Spectrum of sodium channel disturbances in the nondystrophic myotonias and periodic paralyses.
Several heritable forms of myotonia and periodic paralysis are caused by missense mutations in the voltage-gated sodium channel of skeletal muscle. Mutations produce gain-of-function defects, either disrupted inactivation or enhanced activation. Both defects result in too much inward Na current which may either initiate pathologic bursts of action potentials (myotonia) or cause flaccid paralysis by depolarizing fibers to a refractory inexcitable state. Myotonic stiffness and periodic paralysis occur as paroxysmal attacks often triggered by environmental factors such as serum K+, cold, or exercise. Many gaps remain in our understanding of the interactions between genetic predisposition and these environmental influences. Targeted gene manipulation in animals may provide the tools to fill in these gaps.
Cannon
S C
SC
Department of Neurobiology, Harvard Medical School, Massachusetts General Hospital, Boston, USA. cannon@helix.mgh.harvard.edu
D000818:Animals; D006801:Humans; D015640:Ion Channel Gating; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D020125:Mutation, Missense / Q000502:physiology; D009222:Myotonia / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D010245:Paralyses, Familial Periodic / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*
D015222:Sodium Channels