Specific Aims The major goal of this proposal is to understand mechanisms by which astrocytes interact with neurons to modulate neural circuit activity and animal behavior. Many studies over the past two decades have suggested that astrocytes respond directly to neurotransmission and in turn signal back to neurons to regulate circuit activity. Definitive in vivo examples have remained elusive, but if astrocytes indeed receive synaptic information and feedback to modulate neuronal activity it is imperative that we identify and define these mechanisms-astrocyte control of neuronal activity could represent a previously unappreciated but prominent mechanism for regulating information processing in the brain and animal behavior. We recently made the exciting observation that in live preparations Drosophila astrocytes exhibit rhythmic fluctuations in intracellular Ca2+ similar to those observed in astrocytes of awake behaving mice. Astrocyte Ca2+ signaling in larvae is not altered by application of glutamate, GABA, or acetylcholine, but is potently stimulated by octopamine (OA), the invertebrate equivalent of norepinephrine (NE). Intriguingly, NE was recently found to stimulate astrocytic Ca2+ signaling in mice, although the NE site of action (e.g. neurons, astrocytes, or both) remains unclear, molecules required in astrocytes for NE-induced Ca2+ signals have not been identified, and their physiological roles remain enigmatic. Furthermore, using forward genetic approaches we identified the G protein-coupled octopamine-tyramine receptor (Oct-tyrR) and the TRP channel Waterwitch (Wtrw) as novel, astrocyte-expressed molecules required for activation of OA-induced astrocyte Ca2+ transients. Remarkably, depletion of Wtrw from astrocytes leads to defects in both olfaction and touch- induced startle responses, implicating Wtrw and astrocyte Ca2+ signaling in animal behavior. Our identification of Oct-tyrR and Wtrw as novel critical regulators of astrocyte Ca2+ signaling opens the door to an exploration of the functional significance astrocyte Ca2+ signaling in vivo, which is proposed herein. Our work will define new components of the astrocyte Ca2+ signaling machinery and their importance in astrocyte-neuron signaling events (Aim 1); determine how astrocyte Ca2+ signaling events are regulated by neural circuits and how they reciprocally modulate neuronal activity in vivo (Aim 2); and explore the role of astrocyte Ca2+ signaling molecules in simple sensory-driven behaviors, circadian and arousal behaviors, and a touch induced startle response.

Public Health Relevance

Astrocytes are the most abundant cell type in the human brain and have emerged as key regulators of brain development, function, and maintenance. Whether astrocytes also participate in regulating how the brain processes information remains unclear. Our work will determine how astrocytes receive information from neurons and then alter the function of other neurons and ultimately animal behavior. The principles we explore will be highly relevant to normal brain function and a number of neuropsychiatric disorders.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (ZRG1)
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Morris, Jill A
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Oregon Health and Science University
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United States
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Coutinho-Budd, Jaeda C; Sheehan, Amy E; Freeman, Marc R (2017) The secreted neurotrophin SpƤtzle 3 promotes glial morphogenesis and supports neuronal survival and function. Genes Dev 31:2023-2038
Lu, Tsai-Yi; MacDonald, Jennifer M; Neukomm, Lukas J et al. (2017) Axon degeneration induces glial responses through Draper-TRAF4-JNK signalling. Nat Commun 8:14355
Ma, Zhiguo; Stork, Tobias; Bergles, Dwight E et al. (2016) Neuromodulators signal through astrocytes to alter neural circuit activity and behaviour. Nature 539:428-432
He, Jiang; Zhou, Ruobo; Wu, Zhuhao et al. (2016) Prevalent presence of periodic actin-spectrin-based membrane skeleton in a broad range of neuronal cell types and animal species. Proc Natl Acad Sci U S A 113:6029-34
Freeman, Marc R (2015) Drosophila Central Nervous System Glia. Cold Spring Harb Perspect Biol 7:
Kerr, Kimberly S; Fuentes-Medel, Yuly; Brewer, Cassandra et al. (2014) Glial wingless/Wnt regulates glutamate receptor clustering and synaptic physiology at the Drosophila neuromuscular junction. J Neurosci 34:2910-20
Burdett, Thomas C; Freeman, Marc R (2014) Neuroscience. Astrocytes eyeball axonal mitochondria. Science 345:385-6
Tasdemir-Yilmaz, Ozge E; Freeman, Marc R (2014) Astrocytes engage unique molecular programs to engulf pruned neuronal debris from distinct subsets of neurons. Genes Dev 28:20-33
Fuentes-Medel, Yuly; Ashley, James; Barria, Romina et al. (2012) Integration of a retrograde signal during synapse formation by glia-secreted TGF-? ligand. Curr Biol 22:1831-8
Osterloh, Jeannette M; Yang, Jing; Rooney, Timothy M et al. (2012) dSarm/Sarm1 is required for activation of an injury-induced axon death pathway. Science 337:481-4

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