Spatial Restriction of Apoptotic Machinery during Neuronal Apoptosis and Pruning

项目总结/摘要 神经元能够激活诱导整个细胞变性的途径， 细胞凋亡或通过修剪选择性地仅使轴突退化。而caspase的主要成分 在细胞凋亡和修剪过程中激活机器已经被确定，一个基本的问题是， 凋亡机制在整个神经元索马和轴突中被激活，或者在空间上受到限制， 这些事件仍不为人所知。这个问题在修剪的上下文中是最相关的，其中人们预测 凋亡机制被定位于经历变性的靶向轴突。然而，我们 我们惊讶地发现，即使在细胞凋亡期间，胱天蛋白酶的激活也存在意想不到的空间限制， 尽管索马和轴突都退化了，但这些主要限于索马。 在这个建议中，我们将机械地检查空间定位的凋亡机制， 神经元凋亡和修剪。我们将利用在微流控室装置中培养的神经元， 允许神经元胞体和轴突的空间分离和操纵。我们的假设是， 细胞凋亡和修剪，受限制的半胱天冬酶活性导致轴突的“生理性轴突切断”，激活 Sarm 1介导的轴突变性的轴突切断途径。这一概念的发展途径， 细胞凋亡和修剪可以导致轴突切断是新的，因为这些途径被认为是不同的， 损伤引起的轴突切断途径。 在目标1中，我们将定义凋亡过程中神经元凋亡机制的空间限制， 轴突修剪在目标2中，我们重点研究了Sarm 1在细胞凋亡和轴突修剪过程中的功能。在 目的3，我们将研究Sarm 1缺陷小鼠体内修剪缺陷，并评估这些小鼠是否 表现出行为缺陷这个项目开辟了令人兴奋的研究领域，不仅因为它的新概念， 对于细胞凋亡和修剪，但也因为它使人们关注Sarm 1的发育功能， 超出了它在轴突损伤中公认的作用。

Project Summary/Abstract Neurons are capable of activating pathways that induce either the degeneration of the entire cell by apoptosis or to selectively degenerate only the axons by pruning. While the main components of the caspase activating machinery during apoptosis and pruning have been identified, a fundamental question of whether the apoptotic machinery is activated throughout the neuronal soma and axons, or is spatially restricted, during these events remains unknown. This question is most relevant in the context of pruning where one predicts the apoptotic machinery to be localized to the targeted axons undergoing degeneration. However, we were surprised to find an unexpected spatial restriction of caspase activation even during apoptosis, where we found these to be restricted primarily to the soma, even though both soma and axons degenerate. In this proposal, we will mechanistically examine the spatial localization of the apoptotic machinery in neurons during apoptosis and pruning. We will utilize neurons cultured in microfluidic chamber devices to allow for the spatial segregation and manipulation of neuronal somas and axons. Our hypothesis is that during apoptosis and pruning, the restricted caspase activity causes the “physiological axotomy” of axons, activating the Sarm1-mediated axotomy pathway of axon degeneration. The concept that the developmental pathways of apoptosis and pruning can cause axotomy is novel because these pathways were considered to be distinct from the injury-induced axotomy pathway. In Aim 1, we will define the spatial restriction of the apoptotic machinery in neurons during apoptosis and axon pruning. In Aim 2, we focus on examining the function of Sarm1 during apoptosis and axon pruning. In Aim 3, we will investigate the Sarm1-deficient mice for pruning defects in vivo and evaluate if these mice exhibit behavioral deficits. This project opens exciting areas of research not only because of its new concepts for apoptosis and pruning, but also because it brings into focus a developmental function of Sarm1 that is beyond its recognized role in axon injury.