Cellular and genetic analysis of central nervous system myelination in zebrafish

髓鞘是一种特殊的神经胶质细胞的质膜延伸，它包裹着神经元的突起，称为轴突：在这样做的过程中，髓鞘允许神经冲动的快速传导。髓磷脂的损伤引起许多人类疾病的症状，包括多发性硬化症（MS）和腓骨肌萎缩症（CMT）神经病。髓鞘形成（髓鞘形成）是比增加神经传导的替代方式（即增加轴突直径）有效得多的机制。大直径的轴突占据空间，这限制了只能使用这种策略进化的生物体的大小和复杂性。因此，公平地说，复杂的神经系统，如我们自己的神经系统，在很大程度上是由于髓鞘的特性而进化的。因此，了解控制髓鞘形成的机制具有基本的生物学和医学意义。斑马鱼是一个强大的模式生物，在其中解剖髓鞘形成的细胞和遗传基础。斑马鱼胚胎是透明的，并且存在工具来观察荧光标记的细胞在活体中的真实的时间行为，其细节水平在其他脊椎动物实验室动物中是不可行的。斑马鱼的第二个主要吸引力是能够进行大规模的负担得起的遗传筛选，以找到特定生物过程所需的基因。在我们实验室进行的遗传筛选中，我们确定了有髓鞘轴突发育所需的10个基因。虽然我们已经了解了很多，但我们的筛选肯定没有范围来识别所有调节髓鞘形成的基因。我们目前对中枢神经系统（大脑和脊髓）髓鞘形成的遗传和细胞基础的理解仍然特别初级。因此，我建议的总体目标是确定斑马鱼中枢神经系统髓鞘形成的细胞和遗传基础。1.我将直接观察精确的轴突和神经胶质细胞之间的细胞相互作用，最终在髓鞘形成，通过高分辨率的延时显微镜在斑马鱼。2.先前的研究已经导致了一个有趣的假设，即神经元活动的水平可以调节髓鞘的产生，这可能代表了局部脑活动可以增强神经系统功能的基本机制。我将通过改变斑马鱼胚胎的神经活动水平，并观察不同治疗对髓鞘生成和神经生理学的影响，首次在完整的动物中验证这一假设。3.最近，一种特定的遗传途径（神经调节蛋白-erbb途径）被认为是周围神经系统（大脑和脊髓外的神经系统部分）髓鞘形成的关键调节因子，但其在CNS中的作用有些争议。我有令人兴奋的初步数据，我现在将充分探索这一基本的调节途径确实调节中枢神经系统的髓鞘形成。4.我们仍然不知道中枢神经系统髓鞘形成所需的许多基因的身份。我将在斑马鱼中进行一项新的遗传筛查，特别关注中枢神经系统髓鞘形成所需的基因。通过高分辨率分析，如延时显微镜，将特定基因突变的动物与正常动物进行比较，我将能够准确地确定髓鞘形成的哪些方面通常需要这些基因。我希望在爱丁堡大学建立自己的独立研究小组，这些实验室是小法兰西生物医学科学中心新的6亿英镑研究开发的一部分。这种环境将提供世界一流的基础设施，我将与髓鞘生物学领域的两位领先研究人员相邻，这将提供智力支持和潜在合作的理想环境，继续揭开髓鞘形成的奥秘。

The myelin sheath is a plasma membrane extension of specialized glial cells that wraps around neuronal processes, called axons: in so doing, myelin permits the rapid conduction of nerve impulses. Damage to myelin causes the symptoms of many human diseases including multiple sclerosis (MS) and Charcot-Marie-Tooth (CMT) neuropathies. Myelin formation (myelination) is a much more efficient mechanism than the alternative way to increase nerve conduction, namely increasing axon diameter. Large diameter axons take up space, which constrains the size and complexity of organism that can evolve using only this strategy. It is fair to say, therefore, that complex nervous systems, such as our own, have evolved in large part due to the properties of the myelin sheath. Understanding the mechanisms that control myelination is thus of both fundamental biological and medical relevance. The zebrafish is a powerful model organism in which to dissect the cellular and genetic basis of myelination. Zebrafish embryos are transparent, and tools exist to watch fluorescently labeled cells behave in real time in the living organism, at a level of detail that is not feasible in other vertebrate laboratory animals. A second major attraction of the zebrafish is the ability to carry out large-scale affordable genetic screens to find genes required for specific biological processes. In a genetic screen carried out in our lab we identified 10 genes required for the development of myelinated axons. Although we have learned a great deal our screen certainly did not have the scope to identify all the genes that regulate myelination. Our current understanding of the genetic and cellular basis of myelin formation in the central nervous system (the brain and spinal cord) remains particularly rudimentary. The overall goal of my proposal, therefore, is to determine the cellular and genetic basis of myelin formation in the zebrafish central nervous system. 1. I will directly observe the precise cellular interactions between axons and glial cells that culminate in myelination, by high-resolution time-lapse microscopy in zebrafish. 2. Previous studies have led to the intriguing hypothesis that the level of neuronal activity can regulate myelin production, which may represent a fundamental mechanism by which localized brain activity could enhance nervous system function. I will test this hypothesis in intact animals for the first time by altering levels of neural activity in zebrafish embryos and looking at the effects of different treatments on myelin production and on neurophysiology. 3. Recently a particular genetic pathway (the neuregulin-erbb pathway) has been implicated as a key regulator of myelin formation in the peripheral nervous system (the part of the nervous system outside of the brain and spinal cord), but its role in the CNS is somewhat controversial. I have exciting preliminary data that I will now fully explore that this fundamental regulatory pathway does indeed regulate myelination in the CNS. 4. We still do not know the identity of many of the genes that are required for myelination in the CNS. I will perform a new genetic screen in zebrafish and focus in particular on genes that are required for myelination in the CNS. By comparing animals with mutations in specific genes with normal animals by high-resolution analyses such as time-lapse microscopy I will be able to define exactly which aspects of myelination those genes are normally required for. I hope to set up my own independent research group at the University of Edinburgh, in laboratories that are part of a new £600m research development at the Little France Biomedical Sciences Centre. This environment will provide a world-class infrastructure, and I will be adjacent to two of the leading researchers in the field of myelin biology, which will provide an ideal environment of intellectual support and potential collaboration, to continue to unravel the mysteries of myelination.