PATTERNED EPIDERMAL-CELL DEATH IN WILD-TYPE AND SEGMENT POLARITY MUTANT DROSOPHILA EMBRYOS

Programmed cell death plays an essential role in the normal embryonic development of Drosophila melanogaster. One region of the embryo where cell death occurs, but has not been studied in detail, is the abdomin al epidermis, Because cell death is a fleeting process, we have used t ime-lapse, fluorescence microscopy to map epidermal apoptosis througho ut embryonic development. Cell death occurs in a stereotypically strip ed pattern near both sides of the segment border and to a lesser exten t in the middle of the segment, This map of wild-type cell death was u sed to determine how cell death patterns change in response to genetic perturbations that affect epidermal patterning. Previous studies have suggested that segment polarity mutant phenotypes are partially the r esult of increased cell death. Mutations in wingless, armadillo, and g ooseberry led to dramatic increases in apoptosis in the anterior of th e segment while a naked mutation resulted in a dramatic increase in th e death of engrailed cells in the posterior of he segment. These resul ts show that segment polarity gene expression is necessary for the sur vival of specific rows of epidermal cells and may provide insight into the establishment of the wild-type epidermal cell death pattern.