Wednesday, January 05, 2005

The death of a very special chimpanzee

CLINT, the chimpanzee whose genome sequence will soon be published, has died. His demise has sparked a debate about whether more effort should be made to preserve samples from the individuals that are sequenced.

"The manifestations of these sequenced genomes must be preserved for posterity. If anyone wants to go back and study them, they have to have something to go to," says Robert Hanner of the Coriell Institute for Medical Research in Camden, New Jersey. "We have already missed many opportunities. It's a damn shame." Like other creatures whose genomes have been sequenced, including entrepreneur Craig Venter and his poodle Shadow, Clint was the living reference point for millions of dollars' worth of genetic code. One of the reasons he was chosen was his youth and clean bill of health: if researchers needed to take more tissue samples to validate the DNA sequence, he would be around to provide them. And as insights into the function of his genes emerged, they would be able to examine his morphology, behaviour and physiology.

But Clint has been put down aged just 24, New Scientist has learned. The Yerkes National Primate Research Center in Atlanta, Georgia, where Clint was kept, will not say what disease he was suffering from.

Hanner has convinced the primate centre to let him ship Clint's body to a museum. Curators there will preserve his remains, but it is unclear if any samples were taken and frozen immediately after his death, before decay set in. It would be a shame if this has not been done, says Evan Eichler of the University of Washington in Seattle, who works on the chimp genome. Two years ago, he worked with Yerkes to set up a programme to keep close watch on sick primates to ensure rapid tissue collection when an animal dies. "It doesn't cost very much," he says.

The Coriell Institute does have two cell lines from Clint, which can be used to work out any kinks and gaps in the chimp sequence. But living cell lines are not the perfect way to preserve a genome, because they mutate and change. They can also die, which is what happened to a few cell lines created during the publicly funded Human Genome Project. The anonymity of the donors meant new lines could not be established, and the lack of back-up cell lines caused trouble when unexpected patterns appeared in the DNA sequence, says Eichler. Ideally, researchers would like to have both cell lines and a variety of frozen samples from each animal that has been sequenced. This would not only preserve the original genome for checking, but also allow researchers to compare gene expression in different tissues, for instance.

These kinds of precautions are especially important for genetically variable creatures such as chimps. Most of the other animals being sequenced come from highly inbred lines, meaning that if the original individual dies, other animals with virtually identical genomes will remain available for study.

The National Human Genome Research Institute in Bethesda, Maryland, is attempting to archive tissue from sequenced animals, says Jane Peterson, director of the institute's comparative sequencing programme. But she thinks the real priority should be to reduce the cost of sequencing.

She points out that sequencing the human genome cost several hundred million dollars. Sequencing Clint cost only about $18 million. If prices continue to fall this steeply, sequencing other individuals will be so cheap that preserving biological material from the first individual of a species to be sequenced will be unnecessary, she says. "We are pushing for the $1000 genome, then the $100 genome."

Thanks to NewScientist and Eurekalert for the press release.

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