Axonal Varicosity Dynamics in Central Neuron Mechanosensation and Injury

中枢神经元机械感觉和损伤中的轴突静脉曲张动力学

• 批准号: 10211722
• 负责人: CHEN GU
• 金额: $ 38.23万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-15 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10211722
• 关键词: 3-Dimensional; Acceleration; Adult; Affect; Alleles; Alzheimer' s Disease; Autopsy; Axon; Behavior; Behavioral; Binding; Biological Assay; Biomechanics; Brain; Brain Concussion; Brain region; Calmodulin; Calmodulin-Binding Proteins; Coculture Techniques; Cognitive; Collaborations; Confocal Microscopy; Corpus Callosum; Cryo-electron tomography; Demyelinations; Development; Diffuse Axonal Injury; Electron Microscopy; Electrophysiology (science); Engineering; Funding; Heterogeneity; Image; Imaging Techniques; Injury; Interneurons; Knock-out; Knockout Mice; Label; Link; Liquid substance; Location; MAPT gene; Mechanical Stress; Mechanics; Mediating; Methods; Microtubule Stabilization; Microtubule-Associated Proteins; Microtubules; Modeling; Morphology; Multiple Sclerosis; Mus; Myelin; Neuraxis; Neurons; Oligodendroglia; Outcome; Pathologic; Process; Property; Proteins; Proteomics; Rattus; Recovery; Regulation; Reporting; Research; Risk; Role; Rotation; Signal Pathway; Small Interfering RNA; Stress; Structure; Swelling; Synapses; Synaptic Transmission; Testing; Tissues; Transmission Electron Microscopy; Varicosity; Virus; axon injury; base; behavior test; behavioral impairment; cell type; chronic traumatic encephalopathy; head impact; in vivo; insight; interdisciplinary approach; knock-down; mild traumatic brain injury; mouse model; nervous system disorder; new therapeutic target; novel; overexpression; polypeptide; protein expression

PROJECT SUMMARY Little is known about the role of micromechanical stress in regulating morphology and function of neurons in the central nervous system (CNS). Axonal varicosities (swelling or beading) are enlarged, heterogeneous structures along axonal shafts, profoundly affecting axonal conduction and synaptic transmission. They are a key pathological feature believed to represent slow accumulation of axonal damage that occurs during irreversible degeneration, for example in mild traumatic brain injury (mTBI), Alzheimer’s disease (AD), and multiple sclerosis. In the first funding period of this R01, we discovered that fluid mechanical stress immediately and reversibly induced varicosities in unmyelinated axons of cultured CNS neurons, and we further visualized varicosity induction in vivo. Most brain regions including the corpus callosum in healthy adults contain both myelinated and unmyelinated axons, while myelin appears to protect the axon from initial mechanical injury. Using a mouse model mimicking concussion, our new studies have found immediate varicosity formation in unmyelinated axons of cortical neurons and delayed demyelination in the cortex after mechanical impact. Our new results have also indicated that microtubule (MT)-associated protein 6 (MAP6) regulates axonal varicosity formation through its properties of MT stabilization and Ca2+/calmodulin binding. Based on our new findings, we hypothesize that mechanical impact immediately induces varicosity formation in unmyelinated axons, which is restrained by MAP6-mediated MT stabilization and subsequently promotes adjacent demyelination that increases axon vulnerability to second impact, leading to a vicious cycle in repeated mTBI and hence worsened behavioral impairment. To test this original hypothesis, we will use a multidisciplinary approach including mTBI and demyelination mouse models, cell-type-specific overexpression, knockout and rescue, confocal and electron microscopy, behavioral testing, electrophysiological recording, a versatile biomechanical assay, myelin coculture and state-of-the-art imaging techniques. We will determine (Aim 1) whether mTBI-induced axonal varicosity formation and behavioral impairment can be aggravated by MAP6 deletion and ameliorated by MAP6-mediated MT stabilization, (Aim 2) how MAP6 regulates axonal varicosity initiation, recovery, location, heterogeneity and long-term fate through distinct signaling pathways in partially myelinated axons, and (Aim 3) how MAP6 regulates oligodendrocyte mechanosensation, and whether preexisting demyelination and/or preexisting axonal varicosities increase the risk of injury from repeated mechanical impact. This project represents an underexplored research field with many open questions. This research is significant because it will provide novel mechanistic insights into central neuron mechanosensation and mTBI primary injury.

项目总结 对微机械应力在调节血管形态和功能中的作用知之甚少。 中枢神经系统(CNS)中的神经元。轴索静脉曲张(肿胀或串珠)增大， 沿着轴突的异质结构，深刻影响轴突传导和突触 变速箱。这是一个关键的病理特征，被认为是轴突损伤缓慢积累的表现。 这发生在不可逆转的退化过程中，例如轻度创伤性脑损伤(MTBI)、阿尔茨海默氏症 疾病(AD)和多发性硬化症。在这款R01的第一个资助期，我们发现流体机械 应激即刻和可逆性诱导培养的中枢神经系统神经元无髓轴突静脉曲张 进一步可视化体内静脉曲张的诱导。健康成人的多数脑区，包括胼胝体 同时含有有髓和无髓轴突，而髓鞘似乎保护轴突免受初始 机械性损伤。使用模拟脑震荡的小鼠模型，我们的新研究发现立即 大脑皮层神经元无髓轴突静脉曲张形成和延迟性脱髓鞘 机械撞击。我们的新结果还表明，微管相关蛋白6(MAP6) 通过其稳定MT和结合钙/钙调素的特性来调节轴索静脉曲张的形成。 根据我们的新发现，我们假设机械撞击会立即导致静脉曲张。 无髓鞘轴突的形成受MAP6介导的MT稳定化和 随后促进邻近的脱髓鞘，增加轴突对二次撞击的易感性， 导致反复的mTBI的恶性循环，从而加重行为障碍。为了测试这一点 最初的假设，我们将使用多学科方法，包括mTBI和脱髓鞘小鼠模型， 细胞类型特异性过表达，基因敲除和挽救，共聚焦和电子显微镜，行为测试， 电生理记录，多功能生物力学测试，髓鞘共培养和最先进的成像 技巧。我们将确定(目标1)mTBI诱导的轴索静脉曲张的形成和行为 MAP6缺失可加重损伤，而MAP6介导的MT稳定化可改善损伤(目标2) MAP6如何调节轴索静脉曲张的起始、恢复、位置、异质性和长期命运 部分有髓轴突中不同的信号通路，以及(目标3)MAP6如何调节少突胶质细胞 机械感觉，以及先前存在的脱髓鞘和/或先前存在的轴索静脉曲张是否增加了 因反复机械冲击而受伤的风险。这个项目代表了一个未被开发的研究领域， 许多悬而未决的问题。这项研究具有重要意义，因为它将为中央 神经元机械感觉与mTBI原发损伤。