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.

项目概要 关于微机械应力在调节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。轴突静脉曲张（肿胀或串珠）增大， 沿轴突轴的异质结构，深刻影响轴突传导和突触 传播。它们是一个关键的病理特征，被认为代表轴突损伤的缓慢积累 发生在不可逆转的退化过程中，例如轻度创伤性脑损伤 (mTBI)、阿尔茨海默病 疾病（AD）和多发性硬化症。在这个 R01 的第一个资助期，我们发现流体机械 应激立即且可逆地诱导培养的中枢神经系统神经元的无髓鞘轴突中的静脉曲张，并且我们 进一步可视化体内静脉曲张诱导。健康成年人的大多数大脑区域，包括胼胝体 包含有髓鞘和无髓鞘轴突，而髓磷脂似乎可以保护轴突免受初始影响 机械损伤。使用模拟脑震荡的小鼠模型，我们的新研究发现立即 皮质神经元无髓鞘轴突的静脉曲张形成和皮质延迟脱髓鞘 机械冲击。我们的新结果还表明微管 (MT) 相关蛋白 6 (MAP6) 通过其 MT 稳定和 Ca2+/钙调蛋白结合的特性调节轴突静脉曲张的形成。 根据我们的新发现，我们假设机械冲击立即引起静脉曲张 无髓鞘轴突的形成受到 MAP6 介导的 MT 稳定的抑制 随后促进邻近的脱髓鞘，增加轴突对第二次冲击的脆弱性， 导致反复 mTBI 的恶性循环，从而加剧行为障碍。为了测试这个 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， 细胞类型特异性过度表达、敲除和拯救、共聚焦和电子显微镜、行为测试、 电生理记录、多功能生物力学测定、髓磷脂共培养和最先进的成像 技术。我们将确定（目标 1）mTBI 是否诱导轴突静脉曲张形成和行为 MAP6 缺失可能会加剧损伤，而 MAP6 介导的 MT 稳定可以改善损伤（目标 2） MAP6 如何通过调节轴突静脉曲张的起始、恢复、位置、异质性和长期命运 部分髓鞘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/或先前存在的轴突静脉曲张是否会增加 反复机械撞击造成伤害的风险。该项目代表了一个尚未充分探索的研究领域 许多悬而未决的问题。这项研究意义重大，因为它将为中枢神经系统提供新颖的机制见解。 神经元机械感觉和 mTBI 原发性损伤。