Tissue-specific differential DNA methylation at Igf2/H19 locus in a mouse model for embryonal ethanol exposure

Objective: Maternal ethanol consumption during pregnancy could induce birth defects. Fetal heart, brain and placenta are usually targeted organs. Differential methylation regions (DMRs) in the Igf2/H19 locus are sensitive to environmental conditions. However, the effects of prenatal ethanol consumption on fetal heart, brain and placenta remain largely unknown. The aim of our study is to investigate tissue-specific effects of ethanol consumption during pregnancy on DNA methylation within Igf2/H19 DMRs and the expression of Igf2 in fetal mouse heart, brain, and placenta. Methods: We established a pregnant mouse ethanol gavage model (0.025 ml/g/day; 25% vol: vol). Ethanol was delivered between gestational day (GD) 0.5 and 15.5. Using a MassARRAY EpiTYPER assay, methylation patterns of 4 DMRs, including Igf2 DMR0, Igf2 DMR1, Igf2 DMR2, and H19 DMR, within the Igf2/H19 locus were evaluated in fetal tissues. In parallel, the expression of insulin-like growth factor (Igf2) gene was measured by qRT-PCR and immunohistochemistry. Results: We found decreased DNA methylations at Igf2 DMR1, Igf2 DMR2, and H19 DMR in response to ethanol exposure in murine fetal heart, brain, and placenta, respectively. However, no significant methylation changes were observed at Igf2 DMR0 in all above examined tissues. Importantly, we detected increased Igf2 expression at mRNA and protein levels in corresponding fetal mice brain in response to ethanol exposure. Moreover, for ethanol-treated group, decreased Igf2 expression in fetal mice heart and increased Igf2 expression in fetal mice placenta at mRNA and protein levels were observed compared to controls, although the changes showed no significant differences. Conclusion: Our data indicates that the underlying mechanisms by which fetal developmentally important imprinting genes are dysregulated in a tissue-specific fashion in response to maternal ethanol exposure.