At Nature:
“We provided functional evidence that transcriptional activation of MERVL is essential for progression of development in mouse preimplantation embryos. Depletion of MERVL transcripts [retrotransposons] results in embryonic lethality with profound defects in development and is associated with dysregulation of MERVL including their adjacent transcripts, and retaining two-cell-like transcriptome and chromatin state (Fig. 6i). These findings suggest the possibility that MERVL transcription in totipotent cells may act as a switch for the transition from totipotency to pluripotency and is responsible for the onset of differentiation and ontogeny.” – Akahiko Sakashita et al. (March 2, 2023)
The paper is open access.