CAREER: Circadian Control and Integration of Feeding and Metabolic Rhythms in Drosophila

生物体在行为和生理过程中表现出~24小时(昼夜节律)的节律，这取决于大脑中专用时钟细胞的存在，这些细胞通过维持每日基因表达节律的分子时钟来计时。此外，分子钟存在于大多数外周组织中，在那里它们具有组织特有的功能。这些共同构成了一个扩展的时钟网络，它将行为和生理过程与外部环境同步，并将它们相互组织起来。例如，昼夜节律系统产生摄食行为的节律，使摄食在一天中的最佳时间发生，并同时上调代谢途径，以预期食物摄入量增加。适当的昼夜节律组织对于生物体的健康至关重要，但昼夜节律产生并跨多个含有时钟的组织整合的细胞和分子机制尚不清楚。为此，本项目概述的实验将使用果蝇这种强大的模式生物--黑腹果蝇--来识别神经元通路，时钟细胞通过这些通路建立摄食行为的昼夜节律，并进一步描绘摄食节律与外周代谢节律是如何协调的。这些实验将与实验室的博士后和本科生研究人员合作进行，他们还将担任一个暑期高中实习项目的导师，该项目将扩大参与到传统上在科学中代表较少的群体。要了解昼夜节律系统调节行为输出并将其与生理节奏协调的方式，除了分析休息和活动之外，还需要分析新的昼夜节律终点，这一直是迄今为止大多数昼夜节律研究的重点。目标1将使用新开发的摄食监测器来确定中央时钟调节摄食节奏的细胞逻辑。为了确定不同的中枢时钟机制是否控制摄食和运动活动节律，将在改变离散时钟细胞群中的分子时钟功能或神经元活动的遗传操作之后测量摄食节律的周期和强度。目标2将研究产生摄食节律的下游输出途径。为了制定行为节律，昼夜节律信息必须通过输出通路传输到调节行为的大脑区域。卡瓦诺实验室最近发现，表达Sifa肽的神经元是控制摄食的昼夜输出通路的一个组成部分。为了继续追踪昼夜节律的摄食回路，将进行基于RNA干扰的行为筛选，以识别正常摄食节律必须存在SifA受体的细胞。最后，目标3将调查摄食和代谢节律是如何通过时钟网络协调的。脂肪体是提供新陈代谢功能的外周时钟组织。将使用转录和代谢组学相结合的方法来确定大脑或脂肪体中Sifa信号的丢失或选择性分子时钟消除如何影响脂肪体基因振荡和整个动物代谢物的丰度。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Organisms exhibit ~24-hour (circadian) rhythms in behavioral and physiological processes that depend on the presence of dedicated clock cells in the brain that keep time through a molecular clock that maintains daily rhythms of gene expression. In addition, molecular clocks are present in most peripheral tissues, where they serve tissue-specific functions. Together, these make up an extended clock network that synchronizes behavioral and physiological processes with the external environment and organizes them with respect to one another. For example, the circadian system generates rhythms in feeding behaviors such that feeding occurs at optimal times of day, and concurrently upregulates metabolic pathways in anticipation of increased food intake. Proper circadian organization is essential for organismal fitness, but the cellular and molecular mechanisms through which circadian rhythms are generated and integrated across multiple clock-containing tissues are unknown. To that end, experiments outlined in this project will use the powerful model organism of the fruit fly, Drosophila melanogaster, to identify neuronal pathways through which clock cells establish circadian rhythms of feeding behavior and to further delineate how feeding rhythms are coordinated with peripheral metabolic rhythms. These experiments will be conducted in collaboration with postdoctoral and undergraduate researchers in the lab who will also serve as mentors for a summer high school internship program that will expand participation to groups traditionally underrepresented in the sciences.An understanding of the manner through which the circadian system modulates behavioral outputs and coordinates these with physiological rhythms requires analysis of novel circadian endpoints in addition to rest and activity, which has thus far been the focus of most circadian research. Objective 1 will use a newly-developed feeding monitor to determine the cellular logic through which the central clock regulates feeding rhythms. To determine whether distinct central clock mechanisms control feeding and locomotor activity rhythms, period and strength of feeding rhythms will be measured following genetic manipulations that alter molecular clock function or neuronal activity in discrete clock cell populations. Objective 2 will investigate downstream output pathways through which feeding rhythms are produced. To enact behavioral rhythms, circadian information must be transmitted across output pathways to brain areas that regulate behaviors. The Cavanaugh laboratory recently implicated SIFa peptide-expressing neurons as a component of the circadian output pathway controlling feeding. To continue to trace the circadian feeding circuit, an RNA interference-based behavioral screen will be conducted to identify cells in which the SIFa receptor must be present for normal feeding rhythms. Finally, Objective 3 will investigate how feeding and metabolic rhythms are coordinated by the clock network. The fat body is a peripheral clock tissue that serves metabolic functions. A combined transcriptomic and metabolomic approach will be employed to determine how loss of SIFa signaling or selective molecular clock abrogation in the brain or fat body affects fat body gene oscillations and whole-animal metabolite abundance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.