HCN4 and atrial fibrillation: Indeed, ERRg ChIP-seq peaks overlapped with AF-associated loci around genes encoding cardiac ion channels (CAMK2D, KCNJ5, KCNH2 and HCN4), where active histone marks such as H3K27ac and H3K4me3 in induced pluripotent stem cell (iPSC)-derived cardiac cells were also observed (Extended Data Fig. 4).