Effect of Superovulation Treatment on Oocyte’s DNA Methylation

Abstract

Controlled ovarian stimulation is a necessary step in some assisted reproductive proce-dures allowing a higher collection of female gametes. However, consequences of this stimulationfor the gamete or the offspring have been shown in several mammals. Most studies used compari-sons between oocytes from different donors, which may contribute to different responses. In thiswork, we use the bovine model in which each animal serves as its own control. DNA methylationprofiles were obtained by single-cell whole-genome bisulfite sequencing of oocytes from pre-ovu-latory unstimulated follicles compared to oocytes from stimulated follicles. Results show that theglobal percentage of methylation was similar between groups, but the percentage of methylationwas lower for non-stimulated oocytes in the imprinted genes APEG3, MEG3, and MEG9 and higherin TSSC4 when compared to stimulated oocytes. Differences were also found in CGI of imprintedgenes: higher methylation was found among non-stimulated oocytes in MEST (PEG1), IGF2R,GNAS (SCG6), KvDMR1 ICR UMD, and IGF2. In another region around IGF2, the methylation per-centage was lower for non-stimulated oocytes when compared to stimulated oocytes. Data drawnfrom this study might help to understand the molecular reasons for the appearance of certain syn-dromes in assisted reproductive technologies-derived offspring.