CASQ2 and cardiac arrhythmia: As previously reported26,27, wild-type mice are relatively insensitive to the administration of caffeine and adrenaline, whereas arrhythmia-prone mice, such as those carrying mutation or deletion of the ryanodine receptor (Ryr2) or calsequestrin (Casq2) genes, progress rapidly to bidirectional ventricular tachycardia (BVT).