Drosophila epigenome reorganization during oocyte differentiation and early embryogenesis.

In sexually reproducing organisms, propagation of the species relies on specialized haploid cells (gametes) produced by germ cells. During their development in the adult germline, the female and male gametes undergo a complex differentiation process that requires transcriptional regulation and chromatin reorganization. After fertilization, the gametes then go through extensive epigenetic reprogramming, which resets the cells to a totipotent state essential for the development of the embryo. Several histone modifications characterize distinct developmental stages of gamete formation and early embryonic development, but it is unknown whether these modifications have any physiological role. Furthermore, accumulating evidence suggests that environmentally induced chromatin changes can be inherited, yet the mechanisms underlying zygotic inheritance of the gamete epigenome remain unclear. This review gives a brief overview of the mechanisms of transgenerational epigenetic inheritance and examines the function of epigenetics during oogenesis and early embryogenesis with a focus on histone posttranslational modifications.