Cdk5 and adult hippocampal neurogenesis

描述(由申请人提供)：识别影响成人神经发生的新的细胞内和微环境信号是一个主要的研究重点。在这里，我们提供了细胞周期蛋白依赖性激酶5(CDK5)在成人神经发生中的新作用的证据。这是惊人的，因为与其他周期蛋白不同，CDK5及其辅助因子P35和P39在有丝分裂后神经元中丰富。根据我们的初步数据，我们假设成年海马区的CDK5活性调节成年神经前体的增殖和成熟。为了验证这一假设，我们提出了在两年内实现三个目标。目的1：研究颗粒下带(SGZ)前体细胞成熟过程中CDK5的蛋白表达及其所需的辅因子。我们已经验证了一种新的CDK5抗体用于蛋白质分析，包括免疫组织化学。在我们的初步数据的指导下，我们将确定CDK5蛋白及其所需的辅助因子p35和p39在成熟的SGZ细胞中何时表达。目的2：研究CDK5前体细胞及其后代对神经发生的影响。我们的Nestin-CreERT2小鼠的新的试点数据表明，SGZ前体及其后代的CDK5的可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、前体特异性的CDK5消融对这些细胞在成熟为齿状回神经元时a)数量、b)表型和c)形态的影响。我们推测，前体细胞及其后代中CDK5的缺失将对其分化产生负面影响，但对增殖没有影响。目的：探讨去势齿状回CDK5对SGZ神经发生的影响。我们的新数据显示，成熟齿状回神经元中CDK5的缺失对SGZ前体和未成熟神经元具有深远的负面影响。我们将测试这一假设，即海马区成熟神经元中的CDK5对于维持SGZ神经源性生态位至关重要。我们将使用病毒诱导的CDK5消融来量化从成熟的齿状回神经元中消融CDK5对SGZ前体和未成熟神经元a)数量和b)形态的影响。这些研究将从根本上深入了解CDK5对成人神经干细胞发育的潜在细胞自主作用(目标1，2)，以及成熟神经元中CDK5通过改变神经发生微环境对成年海马神经发生的非自主作用(目标3)。这些研究将有助于阐明CDK5的生理和病理功能，并有可能揭示CDK5在成年海马区结构和功能调节中的新作用。与长期以来认为大脑不能再生的看法相反，现在人们知道成年人的大脑在整个生命过程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(如学习和记忆)的关键，并可能允许我们利用这些新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因子--细胞周期蛋白依赖性激酶5--对成人大脑中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.