Neuronal voltage-gated ion channels are genetic modifiers of generalized epilepsy with febrile seizures plus

Nicole A. Hawkins, Melinda S. Martin, Wayne N. Frankel, Jennifer A. Kearney*, Andrew Escayg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

Mutations in the neuronal voltage-gated sodium channel genes SCN1A and SCN2A are associated with inherited epilepsies, including genetic epilepsy with febrile seizures plus (GEFS+) and Dravet syndrome (severe myoclonic epilepsy of infancy). The clinical presentation and severity of these epilepsies vary widely, even in people with the same mutation, suggesting the action of environmental or genetic modifiers. To gain support for the hypothesis that genetic modifiers can influence clinical presentation in patients with SCN1A-derived GEFS+, we used mouse models to study the effect of combining the human GEFS+ mutation SCN1A-R1648H with SCN2A, KCNQ2, and SCN8A mutations. Knock-in mice heterozygous for the R1648H mutation (Scn1a RH/+) have decreased thresholds to induced seizures and infrequent spontaneous seizures, whereas homozygotes display spontaneous seizures and premature lethality. Scn2a Q54 transgenic mice have a mutation in Scn2a that results in spontaneous, adult-onset partial motor seizures, and mice carrying the Kcnq2-V182M mutation exhibit increased susceptibility to induced seizures, and rare spontaneous seizures as adults. Combining the Scn1a-R1648H allele with either Scn2a Q54 or Kcnq2 V182M/+ results in early-onset, generalized tonic-clonic seizures and juvenile lethality in double heterozygous mice. In contrast, Scn8a mutants exhibit increased resistance to induced seizures. Combining the Scn1a-R1648H and Scn8a-med-jo alleles restores normal thresholds to flurothyl-induced seizures in Scn1a RH/+ heterozygotes and improved survival of Scn1a RH/RH homozygotes. Our results demonstrate that variants in Scn2a, Kcnq2, and Scn8a can dramatically influence the phenotype of mice carrying the Scn1a-R1648H mutation and suggest that ion channel variants may contribute to the clinical variation seen in patients with monogenic epilepsy.

Original languageEnglish (US)
Pages (from-to)655-660
Number of pages6
JournalNeurobiology of Disease
Volume41
Issue number3
DOIs
StatePublished - Mar 2011

Keywords

  • Epilepsy
  • Modifier
  • Potassium channel
  • Sodium channel

ASJC Scopus subject areas

  • Neurology

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