MOLECULAR CHARACTERIZATION OF OVARIAN-TUMORS IN DROSOPHILA

Certain female-sterile mutations in Drosophila result in the uncontrol led proliferation of X/X germ cells. It has been proposed that this ov arian tumor phenotype results from the sexual transformation of X/X ge rm cells to a male identity. We present findings inconsistent with thi s model. We demonstrate that the tumorous cells produced by mutations in the ovarian tumor (otu), Sex-lethal (Sxl) and sans fille (snf) gene s are capable of female-specific transcription and RNA processing. Thi s indicates that these ovarian tumor cells still retain some female id entity. Therefore, we propose that mutations in these genes do not cau se a male transformation of the X/X germ line but instead either cause an ambiguous sexual identity or block specific stages of oogenesis. O ur findings indicate that while Sxl is the master sex determination ge ne in somatic cells, it appears to play a more subsidiary role in the germ line. Finally, we demonstrate that the germ line function of Sxl depends on the activity of a specific OTU isoform.