How do non-myelinating glia ensheath axons?

非髓鞘神经胶质细胞如何包裹轴突？

基本信息

批准号：
9797524
负责人：
Marc R Freeman
金额：
$ 33.69万
依托单位：
OREGON HEALTH & SCIENCE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-06-15 至 2024-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9797524
关键词：
Address Affect Automobile Driving Axon Behavioral Assay Binding Biochemical Biological Assay Biology Cell Surface Receptors Cells Cellular biology Clinical Collagen Collagen Receptors Collagen Type XVIII Collection Communication Complex Data Defect Development Disease Dominant Genetic Conditions Drosophila genome Drosophila genus Endostatins Epidermal Growth Factor Receptor Exhibits Expression Profiling Fiber Fibroblast Growth Factor Receptors Genes Genetic Health Homologous Gene Human Impairment Individual Injury Integrin beta Chains Invertebrates Ligands Maintenance Mammals Mediating Membrane Metabolic Modeling Molecular Molecular Genetics Multiple Sclerosis Mus Myelin Nerve Nervous System Physiology Nervous system structure Neuroglia Neurons Neuropathy Oligodendroglia Orthologous Gene Pain Pathway interactions Peripheral Peripheral Nerves Peripheral Nervous System Peripheral Nervous System Diseases Phase Phenotype Physiological Physiology Process RNA Interference RNA interference screen Reagent Receptor Protein-Tyrosine Kinases Receptor Signaling Role Schwann Cells Sensory Signal Pathway Signal Transduction Signaling Molecule Structure Testing Vertebrates Work autocrine discoidin receptor fly glial cell development in vivo insight intercellular communication interest knock-down leukodystrophy molecular array mouse model mutant myelination neurotransmission novel receptor receptor function remyelination tool

项目摘要

Project summary Glial ensheathment of axons is a conserved feature of nervous systems that is essential for proper nervous system function. Impairment or loss of axonal wrapping underlies many debilitating conditions including multiple sclerosis, leukodystrophies, peripheral neuropathies, and CMT diseases. Despite many years of work our understanding of the molecular pathways that control glial development, glial-axon communication, and ensheathment of long axons, including myelination, is far from complete. Our understanding of non-myelinating forms of axon ensheathment is particularly sparse, despite the fact that the majority of peripheral axons (~70%) in humans are unmyelinated and encased by Remak Schwann cells. To address this gap in our understanding we propose to use the genetically tractable model Drosophila to characterize novel molecular mechanisms that promote glial ensheathment of axons and to study the functional roles of non-myelinating ensheathment in axon health and function in vivo. In Drosophila, specialized glia called wrapping glia (WG) ensheath peripheral axons in a manner closely resembling vertebrate Remak SCs. Recent studies (including our own preliminary data) have found that many genes that control the formation of vertebrate myelin also control axon ensheathment by WG in the fly, supporting strong molecular conservation between these forms of ensheathment. We have taken advantage of the fly to conduct a large-scale RNAi screen for novel regulators of ensheathment, and have identified a number of exciting new genes required for glial ensheathment of axons. One candidate to emerge from the screen, discoidin domain receptor (Ddr), encodes an evolutionarily conserved receptor tyrosine kinase activated by collagens. We show that loss of Ddr in WG results in profound defects in axonal ensheathment: although WG can grow longitudinally along the nerve they fail to insert processes between bundled axons to sort and ensheath them. Intriguingly, murine Ddr1 is highly expressed in oligodendrocytes and detailed expression profiling reveals that mDdr1 expression increases at the onset of wrapping during development and with the initiation of remyelination after injury, but functional roles for mDdr in ensheathment or myelination has not been investigated. Our preliminary work has also identified the Type XV/XVIII collagen homolog Multiplexin as required for axon ensheathment, possibly by acting as a ligand for Ddr. In Aim 1 we will characterize the role of Ddr in promoting axonal ensheathment, determine its autonomy of action, and perform a structure function analysis to define key aspects of Ddr signaling in vivo. In Aim 2 we will investigate the role of Mp in driving ensheathment and directly test our model that Mp acts in an autocrine fashion to activate the Ddr receptor on WG. Finally, in Aim 3 we will take advantage of the many genes identified in the screen that have mild to strong ensheathment defects to probe the function of non-myelinating ensheathment on neuronal health and physiology using behavioral assays and in vivo physiological studies. Our work will define the mechanistic basis of Ddr and Mp signaling during nerve assembly and glial ensheathment of axons, and help define the enigmatic but essential functions of non-myelinating forms of ensheathment in complex nervous systems.

项目概要轴突的胶质鞘是神经系统的保守特征，对于正常的神经系统至关重要功能。轴突包裹的损伤或丧失是许多使人衰弱的疾病的基础，包括多发性硬化症、脑白质营养不良、周围神经病和 CMT 疾病。尽管经过多年的工作，我们对控制神经胶质发育、神经胶质轴突通讯和长轴突鞘的分子途径，包括髓鞘形成还远未完成。我们对轴突鞘的非髓鞘形式的理解特别重要稀疏，尽管事实上人类的大多数外周轴突（约 70%）是无髓鞘的并且被 Remak 包裹雪旺细胞。为了解决我们理解中的这一差距，我们建议使用遗传易处理的模型果蝇表征促进轴突神经胶质鞘的新分子机制并研究其功能作用非髓鞘鞘对体内轴突健康和功能的影响。在果蝇中，特殊的神经胶质细胞称为包裹神经胶质细胞（WG）以与脊椎动物 Remak SC 非常相似的方式包裹外周轴突。最近的研究（包括我们的自己的初步数据）发现许多控制脊椎动物髓磷脂形成的基因也控制轴突 WG 在飞行中形成鞘，支持这些形式的鞘之间的强分子守恒。我们有利用果蝇进行大规模 RNAi 筛选，寻找新的鞘鞘调节因子，并鉴定出神经胶质轴突鞘所需的许多令人兴奋的新基因。一位候选人从屏幕中出现，盘状结构域受体 (Ddr) 编码一种由胶原蛋白激活的进化保守受体酪氨酸激酶。我们发现 WG 中 Ddr 的缺失会导致轴突鞘的严重缺陷：尽管 WG 可以生长沿着神经纵向，它们无法在成束的轴突之间插入突起来分类和包裹它们。有趣的是，鼠 Ddr1 在少突胶质细胞中高表达，详细的表达谱表明 mDdr1 表达在发育过程中包裹开始时以及损伤后髓鞘再生开始时增加，但功能性 mDdr 在鞘或髓鞘形成中的作用尚未得到研究。我们的前期工作还确定了 XV/XVIII 型胶原同源物 Multiplexin 作为轴突鞘所需的，可能通过充当 Ddr 的配体。在目标 1 中，我们将描述 Ddr 在促进轴突鞘的作用，确定其行动的自主性，以及进行结构功能分析以定义体内 Ddr 信号传导的关键方面。在目标 2 中，我们将研究角色 Mp 在驱动鞘中并直接测试我们的模型，Mp 以自分泌方式激活 Ddr WG 上的受体。最后，在目标 3 中，我们将利用筛选中发现的许多基因，这些基因具有轻度至强鞘缺陷探讨非髓鞘鞘对神经元健康和生理学的功能使用行为测定和体内生理研究。我们的工作将定义 Ddr 和 Mp 的机制基础神经组装和轴突神经胶质鞘期间的信号传导，并有助于定义神经组装和神经胶质鞘的神秘但重要的功能复杂神经系统中的非髓鞘形式。