Recently, we have shown that “atrial-like” hESC-CMs and hiPSC-CMs generated by modulating retinoic acid (RA) signalling provide a very promising pre-clinical model system to test pharmacological compounds for atrial selectivity [21] and study AF related arrhythmias due to Kv1.5 dysfunction [22]. Here, KCNA5 is linked to atrial fibrillation.