The regulation of the genome outside of the context of the nucleotide sequence is referred to as epigenetics; it is both a stable and dynamic regulator of gene activity and function. Direct modifications of nucleotides via methylation and/or modifications to the histones in the surrounding chromatin constitute the realm of epigenetics markers, which are coordinated via enzymatic modifications. An additional level of transcriptional and translational regulation occurs via noncoding RNAs; many varieties of these are known (i.e., microRNA, piRNA, siRNA etc.) but are only beginning to be appreciated. The centrality of epigenetics to reproduction begins with the critical role of histone and DNA methylation in the early zygote and during formation of new germ cells in order to reset for the next generation, although the transgenerational persistence of some markers reveals the incompleteness of these processes. The silencing of one X chromosome in female mammalian cells and the imprinting of genes in order to control parent-of-origin allelic expression are primary examples of epigenetics in reproduction. More recently, an emphasis on epigenetic changes in the brain have emerged; these appear to be highly dynamic, impacted by steroids and responsive to environmental cues, including positive or adverse experience, toxins, and endocrine-disrupting compounds. The importance of epigenetics to the enduring effects of hormonally mediated sexual differentiation of the brain and behavior and the timing of puberty are emerging areas of interest. A review of current methodological practices is presented as a guide to further understanding in this rapidly changing field.
McCarthy, M. M., & Rissman, E. F. (2014). Epigenetics of Reproduction. In Knobil and Neill’s Physiology of Reproduction: Two-Volume Set (Vol. 2, pp. 2439–2501). Elsevier Inc. https://doi.org/10.1016/B978-0-12-397175-3.00052-1