library_construction_protocol: The single-cell isolation procedures were performed according to the protocol previously described (Ma et al., 2019a). In brief, the pIVC cynomolgus embryos were  dissected by removing the extraembryonic tissues, then the inner embryonic bodies were digested with 500 μL of 1 × TrypLE for 15 min at 37°C and dissociated into single cells by mouth pipetting. Advanced DMEM/F12 containing 10% FBS was added to terminate the enzymatic reaction and the cells were centrifuged at 300 g for 5 min at room temperature, followed by the resuspension with 100 μL pre-cold 0.1% BSA/PBS. An RNA-seq library was prepared by following the instruction manual of the NEBNext UltraII DNA Library Prep Kit for Illumina (New England Biolabs)