Much of our understanding of mammalian preimplantation development comes from studies of mouse embryos. As a consequence, comparatively little is known about early human and non-human primate embryogenesis. To address this, Paul Bertone and co-workers examine the transcriptomes of mouse, human and marmoset preimplantation embryos. By combining single cell RNA-sequencing data from published studies and newly-generated samples, they generate a complete transcriptomic dataset that spans a uniform time course of preimplantation development in the three species. Analysis of this dataset reveals that global transcriptional programs differ in timing and lineage progression between mouse and primates, reflecting the protracted development of primate embryos. The authors further report that the primate maternal program is enriched for ribosomal genes, presumably to allow for extended translation of maternal RNAs until the onset of zygotic genome activation, which occurs later in primates than in rodents. The authors also note differences in transposable element expression across species. Finally, they reveal that, while the transcription factor networks governing cell fate decisions are mostly conserved, the primate pluripotency network lacks certain regulators that operate in mice, whereas the network controlling primitive endoderm specification includes primate-specific components. Together, these findings uncover common and divergent features of mammalian preimplantation development, and provide a valuable analytical resource for the community.
