Glial Mechanisms Governing the Removal and Repair of Degenerating Myelin

项目摘要 来自母基金R 01 NS 122800：髓鞘已经进化到加速，微调，并增加代谢 大脑中电信号传输的效率。然而，在许多人类疾病中， 退化，最终导致毁灭性的运动和认知障碍。重要的是，为了使组织 髓鞘损伤发生后，修复进行，许多层压实的细胞膜，构成 髓磷脂鞘必须被脑中驻留的吞噬细胞快速有效地除去。缺陷 这些碎片的去除与许多退化性病症有关，包括但不限于， 多发性硬化症和衰老，但我们对细胞动力学和分子机制知之甚少， 这些过程。为了研究这些关键的细胞事件并回答以哪个细胞为中心的问题， 以及这些不同类型的细胞所起的作用，我们已经开发出先进的技术， 用于在宽范围的时间尺度上成像和操纵活体动物中的这些离散事件 几秒到几个月这些技术包括基于荧光团的新组合的活体成像。 不同神经元和神经胶质细胞群体的非转基因标记以及无标记成像方式 对致密髓磷脂有特异性。除了这些强大的标记和光学成像策略，我们还 开发了一种新的技术，有针对性地诱导单细胞死亡，我们最近建立了一个 小鼠皮质灰质中的按需和可滴定脱髓鞘模型。结合这些技术 现在允许在靶向遗传背景下动态研究脱髓鞘和髓鞘再生， 人类疾病的动物模型。使用这些强大的工具，该项目将调查三个 中心目标。首先，越来越多的证据表明，除了小胶质细胞，大脑的初级吞噬细胞， 其他固有的神经胶质细胞类型，即星形胶质细胞和NG 2神经胶质细胞，也参与其中，并在其中发挥重要作用。 吞噬和修复过程。我们将确定每种胶质细胞类型在动态中的精确贡献。 检测和清除退化的髓鞘碎片。接下来，我们和其他人已经表明了 磷脂酰丝氨酸受体在有效检测和清除垂死的神经元和其他细胞在不同的 机关我们将确定吞噬细胞受体和碎片缺陷的作用和后果 NG 2神经胶质细胞对皮质脱髓鞘和髓鞘再生的动态反应的消化信号传导 成功和髓磷脂模式。最后，有证据表明，神经元活动和/或感觉经验， 修改髓鞘再生，但较少了解神经元活动对吞噬功能的作用， 脱髓鞘我们将确定双向神经元活动变化对反应的后果 从吞噬细胞到单细胞脱髓鞘。最终，这些研究将揭示哪些细胞参与了 髓鞘碎片清除，主要细胞碎片识别途径在成功清除和修复中的作用， 以及神经元活动和感觉经验如何改变吞噬胶质细胞对脱髓鞘的反应 活动

PROJECT SUMMARY From the parent grant R01NS122800: Myelin has evolved to speed up, finely tune, and increase the metabolic efficiency of electrical signal transmission in the brain. In numerous human diseases however, myelin degenerates, ultimately resulting in devastating motor and cognitive impairment. Importantly, in order for tissue repair to proceed after myelin damage has occurred, the many layers of compacted cell membrane that constitute the myelin sheath must be rapidly and efficiently removed by resident phagocytic cells in the brain. Defective removal of these debris has been implicated in a number of degenerative conditions, including but not limited to, multiple sclerosis and aging, yet we know little about the cellular dynamics and molecular mechanisms governing these processes. In order to study these critical cellular events and answer questions centered on which cell populations are involved and what roles these different cell types play, we have developed advanced techniques for imaging and manipulating these discrete events in the live animal over a wide range of temporal scales from seconds to months. These techniques include intravital imaging of new combinations of fluorophore-based multicolor transgenic labels of distinct populations of neurons and glia together with label-free imaging modalities specific for compact myelin. In addition to these powerful labeling and optical imaging strategies, we have also developed a new technique for targeted induction of single-cell death, which we have recently established as a model of on-demand and titratable demyelination in the mouse cortical gray matter. Combining these techniques now allows dynamic investigation of demyelination and remyelination in the context of targeted genetic manipulations and animal models of human disease. Using these powerful tools this project will investigate three central aims. First, there is increasing evidence that in addition to microglia, the primary phagocytes of the brain, other resident glial cell types, namely astrocytes and NG2 glia, are also involved and play important roles in the phagocytosis and repair process. We will determine the precise contribution of each glial cell type in the dynamic detection and clearance of degenerating myelin debris. Next, we and others have shown the importance of phosphatidylserine receptors in the efficient detection and clearance of dying neurons and other cells in different organs. We will determine the role and consequences of both defective phagocytic receptors and debris digestion signaling on the dynamic response by NG2 glia to cortical demyelination and the resulting remyelination success and myelin patterning. Finally, there is evidence that neuronal activity and/or sensory experience can modify remyelination, but less is known about the roles of neuronal activity on phagocytic function in the context of demyelination. We will determine the consequences of bidirectional neuronal activity changes on the response by phagocytic cells to single-cell demyelination. Ultimately, these studies will reveal which cells are involved in myelin debris clearance, the role of major cell debris recognition pathways in successful clearance and repair, and how neuronal activity and sensory experience modify the response of phagocytic glia to a demyelinating event.