Polarity of the mouse embryo is established at blastocyst and is not prepatterned

摘要: Polarity formation in mammalian preimplantation embryos has long been a subject of controversy. Mammalian are highly regulative, which led to the conclusion that polarity specification does not exist until blastocyst stage; however, some recent reports have now suggested predetermination egg. Our time-lapse recordings demonstrated first cleavage plane is predetermined mouse Here we show that, contrast previous claims, two-cell blastomeres do differ and their precise future contribution inner cell mass and/or trophectoderm cannot be anticipated. Thus, all evidence so far strongly suggests absence axes We observe ellipsoidal zona pellucida exerts mechanical pressure space constraints as coalescing multiple cavities restricted one end axis blastocyst. propose these cues, conjunction with epithelial seal outer layer, lead embryonic-abembryonic axis, thus establishing embryo.