FIGURE 1. Expression of germ-cell-specific genes during EB development.

RNA was prepared from ES cells, day 3–9 EBs and adult testis, and processed for RT–PCR. Hprt served as a control. Stella is expressed at high levels in primordial germ cells and oocytes but is almost absent from adult testis⁵. Fgls is expressed in the cells surrounding the germ cells⁵. Dazl is expressed only in germ cells in both testis and ovary^7,29. Piwil2, Rnf17, Rnh2, Tdrd1 and Tex14 are germ-cell-specific and expressed in the male gonad⁶.