Practice question

Mammalian embryo displays highly regulative development: early blastomeres retain remarkable flexibility and equipotency. Murine four-cell embryo blastomeres remain totipotent as demonstrated by ability of isolated single cell to contribute to both trophectoderm and inner cell mass compartments and to support full-term development when aggregated with carrier cells or transplanted into foster mothers. Single-nucleus RNA sequencing shows equal expression of Oct4 and Cdx2 potentiality. Potency restriction occurs at compaction and blastocyst stage when Cdx2 and Oct4 become mutually exclusive, separating trophoblast from pluripotent inner cell mass lineage irreversibly.