LAUSR

Preimplantation development in rodent and primate establishes the founding cell population of the foetus in the epiblast and segregates two extraembryonic lineages, trophoblast and hypoblast. Most of our current knowledge about these cell-fate decisions is derived from studies in mouse. However, transcriptional profiling of human embryos has suggested substantial differences to the mouse paradigm. Here, we set out to delineate the primate-specific aspects of preimplantation development. We present a high-quality single-cell RNA-seq dataset from zygote to late blastocyst in marmoset (Callithrix jacchus). In addition, we generated stage-matched samples in mouse (Mus musculus) and re-analysed three human single-cell datasets. Weighted gene network analysis independently identified the establishment of epiblast and hypoblast transcriptional modules. NANOG, SOX2, TDGF1 and TFCP2L1 were highly expressed in the epiblast of all three species. In contrast, KLF17, ARGFX, KHDC3L, LEFTY2 and CTSF represented primate-specific factors of the pluripotency network in vivo. Global features of epiblast and hypoblast segregation included the ERK cascade, apoptosis and extracellular matrix, while we identified elevated levels of BMP and WNT signalling components in primates. Strikingly, the mouse epiblast marker Otx2 is specifically expressed in human and marmoset hypoblast. Our cross-species analysis approach demarcates conserved and primate-specific features of mammalian preimplantation development and provides a rich resource for comparative embryology.