Circadian Structural Plasticity in Central Pacemakers

摘要 昼夜节律依赖于分子转录/翻译负反馈环（TTL）， 时钟神经元，以及这些神经元的网络特性。在可以招募的财产中， 由昼夜节律钟是在前/后突触伴侣的身份和/或强度的变化， 生物钟神经元之间的连接，一个属性统称为昼夜结构可塑性。中央 我们父母奖假设是， 哺乳动物位于视交叉上核（SCN）内，是时间编码机制的一部分。一个 阿尔茨海默病（AD）的早期症状是睡眠和昼夜节律的破坏。为此 补充，我们测试的假设，这些症状可能会导致部分从昼夜节律的破坏 SCN内的结构可塑性。 特定目标2D将通过PER 2-LUC评估AD对时钟基因PER 2表达的影响 报告来自AD或WT小鼠的离体SCN切片。本实验将确定AD对 时钟基因表达节律的幅度和SCN内细胞之间的同步性 神经网络 具体目标2 E将检查AD对SCN VIPergic神经元中的昼夜节律结构重塑的影响， 其是计时机制的重要组成部分，通过病毒介导的VIP标记， 神经元与突触素-mCherry，然后离体荧光报告的昼夜节律， 突触前纤维的收缩/伸展。 具体目标2F和2G将使用连续块面扫描电子显微镜检查昼夜节律可塑性 在超微结构水平上，通过检查突触结构变化（2F）和星形胶质细胞过程的变化 包绕神经元（2G）。 我们的实验验证了这一假设的预测，即睡眠和昼夜节律的中断， AD早期阶段的特征可能来自疾病对关键昼夜节律可塑性的影响 主生物钟的变化。阐明这些早期症状背后的潜在机制 可能为治疗AD患者的睡眠和昼夜节律紊乱提供新的机会。

SUMARY Circadian rhythms depend on the molecular transcription/translation negative feedback loop (TTL) operating in clock neurons, and on the network properties of these neurons. Among the properties that could be recruited by the circadian clock are changes in the identity of pre/post synaptic partners and/or strength of the connectivity between clock neurons, a property collectively termed as circadian structural plasticity. The central hypothesis for our parent Award is that circadian structural plasticity within the central circadian clock of mammals, located within the suprachiasmatic nucleus (SCN), is part of the time-encoding mechanism. An early-stage symptom of Alzheimer’s disease (AD) is the disruption of sleep and circadian rhythms. For this Supplement, we test the hypothesis that these symptoms may result in part from the disruption of circadian structural plasticity within the SCN. Specific aim 2D will assess the effect of AD on the expression of the clock gene PER2 through PER2-LUC reporting in ex vivo SCN slices from either AD or WT mice. This experiment will determine the effect of AD on the amplitude of the rhythm of clock gene expression and on the synchrony between cells within the SCN neuronal network. Specific aim 2E will examine the effect of AD on circadian structural remodeling in SCN VIPergic neurons, which are an essential component of the timekeeping mechanism, through virally mediated labeling of VIP neurons with synaptophysin-mCherry followed by ex vivo fluorescent reporting of circadian rhythms of retraction/extension of presynaptic fibers. Specific aims 2F and 2G will use serial blockface scanning electron microscopy to examine circadian plasticity at the ultrastructural level by examining synaptic structural changes (2F) and changes in astrocytic processes that ensheath neurons (2G). Our experiments test predictions of the hypothesis that disruptions of sleep and circadian rhythms that are characteristic of early stages of AD may emerge from the effect of the disease on key circadian plasticity changes within the master circadian clock. Elucidating the potential mechanisms behind these early symptoms of AD could open new opportunities to treat sleep and circadian disruptions in AD patients.