Dissecting molecular elements of threat behavior

摘要 动物有一种内在的能力来应对环境中的威胁，但潜在的机制是 人们对此知之甚少。要完全理解这些复杂的应激诱导行为，需要 所有参与神经元的特征、它们的连接以及它们与其他组织的相互作用 (包括肠道、循环系统、肌肉等的交感神经连接)。然而，这一水平的 在复杂的脊椎动物有机体中很难实现分析。一种理性的方法是分析这些 在更简单的无脊椎动物模型中的过程。这项提议旨在了解 在无脊椎动物模型系统中对威胁响应(包括行为和生理)进行编码。线虫， 秀丽隐杆线虫提供了一个独特的机会来分析基因、细胞和调节 复杂的行为。Chalasani实验室开发了一种新的威胁行为模型，包括 秀丽线虫与另一种捕食性线虫--太平洋Pristionchus的相互作用。一个挨饿的人 太平洋疟原虫将在30分钟内攻击并吞噬一种线虫。而秀丽隐杆线虫则试图避开太平洋隐杆线虫 以及它的分泌物。Chalasani实验室描述了一种新的、冗余的神经电路，它可以检测P。 和平食肉动物，并驱动快速回避行为，这导致运动逆转，随后是 广角转弯。除了这种快速的避免，实验室还发现线虫暴露在 捕食者的分泌物长时间(30分钟)表现出运动(冻结)减慢，卵减少- 产卵行为，以及多个组织中线粒体应激的诱导。这些响应最多可持续一次 在捕食者线索被移除后一小时，这让人想起在其他捕食者身上观察到的防御行为- 猎物模型。一项初步的遗传筛查确定了SEB-3(促肾上腺皮质激素释放因子的线虫同源物 受体1(CRFR1)是这些长期行为和生理变化所必需的。这是第一次 CRF信号影响行为和生理以响应外部威胁的证据 无脊椎动物。此外，使用细胞培养鉴定系统鉴定了一个同源配体NLP-49，该配体 激活SEB-3受体。在这里，将使用遗传方法来表征CRF所起的作用 在协调行为和生理变化以应对外部威胁方面的信号。目标1将 探讨CRF信号成分(SEB-3受体、NLP-49配体等)的作用 配体)在驱动捕食者介导的行为变化中的作用。潜伏的神经回路将被映射。在……里面 目的2，CRF信号在神经元中传递到其他组织的机制，从而导致诱导 线粒体的压力，将会被确定。在目标3中，将进行重点遗传筛查，以识别 CRF信号通路的其他组件，负责应激诱导的行为和 生理变化。这些研究将揭示神经回路和CRF信号通路是如何处理的 关于环境威胁的信息，以产生适应性压力反应。

Summary Animals have an intrinsic ability to respond to threats in their environments, but the underlying mechanisms are poorly understood. A complete understanding of these complex stress-induced behaviors requires the characterization of all participating neurons, their connections, and their interactions with other tissues (including sympathetic connections in the gut, the circulation system, muscles, etc.). However, this level of analysis is difficult to achieve in complex vertebrate organisms. One rational approach is to analyze these processes in simpler invertebrate models. This proposal aims to understand the neural mechanisms that encode threat responses (both behavioral and physiological) in an invertebrate model system. The nematode, Caenorhabditis elegans, provides a unique opportunity to analyze the genes, cells, and circuits that regulate complex behaviors. The Chalasani lab has developed a novel model of threat behaviors that involves interactions between C. elegans and a second predatory nematode species, Pristionchus pacificus. A starving P. pacificus will attack and devour a C. elegans in 30 minutes. C. elegans in turn, seeks to avoid P. pacificus and its secretions. The Chalasani lab has characterized a novel, redundant neural circuit that detects the P. pacificus predator and drives rapid avoidance behavior, which entails a reversal in locomotion followed by a wide-angle turn. In addition to this rapid avoidance, the lab also discovered that C. elegans exposed to predator secretions for a long period of time (30 minutes) exhibit slowed locomotion (freezing), reduced egg- laying behavior, and the induction of mitochondrial stress in multiple tissues. These responses last up to one hour after the predator cue is removed, and are reminiscent of defensive behaviors observed in other predator- prey models. A pilot genetic screen identified seb-3 (the C. elegans homolog of corticotrophin releasing factor receptor 1 (crfr1)) as required for these long-term behavioral and physiological changes. This is the first evidence that CRF signaling affects behavior and physiology in response to an external threat in an invertebrate. Additionally, a cell culture assay system was used to identify a cognate ligand, NLP-49, that activates the SEB-3 receptor. Here, genetic methods will be used to characterize the role played by CRF signaling in coordinating behavioral and physiological changes in response to an external threat. Aim 1 will probe the role of CRF signaling components (the SEB-3 receptor, the NLP-49 ligand, and other potential ligands) in driving predator-mediated behavioral changes. The underlying neural circuits will be mapped. In Aim 2, the mechanism by which CRF signaling in neurons is relayed to other tissues, resulting in the induction of mitochondrial stress, will be determined. In Aim 3, a focused genetic screen will be performed to identify additional components of the CRF signaling pathway that are responsible for stress-induced behavioral and physiological changes. These studies will reveal how neural circuits and the CRF signaling pathway process information about environmental threats to generate adaptive stress responses.