TBX20 and atrial septal defect: Mutations in several transcription factors such as HAND1, HAND2, TBX5, GATA4, NKX2.5 and TBX20 have been identified in patients affected with distinct congenital heart diseases, such as atrial septal defects (TBX5, GATA4, NKX2.5, TBX20), Tetralogy of Fallot (TBX5, TBX20), ventricular septal defects (HAND2), double outlet right ventricle (HAND1), either syndromic (Holt-Oram; TBX5) or isolated (see for recent reviews [110,111]).