Role of synaptic Schwann cells in NMJ and skeletal muscle aging

项目摘要：广泛的研究已经确定，神经肌肉的进行性变性 在老年，神经肌肉连接（NMJ）导致肌肉减少症和运动缺陷。因此，为了保持 NMJ可能在衰老过程中维持肌肉质量和运动功能方面至关重要。由于这些原因， 继续作出重大努力，以确定防止与年龄有关的NMJ下降的机制。 到目前为止，有丰富的信息骨骼肌和运动神经元在NMJ老化的作用。在 形成鲜明对比的是，突触周施万细胞（PSC）在NMJ衰老中的作用仍然未知。PSC是突触性的 神经胶质细胞，专门与NMJ相关，并对其成熟、稳定、功能和修复至关重要。 突出了它们的重要性，PSC的靶向消融导致轴突变性和突触后丢失。 虽然一些研究提供了PSC可能影响NMJ退化过程的线索，但随着年龄的增长， 全面检查PSC的进行性年龄相关变化，因为它们与NMJ恶化有关， 一个巨大的知识鸿沟。这项提案的首要目标是揭示细胞和分子 PSC老化的基础，以确定其对年龄相关的NMJ和肌肉退化的贡献。目的 1将检查PSC老化的进行性及其与NMJ变性和肌肉萎缩的关系。 因此，PSC、NMJ和肌纤维中与年龄相关的形态变化的时间将是 通过光学和电子显微镜测定。PSC的生物物理特性将通过钙离子追踪。 显像一个新的转基因小鼠品系沿着与RNA-Seq和ATAC-Seq将用于鉴定分子 衰老过程中PSC的内在通路失调。在最初的分子研究中，NGR 1-III和MEGF 10 被确定为PSC老化的有前途的调节剂。运动轴突衍生的NRG 1-III可能是最好的描述 PSC生理学的分子介质。然而，PSC中NRG 1-III通路的下游效应物具有 尚未确定，我们不知道它是如何受到老化的影响。目标2将评估NRG 1的作用- 通过功能获得和丧失实验在PSC老化中的III信号传导。初步数据显示， NRG 1-III信号在老化的PSC中增强，表明减少该信号通路可以保护 老化期间的PSC。额外的数据表明，NRG 1-III信号通过抑制MEGF 10影响PSC的老化 表情MEGF 10是一种众所周知的调节细胞空间组织和突触重塑的基因。 中枢神经系统（CNS）;然而，其在PSC中的功能尚未被探索。目标3将审查 使用MEGF 10 fl/fl小鼠系，MEGF 10在指定老化PSC的组织和修复功能中的作用。 这些研究将是第一个定义加速衰老的生理、细胞和分子变化的研究 的PSC。这项提案也将首次确定NRG 1-III信号传导和MEGF 10在衰老中的功能。 私营保安公司和国家司法人员。总之，这些研究将为开发治疗方法提供新的机会， 在衰老过程中的NMJ，从而治疗肌肉减少症。

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.