DISSECTING MOLECULAR AND GENETIC MECHANISMS THAT PROMOTE MYELINATION

描述（由申请人提供）：髓磷脂是一种多层膜，在脊椎动物神经系统中包裹轴突。在周围神经系统中，被称为许旺细胞的专门胶质细胞将自身包裹在轴突节段周围以形成髓鞘。髓磷脂对于神经元的营养支持是必不可少的，并且提供绝缘以有效地传导神经冲动。外周髓鞘的破坏可导致破坏性神经病，如腓骨肌萎缩症（CMT）。目前还没有预防脱髓鞘或刺激髓鞘再生的治疗方法，这些疗法的发展受到对驱动许旺细胞形成髓鞘的遗传和分子因素的不完全理解的阻碍。雪旺细胞髓鞘形成需要Gpr 126，一种孤儿粘附家族G蛋白偶联受体（aGPCR）。在脊椎动物模型中Gpr 126功能的丧失导致在早髓鞘形成状态下的雪旺细胞的发育停滞和外周髓鞘的减少或缺失。虽然Gpr 126是必不可少的外周髓鞘形成，很少有人知道的机制，它的功能。本研究将利用斑马鱼模型系统来确定Gpr 126在髓鞘形成中的作用。在第一个目标中，我将使用结构-功能分析来确定Gpr 126的分子结构域，其调节外周髓鞘形成的关键步骤。我预测，Gpr 126的大的N-末端结构域具有不同的功能，在一个单一的大口径轴突周围的每个雪旺细胞的排序。相比之下，我假设跨膜的C-末端的Gpr 126是足以指导雪旺细胞包裹轴突后排序。我 将产生特定的斑马鱼突变体，并进行体内分析，以测试这些假设。在我的第二个目标中，我将进行一个创新的正向遗传筛查，以增强或抑制gpr 126亚型突变体中髓鞘缺陷的突变。该增强子/抑制子筛选将鉴定Gpr 126髓鞘形成程序的调节子以及与Gpr 126平行用于髓鞘形成的新因子。通过确定促进髓鞘形成的分子和遗传因素，这些研究将为确定遗传性神经病（如CMT）的致病突变提供基础。这项工作也将加深我们对许旺细胞生物学的理解，并为开发治疗脱髓鞘和促进周围神经髓鞘再生的疗法奠定基础。

DESCRIPTION (provided by applicant): Myelin is a multilayered membrane that ensheathes axons in vertebrate nervous systems. In the peripheral nervous system, specialized glia called Schwann cells wrap themselves around axonal segments to form the myelin sheath. Myelin is essential for trophic support of neurons and provides insulation to efficiently conduct nerve impulses. Disruption of the peripheral myelin sheath can result in devastating neuropathies such as Charcot-Marie-Tooth (CMT) disease. There are currently no treatments to prevent de-myelination or stimulate re-myelination, and development of these therapies is hindered by an incomplete understanding of the genetic and molecular factors that drive Schwann cells to form the myelin sheath. Schwann cell myelination requires Gpr126, an orphaned adhesion family G protein-coupled receptor (aGPCR). Loss of Gpr126 function in vertebrate models results in arrested development of Schwann cells at the promyelinating state and reduced or absent peripheral myelin. Although Gpr126 is essential for peripheral myelination, very little is known about the mechanism by which it functions. This study will utilize the zebrafish model system to define the role of Gpr126 in myelination. In the first aim, I will use structure-function analysis o define the molecular domains of Gpr126 that regulate key steps in peripheral myelination. I predict that the large N-terminal domain of Gpr126 has a distinct function in sorting each Schwann cell around a single large-caliber axon. In contrast, I hypothesize the transmembrane C-terminus of Gpr126 is sufficient to direct the Schwann cell to wrap the axon following sorting. I will generate specific zebrafish mutants and perform in vivo analyses to test these hypotheses. In my second aim, I will perform an innovative forward genetic screen for mutations that enhance or suppress myelin defects in gpr126 hypomorphic mutants. This enhancer/suppressor screen will identify regulators of the Gpr126 myelination program as well as novel factors that function in parallel to Gpr126 for myelination. By defining the molecular and genetic factors that promote myelination, these studies will provide the basis for identifying causative mutations for genetic neuropathies like CMT. This work also will also deepen our understanding of Schwann cell biology and can lay the foundation for developing therapies to treat demyelination and promote re-myelination of peripheral nerves.