DNA methylation changes during cleft palate formation induced by retinoic acid in mice

The aim of this study was to analyze epigenetic (specifically, DNA methylation) participation in the mechanisms of cleft palate only induced by maternal exposure to all-trans retinoic acid in mice.

Cleft palate only was induced in fetuses by maternal exposure to all-trans retinoic acid. Their secondary palates were excised for analysis. Cytosine extension assay and restriction landmark genomic scanning were performed to analyze DNA methylation status. The expression levels of the DNA methyltransferases were examined by real-time reverse transcriptase-polymerase chain reaction.

Using cytosine extension assay, on gestation day 14.5, the status of DNA methylation within CpG islands and in global DNA was decreased significantly in all-trans retinoic acid-treated groups compared with the controls (p < .01 and p < .05). In the controls, the status within CpG islands on gestation day 14.5 was significantly increased compared with gestation days 13.5 and 18.5 (p < .01). Using real-time reverse transcriptase-polymerase chain reaction, there was no significant change in the expression of DNA methyltransferases, except on gestation day 18.5. Using restriction landmark genomic scanning on gestation day 18.5, five spots (0.49%) in the controls and one spot (0.1%) in all-trans retinoic acid-treated groups were specifically detected.

These results indicate that changes in DNA methylation may play an important role in the manifestation of cleft palate only caused by environmental factors such as maternal exposure to all-trans retinoic acid.