Chemokine Receptor Function in the Nervous System

描述(申请人提供)：在我们最初的提案中，我们试图展示成人大脑中神经前体细胞的趋化因子受体的表达，检测SDF1/CXCR4信号对齿状回(DG)成年神经前体细胞的影响，并探讨HIV1对这一过程的影响。我们已经成功地推行了这些项目。事实上，这种情况已经发生到如此程度，以至于从我们的工作中自然地形成了几个新的具体目标。 一项重大的成就是发展了几个不同的双色BAC转基因小鼠，它们报告了趋化因子(SDF1，MCP1-red)及其受体(CXCR4，CCR2-green)的表达。这些小鼠让我们证明了SDF1扮演了一个新的角色，并在成年DG的神经干细胞利基(NSN)中扮演了神经递质的角色。我们证明了SDF1与GABA在向DG NSN表达神经前体的CXCR4的突触传递中具有协同作用。这些观察表明，HIV1(T嗜性)或长期使用吗啡可能通过利用DG NSN中的突触影响SDF1直接影响神经发生，这是我们现在希望追求的新目标。 我们还观察到SDF1在DG NSN的血管内皮细胞中表达，表明可能从血管和神经元来源释放的SDF1可能影响神经发生。 这些观察结果提出了一个新的目标，即我们将从神经元或内皮细胞来源中从基因上删除SDF1，并检查其在正常和病理条件下对神经发生的影响。我们已经创造了一个带有条件SDF1等位基因的小鼠品系，现在希望实现这个额外的目标。 我们新的MCP-1-Red/CC2-Green小鼠的使用使我们能够检查先天免疫反应在DG NSN中的作用。先天免疫反应由HIV1激活，并将激活的小胶质细胞和白细胞等细胞招募到DG NSN。利用这些小鼠，我们观察到了HIV1和其他类型的感染或脑损伤对先天免疫反应的激活。在病理条件下，构成先天免疫反应的细胞也可能构成DG NSN的一部分，这是一个新的想法，表明了先天免疫可能与成人神经发生相互作用的方式。这些观察结果提出了一个新的目标，即我们将研究由HIV1和吗啡引发的先天免疫对DG NSN神经发生的整体影响。我们认为，趋化因子信号，特别是涉及通过CCR2受体作用的MCP1，将介导这种作用。 与公共卫生相关。我们已经证明了趋化因子SDF1可以影响成年齿状回干细胞龛中的神经发生。SDF1表达的神经元与GABA合作形成神经前体细胞的突触输入。我们现在希望确定由HIV1触发的先天免疫反应如何影响成年DG神经元的发育，以及这种影响如何被慢性吗啡治疗改变。我们将利用新的趋化因子报告基因和基因敲除小鼠来确定天然免疫系统的细胞元件如何形成成人干细胞生态位的功能部分，以及在正常条件下和在神经病理学的背景下，趋化因子及其受体如何调节神经源性事件。

DESCRIPTION (provided by applicant): In our original proposal we sought to demonstrate the expression of chemokine receptors by neural progenitor cells in the adult brain, to examine the effect of SDF1/CXCR4 signaling on adult neural progenitor cells in the dentate gyrus (DG), and to investigate the effects of HIV1 on this process. We have successfully pursued these projects. Indeed, this has occurred to such an extent that several new Specific Aims have naturally developed from our work. A significant achievement has been the development of several different lines of two color BAC transgenic mice that report the expression of chemokines (SDF1, MCP1-RED) and their receptors (CXCR4, CCR2-GREEN). These mice allowed us to demonstrate that SDF1 took on a new role and acted as a neurotransmitter within the neural stem cell niche (NSN) of the adult DG. We demonstrated that SDF1 cooperated with GABA in synaptic transmission to CXCR4 expressing neural progenitors in the DG NSN. These observations indicate that both HIV1 (T-tropic) or chronic morphine use may directly influence neurogenesis by impacting this SDF1 utilizing synapse in the DG NSN, a new Aim which we now wish to pursue. We also observed that SDF1 was expressed by endothelial cells that line blood vessels in the DG NSN indicating that SDF1 potentially released from both vascular and neuronal sources may influence neurogenesis. These observations have suggested a new Aim in which we would genetically delete SDF1 from either neuronal or endothelial sources and examine its effects on neurogenesis under normal and pathological conditions. We have created a line of mice with a conditional SDF1 allele and now wish to carry out this additional Aim. The use of our new MCP-1-Red/CC2-Green mice has allowed us to examine the role of the innate immune response in the DG NSN. The innate immune response is activated by HIV1 and recruits cells such as activated microglia and leukocytes to the DG NSN. Using these mice we have observed the activation of the innate immune response by HIV1 and by other types of infection or brain damage. The idea that cells that form part of the innate immune response may also constitute part of the DG NSN under pathological conditions is a new idea suggesting ways in which innate immunity may interact with adult neurogenesis. These observations have suggested a new Aim in which we will examine the overall effect of innate immunity triggered by HIV1 and morphine on neurogenesis in the DG NSN. We believe that chemokine signaling, particularly involving MCP1 acting via the CCR2 receptor will mediate such actions. PUBLIC HEALTH RELEVANCE. We have demonstrated that adult neurogenesis in the dentate gyrus stem cell niche can be influenced by the chemokine SDF1.SDF1 expressing neurons cooperate with GABA in forming synaptic inputs to neural progenitor cells.We now wish to determine how the innate immune response that is triggered by HIV1 can influence the development of neurons in the adult DG and how this can also be modified by chronic morphine treatment.We shall utilize novel lines of chemokine reporter and knockout mice to determine how the cellular elements of the innate immune system can form a functional part of the adult stem cell niche and how neurogenic events can be regulated by chemokines and their receptors under normal conditions and in the context of neuropathology.