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The cow, her cloned bison calf and a new era in saving endangered species
Next goal for scientists is to use 'Dolly' technique to recreate extinct animal Special report: the ethics of genetics
James Meek, science correspondent Monday October 9, 2000
When Bessie, a regular American cow, goes into labour next month, humankind will be on the threshold of a new era in its efforts to repair the damage it has done to the world's wildlife. US scientists announced yesterday that, if all goes well, Bessie will give birth to something extraordinary - a cloned Indian bison, or gaur, a giant ox-like animal whose existence in the wild of southern Asia is threatened.
By using the technique which created Dolly the sheep to generate endangered animals in the eggs and wombs of common creatures such as cows, researchers have opened the door to a future where even extinct species such as mammoths could walk the earth again.
The scientists, from a commercial firm, Massachusetts-based Advanced Cell Technology (ACT), have already announced plans to recreate one extinct species - a Pyrenean mountain goat called the bucardo, the last one of which was killed by a falling tree in January.
Even before the gaur calf is born, the scientists who created it have given it a portentous name, Noah, after the Biblical character who saved the world's animals from destruction. In their vision, the arks of the future will consist of frozen tissue banks, and disembarkation will be by cloning - with black bears giving birth to pandas, one kind of tiger giving birth to another and, in the remote future, elephants giving birth to mammoths.
"The technology is no longer science fiction. It's very real, and we expect the first endangered species in a few weeks," Robert Lanza, of ACT, said yesterday.
Huge drawbacks
But the plans were criticised by other scientists who said cloning and tissue banks had huge drawbacks compared to other ways of conserving threatened species.
Pointing out that the gaur was not, as ACT claimed, "on the brink of extinction", Bill Holt, of the Zoological Society in London, said: "Unless there's a really special reason - and there may be, in a small number of cases - we should go for much simpler techniques of conservation."
Whatever the application of the technique, ACT has crossed a new line in cloning. To create Noah, Lanza's team took 692 skin cells from a bull gaur which died naturally. Using the "Dolly" technique, they removed the DNA from an equivalent number of ordinary cow eggs, and injected the adult guar cells, with their DNA, into the hollowed-out eggs.
A tiny jolt of electricity fused DNA and egg together and the guar-cow cells began to grow into embryos. Only 81 grew enough to be implanted into cow wombs, only eight cows became pregnant, and five miscarried - reflecting the typically high failure rate of cloning.
Two other embryos were removed early to see how they were faring; Noah appears to be a normal gaur calf, on track to make his appearance next month.
"Most scientists thought this was impossible," said Dr Lanza. "For the first time, a species has been conceived using the eggs and surrogate mother of an entirely different species.
"Up till now there have only been a few reports of this technique of embryo formation in petri dishes. We've taken it out of the lab and into the barnyard, and not only were we able to get embryos, but we've been able to get beautiful little gaurs."
Noah is not strictly 100% gaur, because even though the nucleus of the cow egg is removed, the rest of the egg contains a tiny amount of its own DNA. But Dr Lanza said he believed it would be possible to get round this.
The next goal for ACT is to clone its first extinct animal, the bucardo. After Spanish gamekeepers came across the corpse of the last bucardo, Spanish scientists took tissue samples and froze them, meaning there are likely to be cells with intact DNA which ACT can use to transfer into goat eggs. Goats have already been cloned, so given the closeness of domestic and mountain goats, there would appear to be no major obstacle to regenerating the extinct species.
Saving the panda
Dr Lanza's team is also looking at ways of saving the panda. Its closest relatives are racoons and rabbits, but panda cubs would be a hefty burden for a small animal to become pregnant with, so ACT hopes to use black bears as egg donors and surrogate panda mothers. The firm is harvesting eggs from female black bears shot dead by hunters. The black bear is not an endangered species.
The company has no plans to try to revive long extinct animals such the Tasmanian tiger or the dodo, let alone the dinosaur - although there are major projects under way to try to recover and repair DNA from mammoths and Tasmanian tigers for cloning.
"I have a brontosaurus bone at home weighing 800lbs," said Dr Lanza. "The first thing everybody asks me is: 'Are you going to clone that?' I tell them you need a living cell. Even if you could get one, a brontosaurus weighs 30 to 50 tons - where would you get a female animal to carry one?"
Dr Holt opposes cloning to bring back the bucardo from a single animal. This would result in a population of genetically identical animals, he warned, with all the dire consequences of inbreeding. If disease or environmental change hit a wild population of clones, hesaid, and one animal died, the chances are they would all die.
He questioned whether the complexity and cost of cloning pandas was worthwhile when they could be artificially inseminated, and argued that it was banks of endangered animals' eggs and sperm, rather than tissue, which needed to be created to preserve genetic diversity.
On the likes of mammoths, he said: "We've got enough endangered species which we need to support without bring ing back more which are probably doomed anyway."
Professor David Macdonald, director of the wildlife conservation unit at Oxford University, was more equivocal. "These molecular techniques do hold enormous potential for contributing good in ingenious ways to conservation," he said.
Rescuing lost genes
"There are hierarchies of priorities and, in mine, saving the habitats of existing, viable species is a higher priority. Reconstituting something that's extinct, while having a certain fascination, is less urgent than saving more things from becoming extinct. But I'm not saying this is a waste of time, trivial or wrong."
Dr Lanza denied he and his colleagues wanted to make cloning the focus of conservation. "The aim here is not to use cloning to generate large numbers of animals," he said. "Habitat conservation is the cornerstone of all preservation efforts. But this is a tool to rescue genes that would be otherwise lost."
Species: Panda Status: Endangered. Fewer than a thousand remain in their shrinking natural habitat in south-west China, with 100 in zoos. They have sex rarely, dislike breeding in captivity and are picky eaters.
Cloning potential: High. Chinese scientists have produced cloned panda embryos by inserting a panda cell nucleus into a rabbit egg. US scientists hope to use black bear eggs and surrogate mothers.
Species: Tasmanian tiger Status: Extinct. The last known representative of this striped, wolf-like marsupial species died in a zoo in Hobart in 1936.
Cloning potential: Poor , were it not for the huge effort to bring it back. The New South Wales government has given the Australian Museum in Sydney $1m to do it. But the DNA available for cloning is 134 years old and in bad condition.
Species: Barbary lion Status: Unknown. Thought to be the species which devoured Christians in the Roman circus, the last Barbary lion in its natural habitat, north Africa, was killed in Morocco in 1922, but it is thought some may live on in Middle Eastern zoos.
Cloning potential: Fair , but only if a survivor can be found, or genes can be recovered from hybrids.
Species: Mammoth Status: Extinct 4,000 years. The existence of this furry elephant is known only from bones, tusks, frozen remains in Siberia and cave drawings.
Cloning potential: Poor. Scientists hope to get a crack at injecting an elephant egg with DNA from a frozen mammoth cell, but the DNA is likely to be damaged by its time in the permafrost.