Stepwise differentiation from naïve state pluripotent stem cells to functional primordial germ cells through an epiblast-like state

A group of pluripotent cells appearing during mammalian embryogenesis is the source for all the cell lineages that compose the embryo proper. In mice, pluripotent cells are first established in the inner cell mass (ICM) of the preimplantation blastocyst. After implantation, the ICM soon transforms into a cup-shaped epithelium, called the postimplantation epiblast. The two types of pluripotent cells, the ICM and postimplantation epiblast cells, are distinct, based on the differences in their gene expression profiles, epigenetic status, and differentiation capacity. During gastrulation, some of the postimplantation epiblast cells adjacent to the extraembryonic ectoderm are specified as primordial germ cells (PGCs), precursors of the germ cell lineage, in response to bone morphogenetic protein 4 (BMP4). Recently, we succeeded in reconstituting epiblast differentiation and PGC specification in vitro using pluripotent stem cells. Here, we describe the culture method of a stepwise differentiation from pluripotent stem cells to functional PGCs.