Mouse with Nav1.1 haploinsufficiency, a model for Dravet syndrome, exhibits lowered sociability and learning impairment

Dravet syndrome is an intractable epileptic encephalopathy characterized by early onset epileptic seizures followed by cognitive decline, hyperactivity, autistic behaviors and ataxia. Most Dravet syndrome patients possess heterozygous mutations of SCN1A gene encoding voltage-gated sodium channel αI subunit (Nav1.1). We have previously reported that mice heterozygous for a nonsense mutation in Scn1a developed early onset epileptic seizures. However, the learning ability and sociability of the mice remained to be investigated. In the present study, we subjected heterozygous Scn1a mice to a comprehensive behavioral test battery. We found that while heterozygous Scn1a mice had lowered spontaneous motor activity in home cage, they were hyperactive in novel environments. Moreover, the mice had low sociability and poor spatial learning ability that correspond to the autistic behaviors and cognitive decline seen in Dravet syndrome patients. These results suggest that Nav1.1 haploinsufficiency intrinsically contributes to not only epileptic seizures but also lowered sociability and learning impairment in heterozygous Scn1a mutant mice, as it should also be the case in patients with Dravet syndrome.