Clone experts puzzled as Dolly grows old too soon
By David Derbyshire and Tom Peterkin
Telegraph.co.uk. (Filed: 05/01/2002)
DOLLY the sheep suffers from an unusual form of arthritis rarely found
in ewes her age, raising concerns that cloning could trigger premature
ageing.
Professor Ian Wilmut, the leader of the British team that created Dolly,
said the ailment was likely to be linked to the cloning process and called
for more research into the long-term health of clones.
But he added that Dolly's pampered "celebrity" lifestyle, which has
included overfeeding from visitors, might also have taken its toll.
Animal welfare campaigners said the discovery proved that cloning was
cruel.
Dolly, the first mammal cloned from a single cell from an adult animal, is
enjoying an early retirement at the Roslin Institute in Edinburgh, where
she was born in 1996.
Shortly before Christmas she became lame in the left hind leg. X-rays at
the University of Edinburgh confirmed that she had arthritis in the hip
and knee and she was given anti-inflammatory drugs to ease discomfort.
Tim King, a Roslin vet, said: "Arthritis in sheep is quite common, but it
is comparatively unusual for it to be in these joints. In all other ways,
Dolly is in good health and she has produced six healthy lambs."
Prof Wilmut said the discovery of Dolly's ailment was a disappointment.
The unusual nature of the arthritis meant it was "likely" to be linked to a
limitation in the cloning process.
"It is not possible to know if her condition is in any way a result of her
being a clone," he said.
"However, this occurrence emphasises the need to monitor the health of
a considerable number of clones throughout their expected lifespan to
discover if any condition normally associated with age develops in
unusually young animals."
Dolly's arthritis highlights the difficulty in cloning. Most clones die
before birth or are born with oversized organs and weakened immune
systems. Dolly was the only successful clone out of 247 attempts.
One of the key unanswered questions about Dolly is her true "genetic"
age. Although she was born in 1996, all the cells in her body sprung from
a single cell in a six-year-old ewe. To complicate things, the donor's
udder tissue had been cultured in a laboratory before use.
In 1999 researchers found evidence that she may be ageing prematurely.
Scientists at PPL Therapeutics, the company that worked with the Roslin
Institute to create Dolly, looked at structures in her cells called telomeres.
Made from protein and nucleic acid, these cap the ends of chromosomes,
protecting them from fraying.
Telomeres have been linked to the natural life cycle of cells. Each time a
cell divides, the telomeres become shorter until, after a predetermined
number of divisions, they crumble away, allowing the cell to die.
Dolly's telomeres appear to be shorter than normal, suggesting that she
may be genetically older than chronological age.
Sarah Kite, of the British Union of Anti Vivisectionists, said: "Scientists
seem to think that they can they can mix and match animals' genes in a
controlled way; but actually the control is an illusion.
"No one yet understands exactly how genes work or what the effects
will be on the innocent animals who are subjected to biotechnology.
"Just to produce Dolly involved the wastage of hundreds of sheep who
did not survive or who developed deformities and were miscarried
because cloning technology is imperfect."
This week, PPL Therapeutics announced the birth of five cloned piglets,
born without a specific gene, which should help to prevent their organs
being rejected by humans.
Shares in PPL Therapeutics fell by about 15 per cent after news of
Dolly's illness yesterday, losing some of the gains on Wednesday on
news of the piglets' birth.
Earlier this year, Advanced Cell Techology, an American biotechnology
company, released a report on 24 cows cloned four years ago. Although
it concluded that all were healthy, other scientists said it was too soon to
say whether they were ageing prematurely.
Oryginal:
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