Vlgr1 knockout mice show audiogenic seizure susceptibility

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Abstract
Susceptibility to audiogenic seizures, which are reflex seizures provoked by loud noise, can be induced in rodents by acoustic priming (exposing animals to strong auditory stimuli at an early developmental stage). Some strains of mice and rats are susceptible to audiogenic seizures without priming and these have been used as good experimental models with which to study epilepsies. Here we identified Vlgr1d and Vlgr1e, novel alternatively-spliced variants of Vlgr1b/MGR1, which, upon sequence analysis, were shown to be transcripts from a locus previously characterized as mass1. Vlgr1 (Vlgr1b, Vlgr1d and Vlgr1e) mRNA is expressed predominantly in the neuroepithelium of the developing mouse brain. Our protein-tagged experiment suggested that Vlgr1d and Vlgr1e are secretory molecules, while Vlgr1b is a receptor. Knockout mice lacking exons 2-4 of Vlgr1 were susceptible to audiogenic seizures without priming, although there were no apparent histological abnormalities in their brains. Ninety-five percent of these knockout mice exhibited wild running, a feature typical of the preconvulsive phase of audiogenic seizures triggered by loud noise (11 kHz, 105 dB), and 68% exhibited tonic convulsions at 3 weeks after birth. Our monogenic mice, which have a unique genetic background, serve as a useful tool for further studies on seizures.