Circuit Assembly in the Vertebrate Retina

描述(申请人提供)：中枢神经系统(CNS)的正常运作需要它的许多细胞组件适当地连接，以便处理和编码大脑每个部分特有的信息。因此，确定中枢神经系统在发育过程中是如何准确连接的是至关重要的。尽管我们已经对电路发展至关重要的细胞和分子机制有了很大的了解，但仍有许多事情要揭开。发现这些机制需要一些方法来阐明细胞之间如何相互作用以形成和维持联系。我们的长期目标是了解脊椎动物视网膜的许多细胞类型之间是如何建立高度特异的突触连接的，主要有两个原因：(1)视网膜对视觉是必不可少的；(2)它的结构和功能密切相关，使其成为研究神经环路在发育过程中如何组织的极佳模型。在这项研究中，我们将重点放在视网膜的第一层突触上，即外丛状层(OPL)，视觉信号首先在该层内在视觉系统中进行处理。在OPL中，光感受器接触双极细胞，然后将信号沿着不同的路径传递到视网膜输出细胞。水平细胞调制光感受器传递的信息。尽管OPL的视觉处理很重要，但人们对其在开发过程中的组装知之甚少。我们建议使用并产生转基因小鼠来研究不同的视网膜外细胞类型如何相互作用来建立OPL中的回路。我们将标记活体动物的光感受器、双极细胞和水平细胞，通过使用细胞特异性启动子使它们表达荧光蛋白。最先进的光学成像方法将被应用于可视化和跟踪这些细胞的过程如何相互形成适当的接触。我们还将使用和产生突变小鼠，以解决水平细胞的重要性，水平细胞发育最早，在调节OPL的结构和功能发育方面。我们的结果应该可以更深入地理解细胞之间的相互作用如何导致它们的电路的建立，从而为神经系统的发育障碍提供进一步的洞察。我们的发现可能有助于将重点放在未来的研究上，目的是设计策略，在创伤或疾病中重建视网膜功能。

DESCRIPTION (provided by applicant): The proper functioning of the central nervous system (CNS) requires that its many cellular components are connected appropriately, in order to process and encode information specific to each part of the brain. Thus, determining how the CNS is wired up precisely during development is fundamentally important. Although we have gained a significant understanding of the cellular and molecular mechanisms that are critical for circuit development, much has yet to be unraveled. Discovering these mechanisms requires approaches that will elucidate how cells interact with each other to form and maintain connections. Our long term goal is to understand how highly specific synaptic connections are established between the many cell types of the vertebrate retina, largely for 2 reasons: The retina is (1) essential for vision; and (2) its strongly correlated structure and function makes it an excellent model for investigating how neural cricuits are organized during development. In this proposal, we will focus on the first synaptic layer of the retina, the outer plexiform layer (OPL), within which visual signals are first processed in the visual system. In the OPL, photoreceptors contact bipolar cells that then relay signals along distinct pathways to retinal output cells. Horizontal cells modulate information conveyed from photoreceptors. Despite the importance of visual processing by the OPL, little is understood concerning its assembly during development. We propose to use and generate transgenic mice to examine how the various outer retinal cell types interact with each other to establish circuitry in the OPL. We will label photoreceptors, bipolar and horizontal cells in live animals, by causing them to express fluorescent proteins using cell-specific promoters. State-of-the-art optical imaging methods will be applied to visualize and follow how processes of these cells come to form appropriate contact with each other. We will also use and generate mutant mice to address the importance of horizontal cells, which develop earliest, in regulating the structural and functional development of the OPL. Our results should provide a deeper understanding of how interactions between cells lead to the establishment of their circuits, and thus provide further insight into developmental disorders in the nervous system. Our findings could potentially help focus future investigations aimed at designing strategies to re-establish retinal function in trauma or disease.