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A TASK3 channel (KCNK9) mutation in a genetic model of absence epilepsy

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  • Receptors And Channels
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Abstract

Childhood absence epilepsy is an idiopathic, generalized, nonconvulsive epilepsy with a multifactorial genetic etiology. The KCNK9 gene coding for the TASK3 (Twik-like acid-sensitive K +) channel is present on chromosome 8 at position 8q24, a locus that has shown positive linkage to the human absence epilepsy phenotype. Sequencing of the KCNK9 gene in the genetic absence epilepsy rats from Strasbourg (GAERS), a well established genetic model of this disease, reveals an additional alanine residue in a polyalanine tract within the C-terminal intracellular domain. This additional alanine is absent in the inbred nonepileptic control (NEC) strain, Wistar, and Wistar albino Glaxo strain bred in Rijswijk, another inbred rat model of absence epilepsy. Expression of the mutant channel in CHO cells produces a K+ current that is blocked by acidic pH and millimolar concentrations of barium or ruthenium red and is not different from the wild-type channel. In brain slices, thalamic neurons display a prominent pH-sensitive tonic K+ current, but no difference was observed between GAERS and NEC or Wistar rats. Ruthenium red had no effect in cortical, reticular thalamic, or sensory thalamic neurons in either GAERS or NEC, indicating that the TASK3 homodimer is not present in these structures. Twik-like acid-sensitive K+ (TASK3) channels, therefore, are probably associated with TASK1 to form ruthenium red-insensitive heterodimers in these neurons. Finally, no difference was found between GAERS and NEC rats in the modulation of the leak K+ current following activation of muscarinic receptors. These studies describe the first mutation found in a genetic model of absence epilepsy. Although our experiments showed no difference in the leak K+ current between GAERS and NEC rats, further work is needed to ascertain whether this mutation contributes to the generation of absence seizures, possibly by mechanisms related to the expansion of the polyalanine run.

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  1. Jethro Holter

    Present address: Department of Physiology, University of Oslo, Blindern, NO-0317, Oslo, Norway

Authors and Affiliations

  1. School of Bioscience, Cardiff University, CF10 3US, Cardiff, UK

    Jethro Holter, David Carter & Vincenzo Crunelli

  2. Equipe Neurobiologie Cellulaire, UMR 7102, CNRS Université Paris VI, F-75005, Paris, France

    Nathalie Leresche & Pierre Vincent

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  1. Jethro Holter
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  2. David Carter
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  3. Nathalie Leresche
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  4. Vincenzo Crunelli
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Correspondence to Jethro Holter.

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Holter, J., Carter, D., Leresche, N. et al. A TASK3 channel (KCNK9) mutation in a genetic model of absence epilepsy. J Mol Neurosci 25, 37–51 (2005). https://doi.org/10.1385/JMN:25:1:037

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  • DOI: https://doi.org/10.1385/JMN:25:1:037

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