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

描述（由申请人提供）：在中枢神经系统（CNS）发育期间，少突胶质细胞祖细胞在离散的生发区产生，从那里它们迁移到预期的有髓鞘区域。在这些最终的目的地，少突胶质细胞成为髓鞘形成前、迁移后的细胞，其延伸出一个大而复杂的过程网络以寻找要髓鞘形成的轴突节段。在适当的靶相互作用后，髓鞘形成前、迁移后的少突胶质细胞过程从过程生长过渡到膜片形成。少突胶质细胞成熟的这些关键的最后和不同的步骤由少突胶质细胞的突起（即过程）与其细胞外环境的复杂相互作用来调节，并且它们被认为对于有效的髓鞘形成至关重要。然而，很少有人知道的细胞外因子和分子机制协调的复杂序列的事件发生在从几个过程轴承到一个复杂的过程网络延伸，然后到髓鞘细胞的进展。因此，作为一种更好地理解髓鞘形成调控的方法，这些研究的长期目标是深入了解由髓鞘形成前、迁移后少突胶质细胞延伸的突起的生长和成熟的调控。我们实验室产生的数据表明，在髓鞘形成的初始阶段由髓鞘形成前、迁移后的少突胶质细胞释放的基质细胞蛋白磷酸二酯酶-I1/自分泌运动因子（PD-Ia/ATX）对少突胶质细胞突起的成熟起着至关重要的作用。基于我们发表的和初步的数据，我们提出了中心假设，即PD-Ia/ATX通过三个不同的功能活性位点的协同作用，促进从早期髓鞘形成前、迁移后的少突胶质细胞进展为完全功能的髓鞘形成细胞。具体而言，我们计划完成以下研究以解决上述中心假设：1）我们将在体外表征由所提出的PD-Ia/ATX的MORFO结构域的两个功能活性位点介导的分子机制，其参与促进髓鞘形成前、迁移后少突胶质细胞突起成熟为复杂过程网络。2)我们将在体外表征由PD-Ia/ATX的lysoPLD活性位点介导的分子机制，并参与促进髓鞘形成前、迁移后少突胶质细胞突起成熟为膜片。3)我们将在体内的作用，PD-Ia/ATX及其功能活性位点的少突胶质细胞突起的重塑和初始髓鞘形成的斑马鱼作为模型系统的特点。在这些和随后的研究中获得的数据不仅可能显着推进我们对发育髓鞘形成的认识，而且还可能揭示改善髓鞘再生的新治疗靶点。公共卫生相关性：多发性硬化症（MS）是人类最主要的脱髓鞘疾病，也是神经创伤后最常见的致残性神经系统疾病。不幸的是，髓鞘的内源性修复在CNS内是有限的，并且目前不存在促进髓鞘再生的疗法，尽管髓鞘再生是目前经证实的功能恢复和神经保护的最佳策略。为了更好地理解刺激髓鞘再生所必需的调节回路，本授权申请研究了细胞外因子磷酸二酯酶-Ia/自分泌运动因子（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.