Integration of circadian and homeostatic signals in a peptidergic circuit in Drosophila

迅速积累的证据表明，睡眠、活动和进食的昼夜节律模式的扰乱会导致有害的健康后果。虽然生物钟机制已经被很好地研究了，但人们对一天中的时间提示和饥饿等动态平衡驱动之间的关系知之甚少。昼夜节律信息与营养线索的整合发生在大脑核心时钟细胞下游的多个行为回路的交叉处。这项建议利用果蝇的黑腹果蝇遗传模型来研究昼夜节律信号与摄食回路相结合的机制，以协调运动节奏和摄食行为。果蝇大脑间部(PI)是哺乳动物下丘脑的类似物，是一种同时接收时间和营养状态信息的肽能中枢。根据已发表的和初步的发现，我认为PI通过神经肽信号接受核心时钟神经元的兴奋性输入，以及来自产生胆碱能Hugin的味觉中间神经元的抑制性输入。我假设每个多肽能PI种群(DH44，胰岛素样肽产生，SIF酰胺和桃铁)接收一组唯一的输入，然后这些输入必须整合到PI中以协调行为输出，并且这种整合是通过PI内旁分泌神经肽信号发生的。因此，PI种群可能同时调节休息：活动节律和摄食行为，这取决于营养状态，以允许对急性环境提示的反应。在这个项目的指导阶段，我将描述从中央大脑时钟(目标1)和Hugin味觉中间神经元(目标2)到PI的连接，并研究这些电路中的每一个是如何调节摄食和休息：活动行为(目标1和2)的。在这个项目的独立阶段，我将使用在指导阶段获得的技能来研究饥饿如何超过PI神经元生理和行为的时钟控制(目标3)，以及PI内部连接在协调运动节律和摄食行为中的作用(目标4)。为了实现这些目标，我将结合使用包括RNAi和CRISPR在内的遗传工具，包括电生理学和钙成像在内的生理分析，以及运动节律和进食的行为分析。该项目的成功完成将在神经回路和行为水平上提供重要的进步。首先，它将开始阐明交叉回路是如何使用神经调节肽进行通信的。神经调节信号在哺乳动物系统中的研究已被证明是困难的，这项工作可以提供适用于哺乳动物神经肽能区域的研究，特别是在下丘脑。其次，它将促进对昼夜节律和摄食在电路和行为层面上的复杂相互作用的理解。不仅了解电路如何塑造行为，而且了解改变的摄食模式等行为如何反馈到大脑，对于开发改善人类健康的干预措施非常重要。

There is rapidly accumulating evidence that disruptions of circadian patterns of sleep, activity and feeding lead to deleterious health consequences. While circadian clock mechanisms are well-studied, the relationship between time-of-day cues and homeostatic drives such as hunger are poorly understood. The integration of circadian information with nutritional cues occurs downstream of the core clock cells in the brain at the intersection of multiple behavioral circuits. This proposal exploits the Drosophila melanogaster genetic model to examine the mechanism by which circadian signals integrate with feeding circuitry to coordinate locomotor rhythms with feeding behavior. The Drosophila pars intercerebralis (PI), an analog of the mammalian hypothalamus, is a peptidergic center that receives both time-of-day and nutritional state information. Based on published and preliminary findings, I propose that the PI receives excitatory input from core clock neurons via neuropeptide signals, as well as inhibitory inputs from cholinergic Hugin-producing gustatory interneurons. I hypothesize that each of the peptidergic PI populations (DH44+, insulin-like peptide producing, SIFamide+ and Taotie) receives a unique set of inputs, which must then be integrated within the PI to coordinate behavioral outputs, and that this integration occurs via intra-PI paracrine neuropeptide signaling. Thus, PI populations likely modulate both rest:activity rhythms and feeding behavior depending on nutritional state to allow responses to acute environmental cues. In the mentored phase of this project I will characterize the connectivity from the central brain clock (Aim 1) and the hugin+ gustatory interneurons (Aim 2) to the PI and examine how each of these circuits modulates feeding and rest:activity behavior (Aims 1 and 2). In the independent phase of this project I will use skills gained in the mentored phase to investigate how starvation overrides clock control of PI neuron physiology and behavior (Aim 3) and the role of intra-PI connectivity in coordinating locomotor rhythms and feeding behavior (Aim 4). To pursue these aims I will use a combination of genetic tools including RNAi and CRISPR, physiological assays including electrophysiology and calcium imaging, and behavioral assays for locomotor rhythms and feeding. Successful completion of this project will offer important advances at both the level of neural circuitry and behavior. First, it will begin to elucidate how intersecting circuits communicate using neuromodulatory peptides. Neuromodulatory signaling has proven difficult to study in mammalian systems, and this work can offer insights that will be applicable to studies of neuropeptidergic regions in mammals, particularly in the hypothalamus. Second, it will advance understanding of the complex interplay of circadian rhythms and feeding both at the circuit and behavioral levels. Understanding not only how circuitry shapes behavior, but how behavior such as altered feeding patterns feeds back to the brain is important for developing interventions to improve human health.