Life on earth is profoundly rhythmic. Animals, plants, and microbes resonate deeply with the predictable and often severe daily changes imposed by our rotating planet. In animals, circadian clocks residing deep within the brain produce an endogenous sense of time that is used to orchestrate many important biological processes, including the daily oscillation between wakefulness and sleep. In animals, the circadian clock is composed of a network of neurons within the brain, each of which expresses a highly conserved molecular clock. The proper function of this network and communication to downstream brain regions is critical for human health and psychological well-being. The research program supported by this award seeks to understand how the clock network of the brain produces an endogenous sense of time and how it communicates with downstream brain regions to orchestrate daily behavioral and physiological rhythms. The objective of this project is to determine the neurophysiological basis of circadian clock output in the brain of the fly Drosophila melanogaster, an organism that has consistently enriched our understanding of biological timekeeping in animals. The studies will address a fundamental mystery in the neuroscience of circadian timekeeping and could help guide efforts to alleviate the negative metabolic and psychological consequences of human circadian dysfunction created by our modern around-the-clock society.
The broad goal of this investigation is to understand the neurophysiological basis of circadian clock output in the central nervous system of Drosophila melanogaster. The work will take advantage of both well-established neurogenetic techniques and newly emerging live imaging methods for the experimental investigation of clock neuron output in Drosophila. These latter methods make possible the measurement of Ca2+ and cAMP dynamics in central brain networks during the acute excitation of genetically defined classes of CCNN neurons. The specific objectives of this project are to identify the neuronal targets of the CCNN, to determine the roles that specific neuronal oscillators within the CCNN play in the control of feeding and metabolic rhythms, and to develop new genetic tools for the examination of neuronal class specific contributions to clock controlled outputs. These experiments will significantly advance our understanding of how the CCNN modulates the brain centers controlling behavior and metabolism and represent a shift in the experimental approach to clock output in the animal brain. The specific aims of this project are: To determine the functional connectivity between the CCNN and established endocrine, sleep and locomotor centers of the brain; To determine the neural basis the circadian modulation of feeding and metabolism by the CCNN; To conduct a undergraduate-led screen for enhancer-trap flippase elements yielding CCNN sub-class specific GAL4/UAS expression for the focused visualization and manipulation of specific clock neuron subsets. Furthermore, the principle investigator will develop educational and outreach activities to introduce students of various ages to molecular and behavioral neuroscience that incorporate modern genetic tools and teach the fundamentals of experimental design and interpretation.
