Regulation of myelination by myosin II-mediated mechanotransduction

描述(申请人提供)：在中枢多发性硬化(CNS)和周围神经系统(PNS)格林-巴利综合征(PNS)等疾病中，髓鞘丢失导致沿受累轴突的传导障碍，是临床缺陷的特征 这些障碍中。神经功能的恢复与髓鞘再生有关，髓鞘再生不仅恢复神经传导，而且重建有髓轴突的正常分子组织。虽然已经有治疗方法可以解决中枢神经系统和三叉神经节髓鞘的炎症攻击，但目前还没有直接针对髓鞘修复效率和神经功能恢复的治疗方法。我们发现非肌肉肌球蛋白II(NMII)是PNS和CNS中神经胶质细胞分化和髓鞘形成的新的关键调节因子。NMII是雪旺细胞包裹轴突所必需的，它的抑制会损害雪旺细胞的形态分化和形成髓鞘的能力。相反，抑制少突胶质细胞中的NMII会促进细胞分支并促进髓鞘的形成。这些截然相反的作用背后的分子机制目前尚不清楚，但如果了解，可能会提供新的治疗靶点，以促进脱髓鞘神经的修复和神经功能的恢复。在这一应用中，我们建议检验一种假设，即雪旺细胞和少突胶质细胞感知和响应其环境的独特机械属性的能力在这些细胞对NMII抑制的差异反应中起主要作用。与这一应用特别相关的是观察到，细胞分支的程度和未分化细胞的谱系承诺可以通过细胞外基质(ECM)弹性的变化以NMII依赖的方式进行调节。在目标#1中，我们将使用一种允许控制底物弹性的培养系统来表征细胞外基质弹性的差异如何影响神经胶质细胞的形态和分化，并通过进行功能丧失和获得的实验来确定NMII在调节这些影响中的直接作用。在目标2中，我们将使用活细胞成像和功能损失和获得实验相结合的方法，在Rho/ROCK下游的过程扩展和下调NMII活性之间建立直接的机制联系。最后，在目标3中，我们将使用NMIIB在有条件地去除髓鞘CNS和PNS神经胶质细胞的小鼠身上，直接检查NMII与体内髓鞘发育和重新髓鞘形成的相关性。我们研究的长期目标是了解调控雪旺细胞和少突胶质细胞分化的细胞骨架机制，以此来寻找促进髓鞘修复和神经功能恢复的新的治疗靶点。

DESCRIPTION (provided by applicant): In diseases such as Multiple Sclerosis in the central (CNS) and Guilain-Barre Syndrome in the peripheral (PNS) nervous system, loss of myelin results in conduction block along affected axons and underlies the clinical deficits characteristic of these disorders. Recovery of neural function is associated with remyelination, which not only restores nerve conduction, but also re-establish the normal molecular organization of the myelinated axon. Although therapies are available that address the inflammatory attack on CNS and PNS myelin, there are currently no treatments designed to directly target the efficiency of myelin repair and the return of nerve function. We identified non-muscle myosin II (NMII) as a novel key regulator of glial cell differentiation and myelin formation in both the PNS and the CNS. NMII is necessary for the ensheathment of axons by Schwann cells, and its inhibition impairs their morphological differentiation and ability to form myelin. By contrast, inhibition of NMII in oligodendrocytes promotes cell branching and enhances myelin formation. The molecular mechanisms behind these remarkably opposite effects are currently unknown, but if understood might provide novel therapeutic targets to promote repair of demyelinated nerves and restore nerve function. In this application we propose to test the hypothesis that the ability of Schwann cells and oligodendrocytes to sense and respond to the unique mechanical properties of their environment plays a major role in the differential response of these cells to NMII inhibition. Of particular relevance for this application are the observations that the extent f cell branching and the lineage commitment of undifferentiated cells can be regulated by changes in the extracellular matrix (ECM) elasticity in a NMII-dependant manner. In Aim#1 we will characterize how differences in ECM elasticity affect glial cell morphology and differentiatio using a culture system that allows the control of substrate elasticity and determine the direct rol of NMII in mediating these effects by performing loss and gain of function experiments. In Aim#2 we will establish the direct mechanistic link between process extension and downregulation of NMII activity downstream of Rho/ROCK, using a combination of live-cell imaging and loss and gain of function experiment. Finally in Aim#3 we will directly examine the relevance of NMII for myelin development and remyelination in vivo using mice in which NMIIB has been conditionally ablated in myelinating CNS and PNS glia. The long-term goal of our research is to understand the cytoskeletal mechanisms regulating Schwann cell and oligodendrocyte differentiation as a way to identify novel therapeutic targets to promote myelin repair and recovery of nerve function.