The nematode
Caenorhabditis elegans
has provided an elegant model system for the
study of this process.
3
During development of this organism, the fate of each
cell can be reproducibly defined. Of the 1090 cells produced during ontogeny,
precisely 131 undergo PCD. Genetic analysis has defined lineage-specific
genes that are thought to be involved in the tissue-specific signaling required
for PCD. In addition, a series of genes that appear to be involved in PCD in
all cells have been identified. These include several genes whose products
are involved in phagocytosis of the dead cells as well as a nuclease required
for degradation of genomic DNA in the engulfed cells. Three genes involved
further upstream in the cell death process were also genetically identified:
ced-3
,
ced-4
and
ced-9
.
3
Mutation