Using Drosophila to investigate the development and function of nervous systems.

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Monoamines are class of neuromodulators that are crucial for a variety of brain functions, including control of mood, movement, cognition, and sleep. Like mammals, the Drosophila nervous system is enriched in monoamines, mainly dopamine, serotonin and octopamine. Distinct populations of monoaminergic neurons release these modulators within anatomically overlapping regions, allowing the brain to integrate environmental cues and regulate animal physiology. Re-uptake of these monoamines then occurs via specific transport proteins to prevent increased extracellular concentration at synapses. During normal cellular metabolism, monoamines are acetylated by the enzyme dopamine N-acetyl transferase (Dat), a Drosophila member of the conserved family of aaNAT (alkylarylamine N-acetyltransferase) proteins. Interestingly, N-acetyl serotonin is a precursor in the synthesis of melatonin, a hormone that induces sleep. We have made a new antibody to Dat and found it to be expressed in some but not all classes of monoaminergic neurons, and likely in neurons expressing other neurotransmitters such as GABA and glutamate. Strikingly, we also found Dat to be expressed in astrocytes, where it is enriched in the fine membranous processes that infiltrate CNS neuropil. The physiological role of astrocytes in monoamine processing is not well understood. We hypothesize that Drosophila astrocytes take up monoamines from synapses and process them via Dat to affect neuromodulation of specific behaviors. In preliminary experiments we find that Dat produced in astrocytes is required for flies to achieve correct levels and timing of sleep. In this grant application, we propose to use genetic approaches to investigate Dat function in Drosophila astrocytes, and to explore with immunohistochemistry, biochemistry and behavioral assays how Dat function might provide selective activity depending on the cell type in which it is expressed. In Aim 1 we will characterize the spatial and temporal patterns of Dat expression in the adult fly brain. In Aim 2 we will measure the biochemical effects of Dat activity in astrocytes and specific neuronal subtypes. In Aim 3 we will determine how Dat influences sleep in Drosophila.******This grant will create new understanding of cellular and molecular mechanisms that control the bioavailability and function of monoamines in the CNS. Moreover, it will provide excellent conceptual and technical training for undergraduate and graduate students interested in understanding fundamental aspects of brain function.