Organization and Maintenance of Axonal Domains

描述（由申请人提供）：电压门控钠通道在Ranvier节点上的丰富对于神经冲动以跳跃式的方式正确传导是至关重要的。虽然髓鞘形成和胶质细胞与轴突的相互作用促进了特定亚细胞轴突区域内离子通道的分离，但控制节点形成、组织和维持的确切机制尚不清楚。最近，一组被称为神经束蛋白（Nfasc）的细胞粘附分子被认为与轴突结构域的协调和稳定有关。两种主要的同工异构体已被表征，并显示在发育过程中受时空调节。NfascNF155 （NF155）在副神经节髓鞘环内的胶质细胞中特异性表达，而NfascNF186 （NF186）在Ranvier节点富集并在神经元中特异性表达。小鼠Nfasc基因消融导致轴突结构域（节点、旁节点和近旁节点）的完全紊乱，两种亚型的丢失，以及出生后第7天的死亡，这极大地阻碍了对每种亚型在节点发育、协调和稳定中的个体作用的研究。在本研究中，我们试图结合遗传学、细胞生物学、生理学和生物化学方法来确定NF186在节点形成中的具体作用，以及Nfascs在长期轴突结构域组织、轴突完整性和轴突功能中的作用。我们的具体目标是：1。确定NF86在结生物发生和发展中的作用。2. 确定NF186在轴突结构域长期维持和稳定中的作用。3. 确定成人神经束蛋白丢失是否导致轴突变性。

DESCRIPTION (provided by applicant): Enrichment of voltage-gated sodium channels to nodes of Ranvier is vital for the proper conductance of the nerve impulse in a saltatory manner. While myelination and the interaction of glia with axons facilitates the segregation of ion channels within specific subcellular axonal domains, the exact mechanisms governing the formation, organization and maintenance of the node are elusive. Recently, a group of cell adhesions molecules, known as Neurofascins (Nfasc), have been implicated in the coordination and stabilization of axonal domains. Two major isoforms have been characterized and are shown to be spatio-temporally regulated during development. NfascNF155 (NF155) is expressed specifically in glia within the paranodal myelin loops, while NfascNF186 (NF186), is enriched at the nodes of Ranvier and expressed specifically in neurons. Genetic ablation of Nfasc in mice resulted in the absolute disorganization of axonal domains (the node, paranode, and juxtaparanode), loss of both isoforms, and death at postnatal day 7, which has significantly hindered the examination of the individual roles of each isoform in nodal development, coordination, and stabilization. In this proposal, we seek to use a combination of genetic, cell biological, physiological and biochemical methods to determine the specific role of NF186 in nodal formation and the role of Nfascs during long-term axonal domain organization, axonal integrity and axonal function. Our specific aims are to: 1. Determine the role of NF86 during nodal biogenesis and development. 2. Determine the role of NF186 in the long-term maintenance and stabilization of axonal domains. 3. Determine whether loss of neurofascins in adults results in axonal degeneration. PUBLIC HEALTH RELEVANCE: The recent implication of Neurofascins in disease progression and pathology in demyelinating diseases, such as multiple sclerosis, has brought considerable focus towards the elucidation of their functions during axonal domain organization, axonal stability and axonal function. The studies proposed here will help to provide considerable insight into the individual and collective functions of Neurofascins to nodal formation and stabilization, as well as overall axonal domain organization and stability. It is likely that these studies will contribute towards the future development of therapeutic strategies that will allow for the treatment of afflicted individuals, through the restoration of the intimate relationship between axons and glia.