Absence-like seizures and their pharmacological profile in tottering-6j mice

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Recessive ataxic tottering-6j mice possess a mutation in the Cacna1a gene, affecting the Cav2.1 channel.
• This mutation leads to exon 5 skipping and partial deletion within domain I of the Cav2.1 α1 subunit.
• The electrophysiological and pharmacological effects of this specific mutation were previously uncharacterized.

Purpose of the Study:

• To investigate the electrophysiological and pharmacological consequences of the Cacna1a mutation in tottering-6j mice.
• To characterize the seizure phenotype in tottering-6j mice.
• To evaluate the tottering-6j mouse as a model for absence epilepsy.

Main Methods:

• Whole-cell patch recording of recombinant Cav2.1 channels in heterologous expression systems.
• Analysis of electroencephalograms (EEGs) in tottering-6j mice to characterize seizure activity.
• Pharmacological testing of anti-epileptic drugs on seizure activity.

Main Results:

• Mutant Cav2.1 channels showed reduced recovery time from inactivation but no change in peak current density or current-voltage relationship.
• Tottering-6j mice displayed absence-like seizures with synchronous spike-and-wave discharges.
• Seizures were responsive to ethosuximide and valproic acid, similar to human absence epilepsy, but not phenytoin.

Conclusions:

• The Cacna1a mutation in tottering-6j mice alters Cav2.1 channel electrophysiology.
• Tottering-6j mice exhibit a phenotype consistent with absence epilepsy.
• This mouse model is suitable for research into Cav2.1 channel function and related neurological disorders, including absence epilepsy.