Development of Synaptic Pathways in Retina

描述（由申请人提供）：活动依赖性突触重构是中枢神经系统正常发育和退行性疾病的基本特征。充分理解中枢神经系统神经元回路活动依赖性重构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。最近的研究表明，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过程中，与免疫系统相关的蛋白质通常由神经元表达并调节活动依赖性突触可塑性。因此，研究免疫分子在视网膜突触重塑中的功能，将为理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在突触活性和t细胞受体（TCR）的控制下，确定调控RGC树突重塑的机制。我们最近发现TCR的关键成分CD3？，在rgc中表达。CD3基因缺失？显著损害RGC轴突和树突的正常发育。在WT小鼠中，谷氨酸受体（GluR）介导的突触活性的药物阻断表现了CD3？-/-小鼠，但对CD3？突变，表明CD3？可能在glur介导的RGCs树突重塑中发挥关键作用。因为CD3的主要功能是什么？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CD3？通过细胞骨架重组直接调控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树突重塑调控。这项研究的第一个目的是确定CD3？通过检测RGC树突的CD3功能获得性，直接和选择性地调节RGC的树突重塑通过AAV2病毒诱导CD3？在CD3吗?- / -视网膜。第二个目标是研究CD3？在发育过程中通过决定CD3？调节无或有glur介导的突触活性的RGC树突重塑。第三个目标是确定CD3？通过检测Fyn和ZAP70的突变/敲低是否像CD3？Fyn和ZAP70是否与CD3相互作用？-介导的活性在调控RGC树突重塑中的作用。这些研究结果不仅为了解免疫分子如何调节视网膜突触回路的发育提供了重要的见解，而且还解决了突触活动变化如何导致活动依赖性突触可塑性中神经元形态变化的基本问题。

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.