Mutations of two myocardial calcium signaling molecules, ryanodine receptor 2 
(RYR2) and calsequestrin 2 (CASQ2), may cause catecholaminergic polymorphic 
ventricular tachycardia (CPVT), a severe inherited arrhythmic disease 
manifesting with salvoes of exercise-induced bidirectional and polymorphic 
tachycardias. We screened 12 Finnish CPVT probands for mutations in these genes 
and identified three novel RYR2 mutations (V2306I, P4902L, R4959Q), which were 
absent in unaffected and control individuals. Although no obvious 
disease-causing mutations were identified in the CASQ2 gene, the molecular 
screening revealed two novel amino-acid polymorphisms (T66A and V76M). The 
frequencies of these polymorphisms in 185 unrelated probands with long QT 
syndrome and in 280 healthy blood donors were not significantly different. These 
data, combined with our previous findings, show that RYR2 mutations are present 
in at least 6/16 (38%) of the catecholaminergic polymorphic ventricular 
tachycardia families, while CASQ2 mutations must be a rare cause of CPVT.