A mutation that causes ataxia shifts the voltage-dependence of the Scn8a sodium channel

Neuroreport. 1999 Sep 29;10(14):3027-31. doi: 10.1097/00001756-199909290-00028.


A mutation of alanine to threonine in the III S4-S5 linker of the mouse Scn8a sodium channel has previously been identified as causing the ataxia in med(jo) mice. The electrophysiological effects of this mutation in Scn8a sodium channels were characterized in Xenopus oocytes. The med(jo) mutation caused a 10 mV positive shift in the voltage dependence of activation, without any significant changes in the kinetics of either inactivation or recovery from inactivation. The shift in the voltage dependence of activation observed for the mutant channel would reduce the spontaneous activity of Purkinje cells and lead to a decrease in output from the cerebellum, which is consistent with the phenotype of cerebellar ataxia observed in med(jo) mice.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / metabolism
  • Amino Acid Substitution
  • Animals
  • Ataxia / genetics*
  • Electrophysiology
  • Kinetics
  • Mice
  • Mutation / physiology
  • NAV1.6 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins / genetics*
  • Oocytes / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sodium Channels / genetics*
  • Threonine / metabolism
  • Xenopus


  • NAV1.6 Voltage-Gated Sodium Channel
  • Nerve Tissue Proteins
  • Scn8a protein, mouse
  • Sodium Channels
  • Threonine
  • Alanine