Abstract
Oocyt e development from non-growing to metaphase II (MII) stages is largely dependent on timely and correctly controlling gene expression. During the process of biological or postovulatory aging, the epigenetic mechanisms, particularly DNA methylation, histone methylation, and acetylation, exhibit notable changes in oocytes at various stages of development. These changes mainly result from altered expression of the related catalytic enzymes. In this review, changes in DNA methylation, histone methylation, and acetylation marks and expression of the acting enzymes in aging mammalian oocytes have been comprehensively evaluated in the light of existing studies. Potential interactions between these epigenetic mechanisms are also discussed. Finally, possible interventions to regulate them in order to mitigate the loss of female fertility in the later periods of the reproductive lifespan are reviewed.