CASQ2 and cardiac arrhythmia: Catecholaminergic Polymorphic Ventricular Tachycardia type 2 (CPVT2 – OMIM 611938) is a rare form of life-threating arrhythmia caused by mutations in the gene encoding calsequestrin-2 (CASQ2), a luminal Ca2+ binding protein within the sarcoplasmic reticulum (SR).1 CASQ2 binds and sequesters Ca2+ within the SR, releasing it during the systolic phase of contraction.