Identifying Neural Substrates of Behavior in Drosophila

这项研究计划的目标是开发和进一步开发操纵神经活动的技术，以识别特定行为背后的大脑回路。利用果蝇强大的Gal4-UAS基因打靶系统来驱动其产物抑制神经元兴奋性或突触传递的基因的表达，我们选择性地抑制神经元亚群的活动，并分析这种操作对两种行为的影响：休息，类似哺乳动物睡眠的苍蝇，以及展翅，一种荷尔蒙协调和发育编程的行为，由成蝇从蛹出来后不久执行。为了确定这些行为的神经元底物，我们使用了两种方法：一种是定义的神经元子集，另一种是随机子集被抑制(分别使用带有定义的启动子的Gal4线和Gal4增强子陷阱线)。在每种情况下，都识别了影响感兴趣行为的抑制模式，以供进一步表征。使用第一种方法，我们发现抑制合成神经递质多巴胺和5-羟色胺的细胞中的电活动会抑制苍蝇的翅膀扩张和作为休息/活动周期基础的运动活动。我们的结果暗示了5-羟色胺分泌细胞在前一种行为中的作用。我们目前正在应用MARCM技术的一种变体来进一步限制抑制模式，以确定哪些5-羟色胺能细胞是产生这种行为所必需的。使用第二种方法，我们已经确定了10种产生机翼扩张赤字的抑制模式(即增强子-陷阱线)。通过进一步限制这些模式，我们计划识别和表征负责产生这些缺陷的单个细胞。我们对翅膀扩张行为背后的神经元底物的研究应该作为电路映射方法的“概念证明”，该方法稍后可以扩展到哺乳动物行为的研究。新启动的关于休息的工作也有望阐明哺乳动物控制睡眠的神经回路，因为这种进化保守的行为背后有类似的分子机制。

The goal of this research program is to exploit, and further develop, techniques for manipulating neural activity to identify the brain circuits underlying specific behaviors. Using the powerful Gal4-UAS gene targeting system of Drosophila melanogaster to drive the expression of genes whose products inhibit neuronal excitability or synaptic transmission, we are selectively inhibiting the activity of subsets of neurons and analyzing the effects of this manipulation on two behaviors: rest, the fly analog of mammalian sleep, and wing expansion, a hormonally coordinated and developmentally programmed behavior executed by the adult fly shortly after emergence from the pupal case. To identify neuronal substrates of these behaviors we use two approaches: one in which defined subsets of neurons, and the other in which random subsets, are inhibited (using Gal4 lines with defined promoters and Gal4 enhancer-trap lines, respectively). In each case, patterns of suppression that affect the behaviors of interest are identified for further characterization. Using the first approach, we have found that inhibition of electrical activity in cells that synthesize the neurotransmitters dopamine and serotonin suppresses both wing expansion and the locomoter activity underlying rest/activity cycles in flies. Our results implicate a role for serotonin-secreting cells in the former behavior. We are currently applying a variant of the MARCM technique to further restrict the pattern of suppression to determine which serotonergic cells are essential to generate the behavior. Using the second approach, we have identified 10 patterns of suppression (i.e. enhancer-trap lines) that generate wing expansion deficits. By further restricting these patterns we plan to identify and characterize the individual cells responsible for generating these deficits. Our investigation of the neuronal substrates underlying wing expansion behavior should serve as a "proof of concept" of a circuit mapping approach that can later be extended to studies of mammalian behavior. The newly initiated work on rest is also expected to illuminate the mammalian neurocircuitry governing sleep given the similar molecular mechanisms underlying this evolutionarily conserved behavior.