Minor zygotic gene activation is essential for mouse preimplantation development

Abstract

In mice, transcription initiates at the mid-one-cell stage and tran scriptional activity dramatically increases during the two-cell stage, process called zygotic gene activation (ZGA). Associated with ZGA i a marked change in the pattern of gene expression that occurs afte the second round of DNA replication. To distinguish ZGA before an after the second-round DNA replication, the former and latter ar called minor and major ZGA, respectively. Although major ZGA ar required for development beyond the two-cell stage, the function o minor ZGA is not well understood. Transiently inhibiting minor ZG with 5, 6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) resulte in the majority of embryos arresting at the two-cell stage and re tention of the H3K4me3 mark that normally decreases. After releas from DRB, at which time major ZGA normally occurred, transcriptio initiated with characteristics of minor ZGA but not major ZGA, al though degradation of maternal mRNA normally occurred. Thus ZGA occurs sequentially starting with minor ZGA that is critical fo the maternal-to-zygotic transition.