Regulation of node of Ranvier formation and maintenance by astrocytes

正常的神经系统功能依赖于神经元和非神经元胶质细胞之间的相互作用。这些神经元与神经胶质的关系可能是高度特异性的，例如少突胶质细胞对轴突的髓鞘形成。在相邻髓鞘之间的连接处，即兰维耶结处，复杂的结构成分将髓鞘粘附在轴突膜上，并约束结处高密度的Na通道，以实现快速的跳跃传导。星形胶质细胞，另一种胶质细胞，产生高度分叉的形态，有效地填充所有其他细胞之间的空间，以分配营养物质和平衡离子浓度，为神经元通信提供环境。几乎每个Ranvier淋巴结都被结周星形胶质突（PAPs）所覆盖。虽然神经细胞与少突胶质细胞之间的相互作用是Ranvier结构和功能节点所必需的，但星形胶质细胞在节点中的作用及其与少突胶质细胞髓鞘的相互作用几乎完全未知。虽然pap可能有助于维持动作电位产生所需的离子浓度，但pap可能具有额外的功能和结构作用，可以改变淋巴结大小和兴奋性，甚至髓鞘厚度。然而，目前尚不清楚星形胶质细胞何时在淋巴结插入突起，以及星形胶质细胞是否有助于髓鞘形成时淋巴结的初始间距，这是一个在很大程度上决定动作电位传播速度和时间的因素。除了在发育过程中建立髓鞘形成模式的潜在作用外，pap还可能有助于髓鞘形成的准确性。多发性硬化症（MS）等疾病脱髓鞘后，Ranvier离子通道节点和结构蛋白组织被破坏，导致动作电位失效。然而，一些Ranvier淋巴结在脱髓鞘过程中得以维持，或在脱髓鞘形成之前被改造，既可以作为新生成髓鞘的潜在路标，也可以在髓鞘缺失时维持动作电位的传播。增强这一结果将显著影响ms患者脱髓鞘发作后的功能恢复。在本研究中，将确定在Ranvier形成节点期间星形胶质细胞-少突胶质细胞的基本相互作用以及所需的星形胶质细胞遗传因素。发育中的斑马鱼无与伦比的光学特性和遗传工具将用于可视化体内星形胶质细胞的过程动力学，如髓鞘鞘和淋巴结在发育过程中产生，以及在髓鞘重塑过程中被破坏。最后，在小鼠多发性硬化症模型中，星形胶质细胞中控制这些动态的关键基因将被破坏，以确定这些因素在髓鞘再生过程中调节Ranvier维持节点的程度。这些实验、实验室环境和本提案中概述的额外培训机会将提供一个非凡的培训经验，这将提高我的技术技能，进一步发展我的神经胶质细胞生物学知识，并允许我开拓一个研究领域，以独立研究者的身份领导我自己的实验室。

Proper nervous system function depends on interactions between neurons and non-neuronal glial cells. These neuron-glia relationships can be highly specific, such as the myelination of axons by oligodendrocytes. At the junctions between adjacent myelin sheaths, the nodes of Ranvier, complex structural components adhere the sheath to the axon membrane and constrain high densities of Na channels at the node in order to allow rapid saltatory conduction. Astrocytes, another glial cell, produce highly-ramified morphologies that effectively fill the space between all other cells to distribute nutrients and balance ion concentrations to provide an environment for neuronal communication. Nearly every node of Ranvier is covered by perinodal astrocyte processes (PAPs). While the neuron-oligodendrocyte interactions necessary for node of Ranvier structure and function have been extensively studied, the role of astrocytes at nodes and their interactions with oligodendrocytes' myelin sheaths are almost entirely unknown. While PAPs likely help maintain ion concentrations necessary for action potential generation, PAPs may serve additional functional and structural roles that could alter nodal size and excitability and even myelin sheath thickness. However, it remains unknown when astrocytes insert processes at the node and whether astrocytes contribute to the initial spacing of nodes during myelination onset, a factor that considerably shapes the speed and timing of action potential propagation. In addition to a potential role in establishing the pattern of myelination during development, PAPs may also contribute to the accuracy of remyelination. Following demyelination in diseases such as multiple sclerosis (MS), node of Ranvier ion channels and structural protein organization is disrupted, leading to action potential failure. However, some nodes of Ranvier are maintained throughout demyelination or reformed prior to remyelination, serving both as potential guideposts for newly generated myelin sheaths and maintaining action potential propagation in the absence of myelin. Enhancing this outcome would significantly impact functional recovery following a demyelinating attack in people with MS. In this proposal, essential astrocyte-oligodendrocyte interactions during node of Ranvier formation and the required astrocytic genetic factors will be identified. The unparalleled optical properties and genetic tools of the developing zebrafish will be used to visualize astrocyte process dynamics in vivo as myelin sheaths and nodes are created during development, and when they are disrupted during myelin sheath remodeling. Finally, critical genes governing these dynamics will be disrupted in astrocytes in a mouse model of MS to determine the extent to which these factors regulate node of Ranvier maintenance during remyelination. These experiments, lab environment, and additional training opportunities outlined in this proposal will present a phenomenal training experience that will enhance my technical skillset, further develop my knowledge of glial cell biology, and allow me to carve out a research area to lead as an independent investigator with my own laboratory.