NEUROTROPHINS IN NEURONAL SURVIVAL AND DIFFERENTIATION

描述（来自申请人的摘要）：我们的目标是了解 神经营养因子在（i）中枢神经系统（CNS）神经元存活中的作用， (ii)神经元分化，和（iii）保护神经元免受损伤。 神经营养素是一个四成员家族的结构相关的蛋白质;神经 生长因子（NGF），脑源性神经营养因子（BDNF），神经营养素-3 （NT-3）和神经营养因子-4（NT-4）。BDNF、NT-3和NT-4是有效的存活因子， 许多类型的CNS神经元的因子。我们用携带无效突变的小鼠 在个体中以及在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。 在这些小鼠中，我们可以问一些关于神经元存活和分化的问题， 这是以前无法做到的。我们将调查 中枢神经系统神经元存活的神经营养素依赖性， 海马体和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对海马神经元的存活至关重要。 神经元在胚胎和出生后的发展。以前的研究和我们的 初步结果表明，多种/替代性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取决于 神经营养因子在出生后的发育过程中存活。测试这些 假设，将检查NT-4-/-和[BDNF-/-，NT-3-/-，NT-4-/-]小鼠 组织学和免疫组织学以确定（i）是否存在 在（i）胚胎发生和（ii）出生后期间过度的CNS神经元死亡 发展我们的第二个目标是确定神经营养因子在调节 海马神经突生长在出生后的发展。（一） [BDNF-/-，NT-3-/-，NT-4-/-]小鼠将用于确定是否 神经营养因子控制神经突生长。(ii)携带无效突变的小鼠， 将使用单个神经营养因子基因来确定每种基因的特异性。 神经营养因子在神经突生长中的作用。(iii)体育锻炼将适用于 NT-4-/-和野生型小鼠，以确定NT-4是否介导活性依赖性 神经突生长(iv)外源性NT-4将被用于挽救潜在的 异常的神经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损伤方面发挥作用。我们 初步结果表明，NT-4-/-小鼠在神经元损伤中的神经元丢失增加， 缺血(i)将检测缺血期间NT-4和BDNF的表达。（二） 外源性NT-4和BDNF将在我们的缺血性脑损伤中检测保护作用。 模型体外实验表明，神经营养因子调节CNS神经元 生存和分化。我们的神经营养因子敲除小鼠让我们 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.