The Nigral Molecular Clock and Vulnerability to Neurodegeneration

黑质的多巴胺能神经元特别容易随着年龄的增长而功能障碍和丧失 和疾病导致此漏洞的一个潜在因素是需要维护内部 起搏活动。然而，很少有人知道这种起搏活动是如何调节的生理， 和病理状态。了解黑质神经元如何保持其放电率并适应细胞 应激源有可能揭示预防细胞损伤和死亡的新途径。在这 应用，我们建议测试新的假设，即分子钟是一个关键的调节器， 多巴胺能神经元正常功能所需的起搏活性和其他过程， 这种生物钟的破坏导致帕金森病（PD）模型中的细胞功能障碍和死亡。在 为了支持这些假设，我们发现多巴胺能神经元放电率随一天中的时间而变化， 这种变异在中脑特异性缺失特异性转录调节因子的小鼠中被消除， 昼夜节律功能，Bmal 1.此外，我们发现基因表达的昼夜差异 参与黑质的起搏活动，表明黑质功能的重要途径 可能在转录水平上受到分子钟的调控。有趣的是，我们发现了阿尔法 PD显示的突触核蛋白小鼠模型破坏了起搏活动的昼夜差异，导致 假设昼夜节律调节过程的损害可能导致神经元功能障碍， 死于疾病。在目标1中，设计实验以确定分子 生物钟在转录、电生理和行为水平上调节多巴胺能神经元功能， 使用最近开发的工具来评估细胞特异性方式的分子钟节律性和转录。 在目标2中，实验将利用各种方法以一天中的时间依赖性方式重置分子钟， 小鼠与α-突触核蛋白诱导的病理，以确定昼夜节律失调的作用， α-突触核蛋白介导的神经毒性和行为损害。总之，这些实验具有 有可能揭示黑质功能和脆弱性的一种新的调节机制， 深入了解疾病进展和发病机制。

Dopaminergic neurons of the substantia nigra are particularly susceptible to dysfunction and loss with aging and disease. A potential contributor to this vulnerability is the requirement for the maintenance of intrinsic pacemaking activity. However, little is known about how this pacemaking activity is regulated in physiological and pathological states. Understanding how nigral neurons maintain their firing rate and adapt to cellular stressors has the potential to reveal novel pathways for prevention of cellular damage and death. In this application, we are proposing to test the novel hypotheses that the molecular clock is a key regulator of pacemaking activity and other processes required for normal function of dopaminergic neurons and that disruption of this clock contributes to cell dysfunction and death in models of Parkinson Disease (PD). In support of these hypotheses, we have found that dopaminergic neuron firing rate varies with time of day and that this variation is abolished in mice with midbrain-specific deletion of the obligate transcriptional regulator of circadian function, Bmal1. Furthermore, we have found day/night differences in the expression of genes involved in pacemaking activity in the substantia nigra, suggesting that pathways important for nigral function may be regulated at the transcriptional level by the molecular clock. Interestingly, we have discovered alpha synuclein mouse models of PD display disrupted day/night differences in pacemaking activity, leading to the hypothesis that the impairment of circadian-regulated processes could contribute to neuronal dysfunction and death in disease. In Aim 1, experiments are designed to determine the mechanisms by which the molecular clock regulates dopaminergic neuron function at the transcriptional, electrophysiological, and behavioral levels, using recently developed tools to evaluate molecular clock rhythmicity and transcription in a cell-specific way. In Aim 2, experiments will utilize approaches to reset the molecular clock in a time-of-day-dependent manner in mice with α-synuclein- induced pathology to determine the role for circadian dysregulation in the progression of α-synuclein-mediated neurotoxicity and behavioral impairment. Altogether, these experiments have the potential to reveal a novel regulatory mechanism of nigral function and vulnerability and could give critical insight into disease progression and pathogenesis.