Mechanisms of CNS node of Ranvier formation

项目总结 动作电位在哺乳动物神经中的快速高效传播 系统需要髓鞘形成和电压门控离子的高密度聚集 髓鞘缝隙处的通道称为兰维尔结节。虽然很多人 脱髓鞘疾病和损伤会导致节点和神经系统的破坏 功能障碍，负责中央离子通道聚集的机制 兰维尔神经系统(CNS)结节尚不清楚。我们建议三个 不同的细胞和分子相互作用有助于中枢神经系统结节的形成和 维护：1)轴突细胞黏附分子与独特的 中枢神经系统结节细胞外基质，2)轴突和髓鞘胶质细胞之间的相互作用 结旁连接建立了膜蛋白扩散屏障以限制侧向 节点蛋白的迁移率，以及3)节膜蛋白与 结节细胞骨架支架维持高密度的离子通道簇。因此， 中枢神经系统中可能存在多个重叠的机制以促进离子通道 在Ranvier的节点处进行群集。在这个项目中，我们将承担细胞生物学和 用遗传学方法确定Ranvier中枢神经系统结节的机制 队形。我们将专注于外在的、神经胶质衍生的相互作用，这些相互作用是 中枢神经系统结节形成。在第一个目标中，我们将阐明分子相互作用 结节细胞黏附分子与中枢神经系统结节细胞外基质蛋白之间的相互作用。我们会 确定可溶性ECM蛋白是否足以诱导结节蛋白在 纯化的神经细胞培养。在第二个目标中，我们将对单个、 缺乏细胞外基质分子的双重和三重基因敲除小鼠，旁结节 连接和/或细胞骨架相互作用，以揭示存在和要求 对于每一种重叠的机制。

PROJECT SUMMARY Rapid and efficient propagation of action potentials in the mammalian nervous system requires both myelination and the high-density clustering of voltage-gated ion channels at gaps in the myelin sheath called nodes of Ranvier. Although many demyelinating diseases and injuries cause disruption of nodes and nervous system dysfunction, the mechanisms that are responsible for ion channel clustering at central nervous system (CNS) nodes of Ranvier remain unknown. We propose that three distinct cellular and molecular interactions contribute to CNS node formation and maintenance: 1) interactions between axonal cell adhesion molecules and a unique CNS nodal extracellular matrix, 2) interactions between axons and myelinating glia at paranodal junctions set up a membrane protein diffusion barrier to restrict the lateral mobility of nodal proteins, and 3) interactions between nodal membrane proteins and nodal cytoskeletal scaffolds maintain high density clusters of ion channels. Thus, multiple, overlapping mechanisms may exist in the CNS to facilitate ion channel clustering at nodes of Ranvier. In this project we will undertake both cell biological and genetic methods to determine the mechanisms underlying CNS node of Ranvier formation. We will focus on the extrinsic, glial-derived interactions that are necessary for CNS node formation. In the first aim we will elucidate the molecular interactions between nodal cell adhesion molecules and CNS nodal ECM proteins. We will determine if soluble ECM proteins are sufficient to induce clustering of nodal proteins in purified neuronal cultures. In the second aim we will perform genetic analyses of single, double, and triple knockout mice lacking extracellular matrix molecules, paranodal junctions, and/or cytoskeletal interactions to uncover the existence of, and requirement for, each overlapping mechanism.