A Genetic Switch for Epilepsy in Adult Mice
Overview
Authors
Affiliations
Premature death from seizures afflicts gene-targeted mice expressing the Q/R site-unedited glutamate receptor subunit GluR-B(Q) of AMPA receptors in central neurons. Early seizure-related death has now been circumvented by a genetic switch that restricts GluR-B(Q) expression to forebrain principal neurons from postnatal stages onward, prominently in hippocampus and striatum and less so in cortex and amygdala. When switched on, functional receptor incorporation of GluR-B(Q) could be demonstrated by imaging evoked AMPA channel-mediated spinous Ca2+ transients in CA1 pyramidal cells. Sustained GluR-B(Q) expression in adult mice led to smaller excitatory postsynaptic responses in the CA1 region with unchanged presynaptic fiber excitability. Notably, despite the smaller excitatory response, the CA1 cells exhibited a reduced population spike threshold, which might underlie the spontaneous manifestations of epilepsy, including myocloni and generalized seizures with limbic components, observed by synchronous video monitoring and electroencephalographic recordings. No neuropathological symptoms developed when GluR-B(Q) expression was restricted to only hippocampal neurons. Our results show that seizure susceptibility is triggered by GluR-B(Q) expression also in the adult brain and that circuit hyperexcitability is not an immediate consequence of GluR-B(Q) but requires yet unknown downstream events, likely to be induced by non-Hebbian plasticity from Ca2+-permeable AMPA channels in principal neurons.
RNA editing of ion channels and receptors in physiology and neurological disorders.
Zhai J, Koh J, Soong T Oxf Open Neurosci. 2024; 1:kvac010.
PMID: 38596706 PMC: 11003377. DOI: 10.1093/oons/kvac010.
Jin L, Sullivan H, Zhu M, Lavin T, Matsuyama M, Fu X Nat Neurosci. 2024; 27(2):373-383.
PMID: 38212587 PMC: 10849964. DOI: 10.1038/s41593-023-01545-8.
Wright A, Konen L, Mockett B, Morris G, Singh A, Burbano L Mol Neurodegener. 2023; 18(1):65.
PMID: 37759260 PMC: 10537207. DOI: 10.1186/s13024-023-00632-5.
Swenson C, Argueta-Gonzalez H, Sterling S, Robichaux R, Knutson S, Heemstra J ACS Omega. 2023; 8(1):238-248.
PMID: 36643573 PMC: 9835161. DOI: 10.1021/acsomega.2c03568.
Loss of Ca1.3 RNA editing enhances mouse hippocampal plasticity, learning, and memory.
Zhai J, Navakkode S, Yeow S, Krishna-K K, Liang M, Koh J Proc Natl Acad Sci U S A. 2022; 119(32):e2203883119.
PMID: 35914168 PMC: 9371748. DOI: 10.1073/pnas.2203883119.