Intercellular Communication in Retinal Development

描述(申请人提供)：脊椎动物视网膜内的突触连接在结构和功能上都是高度组织的。我们的广泛目标是阐明视网膜电路在发育过程中组装的精确度的潜在机制。视网膜神经节细胞(RGC)将信息从眼睛传递到大脑中的视觉目标，从两类主要的视网膜中间神经元--无长突细胞和双极细胞--接受连接。这些视网膜中间神经元共同帮助形成视网膜节细胞对光刺激的反应特性。双极细胞使用谷氨酸作为神经递质，形成光感受器和视网膜节细胞之间的重要联系。双极细胞和视网膜节细胞之间的突触连接在成熟时被精确地组织起来。这项建议的具体目标是确定双极细胞在发育过程中如何与视网膜节细胞连接，并确定视觉前视网膜的活动如何帮助塑造这些细胞类型之间的连接。在目标1中，通过在视网膜节细胞表达荧光标记的PSD95(PSD95-FP)，定位于谷氨酸能突触的突触后蛋白，将绘制跨发育RGCs的双极输入的分布和密度。将使用实时成像方法来检验这一假设，即双极连接模式是通过突触的形成和消除过程建立的，其连接模式部分是通过RGC树突状突起的结构重塑来组织的。在目标2中，将通过检测视网膜外发育异常的突变动物的RGC树突结构、连接性和活性如何影响RGC树突结构，来确定光无关的光感受器传递在双极-RGC连接成熟中的重要性。总之，这些研究将增加我们对突触输入是如何在RGC树突上建立的，以及视觉之前对外部视网膜功能的干扰如何改变内部视网膜结构和功能的理解。

DESCRIPTION (provided by applicant): Synaptic connections within the vertebrate retina are highly organized both structurally and functionally. Our broad goal is to elucidate the mechanisms underlying the precision by which retinal circuits are assembled during development. Retinal ganglion cells (RGCs) that relay information from the eye to visual targets in the brain receive connections from two major classes of retinal interneurons, the amacrine cells and bipolar cells. Together, these retinal interneurons help shape the response properties of RGCs to light stimuli. Bipolar cells, which use glutamate as a neurotransmitter, form the essential link between photoreceptors and RGCs. Synaptic connections between bipolar cells and RGCs are precisely organized at maturity. The specific goal in this proposal is to determine how bipolar cells connect with RGCs during development, and ascertain how activity in the retina before vision helps shape the connectivity between these cell types. In Aim 1, the distribution and densities of bipolar inputs onto RGCs will be mapped across development, by expressing in RGCs fluorescently-tagged PSD95 (PSD95-FP), a postsynaptic protein localized to glutamatergic synapses. Live imaging approaches will be used to test the hypothesis that bipolar connectivity patterns are established by a process of synapse formation and elimination, and that their connectivity patterns are organized in part by structural remodeling of the RGC dendritic arbor. In Aim 2, the importance of light-independent photoreceptor transmission in the maturation of bipolar-RGC connectivity will be determined by examining how RGC dendritic structure, connectivity and activity are affected in mutant animals with abnormal outer retinal development. Together, these studies will increase our understanding of how synaptic inputs are established on RGC dendrites and how perturbation of outer retinal function prior to vision might alter inner retinal structure and function.