Functional Analysis of Myelin Inhibitors in Spinal Axon Regeneration Failure

描述（由申请人提供）：成年哺乳动物中枢神经系统（CMS）中的轴突再生失败至少部分归因于CNS髓鞘的抑制性质。三个“经典”的髓鞘衍生的神经突起生长抑制剂，Nogo，髓鞘相关糖蛋白（MAG）和少突胶质细胞-髓鞘糖蛋白（OMgp），已被确定，在体外表现出有效的抑制活性的神经突起生长。然而，中心问题仍然是这些抑制剂的贡献CNS轴突再生失败在体内。我们的中心假设是，髓鞘衍生的神经突起生长抑制剂Nogo，MAG和OMgp在阻断脊髓轴突再生中发挥了重要的和潜在的冗余作用。总体方法是检查在一种或多种髓磷脂抑制剂基因缺失的小鼠脊髓中的轴突再生，慢性或急性，特别是解决发育补偿和功能冗余的问题。通过急性基因缺失，我们解决了生殖系突变体的发育补偿问题。通过同时删除三种抑制剂，我们解决了功能冗余的问题。目标1。通过检测急性缺失Nogo或OMgp对皮质脊髓和中缝脊髓神经元能纤维再生的影响，评估Nogo和OMgp在再生失败中的作用。我们将采用诱导敲除系统，急性删除Nogo或OMgp在少突胶质细胞，然后检查皮质脊髓束（CST）和中缝脊髓神经纤维束的再生反应。目标2.通过确定所有三种抑制剂缺乏的小鼠中皮质脊髓和中缝脊髓轴突能纤维束的再生潜力，评估Nogo、MAG和OMgp在CNS轴突再生失败中的联合作用。目标3.测试增加内在生长潜力与去除髓鞘抑制剂在促进脊髓轴突再生中是否具有协同作用。以往的研究表明，在体条件性损伤背根神经节（DRG）神经元的外周分支可增强神经元的内在生长潜能，促进中枢分支的再生。我们将测试这种增强的再生是否在Nogo/MAG/OMgp三重突变体中进一步增强，以及删除三种髓鞘抑制剂和条件损伤之间是否存在协同效应。总之，这些研究将为髓鞘抑制剂在脊髓轴突再生失败中的作用提供重要的见解。了解这些髓鞘抑制剂在CNS轴突再生中的作用对于设计任何治疗干预以促进轴突再生和脊髓修复都是至关重要的。

DESCRIPTION (provided by applicant): Axon regeneration failure in the adult mammalian central nervous system (CMS) has been attributed at least in part to the inhibitory nature of the CNS myelin. Three "classical" myelin-derived neurite outgrowth inhibitors, Nogo, myelin-associated glycoprotein (MAG) and oligodendrocyte-myelin glycoprotein (OMgp), have been identified that exhibit potent inhibitory activity on neurite outgrowth in vitro. However, the central question remains as to the contribution of these inhibitors to CNS axon regeneration failure in vivo. Our central hypothesis is that myelin-derived neurite growth inhibitors Nogo, MAG and OMgp play a significant and potentially redundant role in blocking spinal axon regeneration. The overall approach is to examine axon regeneration in the spinal cord of mice with gene deletion in one or more myelin inhibitors chronically or acutely, specifically addressing the issues of developmental compensation and functional redundancy. By acute gene deletion, we address the issue of developmental compensation in germline mutants. By deleting the three inhibitors simultaneously, we address the issue of functional redundancy. Aim 1. To assess the role of Nogo and OMgp in regeneration failure by examining the effect of acutely deleting Nogo or OMgp on corticospinal and raphespinal serotonergic fiber regeneration. We will employ an inducible knockout system to acutely delete Nogo or OMgp in oligodendrocytes and then examine the regenerative response of the corticospinal tract (CST) and the raphespinal serotonergic fiber tract. Aim 2. To assess the combined contribution of Nogo, MAG and OMgp in CNS axon regeneration failure by ascertaining the regeneration potential of the corticospinal and raphespinal serotonergic fiber tracts in mice deficient in all three inhibitors. Aim 3. To test whether increasing the intrinsic growth potential has a synergistic effect with removing myelin inhibitors in promoting spinal axon regeneration. Previous studies indicate that a conditioning lesion to the peripheral branch of the dorsal root ganglion (DRG) neurons augments the intrinsic growth potential of the neurons and promotes the regeneration of the central branch in vivo. We will test whether this enhanced regeneration is further enhanced in Nogo/MAG/OMgp triple mutant, and whether there is a synergistic effect between deleting the three myelin inhibitors and a conditioning lesion. Together, these studies will provide important insight into the role of myelin inhibitors in spinal axon regeneration failure. Understanding the role of these myelin inhibitors in CNS axon regeneration is crucial to the design of any therapeutic intervention to promote axon regeneration and spinal cord repair targeting this group of molecules.