Furthermore, GWAS of multiple cardiac traits, such as atrial fibrillation and PR interval, identified loci associated with embryonic development-associated genes and genes whose mutations are known to cause serious heart defects, such as TTN, GATA4, MYH6, NKX2-5, PITX2, and TBX52–4. This evidence concerns the gene GATA4 and atrial fibrillation.