Recapitulating mouse germ-cell specification

A new study by Mitinori Saitou and colleagues reveals that expression of three transcription factors (Blimp1, Prdm14 and Tfap2c) in epiblast-like cells efficiently converts them into primordial germ cell (PGC)-like cells. In these conditions, the mesodermal program that accompanies PGC specification in vivo and in vitro by cytokines is bypassed — culture systems reported previously had included cytokines as well as transcription factors. The authors also show that transcription-factor-induced PGC-like cells contribute to spermatogenesis and fertile offspring.