The Role of Neurotrophins in Oligodendrocyte Function

描述（由申请人提供）：目前工作的总体假设是少突胶质细胞（OLG），中枢神经系统的髓鞘形成细胞受到明确定义的营养因子，脑源性神经营养因子（BDNF）的严重影响。BDNF的作用通过trkB及其相关的MAP激酶、PI 3激酶-Akt和PLC-γ途径介导。BDNF在脑发育和整个生命过程中支持OLG增殖和分化。最初供资期间开展的工作支持这一假设。用基底前脑（BF）OLG培养，我们发现BDNF使DNA合成和髓鞘碱性蛋白+（MBP+）细胞数增加2-3倍。使用体内研究，我们发现BDNF敲除的动物表达的NG 2少突胶质细胞祖细胞比野生型同窝仔少38%，BDNF +/_成年小鼠表现出MBP表达减少。此外，共免疫细胞化学分析显示，BDNF受体，trkB，表达在成熟的APC+ OLG在成年小鼠。这些观察结果支持OLG受到BDNF严格调控的可能性。为了扩展这些研究，我们现在建议1）测试培养工作的体内相关性和（2）确定BDNF作用的信号传导机制。我们尤其会：（1）鉴定介导BDNF作用的受体和信号通路，（2）确定OLG中trkB的体内表达模式，和（3）通过使用敲除小鼠确定BDNF和BDNF受体在体内的作用。这些研究探讨了BDNF在体内OLG的发育和维持中可能发挥的作用。我们认为，这项工作可能会提供显着的新的见解髓鞘形成的缺陷，发生在破坏性的神经疾病的特点是少突胶质细胞的损失和无法重新填充病变区域。

DESCRIPTION (provided by applicant): The overall hypothesis of the current work is that oligodendrocytes (OLGs), the myelinating cells of the central nervous system are critically influenced by the well-defined trophic factor, brain-derived neurotrophic factor (BDNF). The effects of BDNF are mediated through trkB and its associated MAP kinase, PI3 kinase-Akt, and PLC-gamma pathways. BDNF supports OLG proliferation and differentiation during brain development and throughout life. Work performed during the initial funding period supports this hypothesis. Using basal forebrain (BF) OLG cultures, we found that BDNF elicits 2-3 fold increases in DNA synthesis and numbers of myelin basic protein + (MBP) cells. Using in vivo studies we found that BDNF knockout animals express 38 percent fewer NG2 oligodendrocyte progenitor cells than wild-type littermates and that BDNF +/_ adult mice exhibit reduced MBP expression. Moreover, coimmunocytochemical analysis revealed that the BDNF receptor, trkB, is expressed on mature APC+ OLGs in adult mice. These observations support the possibility that OLGs are critically regulated by BDNF. To extend these studies we now propose to 1) test in vivo relevance of the culture work and (2) determine signaling mechanisms underlying BDNF actions. In particular, we will: (1) Identify receptors and signaling pathways mediating BDNF effects, (2) Define the in vivo expression pattern of trkB in OLGs and (3) Define the roles of BDNF and BDNF receptors in vivo by using knockout mice. These studies explore the role BDNF may play in the development and maintenance of OLGs in vivo. We suggest that this work may provide significant new insights into deficits in myelination that occur in devastating neural diseases characterized by the loss of oligodendrocytes and an inability to repopulate the lesioned area.