Methuselah’s DNA: Defining Genes That Can Extend Longevity

Abstract

Longevity variants in model systems such as nematodes or yeast provide an express route to discovery of pathways with the potential to greatly extend longevity. C. elegans in particular has provided an especially rich harvest of mutants and RNA-interference targets that postpone death (and many other indicators of aging) by 1.5- to 2.5-fold, and for one gene (age-1) by tenfold. Studies of yeast survival, under several operational definitions, have also yielded diverse mutants that can conjointly (but not individually) confer a tenfold increase – despite fundamental differences in the nature of the “longevity” phenomenon under study in the two taxa. Given that metazoans diverged from unicellular eukaryotes such as yeast on the order of a billion years ago, it is remarkable that there is any overlap at all between pathways that prolong survival in yeast and nematodes. Parallels have emerged, however, which imply that such shared processes are fundamental to the nature of longevity, and extremely likely to be shared by mammals as well. Due however, to the far greater dependence of mammals on the sustained ability of somatic cells to replicate, we anticipate that the benefits of such changes would be limited to non-mitotic tissues. Although this may be sufficient to impart some longevity advantage to mammals, even that would necessitate efficient targeting to restrict the effects of gene silencing to non-dividing cells. In this regard it is encouraging that some non-dividing cells in mammals, such as those of the central nervous system, exert systemic longevity effects in mammals just as they do in invertebrate model organisms. Any greater benefits are likely to require a detailed understanding of the relevant downstream consequences of those mutations, to allow the selective deployment of just those downstream effectors that have no deleterious effects, with fewer or no limitations as to cell type.