Ovarian cystocytes can repopulate the embryonic germ line and produce functional gametes.

Ovarian tumors are formed either in the absence of Bam (bag-of-marbles) in germ-line cells or the overexpression of Dpp (decapentaplegic) in ovarian somatic cells. These tumor cells contain spectrosomes characteristic of ovarian germ-line stem cells and the immediate descendents called cystoblasts. We show that pole cells can successfully populate the gonad after transplantation to the dorsal mesoderm of host embryos following germ-band extension. By using this approach, we demonstrate that bam- cells can populate the gonad and become established as germ-line stem cells. Tumor cells containing the wild-type bam gene under heat shock transcriptional control are able to produce functional oocytes. Thus, stem cells/cystoblasts of the adult ovary are capable of forming stem cells in the embryonic ovary and recapitulating the development of the female germ line.