RYR2 and catecholaminergic polymorphic ventricular tachycardia: Taken together, these observations support the notion that the absence of CPVT phenotype in the RyR2 Ex3-del+/− mutant mice is most likely due to the predominant expression of the WT allele as a result of the markedly reduced expression of the Ex3-del mutant RyR2 allele.