Mutations in calmodulin (Calm) 1 and 3 (underlying CPVT types 4 and 6, respectively) and more recently Calm2, which tether to RyR2 at the cytosolic side, interfere with the complex responsiveness to activation by cytosolic Ca2+ [82]. The gene discussed is RYR2; the disease is catecholaminergic polymorphic ventricular tachycardia.