will provide the foundation for the understanding of the molecular and synaptic mechanisms essential for the pathogenesis in degenerative retinal diseases. The long-term goal of this study is to identify the mechanism that regulates RGC dendritic remodeling under the control of synaptic activity and T-cell receptor (TCR). We recently found that a key component of TCR, CD3?, is expressed in RGCs. Genetic deletion of CD3? significantly impairs the normal development of RGC axons and dendrites. Pharmacological blockage of glutamate receptor (GluR)-mediated synaptic activity in WT mice phenocopies the defects observed in CD3?-/- mice but has no additional effect in CD3? mutants, suggesting that CD3? could play a critical role in GluR-mediated dendritic remodeling of RGCs. Because a primary function of CD3? in immune cells is to regulate cell morphology by reorganizing cytoskeleton, we propose to further investigate whether CD3? directly regulates RGC dendrites via cytoskeleton reorganization. Additionally, we will determine whether GluR-mediated synaptic activity is required for the CD3?-mediated regulation of RGC dendritic remodeling. The first aim of this study is to determine whether CD3? directly and selectively regulates the dendritic remodeling of RGCs by examining RGC dendrites with gain-of-function of CD3? in RGCs through AAV2 virus induced expression of CD3? in CD3?-/- retinas. The second aim will investigate how CD3? interacts with RGC synaptic activity during development by determining whether CD3? regulates RGC dendritic remodeling without or with GluR-mediated synaptic activity. The third aim is to determine whether CD3? regulates RGC dendritic remodeling through Fyn/ZAP70-mediated signaling pathway by examining whether mutation/knockdown of Fyn and ZAP70 impairs RGC dendritic remodeling as that of CD3? deletion, and whether Fyn and ZAP70 interact with CD3?-mediated activity in the regulation of RGC dendritic remodeling. The results of these studies would not only provide important insights into how immune molecules regulate development of retinal synaptic circuits but also address the fundamental question of how changes of synaptic activity lead to changes of neuronal morphology in activity-dependent synaptic plasticity. PUBLIC HEALTH RELEVANCE: Understanding of how neuronal networks of the central nervous system (CNS) are formed during normal development and remodeled under pathological conditions will provide biological basis for the development of treatment strategies to preserve and reestablish the structure and function of the CNS in neuronal diseases. This proposed study will address the question of how synaptic activity and immune molecules regulate the development of retinal ganglion cell (RGC) dendrites. Accomplishment of the experiments proposed in this study would not only open up new areas of research for mechanisms of activity-dependent synaptic plasticity in the CNS but also stimulate future studies of the roles of immune molecules in pathogenesis and treatment of various neuronal diseases.