Furthermore, the CM3 population is enriched in several transcripts identified through AF GWAS in humans, many of which are known regulators of automaticity, e.g., Tbx3, or the channels that allow automaticity, e.g., Hcn4 and Slc24a2 (Supplemental Table 3), suggesting that this population could serve as a direct trigger source. This evidence concerns the gene HCN4 and atrial fibrillation.