Poster abstracts

Poster number 80 submitted by Josh Rieskamp

Excitatory amino acid transporter 1 (EAAT1) is necessary for glutamate-stimulated proliferation of adult mouse hippocampal neural stem cells

Joshua D Rieskamp (Neuroscience Graduate Program), Valentina Valentini (Deptartment of Psychology), John P Bruno (Department of Psychology, Department of Neuroscience), Elizabeth D Kirby (Department of Psychology, Department of Neuroscience, Chronic Brain Injury Program)

Abstract:
Adult neurogenesis supports hippocampal cognition and responds dynamically to physiological and cognitive experience. Activity-driven signaling by the neurotransmitter glutamate is a potential mechanism by which experiences regulate the neurogenic cascade. However, while glutamate is well known to stimulate neurogenesis, remarkably little is known about the molecular mediators. We aimed to identify these molecular mediators in adult hippocampal radial neural stem cells (NSCs). Using a well-characterized monolayer culture model of adult hippocampal NSCs, we found that pharmacological inhibition of excitatory amino acid transporter (EAAT)-mediated glutamate transport, but not of ionotropic and metabotropic glutamate receptors, impaired proliferation and prevented the pro-proliferative effect of glutamate. We then investigated which EAATs mediate glutamate transport in NSCs and found almost exclusive dependence on EAAT1. Similarly, specific pharmacological inhibition of EAAT1 reduced proliferation and prevented the pro-proliferative effects of glutamate. Next, we used bulk RNA seq and gene ontology analysis to interpret the biological processes that differ between NSCs treated with glutamate and EAAT inhibitors. We found that separately, glutamate induced a network supporting macromolecule biosynthesis while EAAT inhibition induced processes related to cell migration and downregulated processes related to cell cycle progression and mitosis. Furthermore, the majority of genes regulated by glutamate alone were regulated in the opposite direction by the combination of glutamate and EAAT inhibition, which suggests that EAAT inhibition largely suppresses the transcriptional program of glutamate. Together, our data indicate that EAAT1-dependent glutamate transport is necessary for glutamate-stimulated proliferation of hippocampal NSCs. Ongoing studies are investigating the in vivo consequences of glutamate transport for adult neurogenesis. Overall, we expect these studies to improve our understanding of how neurotransmitter signaling impacts neurogenesis in the mature brain, and possibly reveal opportunities for regenerative strategies.

Keywords: Neurogenesis, Hippocampus, Neurotransmitter