Figure. Developmental process of mouse primordial germ cells (PGCs). PGCs are specified from a pluripotential cell population by the functions of extracellular stimuli, including bone morphogenetic protein (BMP) signaling, as well as by transcriptional regulatory molecules such as Blimp1, Oct3/4, and Prdm14. During the formation and differentiation of PGCs, they express a number of specific genes, and epigenetic control seems to play an important role in regulating the specific expression of these genes. The specified and differentiating PGCs occasionally develop into pluripotential stem cells under particular conditions, indicating that PGCs sustain plasticity to be converted to a pluripotent cellular status. Hammered lines indicate inhibition of the molecule or the process.