Role of TSC Proteins in Neuronal Polarity and Axon Guidance

描述（由申请人提供）：多发性硬化症（TSC）是一种常染色体显性遗传疾病，其特征是存在称为错构瘤的良性肿瘤，其几乎可以影响身体的每个器官系统。TSC的标志和这种疾病发病的主要原因是神经系统症状，如癫痫，自闭症和精神发育迟滞，发生在95%的受影响个体中。在过去的十年中，在确定TSC调节蛋白质合成和细胞大小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。我们提出了一组实验来研究神经元的连接和网络形成的小鼠模型的TSC。这些实验是基于我们最近的观察，即TSC途径组分在海马神经元的轴突中以高水平表达，从轴突极化的初始阶段开始。此外，我们发现，在缺乏Tsc 2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蛋白不仅对确定细胞大小至关重要，而且对确定大脑中的轴突连接也至关重要。我们提出了两组实验来阐明TSC 1/TSC 2蛋白在轴突极性的建立和轴突寻路的介导中所起的作用。通过使用分离培养物，急性脑切片和脑切片，我们将首先表征TSC蛋白在建立神经元极性中的作用。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获得的轴突通路。TSC蛋白复合物的运作可能是更全面地了解TSC异常神经网络的关键。因此，我们的研究结果可能会提出进一步的探索途径，以阐明TSC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.