Control of developmental timing and body size in Drosophila

描述(由申请人提供)：所有多细胞生物体的正确发育不仅需要对细胞相互作用的正确空间控制，而且还需要在发育过程中正确地选择特定基因表达程序的时间。改变许多发育过程的时间会对动物最终的身体大小、繁殖能力和衰老产生重大影响。在昆虫中，发育转变的时间，即蜕皮和变态，是由20-羟基蜕皮酮(20E)介导的，20-羟基蜕皮酮(20E)是一种循环中的小分子亲脂类固醇激素，与核受体超家族的转录因子结合并激活。虽然控制对20E的反应的遗传层次已经得到了相当大的关注，但目前对控制激素产生和释放的机制知之甚少。在这项提案中，我们将确定促胸腺原激素，一种从支配前胸腺(PGs)的神经元释放的多肽，如何控制激素的产生和释放。在目标1中，我们将确定PG细胞何时接收PTTH信号，以及是什么调节它们这样做的能力。在目标2中，我们将描述通过受体酪氨酸激酶躯干调节PTTH信号的其他上游和下游输入。特别令人感兴趣的是确定PTTH信号是否需要PTTH配体处理，以及PKC、PLC和IP3受体是否对果蝇PTTH信号起作用，以及它们的活动如何与躯干激活相耦合。在目标3中，我们将确定蜕皮激素生物合成酶PHM、DIB和Scookier调节区的关键转录调控元件，以了解PTTH信号如何调控蜕皮激素的产生。在AIM 4中，我们将使用遗传学研究和成像方法来检验这一假说，与目前的看法相反，变态蜕皮过程中前胸腺释放的蜕皮激素是由PTTH刺激的囊泡介导的过程。对人类健康的影响：在人类中，随着青少年获得性成熟，涉及类固醇激素的主要发育转变发生。这种转变也受神经肽信号以及营养和代谢信号的控制，尽管目前还不清楚这些信号是如何整合在一起的，以适当地确定转变的时间。这里描述的研究将有助于识别控制发育过渡的基本分子程序，从而为理解这些过程如何在包括人类在内的脊椎动物中受到调控提供了一个范例。此外，这些研究将提供对内分泌细胞如何释放类固醇激素的新理解。 公共卫生相关性：这里描述的研究将有助于识别调节昆虫中类固醇激素产生和分泌的基本分子程序。由于相关的发育转变和类固醇释放机制存在于包括人类在内的许多生物体中，这项工作将为理解神经内分泌回路如何整合不同的类固醇激素调节信号以控制发育提供一个范例。

DESCRIPTION (provided by applicant): Proper development of all multi-cellular organisms requires not only correct spatial control of cellular interactions, but also correct timing of specific gene expression programs during development. Altering the timing of many developmental processes can significantly affect an animals final body size, reproductive ability and ageing. In insects, timing of developmental transitions, i.e. molting and metamorphosis, is mediated by 20-hydroxyecdysone (20E), a small circulating lipophilic steroid hormone that binds to and activates transcription factors of the nuclear receptor superfamily. Although the genetic hierarchy that controls responses to 20E has received considerable attention, little is presently known about mechanisms that control the timing of hormone production and its release. In this proposal we will determine how prothoraciotropic hormone, a peptide released from neurons that innervate the prothoracic gland (PGs) control hormone production and release. In aim 1 we will determine when the PG cells receive PTTH signals and what regulates their competence to do so. In aim 2 we will characterize additional upstream and downstream inputs that regulate PTTH signaling through the receptor tyrosine kinase Torso. Of particular interest is to determine if the PTTH ligand processing is required for PTTH signaling and if PKC, PLC and the IP3 receptor, contribute to PTTH signaling in Drosophila and how their activity is coupled to Torso activation. In aim 3, we will identify key transcriptional control elements in the regulatory regions of the ecdysone biosynthetic enzymes phm, dib and spookier, in order to learn how PTTH signals regulate ecdysone production. In aim4 we will use genetic studies and imaging methods to test the hypothesis that, contrary to present beliefs, release of ecdysone from the prothoracic gland during the metamorphic molt is a vesicle mediated process stimulated by PTTH. Impact on human health: In humans, a major developmental transition involving steroid hormones takes place as adolescents acquire sexual maturity. This transition is also controlled by a neuropeptide signal in conjunction with nutritional and metabolic cues, although little is presently known about how these signals are integrated to time the transition appropriately. The studies described here will help identify basic molecular programs that control developmental transitions and thereby provide a paradigm for understanding how these processes might be regulated in vertebrates including humans. In addition these studies will provide a new understanding of how steroid hormones are released from endocrine cells. PUBLIC HEALTH RELEVANCE: The studies described here will help identify basic molecular programs that regulate steroid hormone production and secretion in insects. Since related developmental transitions and steroid release mechanisms occur in many organisms, including humans, this work will provide a paradigm for understanding how different steroidogenic regulatory cues are integrated by the neuroendocrine circuit to control development.