Neuropeptide modulation of C. elegans light avoidance circuitry

说明（申请人提供）：神经肽是由神经元和其他细胞类型分泌的信号分子，用于调节各种重要的生理过程和行为，包括昼夜节律、代谢、睡眠、进食、性活动等。这些过程的缺陷会导致严重的病理状况，包括嗜睡症、失眠、糖尿病、肥胖和抑郁症。了解神经肽能功能障碍引起的许多疾病的原因和改善治疗方法需要更完整地了解这些信号模块在体内的功能。 长期目标是了解神经肽如何在神经元回路中发挥作用以调节动物行为。我们研究了保守的神经肽色素分散因子（PDF）在遗传上易处理的模式生物秀丽隐杆线虫中的功能作用。虽然PDF及其同系物血管活性肠肽（VIP）分别介导昆虫和哺乳动物的昼夜节律钟，但PDF在蠕虫中的功能尚不清楚。最近在C.优雅有趣的是，PDF-2表达与LITE-1部分重叠，LITE-1是一种公认的GPCR，被鉴定为蠕虫中的光传感器，这表明蠕虫PDF可能在非昼夜节律但光调制的行为中发挥作用。 在初步研究中，我们发现PDF参与了蠕虫的光反应行为。缺乏PDF-2的突变蠕虫显示出与缺乏LITE-1的蠕虫相似的避光行为缺陷。我们将采用多种遗传操作结合强大的行为测定，以确定PDF-2介导蠕虫对光的运动反应。我们将通过以下具体目标来实现这些目标：（1）检验PDF-2是畏光行为的关键调节剂的假设（2）剖析PDF-2介导的UV回避的细胞基础（3）表征PDF-2在UV回避回路中的生理作用第一个目标将建立在初步观察的基础上，并确定pdf-2基因在对光的行为反应中的作用。第二个目标是鉴定参与避光行为的PDF-2分泌细胞和PDF受体（PDFR）表达细胞。第三个目标将使用遗传编码的钙传感器来确定PDF-2在光回避中对PDFR表达细胞的生理后果。 本研究将探讨PDF在光感电路中的保守作用，并提供体内神经元电路中神经肽信号传导的机制理解。鉴于PDF样肽的序列和功能结构，这些研究可能会揭示PDF信号如何调节哺乳动物的行为，并深入了解神经肽信号缺陷如何导致神经系统疾病。

DESCRIPTION (provided by applicant): Neuropeptides are signaling molecules secreted by neurons and other cell types to regulate a variety of critical physiological processes and behaviors, including circadian rhythms, metabolism, sleep, feeding, sexual activity, etc. Defects in these processes cause serious pathological conditions, including narcolepsy, insomnia, diabetes, obesity, and depression. Understanding the causes and improving treatment methods of the many diseases attributable to neuropeptidergic dysfunction requires more complete knowledge of how these signaling modules function in vivo. The long-term goal is to understand how neuropeptides function within neuronal circuits to regulate animal behavior. We investigated the functional role of a conserved neuropeptide Pigment Dispersing Factor (PDF) in the genetically tractable model organism Caenorhabditis elegans. While PDF and its homolog Vasoactive Intestinal Peptide (VIP) mediate the circadian clock in insects and mammals, respectively, PDF function in worms is unclear. Two PDF encoding genes, pdf-1 and pdf-2, were recently identified in C. elegans. Interestingly, PDF-2 expression partially overlaps with LITE-1, a putative GPCR identified as a light sensor in worms, suggesting that worm PDF could play a role in a non-circadian but light-modulated behavior. In preliminary studies, we have found that PDF is involved in light-response behavior of worms. Null mutant worms lacking PDF-2 show defects in light avoidance behaviors similar to those of worms lacking LITE-1. We will employ a variety of genetic manipulations in conjunction with robust behavioral assays to determine if PDF-2 mediates worm locomotor response to light. We will achieve those goals through the following specific aims: (1) Test hypothesis that PDF-2 is a key modulator of photophobic behavior (2) Dissect cellular basis for PDF-2 mediated UV avoidance (3) Characterize physiological effect of PDF-2 in UV avoidance circuit The first aim will build upon preliminary observations and determine the role of the pdf-2 gene in behavioral responses to light. The second aim will identify the PDF-2 secreting cells and the PDF Receptor (PDFR)- expressing cells involved in light avoidance behavior. The third aim will use a genetically encoded calcium sensor to determine the physiological consequences of PDF-2 on PDFR-expressing cells in light avoidance. This research will explore the conserved roles for PDF in light-sensing circuits and provide mechanistic understanding of neuropeptide signaling in neuronal circuits in vivo. Given the sequence and functional construction of PDF-like peptides, these studies are likely to reveal how PDF signaling regulates behaviors in mammals and yield insight into how defects in neuropeptide signaling can lead to neurological disorders.