Genome activity during the emergence of mouse embryonic totipotency (morpholino)

Fertilization transforms sperm and egg into a totipotent embryo but the underlying mechanisms are unknown. We here report that gene expression initiates during the gamete-to-embryo transition in mouse embryos. Meiotic exit induced by sperm entry enhances a transcriptionally-permissive epigenetic landscape. Time-course analysis of single embryos revealed a succession of genome-wide transcription 'ripples' initiating within 2 hours. Disrupting key pluripotency transcription factor levels prior to sperm entry had little immediate effect, indicating that different mechanisms engender pluripotent and totipotent states. These findings suggest that a hierarchical gene expression program characterizes the emergence of totipotency during the gamete-to-embryo transition, with broad mechanistic implications for the reprogramming of cellular potency. Two-condition experiment in each Morpholino and cRNA mII injected mouse embryos, Morpholino control vs. Morpholino Oct4A and mcherry cRNA vs Oct4A-mcherry cRNA. Biological replicates: 8 control replicates, 12 Morpholino Oct4A replicates, 12 control cRNA replicates, 11 Oct4A-mcherry cRNA replicates.