Role of synaptic Schwann cells in NMJ and skeletal muscle aging

项目摘要：广泛的研究已经证实，神经肌肉的进行性退化 交界处(NMJ)在老年时会导致骨骼减少和运动障碍。因此，保持 在衰老过程中，NMJ可能是维持肌肉质量和运动功能的关键。出于这些原因， 继续作出重大努力，以确定防止NMJ因年龄原因而下降的机制。 到目前为止，关于骨骼肌和运动神经元在NMJ老化中的作用有大量的信息。在……里面 与之形成鲜明对比的是，突触周围雪旺细胞(PSCs)在NMJ衰老中的作用尚不清楚。PSCs是突触的 仅与NMJ相关的胶质细胞，对NMJ的成熟、稳定、功能和修复至关重要。 突显其重要性的是，靶向消融PSCs会导致轴突变性和突触后丢失。 虽然一些研究已经提供了PSCs可能随着年龄的增长影响NMJ退变过程的线索，但 全面检查与NMJ恶化有关的PSC的年龄相关渐进性变化，是 巨大的知识鸿沟。这项提议的首要目标是揭示细胞和分子 PSC老化的基础，以确定它们对年龄相关的NMJ和肌肉退化的贡献。目标 1将研究PSC老化的渐进性及其与NMJ变性和肌肉萎缩的关系。 因此，与年龄相关的PSCs、NMJ和肌肉纤维的形态变化的时间将是 由光学和电子显微镜测定。PSCs的生物物理特性将被钙跟踪 成像。一种新的转基因小鼠品系将与RNA-Seq和ATAC-Seq一起用于分子鉴定 PSCs固有的通路在衰老过程中调节失调。在最初的分子研究中，NGR1-III和MEGF10 被确定为PSC老化的有希望的调节者。运动轴突源性的NRG1-III可能是最好的描述 PSC生理学的分子介体。然而，PSCs中NRG1-III途径的下游效应器 没有被确认，我们也不知道它是如何受到衰老的影响的。目标2将评估NRG1的作用- III通过获得和丧失功能实验研究PSCs老化过程中的信号传递。初步数据显示， NRG1-III信号在衰老的PSCs中增强，表明抑制这一信号通路可能保护 衰老过程中的PSCs。更多数据表明，NRG1-III信号通过抑制MEGF10影响PSCs的衰老 表情。MEGF10是一种众所周知的细胞空间组织和突触重塑的调节剂。 中枢神经系统(CNS)；然而，它在PSCs中的作用还没有被探索。《目标3》将考察该角色 在使用MEGF10FL/FL鼠系指定老化的PSC的组织和修复功能时，使用MEGF10FL/FL鼠系。 这些研究将首次确定加速衰老的生理、细胞和分子变化。 PSC的数量。这项提议也将首次确定NRG1-III信号和MEGF10在衰老中的功能 PSC和NMJ。总而言之，这些研究将提供新的机会来开发保存 NMJ在衰老过程中，从而治疗石棺减少症。

Project Summary: Extensive research has established that progressive degeneration of the neuromuscular junction (NMJ) contributes to sarcopenia and motor deficits in old age. Hence, preserving the integrity of the NMJ is likely to be critical in maintaining muscle mass and motor function during aging. For these reasons, significant efforts continue to be devoted to identifying mechanisms that prevent age-related decline of NMJs. To date, there is a wealth of information about the roles of skeletal muscles and motor neurons in NMJ aging. In stark contrast, the role of perisynaptic Schwann cells (PSCs) in NMJ aging remains unknown. PSCs are synaptic glia that exclusively associate with NMJs and are essential for its maturation, stability, function and repair. Highlighting their importance, targeted ablation of PSCs results in axonal degeneration and postsynaptic loss. While several studies have provided clues that PSCs may impact the course of NMJ degeneration with aging, a comprehensive examination of progressive age-related changes in PSCs, as they relate to NMJ deterioration, is a significant knowledge gap. The overarching objective of this proposal is to uncover the cellular and molecular underpinnings of PSC aging to determine their contribution to age-related NMJ and muscle degeneration. Aim 1 will examine the progressive nature of PSC aging and its relationship to NMJ degeneration and muscle atrophy. Accordingly, the timing of age-related morphological changes in PSCs, NMJs and muscle fibers will be determined by light and electron microscopy. The biophysical properties of PSCs will be tracked by calcium imaging. A novel transgenic mouse line along with RNA-Seq and ATAC-Seq will be used to identify molecular pathways intrinsic to PSCs dysregulated during aging. In initial molecular studies, the NGR1-III and MEGF10 were identified as promising regulators of PSC aging. Motor axon-derived NRG1-III is perhaps the best described molecular mediator of PSC physiology. However, downstream effectors of the NRG1-III pathway in PSCs have not been identified and we do not understand how it is impacted by aging. Aim 2 will assess the role of NRG1- III signaling in PSCs aging through gain- and loss-of-function experiments. Preliminary data demonstrate that NRG1-III signaling is heightened in aged PSCs, indicating that curtailing this signaling pathway may protect PSCs during aging. Additional data suggests that NRG1-III signaling affects aging of PSCs by inhibiting MEGF10 expression. MEGF10 is a well-known modulator of cellular spatial organization and synaptic remodeling in the central nervous system (CNS); however, its function in PSCs has not been explored. Aim 3 will examine the role of MEGF10 in specifying the organization and repair functions of aging PSCs using a MEGF10fl/fl mouse line. These studies will be the first to define the physiological, cellular and molecular changes that precipitate aging of PSCs. This proposal will also be the first to determine the function of NRG1-III signaling and MEGF10 in aging PSCs and NMJs. Altogether, these studies will provide new opportunities to develop therapeutics to preserve NMJs during aging, and thereby treat sarcopenia.