Fig 1.
Proposed timing of selection for REject cells during human embryo development.
REjects segregate at the blastocyst stage and undergo apoptosis at the end of 5 dpf/E5. They express the apoptosis-inducing factor BIK, genes associated with programmed cell death such as BAK1, and their selection is regulated by young transposable elements activity. The ICM is instead characterised by the activity of an old nontransposing endogenous retrovirus (HERVH) that acts to suppress young transposable elements. B1, B2, B3, blastocyst stages; BIK, BCL2-interacting killer; dpf, days post fertilisation; EPI, epiblast; HERVH, human-specific endogenous retrovirus H; ICM, inner cell mass; PrE, primitive endoderm; TE, trophectoderm; TrE, transposable elements. Figure generated using BioRender.com.