Friday, August 05, 2005

Telomeres don't dictate lifespan, worms show

Researchers are claiming to have found "conclusive evidence" that the link between longevity and chromosome caps called telomeres is more complicated than thought.

The shortening of telomeres, which cap the end of all human chromosomes and diminish with cell division, has been linked to aging and physical decline. Preventing this shortening has been seen as one approach to extending healthy lifespan.

Jan Karlseder, Andrew Dillin and colleagues at the Salk Institute for Biological Studies have now shown in Caenorhabditis elegans roundworms, however, that this connection isn't so direct.

The researchers have shown that the worms can succumb to old age despite having long telomeres and can move youthfully despite having short telomeres.

"Some long-lived species like humans have telomeres that are much shorter than the telomeres in species like mice, which live only a few years. Nobody yet knows why. But now we have conclusive evidence that telomeres alone do not dictate aging and lifespan," says Karlseder.

The roundworms are ideal for the study because they spend most of their adult life without having a single dividing cell, yet they still show signs of old age.

This raises questions such as whether telomeres in non-dividing cells erode slowly over time.

"Even in very old people, blood cells, which divide continuously, don't have critically short telomeres," says Karlseder. "In humans and, as we know now, in worms, telomere length is certainly not a limiting factor for lifespan."

The study is reported in the journal PLoS Genetics, and is available online.

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