The Drosophila RNA binding protein RBP9 is ex-pressed in both ovarian germline cells and neuronal cells of the adult central nervous system. Expression is limited to postmitotic cells in both cases. It has been suggested that Rbp9 is involved in the regulation of genes that function in cell proliferation or differentia-tion. We examined the effect of ectopic expression of Rbp9 in germline and somatic cells using the Gal4 sys-tem. Over-expression of Rbp9 in various tissues caused severe developmental defects. In particular, expression during mid-oogenesis using nos-Gal4:VP16 caused apoptosis in stage 10 egg chambers. A similar pheno-type has been reported when one of the effector cas-pases of Drosophila, Dcp-1, is ectopically expressed during mid-oogenesis with the same Gal4 driver. Tight control of Rbp9 transcription seems to be critical for the proper development of Drosophila.

Keywords: Apoptosis, Gal4 System, Drosophila, Oogenesis, Rbp9.