NR4A1 and atrial fibrillation: To characterize the potential role of NR4A1 in atrial fibrogenesis and AF, we performed in vitro mechanistic studies using FBs isolated from LAAs of five individuals with persistent AF and ten control (in SR) donors (Supplementary Table 12) and initially checked the NR4A1 gene and protein expression in these cells (Fig. 4a,b).