Mechanisms of life span determination in Caenorhabditis elegans

Molecular analysis of several gerontogenes of Caenorhabditis elegans has led to the discovery of at least two life span-controlling pathways. An insulin-like signaling cascade consisting of proteins encoded by the genes daf-2, age-1, akt-1, akt-2, daf-16 and daf-18 regulates dauer diapause, reproduction, and longevity. This pathway regulates all three processes systemically. daf-12 interacts with it, affecting dauer diapause and longevity. Life span extension mediated by this pathway probably results from the activation of an enhanced life-maintenance program, which is normally operative during dauer diapause. A different mechanism is specified by the clock genes clk-1, clk-2, clk-3 and gro-1, which regulate metabolic activity and the pace of many temporal processes including longevity. There is some controversy as to whether the life span extension observed in these mutants requires the activity of daf-16. All known gerontogenes appear to confer resistance to environmental stress, usually multiple stress factors, including oxidative stress, high temperature, and exposure to ultraviolet radiation. Caloric restriction extends longevity substantially, and may act by activating the enhanced life-maintenance program. (C) 1999 Elsevier Science Inc. All rights reserved.