NEUROTROPHINS IN NEURONAL SURVIVAL AND DIFFERENTIATION

描述(摘自申请者摘要)：我们的目标是了解 神经营养因子在(一)中枢神经系统神经元存活中的作用(S) (Ii)神经元分化，以及(Iii)保护神经元免受损伤。 神经营养因子是一个由四个成员组成的结构相关蛋白质家族；神经 生长因子、脑源性神经营养因子、神经营养因子-3 (NT-3)和神经营养素-4(NT-4)。脑源性神经营养因子、NT-3和NT-4是强有力的生存因子 影响多种类型中枢神经系统神经元的因素。我们得到了携带零突变的小鼠 在个体以及两个或三个神经营养因子基因中；例如，NT-4-/- 小鼠，[BDNF-/-，NT-4-/-]小鼠，[BDNF-/-，NT-3-/-，NT-4-/-]小鼠等 这些小鼠，我们可以问关于神经元存活和分化的问题 以前不能摆出姿势的活体。我们会调查的 神经营养素依赖对中枢神经系统神经元存活和分化的影响 海马体，以及神经元对缺血的反应。我们的首要目标是 确定神经营养因子是否是海马区生存所必需的 胚胎和出生后发育中的神经元。以前的研究和我们的 初步结果表明，多种/替代神经营养因子可以提供 中枢神经系统神经元存活的信号和中枢神经系统神经元可能依赖于 神经营养因子在出生后发育期间存活。为了测试这些 假设，NT-4-/-和[BDNF-/-，NT-3-/-，NT-4-/-]小鼠将被检验 组织学和免疫组织学以确定(I)是否有 (I)胚胎发育和(Ii)出生后中枢神经系统神经元过度死亡 发展。我们的第二个目标是确定神经营养因子在调节 在出生后发育过程中，海马区突起的生长。(I) [BDNF-/-，NT-3-/-，NT-4-/-]小鼠将被用来确定 神经营养因子控制神经突起的生长。(Ii)携带零突变的小鼠 单个神经营养因子基因将被用来确定每个基因的特异性。 神经营养因子在轴突生长中的作用。(Iii)体育锻炼将应用于 NT-4-/-和野生型小鼠确定NT-4是否介导活性依赖 轴突生长。(4)外源性NT-4将用于挽救潜在的 异常轴突生长。我们的第三个目标是确定神经营养因子 在保护成人神经系统免受伤害方面发挥作用(S)。我们的 初步结果显示，NT-4-/-小鼠的神经元丢失增加 缺血症。(I)检测脑缺血时NT-4和BDNF的表达。(Ii) 外源性NT-4和BDNF将被测试对我们的缺血的保护作用 模特。体外实验表明神经营养因子对中枢神经系统神经元有调节作用 生存和分化。我们的神经营养素基因敲除小鼠允许我们 确定各种神经营养因子在体内的作用。

DESCRIPTION (From the Applicant's Abstract): Our goals are to understand the role(s) of neurotrophins in (i) central nervous system (CNS) neuronal survival, (ii) neuronal differentiation, and (iii) protection against neuronal damage. Neurotrophins are a four-member family of structurally related proteins; Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT-3) and Neurotrophin-4 (NT-4). BDNF, NT-3 and NT-4 are potent survival factors for many types of CNS neurons. We derived mice carrying null mutations in individual as well as in two or three neurotrophin genes; e.g., NT-4-/- mice, [BDNF-/-, NT-4-/-] mice, [BDNF-/-, NT-3-/-, NT-4-/-] mice, etc. Using these mice, we can ask questions about neuronal survival and differentiation in vivo that could not previously be posed. We will investigate neurotrophin-dependence for CNS neuronal survival, neuronal differentiation in the hippocampus, and neuronal response to ischemia. Our first aim is to determine whether neurotrophins are essential for the survival of hippocampal neurons during embryonic and postnatal development. Previous studies and our preliminary results suggest that multiple/alternative neurotrophins can deliver the signal for CNS neurons to survive and CNS neurons may depend on neurotrophins to survive during postnatal development. To test these hypotheses, NT-4-/- and [BDNF-/-, NT-3-/-, NT-4-/-] mice will be examined histologically and immunohistologically to determine (i) whether there is excessive CNS neuronal death during (i) embryogenesis, and (ii) postnatal development. Our second aim is to define neurotrophin function in regulating neurite outgrowth in the hippocampus during postnatal development. (i) [BDNF-/-, NT-3-/-, NT-4-/-] mice will be used to determine whether neurotrophins control neurite outgrowth. (ii) mice carrying null mutations in individual neurotrophin genes will be used to determine the specificity of each neurotrophin in neurite outgrowth. (iii) physical exercise will be applied to NT-4-/- and wild type mice to determine whether NT-4 mediate activity-dependent neurite outgrowth. (iv) exogenous NT-4 will be used to rescue the potential abnormal neurite outgrowth. Our third aim is to determine whether neurotrophins play a role(s) in protecting the adult nervous system against injury. Our preliminary results showed that NT-4-/- mice have an increased neuronal loss in ischemia. (i) NT-4 and BDNF expression during ischemia will be examined. (ii) exogenous NT-4 and BDNF will be tested for protective effects in our ischemic model. In vitro experiments suggest that neurotrophins modulate CNS neuronal survival and differentiation. Our neurotrophin knockout mice allow us to determine the roles of the various neurotrophins in vivo.