Functional analysis of Ca_v3.2 T-type calcium channel mutations linked to childhood absence epilepsy

Purpose: Childhood absence epilepsy (CAE) is an idiopathic form of seizure disorder that is believed to have a genetic basis. Methods: We examined the biophysical consequences of seven mutations in the Ca_v3.2 T-type calcium channel gene linked to CAE. Results: Of the channel variants examined, one of the mutants, a replacement of glycine 848 in the domain II-S2 region with serine, resulted in significant slowing of the time courses of both activation and inactivation across a wide range of membrane potentials. These changes are consistent with increased channel activity in response to prolonged membrane depolarizations. Conclusions: Taken together, these findings suggest that such little changes in channel gating may contribute to the etiology of CAE.