The Cav3.2 gcm mutation significantly increased the percentage of time spent in seizure activity in homozygous rats compared to wild-type rats (3.1% vs 0.5%).
A gain-of-function mutation in the Cav3.2 T-type calcium channel gene in a rat model of absence epilepsy requires specific exonic splicing to express its functional consequences.
Absolute Event Rate: 3.1% vs 0.5%
p-value: p=<0.05
Low-voltage-activated, or T-type, calcium (Ca(2+)) channels are believed to play an essential role in the generation of absence seizures in the idiopathic generalized epilepsies (IGEs). We describe a homozygous, missense, single nucleotide (G to C) mutation in the Ca(v)3.2 T-type Ca(2+) channel gene (Cacna1h) in the genetic absence epilepsy rats from Strasbourg (GAERS) model of IGE. The GAERS Ca(v)3.2 mutation (gcm) produces an arginine to proline (R1584P) substitution in exon 24 of Cacna1h, encoding a portion of the III-IV linker region in Ca(v)3.2. gcm segregates codominantly with the number of seizures and time in seizure activity in progeny of an F1 intercross. We have further identified two major thalamic Cacna1h splice variants, either with or without exon 25. gcm introduced into the splice variants acts "epistatically," requiring the presence of exon 25 to produce significantly faster recovery from channel inactivation and greater charge transference during high-frequency bursts. This gain-of-function mutation, the first reported in the GAERS polygenic animal model, has a novel mechanism of action, being dependent on exonic splicing for its functional consequences to be expressed.
Powell et al. (Wed,) conducted a other in Absence epilepsy (n=44). Cav3.2 gcm mutation (R1584P) vs. Wild-type (null for gcm mutation) was evaluated on Percentage time spent in seizure activity over a 90-minute EEG recording (p=<0.05). The Cav3.2 gcm mutation significantly increased the percentage of time spent in seizure activity in homozygous rats compared to wild-type rats (3.1% vs 0.5%).