Age-specific demographic profiles of longevity mutants in Caenorhabditis elegans show segmental effects

Demographic profiles of several single-gene longevity mutants of the nemato de Caenorhabditis elegans reveal segmental (age-specific) effects on mortal ity. The mortality profiles of wild-type worms were examined across multipl e replicate cultures containing 100,000 or more nematodes and found to be q uite replicable, although clear environmental effects are routinely found. The combined profile of wild type was compared with those of three long-liv ed mutants to determine how age-specific mortality is altered by mutations in age-1, clk-1, or spe-26. In all four genotypes, death rates fit a two-st age Gompertz model better than a one-stage Gompertz; that is, mortality lev els off at later ages. The largest genetic effect on mortality was that of an age-1 mutation, which lowered mortality more than fivefold at most later ages. In contrast, a spe-26 mutant had a tenfold lower mortality until app roximately 2 weeks of age but ultimately achieved a higher mortality, where as clk-1 mutants show slightly higher mortality than wild type during the f ertile period, early in life, but ultimately level off at lower mortality. Each mutant thus has a distinctive profile of age-specific mortalities that could suggest the time of action of each gene.