Cycling in a circadian circuit

 描述(由申请人提供)：我们的总体目标是确定行为的昼夜节律是如何产生的。在这个项目的前期工作中，我们识别和描述了果蝇内源性生物钟的分子机制。我们还启动了研究，以确定从时钟中携带一天中的时间提示并通过大脑传递它们的机制。具体地说，我们确定了节律性休息所需的输出神经元：活动并在解剖学上连接到中枢时钟神经元。这些输出神经元包括背侧神经元1(DN1)组，其中包含一个时钟，以及大脑间部(PI)的两个非时钟簇，PI是相当于哺乳动物下丘脑的一个神经分泌细胞区域。调节静息昼夜节律的两个PI簇：活动分别分泌神经肽DH44和SIF酰胺。我们发现DH44是行为节律所必需的，但SIF酰胺的作用尚未确定。有趣的是，DN1还与已知的昼夜节律输出分子的功能或表达有关，腹部狭窄和未配对。此外，我们的初步数据表明，DN1中另一种输出分子--神经纤维瘤病1(NF1)是休息所必需的：活动节律。我们还发现，在DN1和DH44细胞中，神经活动以24小时节律循环。因此，我们已经开始在我们确定的细胞底物中放置分子成分，并开发检测方法来监测节律信号通过网络的传输。我们假设，在中央时钟单元中产生的一天中的时间提示通过DN1传输以驱动PI中的节律活动， 然后控制休息：通过释放特定的神经肽来控制活动节奏。我们建议：(1)解决DN1节律活动的重要性，并确定这种节律需要哪些时钟单元和输出分子。(2)确定时钟细胞中驱动DH44细胞节律性活动的上游成分，并确定DH44是否有节律性作用。(3)阐述SIF酰胺在REST中的作用：活动节律，并确定与REST相关的其他PI分子：活动节律。总而言之，这些研究有望提供对产生行为节奏的分子网络和细胞电路的全面了解。鉴于已知从苍蝇到人类的时钟机制和分子的保守性，这些研究可能与我们对人类节律的理解有关，人类节律对正常行为和生理至关重要。这些研究还将提供对神经回路的维护和功能的总体洞察，这些回路在几种神经疾病中受到损害。

 DESCRIPTION (provided by applicant): Our overall goal is to determine how circadian rhythms of behavior are generated. In previous work on this project we identified and characterized molecular mechanisms of the endogenous circadian clock in Drosophila. We also initiated studies to identify the mechanisms that carry time of day cues from the clock and transmit them through the brain. Specifically, we identified output neurons that are required for rhythmic rest:activity and connect anatomically to central clock neurons. These output neurons include the Dorsal Neuron 1 (DN1) group, which contains a clock, and two non-clock clusters in the pars intercerebralis (PI), a region of neurosecretory cells equivalent to the mammalian hypothalamus. The two PI clusters that regulate circadian rhythms of rest:activity secretes the neuropeptides DH44 and SIFamide respectively. We found that DH44 is required for behavioral rhythms, but a role for SIFamide has not been determined yet. Interestingly, the DN1s have also been associated with the function or expression of known circadian output molecules, narrow abdomen and unpaired. In addition, our preliminary data indicate that another output molecule, Neurofibromatosis 1 (NF1), is required in DN1s for rest:activity rhythms. We also find that neural activity cycles with a 24 hour rhythm in DN1 and DH44 cells. Thus, we have started to place molecular components in the cellular substrates we identified, and develop assays to monitor the transmission of rhythmic signals through the network. We hypothesize that time-of-day cues generated in central clock cells are transmitted through DN1s to drive rhythmic activity in the PI, which then controls rest:activity rhythms through release of specific neuropeptides. We propose to: (1) Address the significance of rhythmic activity in the DN1s and determine which clock cells and output molecules are required for this rhythm. (2) Identify the upstream components in clock cells that drive rhythmic activity in the DH44 cells, and determine if DH44 acts rhythmically. (3) Address a role for SIFamide in rest:activity rhythms and identify other PI molecules relevant for rest:activity rhythms. Together these studies are expected to provide a comprehensive understanding of the molecular network and cellular circuit that generates a behavioral rhythm. Given known conservation of clock mechanisms and molecules from flies to humans, these studies will likely be relevant for our understanding of human rhythms, which are critical for normal behavior and physiology. These studies will also provide general insight into the maintenance and function of neural circuits, which are impaired in several neurological disorders.