A screen for dominant modifiers of the irreC-rst cell death phenotype in the developing Drosophila retina

Programmed cell death (PCD) in the Drosophila retina requires activity of t he irregular chiasmC-roughest (irreC-rst) gene. Loss-of-function mutations in irreC-rst block PCD during retinal development and lead to a rough eye p henotype in the adult. To identify genes that interact with irreC-rst and m ay be involved in PCD, we conducted a genetic screen for dominant enhancers and suppressors of the adult rough eye phenotype. We screened 150,000 muta genized flies and recovered 170 dominant modifiers that localized primarily to the second and third chromosomes. At least two allelic groups correspon d to previously identified death regulators, Delta and dRas1. Examination o f retinae from homozygous viable mutants indicated two major phenotypic cla sses. One class exhibited pleiotropic defects while the other class exhibit ed defects specific to the cell population that normally undergoes PCD.