ID2 and atrial fibrillation: mRNA levels for six transcriptional factors (NR3C2, T2, SREBF2, KLF6, SREBF1 and RELa) were higher in immature NP as compared to AF regions, while mRNA levels for another seven transcriptional factors (HIF1A, ID3, FOXA2, RUNX1, NFIb, ID2 and CEBPb) were higher in immature AF as compared to NP regions.