Impaired action potential initiation in GABAergic interneurons causes hyperexcitable networks in an epileptic mouse model carrying a human Nav1.1 mutation

Ulrike B S Hedrich, Camille Liautard, Daniel Kirschenbaum, Martin Pofahl, Jennifer Lavigne, Yuanyuan Liu, Stephan Theiss, Johannes Slotta, Andrew Escayg, Marcel Dihné, Heinz Beck, Massimo Mantegazza, Holger Lerche

Research output: Contribution to journalArticle

Abstract

Mutations in SCN1A and other ion channel genes can cause different epileptic phenotypes, but the precise mechanisms underlying the development of hyperexcitable networks are largely unknown. Here, we present a multisystem analysis of an SCN1A mouse model carrying the Nav1.1-R1648H mutation, which causes febrile seizures and epilepsy in humans. We found a ubiquitous hypoexcitability of interneurons in thalamus, cortex, and hippocampus, without detectable changes in excitatory neurons. Interestingly, somatic Na+channels in interneurons and persistent Na+currents were not significantly changed. Instead, the key mechanism of interneuron dysfunction was a deficit of action potential initiation at the axon initial segment that was identified by analyzing action potential firing. This deficit increased with the duration of firing periods, suggesting that increased slow inactivation, as recorded for recombinant mutated channels, could play an important role. The deficit in interneuron firing caused reduced action potential-driven inhibition of excitatory neurons as revealed by less frequent spontaneous but not miniature IPSCs. Multiple approaches indicated increased spontaneous thalamocortical and hippocampal network activity in mutant mice, as follows: (1) more synchronous and higher-frequency firing was recorded in primary neuronal cultures plated on multielectrode arrays; (2) thalamocortical slices examined by field potential recordings revealed spontaneous activities and pathological high-frequency oscillations; and (3) multineuron Ca2+ imaging in hippocampal slices showed increased spontaneous neuronal activity. Thus, an interneuron-specific generalized defect in action potential initiation causes multisystem disinhibition and network hyperexcitability, which can well explain the occurrence of seizures in the studied mouse model and in patients carrying this mutation.

Original languageEnglish
Pages (from-to)14874-14889
Number of pages16
JournalJournal of Neuroscience
Volume34
Issue number45
DOIs
Publication statusPublished - Nov 5 2014

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Keywords

  • Epilepsy
  • Genetics
  • Ion channel
  • Mouse model
  • Network activity

ASJC Scopus subject areas

  • Neuroscience(all)
  • Medicine(all)

Cite this

Hedrich, U. B. S., Liautard, C., Kirschenbaum, D., Pofahl, M., Lavigne, J., Liu, Y., Theiss, S., Slotta, J., Escayg, A., Dihné, M., Beck, H., Mantegazza, M., & Lerche, H. (2014). Impaired action potential initiation in GABAergic interneurons causes hyperexcitable networks in an epileptic mouse model carrying a human Nav1.1 mutation. Journal of Neuroscience, 34(45), 14874-14889. https://doi.org/10.1523/JNEUROSCI.0721-14.2014