Development of Synaptic Pathways in Retina

描述(申请人提供)：活性依赖的突触重塑是中枢神经系统正常发育和退行性疾病的基本特征。完全理解中枢神经系统神经回路的活性依赖性重塑的一个关键障碍是缺乏关于突触活动如何调节神经元结构的知识。最近的研究表明，典型的与免疫系统相关的蛋白由神经元表达，在中枢神经系统的正常发育和许多中枢神经系统疾病的发病机制中调节活性依赖的突触可塑性。因此，研究免疫分子在视网膜突触重构中的作用，将为了解视网膜退行性疾病的分子和突触机制奠定基础。本研究的长期目标是确定在突触活性和T细胞受体(TCR)的控制下调节RGC树突状重塑的机制。我们最近发现TCR的一个关键成分CD3？在视网膜节细胞中表达。CD3基因缺失？显著损害RGC轴突和树突的正常发育。药物阻断谷氨酸受体(GluR)介导的WT小鼠突触活性可复制CD3？/-小鼠的缺陷，但对CD3？/-小鼠无额外影响。突变体，暗示CD3？可能在GluR介导的视网膜节细胞树突状重塑中起关键作用。因为CD3的主要功能？在免疫细胞中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CD3？通过细胞骨架重组直接调节RGC树突。此外，我们将确定Glur介导的突触活性是否需要CD3？介导的RGC树突状细胞重塑的调节。本研究的第一个目的是确定CD3？通过检测RGC树突状细胞的CD3？功能增益，直接和选择性地调节RGC的树突状重构。AAV2病毒诱导视网膜神经节细胞表达CD3？在CD3中？-/-视网膜。第二个目标将调查CD3是如何？在发育过程中，通过决定CD3？在没有或有GluR介导的突触活性的情况下调节RGC树突状细胞的重构。第三个目标是确定CD3？通过检测Fyn和ZAP70突变/敲除是否像CD3一样损害RGC树突状重塑，通过Fyn/ZAP70介导的信号通路调节RGC树突状重塑。以及Fyn和ZAP70是否与CD3？介导的活性在调节RGC树突状细胞重塑中相互作用。这些研究结果不仅将为免疫分子如何调控视网膜突触回路的发育提供重要的见解，而且还将解决突触活性变化如何导致活性依赖突触可塑性中神经元形态变化的根本问题。 公共卫生相关性：了解中枢神经系统(CNS)神经元网络是如何在正常发育过程中形成并在病理条件下重塑的，将为制定治疗策略以保存和重建神经性疾病中中枢神经系统的结构和功能提供生物学基础。这项拟议的研究将解决突触活动和免疫分子如何调控视网膜神经节细胞(RGC)树突发育的问题。本研究中提出的实验的完成不仅将为中枢神经系统中活性依赖的突触可塑性机制开辟新的研究领域，而且将促进未来免疫分子在各种神经性疾病的发病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.