Role of Fat3 at the intersection of neuronal morphology and synapse localization

描述（由申请人提供）：修复损伤、神经退行性疾病或功能障碍发育后的神经系统是生物医学研究的一个重大挑战。了解新生神经元如何在环境信号的引导下形成正确的神经元形态和突触连接，是开发修复这些疾病状态的治疗方法的关键。我们目前对神经元如何形成其特定形状和突触的理解主要是细胞培养研究的结果，其中发育中的神经元不暴露于正常的细胞外信号。该建议结合小鼠遗传学、延时成像和表型分析来了解神经元极化和突触发生是如何在发育组织的背景下精心安排的。非典型钙粘蛋白Fat3为研究突触形成和神经元形态之间的关系提供了一个独特的分子切入点。脂肪3在视网膜的无突细胞和视网膜神经节细胞中表达。小鼠中脂肪3的基因缺失导致无毛细胞的突触异位和形态破坏。这种表型背后的事件是未知的。这一提议将验证Fat3介导轴突和树突位置和形状的细胞间相互作用的中心假设，这反过来又限制了突触的位置。为此，我将研究Fat3在连接细胞外信号和神经元信号中的作用

DESCRIPTION (provided by applicant): Repairing the nervous system after injury, neurodegenerative disease, or dysfunctional development represents a significant challenge to biomedical research. Understanding how newly born neurons are guided by signals in their environment to form the correct neuronal morphology and synaptic connections is key to developing therapies to repair these disease states. Our current understanding of how neurons develop their specific shape and set of synapses is primarily the result of cell culture studies, where developing neurons are not exposed to the normal set of extracellular cues. This proposal combines mouse genetics, time-lapse imaging, and phenotypic analysis to understand how neuronal polarization and synaptogenesis are orchestrated in the context of the developing tissue. The atypical cadherin Fat3 offers a unique molecular entry point to investigate the relationship between synapse formation and neuronal morphology. Fat3 is expressed in the amacrine and retinal ganglion cells of the retina. Genetic deletion of fat3 in mice results in ectopic synapses and disrupted morphology in amacrine cells. The events that underlie this phenotype are unknown. This proposal will test the central hypothesis that Fat3 mediates cell-cell interactions that position and shape axons and dendrites, which in turn restricts synaptic location. To this end I will investigate the role of Fat3 in linking extracellular cues to neuronal polarity and synaptogenesis, and then ask if Fat3 plays a similar role in the development of other neurons. Specific Aim 1 is focused on investigating cellular events that lead to the correct development of amacrine cells, and then determining what events are Fat3-dependent. Establishment of a novel time-lapse retinal slice imaging method will facilitate the analysis of single amacrine cells developing in their natural context in mammals. Additionally, this aim seeks to understand the relationship between neuronal polarization and synaptogenesis. Specific Aim 2 is directed at understanding the role of Fat3-mediated cell-cell interactions with other neurons that controls the development of retinal ganglion cell axonal and dendritic morphology. Deletion of fat3 from specific populations of retinal ganglion and amacrine cells, followed by phenotypic analysis of the morphology of the resulting retinal ganglion cell axon and dendrites will provide a clear understanding of how cell-cell contacts mediate development. Collectively, the work described here will provide novel insight into amacrine and retinal ganglion cell development. Specifically, the results will answer key questions about the relationship between neuronal morphology and synapse formation in the context of the extracellular environment, as well as the role of cellular interactions in forming neuronal circuit.