Is lifespan governed by control of gene activity?

The role of genes in ageing remains unclear. No genes exist just to promote ageing – more likely, some genes are beneficial early in life but harmful later on. Since animals rarely survive to ‘old age’ in nature, natural selection has no chance to eliminate this downside. Recent research on an unusual parasitic worm, by Mike Gardner and Mark Viney in Bristol and David Gems at University College London, suggests that gene regulation could play a major role in controlling lifespan.

Unusually, the nematode Strongyloides ratti has two adult forms: a female-only parasitic form that lives in the rat gut, and a non-parasitic, free-living form. The free-living form is the shortest-living nematode known, with a maximum lifespan of just five days. The parasitic form can live for more than 400 days – some 80 times longer. This is the greatest within-species variation in ageing known to date.

The lifespan difference between the two worms reflects evolutionary adaptation to their very different environments. But they share identical genes, so the differences presumably arise from changes in gene regulation.

The authors suggest that similar mechanisms may underlie the evolution of different lifespans between species – for example, in 5–6 million years, humans and chimpanzees have evolved maximum lifespans that differ by 50 years.

Image: Nematode worm, courtesy of the Wellcome Trust Sanger Institute.

External links

• Gardner MP et al. Extraordinary plasticity in aging in Strongyloides ratti implies a gene-regulatory mechanism of lifespan evolution. Aging Cell 2006;5(4):315–23.