Mechanisms in CNS myelination: Role of PD-Ialpha/ATX

描述(申请人提供)：在中枢神经系统(CNS)的发育过程中，少突胶质前体细胞在离散的生发区生成，它们从那里迁移到预期的有髓区域。在这些最终的终点，少突胶质细胞成为髓鞘前、迁移后的细胞，这些细胞延伸出一个庞大而复杂的过程网络，寻找要髓鞘的轴突节段。在适当的靶相互作用下，髓鞘形成前、迁移后的少突胶质细胞过程从突起生长过渡到膜片形成。少突胶质细胞成熟的这些关键的最终和独特的步骤受少突胶质细胞突起(即突起)与其细胞外环境的复杂相互作用的调节，它们被认为是有效的髓鞘形成的关键。然而，在从几个过程到复杂的过程网络延伸到髓鞘细胞的过程中，协调复杂事件序列的细胞外因子和分子机制知之甚少。因此，作为一种更好地了解髓鞘形成调控的方法，这些研究的长期目标是深入了解髓鞘形成前、迁移后的少突胶质细胞延长突起的生长和成熟的调控。本实验室的数据表明，髓鞘形成前、迁移后的少突胶质细胞在髓鞘形成初期释放的基质细胞蛋白磷酸二酯酶-I1/自体趋化蛋白(PD-Ia/ATX)对少突胶质细胞突起的成熟起着至关重要的作用。基于我们已发表的和初步的数据，我们提出了一个中心假设，即PD-Ia/ATX通过三个不同的功能活性部位的协同作用，促进了从早期髓鞘前期、迁移后的少突胶质细胞向完全功能的髓鞘细胞的演变。具体来说，我们计划完成以下研究来解决上述中心假设：1)我们将在体外表征PD-Ia/ATX Morfo结构域的两个功能活性部位所介导的分子机制，这些机制涉及促进髓鞘形成前、迁移后的少突胶质细胞突起进入复杂过程网络的成熟。2)我们将在体外研究PD-Ia/ATX的溶解PLD活性部位所介导的促进髓鞘形成前、迁移后的少突胶质细胞向膜内突起成熟的分子机制。3)以斑马鱼为模型系统，在体内研究PD-Ia/ATX及其功能活性部位在少突胶质细胞突起重塑和初始髓鞘形成中的作用。在这些和随后的研究中获得的数据可能不仅会显著提高我们对发育髓鞘形成的了解，而且还可能揭开改善髓鞘再分化的新的治疗靶点。公共卫生相关性：多发性硬化症(MS)是人类的主要脱髓鞘疾病，在神经创伤后是年轻人最常见的致残神经疾病。不幸的是，髓鞘的内源性修复仅限于中枢神经系统，目前还没有促进再髓鞘形成的治疗方法，尽管重新髓鞘形成是目前被证明是功能恢复和神经保护的最佳策略。为了更好地了解刺激重新髓鞘形成所必需的调节电路，本研究旨在研究细胞外因子磷酸二酯酶-Ia/自体趋化蛋白(PD-Ia/ATX)在促进负责产生髓鞘的细胞(即髓鞘形成前、迁移后的少突胶质细胞)成熟中的作用。

DESCRIPTION (provided by applicant): During development of the central nervous system (CNS), oligodendrocyte progenitor cells are generated in discrete germinal zones from where they migrate to prospective myelinated areas. At these final destinations, oligodendrocytes become premyelinating, post-migratory cells that extend a large and complex process network in search for axonal segments to be myelinated. Upon appropriate target interaction, premyelinating, post-migratory oligodendrocyte processes transition from process outgrowth to membrane sheet formation. These critical final and distinct steps of oligodendrocyte maturation are regulated by complex interactions of the oligodendrocyte's protrusions, i.e. processes, with their extracellular environment, and they are considered crucial for efficient myelination. However, little is known about the extracellular factors and molecular mechanisms coordinating the intricate sequence of events that occurs during the progression from a few process bearing to a complex process network extending and then to a myelinating cell. Thus, as an approach toward a better understanding of the regulation of myelination, the long-term goal of these studies is to gain insight into the regulation of outgrowth and maturation of protrusions extended by premyelinating, post-migratory oligodendrocytes. Data generated in our laboratory suggest that the matricellular protein phosphodiesterase-I1/autotaxin (PD-Ia/ATX), which is released by premyelinating, post- migratory oligodendrocytes during the initial stages of myelination, plays a crucial role for the maturation of oligodendrocyte protrusions. Based on our published and preliminary data we formulate the central hypothesis that PD-Ia/ATX promotes the progression from an early stage premyelinating, post- migratory oligodendrocyte into a fully functional, i.e. myelinating cell, via the concerted action of three distinct functionally active sites. In particular, we are planning to complete the following studies to address the above stated central hypothesis: 1) We will characterize in vitro the molecular mechanisms that are mediated by the proposed two functionally active sites of PD-Ia/ATX's MORFO domain and that are involved in promoting the maturation of premyelinating, post-migratory oligodendrocyte protrusions into a complex process network. 2) We will characterize in vitro the molecular mechanisms that are mediated by PD-Ia/ATX's lysoPLD active site and that are involved in promoting the maturation of premyelinating, post-migratory oligodendrocyte protrusions into membrane sheets. 3) We will characterize in vivo the role of PD-Ia/ATX and its functionally active sites on the remodeling of oligodendrocyte protrusions and on initial myelination using the zebrafish as a model system. The data obtained in these and subsequent investigations are likely to significantly advance not only our knowledge about developmental myelination but they may also unravel novel therapeutic targets for improving remyelination. PUBLIC HEALTH RELEVANCE: Multiple Sclerosis (MS) is the major demyelinating disease in human and after neurotrauma the most common disabilitating neurological disease in young adults. Unfortunately endogenous repair of the myelin sheath is limited within the CNS and currently no remyelination-promoting therapies exist, despite the fact that remyelination is currently the best proven strategy for functional recovery and neuroprotection. As an attempt to better understand the regulatory circuits that may be necessary for stimulating remyelination, the present grant application investigates the role of the extracellular factor phosphodiesterase-Ia/autotaxin (PD-Ia/ATX) in promoting the maturation of the cells responsible for generating myelin, namely premyelinating, post-migratory oligodendrocytes.