Rossant Janet, Chazaud Claire, Yamanaka Yojiro
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario, M5G 1X5, Canada.
Philos Trans R Soc Lond B Biol Sci. 2003 Aug 29;358(1436):1341-8; discussion 1349. doi: 10.1098/rstb.2003.1329.
The mouse blastocyst, at the time of implantation, has three distinct cell lineages: epiblast (EPI), trophoblast and primitive endoderm (PE). Interactions between these three lineages and their directional growth and migration are critical for establishing the initial asymmetries that result in anterior-posterior patterning of the embryo proper. We have re-investigated the timing of specification of the three lineages in relation to the differential allocation of progeny of the first two blastomeres to the embryonic versus abembryonic axis of the blastocyst. We find that the majority of cells of the inner cell mass (ICM) are specified to be EPI or PE by the mid 3.5 day blastocyst and that this is associated with localized expression of GATA-6 in the ICM. We propose a model for molecular specification of the blastocyst lineages in which a combination of cell division order, signal transduction differences between inner and outer cells and segregation of key transcription factors can produce a blastocyst in which all three lineages are normally set up in an ordered, lineage-dependent manner, but which can also reconstruct a blastocyst when division order or cell interactions are disturbed.
上胚层（EPI）、滋养层和原始内胚层（PE）。这三种谱系之间的相互作用以及它们的定向生长和迁移对于建立导致胚胎体前后模式形成的初始不对称性至关重要。我们重新研究了这三种谱系特化的时间，这与前两个卵裂球的后代向囊胚的胚胎轴与反胚胎轴的差异分配有关。我们发现，到囊胚发育3.5天时，大多数内细胞团（ICM）细胞已特化为EPI或PE，这与ICM中GATA-6的局部表达有关。我们提出了一个囊胚谱系分子特化的模型，其中细胞分裂顺序、内细胞与外细胞之间的信号转导差异以及关键转录因子的分离相结合，可以产生一个囊胚，其中所有三种谱系通常以有序的、依赖谱系的方式建立，但当分裂顺序或细胞相互作用受到干扰时，也可以重建一个囊胚。
