Pregnancy smoking : Tissue- and sex-specific drift of Igf1r and Igf1 methylation in mouse fetuses and neonates

Background: Prenatal smoke exposure (PSE) causes aberrant fetal development and is a risk factor for the offspring9s future health. DNA methylation changes have been shown in children from smoking mothers, but evidence for sex-dependent smoke-induced effects is limited. Insulin like growth factor (IGF) signaling plays a critical role in prenatal tissue growth and maturation. We hypothesized that PSE causes fetal programming of the IGF network. Aim: To assess the effects of PSE on promoter methylation patterns as well as mRNA levels of Igf1r and Igf1 . Methods: Lungs and livers of prenatally smoke exposed fetuses (E17.5) and three day old (D3) offspring were collected and subjected to DNA methylation analysis as well as qPCR. These analyses were followed by correlation analysis to identify possible links between PSE-induced differential methylation status and mRNA levels. Results: Our results suggest that CpG-site specific aberrant DNA methylation patterns of Igf1r and Igf1 vary per sex, organ and time point. Similarly, smoking during pregnancy reduces gene expression of Igf1r and Igf1 in lungs and liver, dependent on sex and developmental stage. Conclusions: We show that PSE sex-dependently alters promoter methylation of Igf1r and Igf1 and also deregulates their gene expression. These findings provide evidence that PSE can cause tissue specific rather than systemic alterations on fetal programming, exemplified by methylation and expression of IGF network representatives. A sex-specific link between PSE, epigenetic modifications and gene expression may be used to identify future targets for therapeutic intervention.