Genes that help one creature live longer could hasten the death of another. A new study shows that genetic variations that confer longevity in some fruit flies often turn out to have adverse effects on flies of the opposite sex or those in a different environment.
Researchers have found mutant forms of genes in flies and worms that lengthen the animals' lifespans, and hope to identify similar life-extending genes in people. But whether certain genes can consistently lengthen lives is a matter of debate. Studies in several organisms have shown that gender and environment affect thebehaviour of genes.
In an attempt to gauge the extent of these effects, Trudy Mackay at North Carolina State University in Raleigh and her colleagues recorded the lifespans of inbred male and female flies raised on different diets at different temperatures. Using genetic mapping techniques, they then searched for genetic variations that correlated with long lifespans.
Each of the 17 variations that Mackay's team found increased longevity only in certain environments, or in a sex-dependent manner, or both. Ten variations that made flies live longer under some conditions made flies die sooner under others. One variation, for example, made females live longer if they experienced a hot spell early in life but die sooner if they lived at constant room temperature, with no effect on males.
"What's really exciting about the study is its relevance to the evolution of ageing," says John Tower, an expert on fruit fly ageing at the University of Southern California. It highlights the fact that mutations that decrease lifespan in some situations are nonetheless selected during evolution because they prove beneficial under other circumstances.
James Curtsinger at the University of Minnesota in St Paul recently performed similar studies, however, and found that environment or gender had virtually no effect on longevity-associated genetic variations. Although he describes the Macka
Contact: Claire Bowles