Hypomethylation of the TBX20 promoter region was observed in the TOF cases, and the high expression of the TBX20 gene may be caused by activated Sp1 transcription factor binding because of the decreasing methylation at the Sp1 transcription factor binding sites within TBX20_M1.
In the current study, the coding regions and splicing junction sites of the <i>TBX20</i> gene, which encodes a T-box transcription factor key to cardiovascular morphogenesis, were sequenced in 175 unrelated patients with CHD, and a novel heterozygous TBX20 mutation, p.K274X, was identified in an index patient with tetralogy of Fallot (TOF).
These data indicate that the frequency of TBX20 missense mutations occurred in Chinese CHD children is low, but they probably contribute to the risk of atrial septal defect (ASD), total anomalous pulmonary venous connection (TAPVC) and tetralogy of Fallot (TOF) in a small subset of Chinese.
Mutation analysis did not reveal any disease causing sequence variation, however, TBX20 is significantly upregulated in tissue samples of patients with TOF, but not VSD.