Guidance of Oligodendrocyte Processes: The Role of Local Protein Synthesis

描述（由申请人提供）：在中枢神经系统（CNS）发育期间，神经元和少突胶质细胞来源的迁移后细胞发出在实质中导航的过程，以寻找诱导其成熟的靶信号，即神经元的突触形成和少突胶质细胞的髓鞘形成。该过程导航的调节已经被很好地表征为神经元细胞，其中感觉运动结构，神经元生长锥，位于过程尖端是感觉环境线索的"细胞器"。相比之下，令人惊讶的是，少突胶质细胞过程的寻路和靶向知之甚少。我们的初步数据表明，少突胶质细胞的过程中拥有在其远端的“细胞器”，在结构上和功能上类似于神经生长锥，我们将称为少突胶质细胞生长锥样结构（OLG生长锥）。在神经元中，生长锥内的mRNA运输和局部限制的蛋白质合成被认为是轴突/神经突寻路和靶向的主要调节剂。我们的初步数据表明，类似的调节机制可能是重要的少突胶质细胞过程的寻路和靶向。因此，我们制定的中央假设，即髓鞘形成后，迁移少突胶质细胞具有OLG生长锥，含有mRNA，其本地限制翻译是至关重要的少突胶质细胞过程寻路和靶向，即髓鞘形成的调节。这一假设将在两个具体目标中得到检验。1)我们将确定OLG生长锥寻路，特别是在响应非许可的线索向化性转向局部限制蛋白质合成的作用。在这组实验中，将确定在寻路OLG生长锥中发生局部限制性蛋白质合成的程度。此外，分离过程的趋化性转向将在蛋白质合成抑制后进行分析。预期抑制局部限制的蛋白质合成将扰乱OLG-生长锥趋化性转向反应。2)使用微阵列的方法，我们将确定的mRNA是存在于OLG生长锥特异性响应轴突靶向信号。这组实验预期揭示对于OLG生长锥靶向（即髓鞘形成的起始）重要的候选蛋白。在继续研究的基础上，目前的建议，我们正计划进一步表征这些蛋白质。因此，拟议的研究代表了一系列实验的第一步，这些实验旨在更好地了解少突胶质细胞寻路和靶向过程的调节。这种知识的进步是特别令人感兴趣的，因为突起生长和轴突识别的缺陷似乎是修复患有人类主要脱髓鞘疾病多发性硬化症的患者的CMS中存在的病变的主要限制因素。

DESCRIPTION (provided by applicant): During development of the central nervous system (CNS) post-migratory cells of both neuronal and oligodendroglial origin send out processes that navigate through the parenchyma in search for a target signal that induces their maturation, i.e. synapse formation for neuronal and myelin sheath formation for oligodendroglial cells. The regulation of this process navigation has been well characterized for neuronal cells, where a sensorimotor structure, the neuronal growth cone, located at the process tip is the "organelle" that senses environmental cues. In contrast, surprisingly little is known about oligodendroglial process pathfinding and targeting. Our preliminary data demonstrate that oligodendrocyte processes possess at their distal ends "organelles" that structurally and functionally resemble neuronal growth cones and that we will refer to as oligodendroglial growth cone-like structures (OLG-growth cones). In neurons, mRNA transport and locally restricted protein synthesis within the growth cone are considered main regulators of axon/neurite pathfinding and targeting. Our preliminary data suggest that similar regulatory mechanisms may be important for the pathfinding and targeting of oligodendrocyte processes. Thus, we formulate the central hypothesis that premyelinating, post-migratory oligodendrocytes possess OLG-growth cones that contain mRNAs, the locally restricted translation of which is critical for the regulation of oligodendroglial process pathfinding and targeting, i.e. myelination. This hypothesis will be tested in two specific aims. 1) We will determine the role of locally restricted protein synthesis for OLG-growth cone pathfinding and in particular for chemotropic turning in response to non-permissive cues. In this set of experiments the extent to which locally restricted protein synthesis occurs in pathfinding OLG-growth cones will be determined. In addition, chemotropic turning of separated processes will be analyzed after inhibition of protein synthesis. It is expected that inhibition of locally restricted protein synthesis will perturb OLG- growth cone chemotropic turning responses. 2) Using a microarray approach, we will identify mRNAs that are present in OLG-growth cones specifically in response to axonal targeting signals. This set of experiments is expected to reveal candidate proteins that are important for OLG-growth cone targeting, i.e. the initiation of myelin sheath formation. In continuing studies based on the findings of the present proposal, we are planning to further characterize these proteins. The proposed studies thus represent a first step into a set of experiments designed to better understand the regulation of oligodendrocyte process pathfinding and targeting. Such advancement in knowledge is of particular interest since deficiencies in process outgrowth and axon recognition appear to be among the main limiting factors for repair of lesions present in the CMS of patients suffering from the major demyelinating disease in humans, Multiple Sclerosis.