Examining neuronal resilience in a mouse model of sporadic ALS

项目摘要/摘要 在大脑受伤后，邻近受损区域的健康神经元有时会 受损的神经元所执行的功能。这一过程在急性神经损伤后被研究得最好。 损伤，但有证据表明，存活神经元的补偿也发生在早期阶段 神经退行性疾病。在肌萎缩侧索硬化症(ALS)中，肌肉样本中的纤维类型分组 从患者身上提取的数据表明，在运动神经元(MN)和肌肉之间的连接最初失去后， 新的神经能够重新连接，使患者在疾病过程中保持运动。一秒钟 尸检时的观察是，绝大多数患者都有积聚的 在存活的MN中，错误定位的蛋白质称为TDP-43。然而，由于这些细胞在早期是无法访问的 疾病阶段，在MN中处理疾病过程的分子机制发出新的 与肌肉的联系尚不清楚。为了确定动态响应可以允许 MN亚群专门处理错位的TDP-43并发出新的轴突连接到 为了防止肌肉瘫痪，我们开发了一个小鼠模型，在这个模型中，我们可以诱导神经元表达 错误定位的人TDP-43，称为rNLS8小鼠。然后我们发现rNLS8小鼠有特定的MN亚群 这些细胞对疾病是唯一脆弱的，存活的MN可以有效地取代这些细胞，甚至 在病程较晚时。 在这项研究中，我们现在将确定负责神经再支配和修复的MN群体 最初的TDP-43触发MN丢失后脆弱肌肉的功能(目标1)，使用神经元组合 追踪技术、肌肉生理学和神经肌肉交界处的成像。然后，我们将查找 大脑免疫细胞小胶质细胞对MN可塑性的上游贡献及其引起的回路变化 (目标2)通过药物消除小胶质细胞并选择性地重新引入小胶质细胞衍生因子 先前已被证明会影响神经功能。最后，MN之间的分子差异 在TDP-43触发轴突死亡前后神经支配同一肌肉将被RNA- 将验证测序和顶级基因靶点在ALS样病中对运动功能的影响 在rNLS8小鼠中(目标3)。这些研究的完成应该会为潜在的 MN亚群耐受细胞质TDP-43积聚的机制。此外，理解 神经元代偿机制可以使旨在支持的疗法的发展成为可能。 存活细胞，以延长其自然可塑性，以减缓疾病和维持患者的功能。

Project Summary/Abstract Following an injury to the brain, healthy neurons that are adjacent to the damaged area can sometimes take over the functions performed by the impaired neurons. This process has been best studied after acute nerve damage, but there is evidence that compensation by surviving neurons is also happening in the early stages of neurodegenerative diseases. In amyotrophic lateral sclerosis (ALS), the fiber type grouping in muscle samples taken from patients suggests that after an initial loss of connections between motor neurons (MNs) and muscles, new nerves are able to reconnect to allow patients to maintain movement during the disease process. A second observation made at the time of autopsy is that the vast majority of patients have an accumulation of a mislocalized protein called TDP-43 in the surviving MNs. However, because these cells are inaccessible in early disease stages, the molecular mechanisms for coping with disease processes in the MNs that send out new connections to muscles are unknown. In order to determine the dynamic responses that could allow a subpopulation of MNs to cope specifically with mislocalized TDP-43 and send out new axonal connections to muscles to prevent paralysis, we developed a mouse model in which we can induce neuronal expression of mislocalized human TDP-43, called rNLS8 mice. We then showed that rNLS8 mice have certain subsets of MNs that are uniquely vulnerable to disease, and that surviving MNs can effectively take the place of these cells, even late into the disease course. In this study, we will now identify the populations of MNs responsible for the reinnervation and restoration of function of vulnerable muscles after the initial TDP-43 triggered MN loss (Aim 1), using a combination of neuronal tracing techniques, muscle physiology, and imaging at the neuromuscular junction. We will then look for the upstream contribution of the brain's immune cells, microglia, to MN plasticity and the resultant circuit changes (Aim 2) by pharmacologically eliminating microglia and selectively reintroducing microglial derived factors that have been previously shown to influence neuronal function. Finally, molecular differences between MNs that innervate the same muscle before and after TDP-43 triggered axonal dieback will be uncovered by RNA- Sequencing and the top gene targets will be validated for their effect on motor function during ALS-like disease in rNLS8 mice (Aim 3). Completion of these studies should provide valuable insights into the potential mechanisms by which subsets of MNs can tolerate a build-up of cytoplasmic TDP-43. Moreover, understanding the mechanisms of neuronal compensation could allow for the development of therapies aimed at supporting surviving cells in order to extend their natural plasticity to slow disease and maintain function in patients.