Estrogen Receptors, via paternal epigenome, regulate genes and pathways involved in embryogenesis

Activation of Estrogen receptors (ER) signaling in adult male rats leads to sub-fertility, and whole genome bisulfite sequencing revealed large-scale genome-wide changes in sperm DNA methylation. In this study, we further probed the developmental consequences of altered sperm methylome. An enrichment map analysis of the differentially methylated genes revealed that clusters related to embryo development and its regulation were most enriched. Genes differentially methylated in sperm and implicated in embryo development were selected for validation in sperm by pyrosequencing. DNA methylation and expression levels of these developmental genes were evaluated in resorbed and normal embryos and placental tissues. The aberrant sperm DNA methylation pattern in developmental genes Cdkn1c, Tgfb1, Bmp4, Gab1, Peg3, Myc, Wt1, Sfmbt2, Sox5 and Hoxa3 was reflected in that of the resorbed embryos, along with their deregulated expression after paternal ER agonist treatment. Whereas, the methylation pattern and expression in normal embryos and placenta for most genes were comparable to those of the controls. Additionally, several key developmental pathways, including MAPK, Tgfβ, Wnt, Notch, Hedgehog, and Scf-cKit signaling, were also found to be affected in resorbed embryos sired by ERα agonist-treated male rats. The results indicate that activation of estrogen signaling during spermatogenesis causes aberrant sperm DNA methylation in developmental genes. These defects could be transmitted to embryos, altering the expression of these genes and pathways and thereby impeding embryonic development and reducing litter size and subfertility. The study provides a mechanism by which ERs epigenetically regulate male fertility and subsequent embryogenesis.