The ins and outs of programmed cell death during C. elegans development.

During the development of the C. elegans hermaphrodite, 131 of the 1090 cells generated undergo programmed cell death. Genetic studies have identified mutations in 14 genes that specifically affect this process. These genes define a genetic pathway for programmed cell death in C. elegans. Two genes, ced-3 and ced-4, are required for cells to undergo programmed cell death, while a third gene, ced-9, protects cells that should live from undergoing programmed cell death. The proteins encoded by ced-3 and ced-9 show significant similarity to proteins that affect programmed cell death in vertebrates, suggesting that the molecular cell death pathway in which ced-3, ced-4, and ced-9 act has been conserved between nematodes and vertebrates.