Robert Horvitz used C. elegans to investigate whether
there was a genetic programme controlling cell death.
In 1986, he identified the first two "death genes", ced-3
and ced-4. He showed that functional ced-3 and ced-4
genes were a prerequisite for cell death to be executed.
Later, Horvitz discovered that another gene, ced-9, protects
against cell death by interacting with ced-4 and ced-3.
He also identified genes directing the elimination of the
dead cell, and he showed that the human genome contains
a ced-3-like gene.

We now know that most genes involved in controlling
cell death in C. elegans have counterparts in humans and
are evolutionarily well conserved. In the human signalling
pathway ced-3-, ced-4- and ced-9-like molecules
participate.