The role of Nrg1 signaling in Schwann cell development and myelination

 描述（由申请人提供）：周围神经病变患者存在使人衰弱的感觉和运动症状。雪旺细胞或轴突的发育缺陷或损伤可导致神经病。在周围神经系统中，许旺细胞包裹神经中的轴突并形成髓鞘。了解调节雪旺细胞的机制对于接近神经病患者的髓鞘再生和预防轴突损伤的治疗至关重要。斑马鱼是一种功能强大的有髓鞘神经的脊椎动物模型系统，对斑马鱼的研究导致了神经发育方面的关键发现，包括一种神经调节蛋白亚型（III型）作为施万细胞在生长神经中迁移的指导线索的作用。我推测，在轴突和ErbB受体上的雪旺细胞驱动不同的发展决定的雪旺细胞的NRG 1 III型的定位或水平的变化，和NRG 1 I型和II型信号与III型合作，以控制雪旺细胞发育的不同步骤。该项目将通过使用基因组编辑来产生异构体特异性Nrg 1突变体，从而发现剩余脊椎动物Nrg 1异构体（I型和II型）的作用。这些新的突变体的表型分析将定义在体内的I型和II型Nrg 1亚型的功能。将在转基因斑马鱼中测试Nrg 1 I型和II型引导雪旺细胞至异位位置的能力。Nrg 1信号在整个雪旺细胞发育过程中发挥作用，控制规范，迁移，增殖和髓鞘形成，但了解Nrg 1如何控制雪旺细胞发育的许多不同步骤仍然是一个重大挑战。一种可能性是Nrg 1水平或分布动态变化，以定义雪旺细胞发育的每个阶段。标记的Nrg 1敲入等位基因的产生将允许在体内监测内源性Nrg 1的定位和水平的变化。Nrg 1信号通过异源二聚体ErbB 2/3受体上的雪旺细胞，因为他们向轴突末端迁移，但它是不知道是否ErbB受体或下游信号分子内迁移雪旺细胞极化。使用抗体和标记的受体，ErbB受体的分布和活性将在迁移的雪旺细胞中进行测试。为了增加ErbB受体活性水平，我们将表达组成型活性ErbB受体并测量对体内迁移、增殖和髓鞘形成的影响。这些实验将研究雪旺细胞发育、髓鞘形成和最终周围神经病变的潜在调节机制。尽管周围神经病变的患病率和严重性，但这些疾病没有治愈方法。这强调了需要了解控制雪旺细胞发育和髓鞘形成的机制，这可能提供治疗髓鞘再生和预防轴突损伤的方法。这一建议将提供新的神经病变的动物模型，阐明神经病变的病理生理学，并提出新的治疗方法的道路。

 DESCRIPTION (provided by applicant): Patients with peripheral neuropathy suffer from debilitating sensory and motor symptoms. Developmental defects or damage to Schwann cells or axons can cause neuropathy. In the peripheral nervous system, Schwann cells wrap the axons in nerves and form the myelin sheath. Understanding the mechanisms that regulate Schwann cells is crucial to approaching therapies for remyelination and prevention of axonal damage in neuropathy patients. Studies in zebrafish, a powerful vertebrate model system with myelinated nerves, have led to key discoveries in nerve development, including the role of one Neuregulin isoform (type III) as a guidance cue for Schwann cells migrating in growing nerves. I hypothesize that changes in the localization or levels of Nrg1 type III on axons and ErbB receptors on Schwann cells drive different developmental decisions of Schwann cells, and that Nrg1 type I and type II signals cooperate with type III to control different steps of Schwann cell development. This project will discover the roles of the remaining vertebrate Nrg1 isoforms (type I and II) by using genome editing to generate isoform-specific Nrg1 mutants. Analyses of the phenotypes of these novel mutants will define the functions of type I and type II Nrg1 isoforms in vivo. The ability of Nrg1 type I and II to guide Schwann cells to ectopic locations will be tested n transgenic zebrafish. Nrg1 signaling functions throughout Schwann cell development to control specification, migration, proliferation and myelination, but it remains a major challenge to understand how Nrg1 controls so many different steps of Schwann cell development. One possibility is that Nrg1 level or distribution changes dynamically to define each stage of Schwann cell development. Creation of a tagged Nrg1 knock-in allele will allow changes in the localization and levels of endogenous Nrg1 to be monitored in vivo. Nrg1 signals though heterodimeric ErbB2/3 receptors on Schwann cells as they migrate towards the axon terminus, but it is not known whether ErbB receptors or downstream signaling molecules are polarized within migrating Schwann cells. Using antibodies and tagged receptors, the distribution and activity of ErbB receptors will be tested in migrating Schwann cells. To increase the levels of ErbB receptor activity, we will express constitutively active ErbB receptors and measure impact on migration, proliferation and myelination in vivo. These experiments will examine the mechanisms underlying regulation of Schwann cell development, myelination, and ultimately peripheral neuropathy. Despite the prevalence and severity of peripheral neuropathies, there is no cure for these diseases. This emphasizes the need to understand the mechanisms that control Schwann cell development and myelination, which may provide approaches toward therapeutic remyelination and prevention of axonal damage. This proposal will provide new animal models of neuropathy, elucidate the pathophysiology of neuropathy, and suggest roads toward new therapies.