Prometea, world's first cloned horse, born to genetic twin
The birth of the healthy clonal foal, announced in today's issue of the journal Nature, brings to eight the number of mammalian species that scientists have cloned from adult cells, along with sheep, mice, rabbits, goats, cats, pigs and cattle.
But the wobbly-legged creature born at a research facility on the outskirts of Cremona has a claim to fame unlike its fellow clones. It is the first to have been gestated in the womb of the same female that donated the skin cell from which it was grown.
So in giving birth to the clone, the mare was really giving birth to her identical twin sister.
"Basically, she foaled herself," said lead researcher Cesare Galli, of the Laboratory of Reproductive Technology.
The birth has settled one important scientific question: It has put to rest suspicions that a mare's immune system would reject a fetus that was not at least a little bit genetically different from herself — by having, for example, some genes from a father.
In addition, cloning could allow the mass-reproduction of prize-winning runners, jumpers and show horses, scientists said, and could help bolster populations of rare and endangered horse breeds.
Cloning could even allow geldings — males that have been castrated to improve their temperaments — to add their DNA to the equine gene pool for the first time.
They would not be fathers in the traditional sense, since they can't make sperm, but they could contribute skin cells to be made into genetically identical foals, in effect siring their own twin brothers. And those foals would grow up to produce the same sperm the gelding would have.
Galli and his colleagues named the newborn clone Prometea, after the Greek god Prometheus.
The Italian team took a single skin cell from a 6-year-old mare and fused it with an egg cell whose own genetic material had been removed. That newly constituted cell grew in a lab dish into an embryo, which was transferred into the mare's uterus for a standard 11-month gestation.
As has been the case with cloning in other species, the process was inefficient. The team created 841 embryos, all but about two dozen of which died during their first week in laboratory dishes.
The researchers transferred 17 embryos to the wombs of surrogate mother horses, resulting in four pregnancies. Two of those pregnancies ended spontaneously within the first 30 days, and a third aborted after about six months, all for unknown reasons.
Prometea was born naturally at 1:45 a.m. on May 28, weighing 79 pounds, about normal weight for her Haflinger breed. She was up and suckling less than a hour after birth, Galli said.
The foal's birth is notable mostly because of horses' special cultural and economic status in human society — primarily their value as racing and show animals. But don't expect to see clones of champion racers in the more prestigious equine competitions.
The 110-year-old Jockey Club, for example, which manages the official registry for North American Thoroughbreds, last year added language to its rules explicitly precluding cloned horses from registering or participating in races.
In March, the American Quarter Horse Association adopted similar language.
Still, there are many other venues open to cloned horses — including various jumping and dressage events, harness racing and other competitions, said Katrin Hinrichs, a leader in the Texas horse cloning effort.
Bob Curran, vice president for corporate communications at The Jockey Club in New York, warned that genes alone do not make a racer great.
"If you had 10 clones of Secretariat in a race, they wouldn't all finish at the same time," Curran said, referring to the 1973 Triple Crown winner, one of racing's greatest champions.