New facets of zona pellucida (ZP) proteins: called oocyte-specific, yet produced by the preimplantation embryo and needed for blastocyst formation

Study question: What does a secreted oocyte-specific protein, ZP2, do inside mouse embryos during cleavage? Summary answer: Contrary to prevalent notion, ZP2 protein synthesis is not silenced after ovulation, but goes on in preimplantation embryos to support the morula-blastocyst transition