Prenatal retinoic acid up-regulates pulmonary gene expression of COUP-TFII, FOG2, and GATA4 in pulmonary hypoplasia

Abstract 

Purpose

Retinoids play an important role in lung development. Recently, prenatal treatment with retinoic acid (RA) has been reported to stimulate alveologenesis in hypoplastic lungs in the nitrofen model of congenital diaphragmatic hernia (CDH). Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is a transcription factor in the steroid/thyroid hormone receptor superfamily, and targeted ablation of COUP-TFII causes CDH and associated lung hypoplasia in mice. Friend of GATA 2 (FOG2) is a zinc finger-containing protein that modulates the transcriptional activity of GATA proteins. GATA4 is a member of a family of DNA-binding proteins, which is found in the promoter regions of many genes. The COUP-TFII, FOG2, and GATA4 genes, regulated by the retinoid signaling pathway, are located on chromosomes 15q26, 8q23, and 8p23.1 respectively, regions reported to be deleted in individuals with CDH. The aim of this study was to examine the pulmonary gene expression of COUP-TFII, FOG2, and GATA4 in the nitrofen model of CDH.

Materials and Methods

Pregnant rats were exposed to either olive oil or 100 mg nitrofen on day 9 of gestation (D9). 5 mg/kg of RA was given intraperitoneally on days D18, D19, and D20. The fetuses were recovered by caesarean section on D21, and the diaphragm was carefully examined for the presence of a hernia under a microscope. Left lungs were obtained from CDH fetuses and controls and divided into four groups: control (n = 9), control + RA (n = 9), CDH (n = 9), and CDH + RA (n = 9). The relative mRNA expression levels of COUP-TFII, FOG2, and GATA4 were analyzed in each lung by real-time reverse transcriptase–polymerase chain reaction from cDNA generated by mRNA from pulmonary total RNA.

Results

The relative mRNA expression levels of COUP-TFII, FOG2, and GATA4 were significantly increased in CDH + RA lungs compared to control, control + RA, and CDH (P < .05).

Conclusions

Up-regulation of pulmonary gene expression of COUP-TFII, FOG2, and GATA4 after prenatal treatment with retinoic acid in the nitrofen model of CDH suggests that RA may have a therapeutic potential in modulating lung growth. Furthermore, these results support the concept that these proteins work together to regulate downstream target genes that play an important role in the development of lung.

Key words: Retinoic acid, Pulmonary hypoplasia, COUP-TFII, FOG2, GATA4