Program of monkey embryogenesis and germ cell formation in vitro

Embryo development of post-implantation and gastrulation is a milestone of embryogenesis. However, the fundamental mechanisms underlying this process remain elusive as technological and ethical limitations. Here, we we improved an in vitro culture system that cynomolgus monkey embryos could develop to 20 days without any maternal tissues, which clearly reveal lineage specification, bi-laminar disc generation, amniotic and yolk sac formation, and primordial germ cell like cells (PGCLC). By applying single cell-omics analysis, unsupervised dimensionality reduction and clustering algorithm data show clear, distinct, stepwise development routes for the epiblast, primitive endoderm, trophectoderm and extra-embryonic mesenchyme lineage. We also found development path of PGCLCs, suggesting origin of PGLCs in amnion instead of EPI. Furthermore, signal pathways analysis showed existence of intimate interactions among lineages. By sequencing (scATAC-seq ) assay for transposase-accessible chromatin, we identify transcription factor grammar specifying of each cell type (EPI, PE and TE) and infer potential master transcriptional regulators. Collectively, the results provide the new insight into understanding molecular and cellular dynamics that underlie monkey post-implantation development, especially beyond E13. Our study provides a basic knowledge about regulation of primate pluripotency in vitro for cell replacement therapy.