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Monday, 11 February, 2002, 15:11 GMT
Fresh warning over cloning dangers
The cloning process
Cloning: An imprecise technology with a low success rate
Helen Briggs

Scientists have issued a fresh warning about the dangers of cloning after new research found some mouse clones died young.

The possible negative long-term effects of cloning give cause for concern about attempts to clone humans

Atsuo Ogura and colleagues
Obesity, problems with the immune system and genetic defects have been seen in many animal clones, but this is the first link between cloning and early death.

It gives new cause for concern about attempts to produce a human baby clone, says the team in Japan responsible for the latest study.

Researchers at the National Institute of Infectious Diseases in Tokyo found that 10 of their 12 mice clones died young.

The rodents were found to be suffering from severe pneumonia, liver failure and tumours.

Spontaneous abortion

The scientists believe the cloning process itself may have damaged the immune systems of the mice.

But they say other factors, such as the underlying genetics of the mice and the type of cell from which they were cloned, could also be to blame.

In the journal Nature Genetics, they write: "Much controversy has been generated over the ethics of human cloning.

"The possible negative long-term effects of cloning, as well as the high incidence of spontaneous abortion and abnormal birth of cloned animals, give cause for concern about attempts to clone humans for reproductive purposes."


Dolly the sheep is still alive, but she is the only animal clone being closely studied for signs of ageing. Her keepers at the Roslin Institute in Scotland recently disclosed that she was suffering from arthritis.

Dr Harry Griffin from the Roslin said the implications of the mouse study for Dolly were unknown.

Cloned calf (BBC)
Many cloned animals are born diseased
"No doubt if Dolly dies before her duly allotted time, it will be put down to premature ageing," he told BBC News Online. "But you can't conclude anything from a single animal."

Different research groups around the world have produced more than 100 mice clones.

Dr Griffin said he would be surprised if all such animals were found to have a shortened lifespan. The animals' early death could be down to the cell type used for cloning or the technique used, he said.

"It's yet another reason why nobody should be attempting to clone a child," he added.

Unethical procedure

Cloning is currently an imprecise technology, with a very low success rate.

Many animals are born diseased or deformed, which has led to widespread condemnation of attempts by a handful of people to produce a cloned human baby.

Dr Donald Bruce, a bioethicist who heads up the Church of Scotland's Society, Religion and Technology Project, told BBC News Online that the Japanese study was a damning piece of research that should serve as a stark warning to those thinking of cloning humans.

"I would be cautious about extrapolating from one mouse paper under one set of conditions to all types of animal cloning, but for human cloning, this is another adverse indicator, to add to problems in pregnancy, Dolly's arthritis and the French paper on problems with a clone of a clone," he said.

"In this case, the risk of creating children who were likely to have much shorter life spans and problems with immune systems or liver function, it would be unethical to attempt the procedure."

The BBC's Helen Sewell
"The scientists also say life expectancy could depend on many factors"
Dr Atsuo Ogura, Genetics researcher
says it is very difficult to draw general conclusions about cloning from these results
Professor Ian Wilmut, Roslin Institute
"We need to know a lot more about cloning and we should be cautious about how we use it"
See also:

04 Jan 02 | Sci/Tech
Dolly's arthritis sparks cloning row
04 Jan 02 | UK
Head-to-head: Cloning
04 Jan 02 | Sci/Tech
Animal cloning: What is the future?
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