Genetic Mechanisms of Myelination in Zebrafish

描述（申请人提供）：在周围神经中，雪旺细胞形成髓磷脂，髓磷脂大大加速轴突传导。髓鞘形成缺陷引起腓骨肌萎缩症和其他周围神经病变的症状，但髓鞘形成的调节机制尚不清楚。研究调节雪旺细胞髓鞘形成的途径将导致对周围神经发育的理解取得重要进展，并确定损伤和疾病后可增强髓鞘形成的机制。该项目的长期目标是确定控制周围神经髓磷脂形成的途径。在目前的资助期内，我们发现孤儿粘附G蛋白偶联受体（aGPCR） Gpr126对于雪旺细胞启动髓鞘形成至关重要。像大多数粘附gpcr一样，激活Gpr126的配体仍然未知。我们有初步证据表明，雪旺细胞细胞外基质中的IV型胶原结合Gpr126并激活表达Gpr126的培养细胞中cAMP的产生。我们也有初步的证据表明，纯化的IV型胶原蛋白刺激纯化的啮齿动物雪旺细胞中cAMP的产生。我们建议验证IV型胶原作为Gpr126的内源性激活配体的假设。我们的具体目的是：(1)分析IV型胶原对啮齿动物雪旺细胞的作用，确定对胶原的反应是否需要Gpr126；(2)分析IV型胶原基因在体内雪旺细胞髓鞘形成中的作用；(3)分析与人类严重神经缺陷相关的Gpr126变异的功能影响。这些实验将定义激活Gpr126信号和髓鞘形成的信号，为细胞外基质在调节髓鞘形成中的作用提供新的见解，并测试与人类严重神经系统疾病相关的Gpr126变体的功能。

DESCRIPTION (provided by applicant): In peripheral nerves, Schwann cells form myelin, which greatly accelerates axonal conduction. Myelination defects cause the symptoms of Charcot-Marie-Tooth disease and other peripheral neuropathies, but the mechanisms that regulate the formation of myelin remain unclear. Investigating the pathways that regulate Schwann cell myelination will lead to important advances in the understanding of peripheral nerve development and define mechanisms that can enhance remyelination after injury and in disease. The long-term goal of this project is to define the pathways that govern the formation of myelin in peripheral nerves. In the current funding period, we discovered that the orphan adhesion G protein coupled receptor (aGPCR) Gpr126 is essential for Schwann cells to initiate myelination. Like most adhesion GPCRs, the ligand that activates Gpr126 remains unknown. We have preliminary evidence that type IV collagen in the Schwann cell extracellular matrix binds Gpr126 and activates cAMP production in cultured cells expressing Gpr126. We also have preliminary evidence that purified type IV collagen stimulates cAMP production in purified rodent Schwann cells. We propose to test the hypothesis that type IV collagen acts as an endogenous activating ligand for Gpr126. Our specific aims are (1) to analyze the action of type IV collagen on rodent Schwann cells, and determine if the response to collagen requires Gpr126; (2) to analyze the function of type IV collagen genes in Schwann cell myelination in vivo; and (3) to analyze the functional effects of a variant in Gpr126 that is linked to a severe neurological deficit in human. These experiments will define the signals that activate Gpr126 signaling and myelination, lead to new insights into the role of the extracellular matrix in regulating myelination, and test the function of a Gpr126 variant linked to severe neurological disease in human.