Plays a role in the ovary in limiting the number of primordial germ cells (PGCs) that develop directly into gametes, allowing them instead to enter the developmental pathway that produces germline stem cells (GSCs) from PGCs and ensuring lifelong production of gametes from these GSCs. Negatively regulates epidermal growth factor receptor (Egfr) signaling. Probably down-regulates EGFR signaling on intermingled cells, a type of somatic stromal cell which contacts PGCs, and the resultant low level of signaling limits the proportion of PGCs which start gametogenesis, maintaining them in an undifferentiated proliferative state. Not uniformly present at the cell membrane but is concentrated at the interface between germ cells. In late third larval instar ovaries, detected in germ cells but not in somatic intermingled cells and is expressed uniformly in the wing disk. In the embryo, expressed in the ventral midline, tracheal placodes, and cells forming the anterior-most row in each segment. In the larva, becomes detectable at the late second larval instar stage and continues to be expressed throughout the larval period. Increase in the number of differentiating germ cells. Belongs to the peptidase M13 family.