Continuous modeling of primate embryogenesis from totipotency to early organogenesis

Embryo-like structures, or embryoids, are powerful models to investigate early embryonic development. Yet, previous models cover only partial developmental stages, restricting their applications. Here, we successfully generate primate organogenetic embryoids from cynomolgus totipotent blastomere-like stem cells (cTBLCs). cTBLCs, reprogrammed from pluripotent stem cells and stably maintained, can display key totipotent-like molecular and functional features resembling zygotes/2-4-cell blastomeres. cTBLCs spontaneously generate well-organized blastoids that further progress through gastrulation to early organogenesis, thus exhibiting neural-tube-like structures and cardiac-like beating activity. Using single-cell RNA sequencing (scRNA-seq), we visualized stepwise cell-state transitions from cTBLCs to organogenetic lineages and identified an intermediate 8-cell/morula-like state. Interestingly, we uncovered a dynamic cascade of regulatory networks originating from cTBLCs, which represented an intrinsic developmental initiation program occurring independently of classical fertilization-associated events. Together, the cTBLC platform provides a unified in vitro framework to investigate developmental initiation, early lineage specification, and organogenesis.