The remarkable conservation of physiological cell death mechanisms from nematodes to humans has allowed the genetic pathways of programmed cell death determined in Caenorhabditis elegans to act as a framework for understanding the biology of apoptosis in mammalian cells. However, it has been unclear whether the C. elegans cell death gene
ced-4 would have a parallel in mammalian cell death. In this issue of Cell, Zou et al. (1997) report the biochemical identification of a human cell death protein whose sequence resembles the nematode protein CED-4, providing a spectacular demonstration of the combined power of genetic analysis of a simple organism with biochemistry of mammalian cells.