In cardiac muscle, gain-of-function mutations in RYR2 and loss-of-function mutations in CASQ2 cause a similar phenotype, i.e. catecholaminergic polymorphic ventricular tachycardia (CPVT), which is caused by excessive SR Ca2+ leak (Knollmann et al., 2006). Here, CASQ2 is linked to catecholaminergic polymorphic ventricular tachycardia.