Organization and Maintenance of Axonal Domains

描述(由申请人提供)：丰富兰维尔结节的电压门控钠通道对于以跳跃式方式适当传导神经冲动至关重要。虽然髓鞘形成和胶质细胞与轴突的相互作用促进了离子通道在特定的亚细胞轴突区域内的分离，但控制结节形成、组织和维持的确切机制尚不清楚。最近，一组细胞黏附分子被称为神经束蛋白(NeuroFascins，NFasc)，参与轴突结构域的协调和稳定。两种主要的异构体已经被表征，并被证明在发育过程中是时空调节的。NFascNF155(NF155)在结旁髓鞘环内的神经胶质细胞中特异表达，而NFascNF186(NF186)则在Ranvier结节特异表达，并在神经元中特异表达。基因消融NFasc导致小鼠轴突域(结节、副阳极和旁副阳极)的绝对解体，两种异构体的丢失，并在出生后7天死亡，这显著阻碍了对每种异构体在结节发育、协调和稳定中的单独作用的研究。在这个方案中，我们试图结合遗传学、细胞生物学、生理和生化方法来确定NF186在结节形成中的特定作用，以及NFascs在长期轴突域组织、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在结节生物发生和发育中的作用。2.确定NF186在轴突域的长期维持和稳定中的作用。3.确定成人神经束蛋白的缺失是否会导致轴突变性。 公共卫生相关性：最近神经束蛋白在多发性硬化症等脱髓鞘疾病的疾病进展和病理中的意义，引起了人们对其在轴突域组织、轴突稳定性和轴突功能中的功能的阐明的相当大的关注。这些研究将有助于深入了解神经束蛋白在结节形成和稳定中的个体和集体功能，以及整个轴突域的组织和稳定。这些研究很可能将有助于未来治疗策略的发展，通过恢复轴突和神经胶质之间的亲密关系，允许对患者进行治疗。

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.