Neurobiology of the Circadian Clock

项目总结 神经科学中的一个基本问题是，基因表达的变化如何转化为基因表达的变化 神经生理学，并最终转化为行为的变化。大脑的24小时计时机制，或者 生物钟，是一个唯一适合研究神经可塑性和基因与行为之间关系的系统 有问题。在生理和行为中产生和驱动昼夜节律的神经网络是 位于下丘脑的视交叉上核(SCN)内。SCN神经元显示内源性 昼夜节律的自发尖峰频率，即使作为单个细胞孤立，并在这些神经元内 形成自我调节转录/翻译反馈环(TTFL)的已定义的“时钟基因”网络 以产生近24小时的节律。 关于SCN的携带机制和起搏器，我们的知识中存在着关键的空白 它所诱导的可塑性。与节律生成不同，实时动态SCN分子和神经网络 卷吸过程中的反应以前是不可观察的，因此关于以下方面的知识有限 在这些水平上的夹带的实际动态拓扑。我们已经开发和建立了新的方法 能够使用一种方法直接观察SCN分子和神经网络夹带拓扑 它将ChrimsonR对时钟神经元电活动的光遗传操作与PER2：：Luc REAL- 时钟基因激活的时间报告(体外昼夜节律计时和激发)。Excite提供 对隔离的SCN的重复输入刺激的精确定时、持续时间和强度，并跟踪SCN时钟 体外3-5周高时空分辨率的分子节律。此中孤立的SCN 该系统惊人地概括了完整动物体内生物钟携带的典型特征，包括 具有周期后效、周期匹配和系统相角差的类光相位响应 偏离24小时的刺激，以及最低可耐受夜间的光周期的差异夹带。 我们将使用EXPICE来研究-(1)SCN包裹的分子和神经网络拓扑 可塑性；(2)夹带SCN神经网络的拓扑结构；(3)光周期的分子机制。 诱导SCN网络塑性。这些目标的成功实现将为SCN提供新的见解 夹带和可塑性-SCN分子和神经网络如何通过光输入来修改以导致 行为可塑性。定义SCN编码光历史和光周期的机制 为操纵SCN神经和转录网络改善昼夜节律紊乱开辟了道路。

PROJECT SUMMARY A fundamental question in neuroscience is how changes in gene expression are translated into changes in neuronal physiology, and ultimately into changes in behavior. The brain’s 24-hour timing mechanism, or biological clock, is a system that is uniquely suited to the study of neural plasticity and the genes-to-behavior problem. The neural network that generates and drives circadian rhythms in physiology and behavior is located within the suprachiasmatic nuclei (SCN) of the hypothalamus. SCN neurons exhibit endogenous circadian rhythms in spontaneous spike frequency, even as single cells in isolation, and within these neurons is a defined network of “clock genes” that forms autoregulatory transcription/translation feedback loops (TTFLs) to generate near 24-hour rhythms. There are key gaps in our knowledge regarding the mechanisms of SCN entrainment and the pacemaker plasticity it induces. Unlike rhythms generation, real-time dynamic SCN molecular and neural network responses during entrainment have been previously un-observable, and thus knowledge is limited regarding the actual dynamic topologies of entrainment at those levels. We have developed and instituted novel methods enabling direct observation of SCN molecular and neural network entrainment topologies using an approach that combines ChrimsonR optogenetic manipulation of clock neuron electrical activity with PER2::LUC real- time reporting of clock gene activation (EX vivo CIrcadian Timing and Entrainment, EXCITE). EXCITE provides precise timing, duration and intensity of recurring input stimulation to the isolated SCN, and tracks SCN clock molecular rhythms at high temporal and spatial resolution for 3-5 weeks ex vivo. The isolated SCN in this system strikingly recapitulates canonical features of circadian clock entrainment in intact animals, including light-like phase responses with period after-effects, period matching and systematic phase angle differences to stimuli that deviate from 24 hours, and differential entrainment to photoperiods with a minimum tolerable night. We will use EXCITE to examine - (1) Molecular and Neural Network Topologies for SCN Entrainment and Plasticity, (2) SCN Neural Network Topology of Entrainment, and (3) Molecular Mechanisms of Photoperiod- Induced SCN Network Plasticity. Successful completion of these aims will provide novel insight into SCN entrainment and plasticity - how the SCN molecular and neural networks are modified by light input to result in behavioral plasticity. Defining the mechanisms by which the SCN encodes light history and photoperiod will open the way for manipulation of SCN neural and transcriptional networks to ameliorate circadian disorders.