Cdk5 and adult hippocampal neurogenesis

描述（由申请人提供）：鉴定影响成人神经发生的新细胞内和微环境信号是一个主要的研究重点。在这里，我们提供了一个新的作用，细胞周期蛋白依赖性激酶5（Cdk 5）在成人神经发生的证据。这是惊人的，因为与其他细胞周期蛋白不同，Cdk 5及其辅因子p35和p39在有丝分裂后的神经元中富集。根据我们的初步数据，我们假设，Cdk 5活性在成年海马调节成人神经前体细胞的增殖和成熟。为了验证这一假设，我们提出了两年内要实现的三个目标。目的1：确定Cdk 5和所需的辅助因子在颗粒下区（SGZ）前体成熟时的蛋白表达。我们已经验证了使用一种新的Cdk 5抗体进行蛋白质分析，包括免疫组织化学。我们的初步数据的指导下，我们将确定Cdk 5蛋白和它所需的辅因子，p35和p39，表达在成熟的SGZ细胞。目的2：确定前体及其后代的Cdk 5消融对神经发生的影响。我们的nestin-CreERT 2小鼠的新试验数据表明，SGZ前体及其后代中Cdk 5的诱导性丢失对成人神经发生的离散阶段是有害的。我们将确定转基因介导的Cdk 5特异性消融如何影响这些细胞成熟为齿状回神经元时的a）数量，B）表型和c）形态。我们推测，Cdk 5从前体和它们的后代的损失将产生负面影响，他们的分化，但对增殖没有影响。目的3：探讨去除齿状回神经元Cdk 5对SGZ神经发生的影响。我们显示了新的数据，在成熟的齿状回神经元Cdk 5的损失有深刻的负面影响SGZ前体和未成熟的神经元。我们将测试的假设，在海马中的成熟神经元中的Cdk 5是至关重要的维持SGZ神经原性生态位。我们将使用病毒诱导的Cdk 5消融来量化Cdk 5从成熟齿状回神经元消融对SGZ前体和未成熟神经元的a）数量和B）形态的影响。这些研究将提供基本的洞察到潜在的细胞自主的影响Cdk 5对成人神经干细胞的发展（目标1，2），和细胞非自主的影响Cdk 5在成熟的神经元对成人海马神经发生通过改变的神经原性微环境（目标3）。这些研究将阐明Cdk 5的生理和病理功能，并可能表明Cdk 5在调节成年海马结构和功能中的高度新颖的作用。与长期以来认为大脑不能再生的观点相反，现在已知成年人的大脑在一生中都会产生新的神经元。了解影响这些成人产生的神经元的线索是至关重要的，因为它可能是理解大脑功能的关键，如学习和记忆，并可能使我们能够利用这些新的神经元来修复受伤或成瘾的大脑。在这里，我们建议探索一种新的调节剂，细胞周期蛋白依赖性激酶5，在成人大脑中的新神经元的诞生的影响。

DESCRIPTION (provided by applicant): Identification of novel intracellular and microenvironmental signals that influence adult neurogenesis is a major research priority. Here we provide evidence for a novel role of cyclin dependent kinase 5 (Cdk5) in adult neurogenesis. This is striking since, unlike other cyclins, Cdk5 and its cofactors p35 and p39 are enriched in post-mitotic neurons. Based on our preliminary data, we hypothesize that Cdk5 activity in the adult hippocampus regulates proliferation and maturation of adult neural precursors. To test this hypothesis, we propose three aims to be accomplished in two years. Aim 1: Define protein expression of Cdk5 and required cofactors in subgranular zone (SGZ) precursors as they mature. We have validated the use of a novel Cdk5 antibody for protein analysis, including immunohistochemistry. Guided by our preliminary data, we will define when Cdk5 protein and its required cofactors, p35 and p39, are expressed in maturing SGZ cells. Aim 2: Determine the impact of Cdk5 ablation from precursors and their progeny on neurogenesis. New pilot data with our nestin-CreERT2 mouse suggest that inducible loss of Cdk5 from SGZ precursors and their progeny is detrimental to discrete stages of adult neurogenesis. We will determine how transgenic-mediated, precursor-specific ablation of Cdk5 impacts the a) number, b) phenotype, and c) morphology of these cells as they mature into dentate gyrus neurons. We hypothesize that loss of Cdk5 from precursors and their progeny will negatively impact their differentiation but have no effect on proliferation. Aim 3: Explore the impact of Cdk5 ablation from dentate gyrus neurons on SGZ neurogenesis. We show new data that loss of Cdk5 in mature dentate gyrus neurons has profound negative effects on SGZ precursors and immature neurons. We will test the hypothesis that Cdk5 in mature neurons in the hippocampus is critical for maintaining the SGZ neurogenic niche. We will use viral-induced ablation of Cdk5 to quantify the impact of Cdk5 ablation from mature dentate gyrus neurons on the a) number and b) morphology of SGZ precursors and immature neurons. These studies will provide fundamental insight into the potential cell autonomous effects of Cdk5 on adult neural stem cell development (Aims 1, 2), and the cell non-autonomous effects of Cdk5 in mature neurons on adult hippocampal neurogenesis via alteration of the neurogenic microenvironment (Aim 3). These studies will shed much-needed light on the physiological and pathological functions of Cdk5, and potentially indicate a highly novel role for Cdk5 in regulation of adult hippocampal structure and function. Contrary to a long-held belief that the brain cannot regenerate, the adult brain is now known to give rise to new neurons throughout life. Understanding the cues that influence these adult-generated neurons is critical, as it may hold the key to understanding brain functions, like learning and memory, and may allow us to harness these new neurons for repair of the injured or addicted brain. Here we propose to explore the impact of a novel regulator, cyclin dependent kinase 5, on the birth of new neurons in the adult brain.