Elevated methylation of the RXRA promoter region may be responsible for its downregulated expression in the myocardium of patients with TOF

Abstract

As an important component of retinoid acid signaling pathway, the retinoid X receptor α (RXRA) is considered to play an important role in the pathogenesis of tetralogy of Fallot (TOF). The expression level of RXRA mRNA and the methylation status of the RXRA promoter region in 26 patients with TOF and 6 controls were detected using real-time PCR and bisulfite-specific PCR and cloning-based sequencing, respectively. Dual-luciferase reporter assays, combined with in vitro methylation assay, were performed to determine the transcriptional regulatory activity of unmethylated and methylated CpG regions in the RXRA promoter. The mRNA expression of RXRA in the right ventricular outflow tract (RVOT) myocardium was significantly decreased in patients with TOF compared with that in the controls. The methylation status of region -1453 to -1000 containing CpG sites 1-23 in the RXRA promoter region was higher in patients with TOF than that in the controls. This region contained several transcription factor sites. In addition, dual-luciferase reporter assays combined with methylation assay in vitro showed that this region had transcriptional regulatory activity, which can be depressed by the methylation of this region. The elevated methylation at RXRA promoter may be responsible for the downregulated mRNA expression in RVOT myocardium of patients with TOF.