The role of mechanosensation in the vertebrate retina

视网膜神经节细胞和Müller神经胶质细胞特别容易受到机械力的影响， 在青光眼等疾病中，压力传导机制与视网膜神经节细胞的激活和变性有关， 没有很好地理解。早期的研究仅限于对遗传、分子、细胞和 RGC损伤的行为后果和神经胶质细胞活化引起的压力升高。虽然许多 高血压眼的生化途径被证明是改变的， 机械力仍然模糊，混淆了对压力诱导的时间依赖性的解释。 视网膜内的重塑变化。关于青光眼压力损伤的主要假设集中在 力对筛板拉伸的作用然而，小鼠患上了这种疾病，但没有胶原蛋白。 层。轴心假说也不能解释温和的压力升高如何引起早期的变化， 树突结构和突触功能，或激活神经胶质而轴突运输没有明显变化。也是 尚不清楚眼内压的生理水平如何影响RGC的生理学，以及它们是否 足以与突触（光）反应整合。最后，尽管神经胶质细胞通常是最早的反应细胞， 机械应力，促使这些细胞机械敏感性的机制以及它们如何影响RGC 生理学仍然是未知的。 建议的工作解决这些混淆，确定mechanotensors和阐明他们的作用 在RGC和Müller胶质细胞钙稳态和压力多模态整合到（病理）生理 视网膜反应该项目测试了中心假设，即树突，胞体和轴突的压力敏感性 RGC和神经胶质细胞的生长受机械敏感性离子通道控制，其维持张力稳态， 调节钙稳态、兴奋性和神经胶质递质释放以响应眼压的变化 或应变。利用最近获得的数据和使用新的机械生物学工具，目标1将确定和 表征RGC质膜中的机械传感离子通道，量化它们在压力下的激活 和基质拉伸，并测试机械应变从质膜传递的假设 通过细胞骨架进入细胞内部在目标2中，我们提出了多模态机制的特征 通过该传感器机械刺激与温度和突触（光）响应的效应相结合， 并测试一个新的假设，关于调节RGC张力稳态。目标3将描述 机械诱导的胶质细胞活化影响RGC生理学的分子机制，从而提供 深入了解青光眼等疾病的早期炎症机制。综合考虑， 研究可能会加深我们对视网膜功能的理解，揭示新的机制， 和慢性机械力，并通过调和目前关于视网膜压力的不同假设 转导 此外，这些研究将有助于了解神经退行性变，这是需要优化早期 诊断和神经保护治疗，这是目前青光眼缺乏的。在过去的几年里， 推定的机械感测离子通道中的突变已经显示出引起许多人类疾病， 包括严重发育不良、神经胶质血管异常和轴突神经病在内的疾病，但它们对 由于缺乏基础研究，视觉信号是未知的。这些研究所提供的资料可能 因此有助于深入了解视网膜疾病的机械敏感机制以及转导 中枢神经系统内的机械应力

Retinal ganglion cells and Müller glia are particularly susceptible to mechanical forces which drive inflammatory activation and RGC degeneration in diseases such as glaucoma, but the pressure transduction mechanisms are not well understood. Earlier studies have been limited to phenotyping the genetic, molecular, cellular and behavioral consequences of RGC injury and glial activation induced by elevated pressure. While many biochemical pathways were shown to be altered in hypertensive eyes, the molecular sensors that transduce mechanical forces remain obscure, confounding interpretations of time-dependence of pressure-induced remodeling changes within the retina. The dominant hypotheses about pressure injury in glaucoma focus on the role of forces on the stretch of the lamina cribrosa yet mice develop the disease but do not have the collagenous lamina. The axocentric hypotheses also cannot explain how mild pressure elevations induce early changes in dendritic architecture and synaptic function, or activate glia without visible changes in axonal transport. It is also not known how physiological levels of intraocular pressure might inform RGC physiology and whether they are sufficient to integrate with the synaptic (light) responses. Finally, although glia are often the earliest responder to mechanical stress, the mechanisms that impel mechanosensitivity to these cells and how they impact RGC physiology remain largely unknown. The proposed work addresses these confounds by identifying the mechanotransducers and elucidating their role in RGC and Müller glial calcium homeostasis and polymodal integration of pressure into the (patho)physiological retinal response. The project tests the central hypothesis that pressure sensitivity of dendrites, somata and axons of RGCs and glia is governed by mechanosensitive ion channels, which maintain tensile homeostasis and modulate calcium homeostasis, excitability and gliotransmitter release in response to changes in ocular pressure or strain. Leveraging the recently derived data and using novel mechanobiological tools, Aim 1 will identify and characterize mechanosensing ion channels in the RGC plasma membrane, quantify their activation by pressure and matrix stretch, and test the hypothesis that mechanical strains are transmitted from the plasma membrane into the cell interior through the cytoskeleton. In Aim 2 we propose to characterize the polymodal mechanism through which mechanical stimuli are integrated with the effects of temperature and synaptic (light) responses, and to test a novel hypothesis regarding the regulation of RGC tensile homeostasis. Aim 3 will characterize the molecular mechanisms whereby mechanically induced glial activation influences RGC physiology, thus providing insight into the early inflammatory mechanisms in diseases such as glaucoma. Taken together, the proposed studies may deepen our understanding of retinal function by uncovering new mechanisms that respond to acute and chronic mechanical forces and by reconciling currently disparate hypotheses about retinal pressure transduction. In addition, these studies will aid in the understanding of neurodegeneration that is required to optimize early diagnosis and neuroprotective treatment, which are currently lacking in glaucoma. During the last few years, mutations in putative mechanosensing ion channels have been shown to cause many human diseases and disorders, including severe dysplasias, gliovascular abnormalities and axonal neuropathies but their impact on visual signaling is unknown due to the absence of basic studies. The information provided by these studies may thus contribute insights into mechanosensitive mechanisms that underlie retinal disease as well as transduction of mechanical stress within the CNS.