Theoretical Gompertzian implications on life span variability among genotypically identical animals.

Aging is a highly polygenic trait (Kirkwood, T.B.L., Franceschi, C., 1992. Is aging as complex as it would appear? Annals of the New York Academy of Sciences 663, 412-417) who's underlying mechanisms are still unresolved. Animal models are an important help for understanding this process and a recent report drew attention to a putative gene which causes variability in the life span among genotypically identical mice (de Haan, G., Gelman, R., Watson, A., Yunis, E., van Zant, G., 1998. A putative gene causes variability in life span among genotypically identical mice. Nature Genetics 19, 114-116). De Haan et al. observed that the time between the death of the first and last member of a group of inbred mice (the death range) is controlled by a locus, which they mapped to chromosome 11. The authors conclude that well-known effects like modifiers, suppressors or epistatic genes might not be able to explain how this variability in genetically identical organisms is generated and that such a trait has broad implications for genetic studies of the aging process. Here we give a possible answer to the question of what mechanism could cause such a phenotype. We show that all genes which affect the Gompertz parameters are possible candidates.