We looked further at these TPC2-dependent arrhythmia models to try to determine what the action(s) of the lysosome might be under these circumstances, and therefore by which specific mechanism lysosomal calcium might be contributing to the genesis of rhythm disturbance under our proarrhythmic conditions, and/or in what way TPC2-KO is protective against arrhythmia. The gene discussed is TPCN2; the disease is Arrhythmia.