In vitro derivation of germ cells from embryonic stem cells.

Embryonic stem cells (ESCs) have the potential to differentiate into cells of all tissue types, as demonstrated by their capability to contribute to the development of all germ layers in chimeras and to form teratomas. Of interest, however, is the lack of evidence of gametogenic gonadal tissues within teratomas, such as testicular tubules or follicles. Although this may reflect the fact that in vivo germ cell development and subsequent gametogenesis are complex biological processes, the generation of putative primordial germ cells (PGCs) has been reported during the differentiation of mouse and human ESCs in in vitro systems.