Several loci have been identified in the nematode worm Caenorhabditis elegans that, when mutated, can increase life span. Three of these genes,
age-1,
daf-2 and
clk-1, have now been cloned. Mutations in these three genes are highly pleiotropic and affect many aspects of worm development and behaviour,
age-1 and
daf-2 act in the same genetic pathway and have similar effects on the worm,
age-1 encodes a homologue of the
p110 subunit of phosphatidylinositol 3-kinase and
daf-2 encodes an insulin receptor family member,
clk-1 encodes a protein of unknown biochemical function similar to the yeast metabolic regulator Cat5p/Coq7p. The implications of these findings for our understanding of organismal ageing are discussed.