Genetic analysis of the TBX20 gene promoter region in patients with ventricular septal defects.

Congenital heart disease (CHD) is the most common human birth defect. The morbidity and mortality of CHD patients are significantly higher than normal population even after surgical correction of cardiac defects, which is likely caused by genetic defects. To date, genetic causes for CHD remain largely unknown. TBX20 gene encodes a T-box transcription factor that plays pivotal roles in cardiac morphogenesis and is required for maintaining adult heart function and maturation. Mutations in TBX20 gene have been reported in familiar and sporadic CHD patients. However, the promoter region of TBX20 gene has not been genetically analyzed in CHD patients. As TBX20 functions as a dosage-dependent regulator during the heart development, we hypothesized that the sequence variants within the promoter region of the TBX20 gene may contribute to CHD. In this study, we bi-directionally sequenced the promoter region of the TBX20 gene in 265 patients with ventricular septal defects (VSD) and 242 controls. Within the promoter region of the TBX20 gene, one single-nucleotide polymorphism (SNP), rs336284 (g.4740T>C), and one novel heterozygous variant g.4741 G>A, which was linked with rs336284 (g.4740 T>C), were found in both VSD patients and controls with similar frequencies. A novel heterozygous variant, g.4932 G>A, was found in one VSD patient, but in none of controls, which significantly inhibited the transcriptional activities of TBX20 gene promoter, suggesting that the variant may contribute to the VSD etiology. Therefore, our data provides new information with respect to TBX20 gene mutations in CHD patients.