Immunologists and stud farmers welcome healthy foal copy.
The world's first cloned foal has been born - to her genetically identical mother1. Previous celebrity clones, including Dolly the sheep, received their DNA from a donor but were raised in the wombs of unrelated surrogates.
The new arrival challenges the idea that for an embryo to survive, it needs to be recognized as different by the mother's immune system. The modified cloning technique might also produce copies of champion horses.
The foal, called Prometea, was created in the lab by fusing an adult skin cell and an empty egg from a female horse, then returning the resulting embryo to the female's womb after a few days. She is perfectly healthy and genetically identical to her mother, says team leader Cesare Galli of the Laboratory of Reproductive Technologies in Cremona, Italy.
Prometea's good health is a pleasant surprise. Inbred mice are more prone to abortion than genetically dissimilar animals, explains immunologist Julia Szekeres-Bartho of Pecs University in Hungary. Cloned animals frequently die in the womb; those that survive often have genetic defects and physical deformities.
The research increases concerns that a human could give birth to her cloned twin. "If it's possible in a horse, it should be possible in a human," says Szekeres-Bartho. "But I don't think it has any practical relevance." Human reproductive cloning is illegal in many countries.
Despite intense efforts, equines have proved hard to copy. The first cloned mule, Idaho Gem, was born earlier this year to an unrelated surrogate, several years after the births of cloned cows, goats and pigs. Prometea - named after the mortal of Greek mythology who stole fire from the Gods and gave it to man - was the only one of 17 implanted embryos to survive.
"The horse has been kind of a toughie for us," says cloning expert Robert Godke of Louisiana State University in Baton Rouge. Breeding seasons are short and eggs are hard to come by. Cesare's team put an eight-day-old embryo into a mare five days after ovulation. This may have helped it to develop, Godke speculates.
"It's a technological achievement," says Ian Wilmut of the Roslin Institute in Edinburgh, UK, whose team created Dolly the sheep.
The race is now on to produce copies of show horses. Many are castrated and cannot breed naturally. "The quality of the sport would be upgraded," says Galli. "It would be like putting ten Ronaldos against ten Beckhams."
Cloning champions may become big business. French company Cryozootech, based near Paris, charges E5000 (US$5,700) for the removal, culture and ten-year cold storage of equine tissue samples. "We have a number of cells stored from horses of high value," says company director Eric Palmer. As the technology improves, punters may expect to pay several hundred thousand euros to see their frozen filly race again.
“It's a technological achievement Ian Wilmut , Roslin Institute”
Although the clones may look similar to their DNA doubles, it's not yet known whether they will retain the same temperament and sporting ability. Trainers are still likely to play a crucial role, says Galli.
The real hurdle may be their acceptance within the horse-breeding community, he cautions. Thoroughbred horses produced by artificial insemination, for example, are not recognized as pedigree animals. "Whether the herd book would register a [cloned] animal like this has yet to be seen," says Galli.
Galli, C. et al. A cloned foal born to its dam twin. Nature, 424, 635, (2003).