MOLECULAR AND GENETIC ANALYSIS OF GPR126 IN PERIPHERAL NERVE.

描述(申请人提供)：髓鞘是一层绝缘层，覆盖了脊椎动物神经系统中称为轴突的神经元投射。在外周神经系统中，被称为雪旺细胞的特殊细胞在轴突周围盘旋，形成髓鞘。髓鞘确保神经冲动快速有效地传播，最终允许整个神经系统正常运作。疾病中(如多发性硬化症或周围神经病)或损伤后(如脊髓创伤)髓鞘的破坏会导致毁灭性的症状和显著的发病率，髓鞘丢失可导致永久性神经元丢失，最终导致瘫痪。目前，还没有预防脱髓鞘或加速髓鞘再生的治疗方法，因此迫切需要开发解决这些问题的治疗方法。为此，我们必须更多地了解髓鞘形成、髓鞘维持和再髓鞘形成的机制。我们发现，孤儿G蛋白偶联受体GPR126是控制髓鞘形成的轴突-雪旺细胞信号联系的重要组成部分。在GPR126突变小鼠中，雪旺细胞与轴突联系在一起，但无法螺旋其膜产生髓鞘。G蛋白偶联受体是很好的药物靶点，至少占所有已批准药物的三分之一；因此，GPR126是一个极具吸引力的潜在靶点，可刺激患有髓鞘疾病或损伤的人类重新髓鞘形成。因此，我们建议剖析GPR126控制髓鞘形成的机制，并确定损伤后髓鞘稳态或再髓鞘形成是否需要GPR126。这些研究围绕着我们的广泛目标，即定义脊椎动物神经系统中形成、维持和再生有髓轴突的机制。在第一个目标中，我们将通过对GPR126突变的组织和细胞进行生化分析来确定GPR126激活的下游信号通路。在第二个目标中，我们将检验这一假设，即雪旺细胞自发地需要GPR126来进行髓鞘形成。我们将使用有条件的小鼠突变体来删除特定于雪旺细胞或神经元中的GPR126，并进行免疫组织化学和超微结构分析，以确定细胞类型特异性丢失的后果。为此，我们还将通过在发育中的胚胎和围产期转基因小鼠中暂时删除GPR126来定义GPR126需求的发育窗口。在第三个目标中，我们将定义GPR126在成人外周血中的作用 很有胆量。具体地说，我们将通过暂时删除成熟神经和受损成熟神经中的GPR126来确定神经损伤后是否需要GPR126来维持髓鞘、脱髓鞘和/或重新髓鞘形成。总之，这些实验将确定GPR126控制髓鞘形成的机制，将阐明成年神经重新髓鞘形成是否需要GPR126，并可能为未来刺激人类髓鞘修复的疗法奠定基础。

DESCRIPTION (provided by applicant): Myelin is a layer of insulation that covers neuronal projections called axons in the vertebrate nervous system. In the peripheral nervous system, specialized cells called Schwann cells spiral themselves around axons to form the myelin sheath. Myelin ensures that nerve impulses travel quickly and efficiently, ultimately allowing for the entire nervous system to function properly. Disruptions to the myelin sheath in disease (like multiple sclerosis or peripheral neuropathy) or after injury (like spinal cord trauma) lead to devastating symptoms, significant morbidity, and myelin loss can lead to permanent neuron loss, and ultimately, paralysis. Currently, no treatments exist to prevent demyelination or to hasten remyelination, and there is therefore a pressing need to develop therapies that address these issues. To this end, we must learn more about the mechanisms that govern myelination, myelin maintenance, and remyelination. We discovered that the orphan G protein-coupled receptor, Gpr126, is an essential component of the incompletely understood axon-Schwann cell signaling nexus that controls myelination. In Gpr126 mutant mice, Schwann cells associate with axons, but fail to spiral their membranes to generate the myelin sheath. G protein-coupled receptors are excellent drug targets, representing at least one-third of all approved drugs; thus, Gpr126 represents an extremely attractive potential target to stimulate remyelination in humans with myelin disease or injury. We therefore propose to dissect the mechanisms by which Gpr126 controls myelination and to determine if Gpr126 is required for myelin homeostasis or remyelination after injury. These studies encompass our broad goals to define the mechanisms that form, maintain, and regenerate myelinated axons in the vertebrate nervous system. In the first aim, we will define the signaling pathway downstream of Gpr126 activation by performing biochemical analyses on Gpr126 mutant tissue and cells. In the second aim, we will test the hypothesis that Gpr126 is required autonomously in Schwann cells for myelination. We will employ conditional mouse mutants to delete Gpr126 specifically in Schwann cells or in neurons, and we will perform immunohistochemical and ultrastructural analyses to determine the consequences of cell type specific loss. In this aim, we will also define the developmental window of Gpr126 requirement by temporally deleting Gpr126 in developing embryonic and perinatal transgenic mice. In the third aim, we will define the roles of Gpr126 in adult peripheral nerve. Specifically, we will determine if Gpr126 is required for myelin maintenance, demyelination, and/or remyelination after nerve injury by temporally deleting Gpr126 in mature nerve and in injured mature nerve. Together, these experiments will define the mechanisms by which Gpr126 controls myelination, will elucidate if Gpr126 is required for remyelination in adult nerve, and may lay the foundation for future therapeutics that stimulate myelin repair in humans.