GJA5 and atrial fibrillation: TBX5 can transactivate multiple downstream genes such as ANP and CX40 alone or in synergy with transcriptionally cooperative partners, including NKX2-5 and GATA4 [20–22], and loss-of-function mutations in some target genes and cooperative partners, including ANF, CX40, NKX2-5 and GATA4, have been associated with AF [16].