CASQ2 and catecholaminergic polymorphic ventricular tachycardia: To determine the cellular origin of ventricular arrhythmias in CPVT, Blackwell et al.260, used conditional murine models with Casq2 expression only in ventricular myocardium or in the specialized conduction system, utilizing the contactin-2 promoter to drive Cre expression and control tissue-specific Casq2 expression.