An isolated nucleic acid molecule encoding a mutant alpha subunit of a mammalian voltage-gated sodium channel, wherein a mutation event selected from the group consisting of point mutations, deletions, insertions and rearrangements has occurred and said mutation event disrupts the functioning of an assembled sodium channel comprising this mutated subunit so as to produce an epilepsy phenotype, with the proviso that the mutation event is not a C2624T transition or a G4943A transition.