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Absence epilepsy, characterized by spike-wave discharges (SWD) in the electroencephalogram, arises from aberrations within the circuitry of the cerebral cortex and thalamus that regulates awareness. The inbred mouse strain C3H/HeJ is prone to absence seizures, with a major susceptibility locus, spkw1, accounting for most of the phenotype. Here we find that spkw1 is associated with a hypomorphic retroviral-like insertion mutation in the Gria4 gene, encoding one of the four amino-3-hydroxy-5-methyl-4isoxazolepropionic acid (AMPA) receptor subunits in the brain. Consistent with this, Gria4 knockout mice also have frequent SWD and do not complement spkw1. In contrast, null mutants for the related gene Gria3 do not have SWD, and Gria3 loss actually lowers SWD of spkw1 homozygotes. Gria3 and Gria4 encode the predominant AMPA receptor subunits in the reticular thalamus, which is thought to play a central role in seizure genesis by inhibiting thalamic relay cells and promoting rebound burst firing responses. In Gria4 mutants, synaptic excitation of inhibitory reticular thalamic neurons is enhanced, with increased duration of synaptic responses-consistent with what might be expected from reduction of the kinetically faster subunit of AMPA receptors encoded by Gria4. These results demonstrate for the first time an essential role for Gria4 in the brain, and suggest that abnormal AMPA receptor-dependent synaptic activity can be involved in the network hypersynchrony that underlies absence seizures.
Pubmed ID: 18316356
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Mus musculus with name C57BL/6J from IMSR.
View all literature mentionsMus musculus with name C3HeB/FeJ from IMSR.
View all literature mentionsMus musculus with name C3H/HeJ from IMSR.
View all literature mentionsMus musculus with name C57BL/6J from IMSR.
View all literature mentionsMus musculus with name C3H/HeJ from IMSR.
View all literature mentionsMus musculus with name C3HeB/FeJ from IMSR.
View all literature mentionsNational public repository system for mutant mice. Archives and distributes scientifically valuable spontaneous and induced mutant mouse strains and ES cell lines for use by biomedical research community. Includes breeding/distribution facilities and information coordinating center. Mice strains are cryopreserved, unless live colony must be established. Live mice are supplied from production colony, from colony recovered from cryopreservation, or via micro-injection of cell line into host blastocysts. MMRRC member facilities also develop technologies to improve handling of mutant mice, including advances in assisted reproductive techniques, cryobiology, genetic analysis, phenotyping and infectious disease diagnostics.
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