KCNA1 and Familial paroxysmal ataxia: Kv1.1 channels located at juxtaparanodes have a profound stabilizing effect on the action potential when it reaches the transition zone near the nerve terminal (Zhou et al., 1999), and mutations in KCNA1 encoding Kv1.1 cause episodic ataxia and myokymia [reviewed in (Jen et al., 2007)].