Advancing Transgenic Neuromodulation Tools with Translational Positron Emission Tomography Applications

Boehm, Matthew Armin

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Overview

Year:: 2023
Contributor:: Boehm, Matthew Armin (creator); Michaelides, Michael (Advisor); Desrochers, Theresa (Reader); Stein, Elliot (Reader); Bradberry, Charles (Reader); Rapp, Peter (Reader); Brown University. Department of Neuroscience (sponsor)
Genre:: theses
Subject:: neuroimaging; Tomography, Emission; Optogenetics; Chemogenetics
Extent:: xvi, 163 p.

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Description

Abstract:: Transgenic neuromodulation tools (i.e., optogenetics and chemogenetics) enable the manipulation of brain activity using targeted genetic delivery strategies for transducing specific cells to produce transgenic opsins or receptors capable of altering neuronal activity with administration of light or selective ligands, respectively. As these tools expand knowledge of the nervous system in preclinical neuroscience, developing translational applications for human therapies is becoming increasingly possible. However, a major obstacle is the need to confirm and monitor the location and function of transgenic opsins and receptors in living subjects. This dissertation work presents solutions to these challenges by leveraging the translational molecular imaging capabilities of positron emission tomography (PET) to visualize the location and function of transgenic opsins and receptors in rats and squirrel monkeys. In optogenetic experiments, we engineered the first PET-compatible opsin, ChRERα, by combining Channelrhodopsin-2 with the ligand binding domain of the human estrogen receptor alpha (ERαLBD). We demonstrated that AAV-mediated ChRERα expression in the brain exhibited conserved opsin function and can be visualized with [18F]-16α-fluoroestradiol (FES), an FDA-approved PET radiotracer. Additionally, we showed ERαLBD can be combined with other opsins for FES-PET localization, and the adaptability of this approach expands the utility of optogenetics by facilitating translational and clinical applications. In chemogenetic experiments, we tested a dual receptor approach by inducing co-expression of hM3Dq (an “excitatory” metabotropic receptor), and PSAM4-GlyR (an “inhibitory” ionotropic receptor) using a co-injection of AAVs in the cortex of rats and squirrel monkeys. To assess effects on brain activity, we performed FDG-PET following injection of the hM3Dq agonist – JHU37160, or PSAM4-GlyR agonist – uPSEM817. Both types of chemogenetic stimulation increased brain activity near the AAV injection site, but PSAM4-GlyR agonism decreased activity in distinct downstream brain regions. In addition, we demonstrated that recently developed PET radiotracers [18F]JHU37107 and [18F]ASEM can be used to visualize hM3Dq and PSAM4-GlyR brain expression. These experiments demonstrate for the first time that hM3Dq and PSAM4-GlyR can be co-expressed in individual subjects and visualized with distinct radiotracers. Collectively, this work supports the feasibility of imaging multiple transgenic constructs (i.e., chemogenetic receptors and/or transgenic opsins) in living subjects using translational PET imaging techniques.
Notes:: Thesis (Ph. D.)--Brown University, 2023

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Citation

Boehm, Matthew Armin, "Advancing Transgenic Neuromodulation Tools with Translational Positron Emission Tomography Applications" (2023). Neuroscience Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:95bne535/

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Neuroscience Theses and Dissertations

Theses and Dissertations for the Neuroscience department.
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