Figure 4.

Establishment of the Embryonic Epigenome during Mammalian Early Development

A schematic model showing sequential establishment of embryonic epigenome in mammalian early development. In pre-ZGA embryos, the epigenome exists as a primitive, transitionary state, featured with widespread, transcription-independent active histone marks and permissive chromatin, as well as missing or immature repressive marks. After ZGA, the active marks of embryonic epigenomes are quickly established (“leading establishment”), while the repressive marks of embryonic epigenomes undergo a slower pace of establishment (“lagging establishment”) at later stages.