A concise review on epigenetic regulation: insight into molecular mechanisms

Abstract

Epigenetic mechanisms are responsible for the regulation of transcription of imprinted genes and those that induce a totipotent state. Starting just after fertilization, DNA methylation pattern undergoes establishment, reestablishment and maintenance. These modifications are important for normal embryo and placental developments. Throughout life and passing to the next generation, epigenetic events establish, maintain, erase and reestablish. In the context of differentiated cell reprogramming, demethylation and activation of genes whose expressions contribute to the pluripotent state is the crux of the matter. In this review, firstly, regulatory epigenetic mechanisms related to somatic cell nuclear transfer (SCNT) reprogramming are discussed, followed by embryonic development, and placental epigenetic issues.

Keywords: SCNT; embryogenesis; epigenetic; gametogenesis; histone modification; methylation; pluripotency; polycomb.

Figure 1

The schematic method used to create a cloned animal. A nucleus is taken from a somatic cell (nucleus donor animal) and injected into enucleated Oocyte (Oocyte donor animal). The zygotic cell begins dividing and the resultant blastocyst (embryo) transfers to a foster mother to develop the cloned animal.

Figure 2

Establishment and maintenance of imprinted genes (epigenetic regulation) during mammalian gametogenesis and development. Sex specific establishment of DNA methylation of imprinted genes occurs during gametogenesis. Just after fertilization, protamine changes occur and follow by the second round of reprogramming begins with embryonic preimplantation. After fertilization, active and passive demethylations happen in parental specific manner. de novo methylation happens significantly during both rounds (for review see [61]).