Characterization of the Myelin-Associated Glycoprotein Receptor NgR2 in vivo

描述(申请人提供)：描述：髓鞘相关糖蛋白(MAG)是一种双功能分子，在中枢和外周神经系统中参与稳定轴突-神经胶质相互作用。此外，MAG已被确定为一种有效的抑制体外轴突生长的药物。我们实验室的工作证实NgR2是MAG的高亲和力受体，足以赋予MAG反应性。这项建议中概述的研究旨在研究NgR2是否为体内的功能性MAG受体。为了研究NgR2的功能，将采用小鼠遗传学方法。我已经通过在NgR2基因的外显子III中引入GFP报告盒来产生缺乏NgR2的小鼠。与MAG突变体类似，NgR2缺失的小鼠可以存活到成年，因此，将使我们能够研究NgR2在成熟中枢神经系统中的作用。抗NgR2和抗MAG免疫荧光的组合将被用来定位NgR2的时空表达模式，以直接与MAG表达进行比较。体外轴突生长实验将用于验证NgR2是MAG受体对MAG介导的抑制视神经损伤后轴突生长和轴突再生所必需的假说。MAG的丢失会导致髓鞘缺陷和轴突变性。为了验证NgR2在体内是MAG受体的假设，我们将对髓鞘进行电子显微镜研究，以检查NgR2的缺失是否会导致类似于先前报道的MAG缺陷小鼠的缺陷。我的初步结果表明，NgR2基因缺失的小鼠坐骨神经出现了髓鞘形成缺陷。作为NgR2小鼠体内视神经再生研究的替代方法，我建议使用NgR1/NgR2双突变小鼠，因为NgR1可能补偿NgR2缺失小鼠中NgR2的丢失。综上所述，这些实验有望为NgR2功能在MAG介导的生长抑制和体内轴突-神经胶质细胞相互作用中的作用提供见解。与公共健康相关：创伤性脑损伤(TBI)、脊髓损伤或中风所造成的损伤通常会导致永久性神经功能障碍。这主要是由于缺乏自发的轴突再生和/或重新髓鞘形成。全面了解NgR2在调节MAG功能中的作用，将有助于开发能够在注意MAG抑制的同时保持其对轴突的保护和稳定作用的治疗剂。

DESCRIPTION (provided by applicant): Description: Myelin-associated glycoprotein (MAG) is a bi-functional molecule that has been implicated in stabilizing axon-glial interactions in both the central and peripheral nervous system. In addition, MAG has been identified as a potent inhibitor of neurite outgrowth in vitro. Work from our laboratory identified NgR2 as a high affinity receptor for MAG sufficient to confer MAG responsiveness. The studies outlined in this proposal are aimed at investigating whether NgR2 is a functional MAG receptor in vivo. To study NgR2 function a mouse genetic approach will be pursued. I have generated mice deficient for NgR2 by introducing a GFP reporter cassette into exon III of the NgR2 gene. Similar to MAG mutants, NgR2 null mice are viable into adulthood and thus, will allow us to study the role of NgR2 in the mature central nervous system. A combination of anti-NgR2 and anti-MAG immunofluorescence will be used to map the tempero-spatial expression pattern of NgR2 in direct comparison to MAG expression. In vitro neurite outgrowth assays will be used to test the hypothesis that NgR2 is a MAG receptor necessary for MAG-mediated inhibition of neurite outgrowth and axonal regeneration following optic nerve injury in vivo. Loss of MAG leads to defects in myelin sheaths and the degeneration of axons. To test the hypothesis that NgR2 is a MAG receptor in vivo, electron microscopical studies of myelin sheaths will be performed to examine whether loss of NgR2 leads to defects reminiscent to the ones previously reporter for MAG deficient mice. My preliminary results suggest that NgR2 null mice show myelination defects in the sciatic nerve. As an alternate approach for optic nerve regeneration studies of NgR2 mice in vivo, I propose to use NgR1/NgR2 double mutant mice, as NgR1 might compensate for the loss of NgR2 in NgR2 null mice. Collectively, the experiments proposed are anticipated to provide insights in the role of NgR2 function in MAG mediated growth inhibition and axon-glia interactions in vivo. RELEVANCE TO PUBLIC HEALTH: The damage that occurs in traumatic brain injury (TBI), spinal cord injury or stroke, often leads to permanent neurological deficits. This is primarily due to the lack of spontaneous axonal regeneration and/or remyelination. A complete understanding of the role NgR2 plays in mediating MAG's function, will aid in the development of therapeutic agents that can attentuate MAG inhibition while preserving its protective and stabilizing effects on axons.