RYR2 and catecholaminergic polymorphic ventricular tachycardia: Hence, unlike most of the CPVT-associated RyR2 mutations, the G357S mutation reduces the maximum fraction of HEK293 cells that show SOICR, but does not appear to enhance the propensity for SOICR in HEK293 cells at low extracellular Ca2+ concentrations.