Development of maternal Oct4–depleted embryos. Totipotency in maternal Oct4–depleted embryos can be established in the absence of Oct4, and these embryos can maintain pluripotency and complete full-term development, supported by the zygotic activation of the paternal allele Oct4 gene at the late 4-cell stage. The lower panel shows that in the absence of both maternal and zygotic Oct4 expression, the Nanog-positive ICM and Cdx2-positive TE lineages are still established. However, this ICM cannot maintain pluripotency and complete the second lineage separation, and it fails to further develop at around the time of implantation. dpc: days post coitum; dpp: days post partum; ZGA: zygotic genome activation.