The E129K mutation, involving conversion from an acidic amino acid residue (Glu) to an alkaline amino acid residue (Lys), occurs within the evolutionarily conserved T-box domain in the highly conserved residue found in TBX1 orthologues of human, chimpanzee, rat, mouse, cattle, chicken, Xenopus, and Danio rerio (Figure 1B).We also detected a homozygous single nucleotide polymorphism c.928G → A; p.G310S in one male patient with HDHS, TA, VSD, TGA, pulmonary stenosis (PS), and atrial septal defect (ASD). Here, TBX1 is linked to atrial septal defect.