GENETIC-CONTROL OF PROGRAMMED CELL-DEATH IN DROSOPHILA

A gene, reaper (rpr), that appears to play a central control function for theinitiation of programmed cell death (apoptosis) in Drosophila w as identified.Virtually all programmed cell death that normally occurs during Drosophila embryogenesis was blocked in embryos homozygous for a small deletion that includes the reaper gene. Mutant embryos contai ned many extra cells and failed to hatch, but many other aspects of de velopment appeared quite normal. Deletions that include reaper also pr otected embryos from apoptosis caused by x-irradiation and development al defects. However, high doses of x-rays induced some apoptosis in mu tant embryos, and the resulting corpses were phagocytosed by macrophag es. These data suggest that the basic cell death program is intact alt hough it was not activated in mutant embryos. The DNA encompassed by t he deletion wascloned and the reaper gene was identified on the basis of the ability of cloned DNA to restore apoptosis to cell death defect ive embryos in germ line transformation experiments. The reaper gene a ppears to encode a small peptide that shows no homology to known prote ins, and reaper messenger RNA is expressed in cells destined to underg o apoptosis.