2018 |
Ackerman, Sarah D |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
In Vivo Analysis of Astroctye-Neuron Dynamics in Circuit Formation, Function, and Maintece
PROJECT SUMMARY The mammalian brain is formed by billions of neurons which communicate at specialized chemical junctions called synapses. Individual neurons connect to form functional circuits which are required for proper learning and memory, and disruption of neuronal circuitry underlies the debilitating symptoms experienced by patients suffering from neurological disorders such as epilepsy and schizophrenia. Although proper formation and maintenance of neuronal circuits is essential for a high quality of human life, the process by which a given neuron finds the correct synaptic pair, and how these synapses are maintained and modified over time is poorly understood. Recent work from our labs and others have identified astrocytes, the most abundant CNS glial cell type, as a major regulator of synaptic development. Astrocytes are both pro-synaptogenic (e.g. loss of astrocytes results in decreased synaptogenesis) as well as anti-synaptogenic (e.g. astrocytes engulf and prune synapses). These important functions of astrocytes in regulating synapse number suggest that astrocytes may regulate broader circuit formation, though this hypothesis has not been fully investigated. Characterization of astrocyte-neuron dynamics within a behaviorally-relevant circuit has not been performed, probably because it requires in vivo manipulation of a defined pair of synaptically-coupled neurons and the associated astrocytes. Given the enormous complexity of the mammalian nervous system, these types of experiments are not yet feasible in mammals. Excitingly, it is now possible to perform these studies in the Drosophila nervous system due to the recent development of tools for astrocyte manipulation from the Freeman lab, and identification of neural circuits governing larval locomotion in the Doe lab. As a co-mentored postdoctoral fellow within the Doe and Freeman laboratories, I will merge these new tools to have the unique ability to visualize and genetically manipulate individual central synapses, which I will couple with targeted manipulation of the associated astrocytes to define the role of astrocytes in synapse formation, maintenance, and function. For all studies, I will use recently identified transgenic lines that label defined synaptic pairs: the excitatory cholinergic synapses between E2 and SA1 interneurons, and the inhibitory, GABAergic synapses between A31k interneuron and RP2 motor neuron. Astrocytes will be visualized using anti-Gat immunofluorescence or expression of UAS-myr::Cerulean under alrm-GAL4. In my first aim, I will couple astrocyte ablation experiments with mutant analyses to test the necessity of functional astrocytes in the development (formation) of excitatory and inhibitory synapses. In my second aim, I will use an optogenetic strategy to measure the activity (function) of excitatory and inhibitory synapses in response to changes in astrocyte function. Finally, in my third aim, I will manipulate neuronal activity (through constitutive activation or silencing of defined pre-synaptic neurons) and test the hypothesis that neuronal activity influences both astrocyte morphology and function. In sum, these experiments will define the in vivo role of astrocytes in the formation, function, and maintenances of excitatory and inhibitory synapses within a behaviorally-relevant, sensorimotor circuit.
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0.958 |
2021 |
Ackerman, Sarah D |
K99Activity Code Description: To support the initial phase of a Career/Research Transition award program that provides 1-2 years of mentored support for highly motivated, advanced postdoctoral research scientists. |
The Role of Astrocyte-Neuron Signaling in Closing a Critical Period Required For Motor Circuit Structure, Function, and Behavior
PROJECT SUMMARY Significance: Neural circuit assembly requires activity-dependent refinement of circuit architecture (e.g. plasticity) to produce stereotyped behavior. Neurons are particularly susceptible to functional and structural plasticity during early developmental windows called critical periods. It is clear that failure to terminate critical period plasticity adversely affects mature circuit function in both animal models and humans (e.g. autism and epilepsy), yet the mechanisms that close critical periods are largely unknown. This Pathway to Independence Award proposal seeks to understand the cellular and molecular mechanisms that promote critical period closure, and to define how critical periods shape circuit architecture to ensure proper locomotor behavior. Candidate and environment: Dr. Ackerman was trained in molecular genetics and developmental neuroscience in the laboratory of Dr. Kelly Monk at WashU School of Medicine, where she used forward and reverse genetic strategies to uncover regulators of myelination (NS087801). She then joined the laboratory of the renowned neurobiologist Dr. Chris Doe (UO, HHMI/NAS). Here, she defined a novel critical period of plasticity in the developing Drosophila motor circuit, and uncovered a series of astrocyte-derived molecular regulators of critical period closure (NS098690). In this proposal, Dr. Ackerman will extend her current skills in molecular genetics, live imaging, and circuit analysis to include training in electrophysiology and single cell RNAseq (scRNAseq), two completely new techniques for her. Further, she will use two model systems (fly and zebrafish) to determine how these novel, astrocyte-derived factors restrict motor circuit plasticity (Aim 1), to define how the critical period contributes to motor circuit connectivity, function, and behavior (Aim 2), and to determine how motor circuit plasticity is developmentally constrained in vertebrates (Aim 3). Career development: In addition to continued mentorship by Dr. Doe, the candidate has assembled an exceptional team of mentors and collaborators from the University of Oregon and beyond. During the mentored phase, the candidate will train in NMJ electrophysiology from Dr. Dion Dickman (USC) in order to define how the level of activity experienced by motor neurons during the critical period shapes motor output and behavior. This training is essential for future studies of motor circuit function in the candidate's own lab. Further, she has gathered a local team of advisors from the zebrafish community, Dr. Judith Eisen and Dr. Adam Miller, who have a combined 40 years of experience in zebrafish motor circuits. Drs. Eisen and Miller will facilitate training in scRNAseq, and will provide critical career development advice from the complementary perspectives of a seasoned (Dr. Eisen) and recently-established (Dr. Miller) principal investigator. Funding of this proposal will equip Dr. Ackerman with the unique skillset required to launch a robust and successful research program that pushes the boundaries of our understanding of circuit plasticity, from molecules to behavior.
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0.958 |