Role of TSC Proteins in Neuronal Polarity and Axon Guidance

描述（由申请人提供）：结节性硬化症（TSC）是一种常染色体显性疾病，其特征是存在称为错构瘤的良性肿瘤，几乎可以影响身体的每个器官系统。TSC的标志和该病发病的主要原因是神经系统症状，如癫痫、自闭症和智力迟钝，95%的患者会出现这些症状。在过去的十年中，在确定TSC在调节蛋白质合成和细胞大小方面的功能方面取得了重大进展。然而，TSC患者神经系统症状的原因尚未得到解决。我们提出了一套实验来研究小鼠TSC模型中的神经元连接和网络形成。这些实验是基于我们最近的观察，即从轴突极化的初始阶段开始，TSC通路成分在海马神经元轴突中高水平表达。此外，我们发现在缺乏Tsc2的小鼠中，与野生型小鼠相比，大脑中连接的地形图是异常的。这些发现使我们假设TSC蛋白不仅对决定细胞大小至关重要，而且对决定大脑中轴突的连通性也至关重要。我们提出了两组实验来阐明TSC1/TSC2蛋白在轴突极性的建立和轴突寻径的介导中的作用。通过分离培养、急性脑切片和脑切片，我们将首先表征TSC蛋白在神经元极性建立中的作用。在该项目的第二阶段，我们将描述TSC蛋白在轴突寻路和生长锥动力学中的作用。最终，我们的工作将通过检查TSC缺陷小鼠的视觉通路来确定TSC蛋白在神经元网络形成中的作用-这是中枢神经系统中研究得最好和最容易接近的轴突通路。了解TSC蛋白复合物的功能可能是全面认识TSC异常神经网络的关键。因此，我们的结果可能提示进一步的探索途径，以阐明TSC特征的破坏性神经症状的复杂原因。

DESCRIPTION (provided by applicant): Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterized by the presence of benign tumors, called hamartomas, which can affect virtually every organ system of the body. The hallmark of TSC and the predominant cause of morbidity in this disease are the neurological symptoms, such as epilepsy, autism and mental retardation, which occur in 95% of affected individuals. Over the last decade, significant progress has been made in identifying a function for TSC in regulating protein synthesis and cell size. However, the cause of the neurological symptoms in TSC patients has not yet been resolved. We propose a set of experiments to investigate neuronal connectivity and network formation in mouse models of TSC. These experiments are based on our recent observation that TSC pathway components are expressed in axons of hippocampal neurons at high levels starting with the initial stages of axonal polarization. Furthermore, we find that in mice lacking Tsc2, topographic mapping of connections in the brain are aberrant compared to wild-type mice. These findings have led us to hypothesize that TSC proteins are crucial not only for determining cell size, but also for determining axonal connectivity in the brain. We propose two sets of experiments to elucidate the role played by TSC1/TSC2 proteins in the establishment of axonal polarity and the mediation of axonal pathfinding. By using dissociated cultures, acute brain slices, and brain sections, we will first characterize the role of TSC proteins in the establishment of neuronal polarity. In the second phase of the project, we will characterize the role of TSC proteins in axon pathfinding and growth cone dynamics. Ultimately, our work will determine the role of TSC proteins in neuronal network formation by examining the visual pathways in Tsc-deficient mice - the best-studied and most accessible axon pathway in the central nervous system. The operations of TSC protein complex may be the key to a fuller understanding of the abnormal neural networks of TSC. Our results, thus, may suggest further avenues of exploration to illuminate the complex causes of the devastating neurological symptoms that characterize TSC.