Fig. 2.

Generation of fertile gametes from ESCs in mouse. A Schematic of mouse germline specification in vitro. (i) mESCs were induced to differentiate into EpiLCs for 2 days in the presence of Activin A and bFGF. mEpiLCs were induced into mPGCLCs for 6 days by cytokines including BMP4 and BMP8. mPGCLCs were able to form fertile spermatozoa or oocytes in vivo [5, 6]. (ii) mESCs were transfected with DOX-inducible vectors, differentiated into mPGCLCs through a similar EpiLC process, and then aggregated by adding DOX to induce overexpression of Blimp1, Prdm14 and Tfap2C. The efficiency of PGC derivation was improved just by overexpression of Prdm14 [35]. (iii) mESCs were cultured without 2i before induction for 3 days and cocultured with OP9 cells with MEK inhibitor and without LIF to induce the PGC fate [38]. 2i, GSK inhibitor and MEK inhibitor. (iv) mESCs were induced to differentiate into EpiLCs as described above, which were further induced into mPGCLCs without cytokines by overexpression of Nanog [39]. B Schematic of gamete specification from mPGCLCs in vitro. (i) Male mPGCLCs were cocultured with testicular cells supplemented with RA, BMPs, Activin A and testosterone, FSH and BPE to form mSLCs [9]. Male mPGCLCs were aggregated with somatic cells from embryonic gonads to form reconstituted testes (rTestes) by gas-liquid interphase culture and then cultured with GNDP, bFGF, LIF and EGF to form mGSCLCs [8]. mSLCs, mouse spermatid-like cells,mGSCLCs, mouse germline stem cell-like cells. (ii) Female mPGCLCs were aggregated with E12.5 gonadal somatic cells to form reconstituted ovaries (rOvaries). rOvaries were cultured and differentiated for 5 weeks to further produce mature oocytes [7].