Genetic mechanisms of myelination in zebrafish

这个项目将利用斑马鱼的细胞和遗传方法的力量来阐明 脊椎动物神经系统中雪旺细胞发育和髓鞘形成所必需的新基因。 在外周神经系统中，雪旺细胞形成包裹轴突的髓鞘，并允许 动作电位的快速传递。髓鞘破坏会导致周围神经病变，使人虚弱 影响美国150万人的疾病。在对信号的理解上存在差距 控制髓鞘的形成阻碍了有髓轴突修复疗法的发展。 在对破坏髓鞘形成的突变的基因筛查中，我们发现了10个不同基因的13个突变 有髓轴突发育中的特殊功能。细胞和分子研究表明 这些突变定义了在有髓轴突发育的许多阶段发挥作用的基因，包括胶质细胞 命运指定、雪旺细胞迁移、兰维尔结节的组织、特定髓鞘的运输 髓鞘胶质细胞内的mRNAs，以及雪旺细胞对髓鞘形成的承诺。在此应用程序中，我们关注 一组在雪旺细胞发育和髓鞘形成中起关键作用的基因。 (1)在以前的研究中，我们已经确定了ERBB2和erbB3基因的突变，这两个基因编码一种 神经调节蛋白的异构体受体(NRG)信号，并表明ErbB信号是定向的 雪旺细胞的迁移。在本应用中，我们建议识别操作信号并测试 NRG信号的两个阶段指导雪旺细胞沿生长轴突迁移的假说 周围神经。我们建议确定哪些NRG亚型引导雪旺细胞迁移，以确定 这些异构体是否由神经元或雪旺细胞表达和所需，并确定 NRG信号足以引导雪旺细胞迁移到异位位置。 (2)在最近的工作中，我们发现我们的两个突变破坏了G蛋白偶联受体的一个成员 超级大家庭。我们建议确定蛋白质是作为信号还是作为受体，或者两者兼而有之，并测试 该假说认为该基因在神经元中起作用，指示雪旺细胞启动髓鞘形成。 (3)我们的初步研究表明，我们正在努力通过定位克隆来鉴定的st64基因是 这是雪旺细胞发育早期所需的。在标记基因表达分析中，st64突变体 其表型非常类似于erbB3功能的部分丧失。我们的初步研究表明，分析 将定义一个在雪旺细胞中起重要作用的新基因的功能 发展。我们建议通过表型来确定st64基因的细胞和生化功能。 突变株的分析和突变基因的分子分析。

This project will exploit the power of cellular and genetic approaches in zebrafish to illuminate the functions of new genes that are essential for Schwann cell development and myelination in the vertebrate nervous system. In the peripheral nervous system, Schwann cells form the myelin sheath that wraps axons and allows for the rapid transmission of action potentials. Disruption of myelin causes peripheral neuropathies, debilitating diseases that affect 1.5 million people in the United States. Gaps in the understanding of the signals that govern the formation of myelin have hindered the development of therapies for the repair of myelinated axons. In genetic screens for mutations that disrupt myelination, we identified 13 mutations in 10 different genes with specific functions in the development of myelinated axons. Cellular and molecular studies demonstrate that the mutations define genes that function at many steps of the development of myelinated axons, including glial fate specification, Schwann cell migration, organization of the nodes of Ranvier, transport of specific myelin mRNAs within myelinating glia, and commitment of Schwann cells to myelination. In this application, we focus on a group of genes that have key functions in Schwann cell development and myelination. (1) In previous studies, we have identified mutations in erbb2 and erbb3, genes that encode components of a heteromeric receptor for Neuregulin (Nrg) signals, and showed that ErbB signaling is essential for directed migration of Schwann cells. In the present application, we propose to identify the operative signals and test the hypothesis that two phases of Nrg signaling direct Schwann cells as they migrate along axons of growing peripheral nerves. We propose to determine which Nrg isoforms guide Schwann cell migration, to determine whether these isoforms are expressed by and required in neurons or Schwann cells, and to determine whether Nrg signals are sufficient to guide migrating Schwann cells to ectopic locations. (2) In recent work, we found that two of our mutations disrupt a member of the G-protein coupled receptor superfamily. We propose to determine whether the protein acts as a signal or a receptor, or both, and to test the hypothesis that the gene acts in neurons to instruct Schwann cells to initiate myelination. (3) Our preliminary studies show that the st64 gene, which we are working to identify by positional cloning, is required for an early step in Schwann cell development. In analyses of marker gene expression, st64 mutants have a phenotype very similar to a partial loss of erbb3 function. Our preliminary studies suggest that analysis of the st64 mutation will define the function of a novel gene with an essential role in Schwann cell development. We propose to define the cellular and biochemical functions of the st64 gene by phenotypic analysis of the mutants and molecular analysis of the mutated gene.