T-box family genes, including transcription factors important in heart development such as TBX1 and TBX20, have also been reported to be the cause of ASD, AVSD, DORV, LVOTO, TA, TOF, PTA, and VSD [6,7,45,53,64,65]. This evidence concerns the gene TBX20 and familial atrioventricular septal defect.