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Science leads a hand - Researchers clone mule

Friday, May 30, 2003

WASHINGTON -- The first member of the horse family to be cloned is a mule named Idaho Gem, the genetic brother of a champion racer. Researchers say two other mule clones are expected to be born this summer.

The May 4 birth of Idaho Gem adds mules to the barnyard of cloned animals that already included sheep, cows, pigs, cats and rodents.

University of Idaho researchers cloned the mule using a cell from a mule fetus and an egg from a horse. Idaho Gem is the genetic brother of Taz, a champion racing mule, and the researchers said the cloned mule also will be trained to race.

Cloning a mule is particularly unusual because such animals, hybrids from a donkey and a horse, are almost without exception sterile and unable to produce young.

"A mule can't do it himself, so we thought we would give it a hand," said Gordon L. Woods of the University of Idaho, the leader of the mule cloning team.

Now, said Woods, he plans to use the same techniques that worked on Idaho Gem to clone horses.

"We think the same sort of advances that we had to make to produce this cloned mule are important for cloning horses," said Woods. He is first author of a report appearing Friday in the journal Science.

Other researchers, however, said they expect the birth later this year of cloned horses produced by techniques slightly different from that used by the Idaho team.

Mules are bred by mating a male donkey with a female horse.

The breeding success is about the same as among horses alone. Mating a male horse with a female donkey produces an animal called a hinnie.

Both mules and hinnies can be either male or female, but they are almost invariably sterile.

Champion bloodline

Taz, Idaho Gem's brother, is a champion on the mule racing circuit in California and Nevada. Taz has gained fame in showdown races with another mule, Black Ruby, who has dominated the circuit.

To clone the racing mule's brother, researchers bred Taz's parents, a jack donkey and a horse mare, and allowed the resulting fetus to grow for 45 days. This provided the DNA needed for the clone.

The researchers then harvested eggs from horse mares. After removing the nucleus from each egg, the researchers inserted the DNA from the male fetal cells. The eggs were then placed into the wombs of female horses.

Out of 307 attempts, there were 21 pregnancies and three carried to full term. Idaho Gem was born on May 4 and Woods said identical mule brothers will be born in June and August.

Donald W. Jacklin, a businessman in Rathdrum, Idaho, paid $400,000 to finance the four-year mule cloning project.

"Our first goal was to clone an equine, but I have a special interest in mules," said Jacklin, who is president of the American Mule Racing Association.

Since mules usually are sterile, racing mule owners cannot breed new animals from proven race stock to build up their stable as thoroughbred and quarter horse owners do. Mule cloning could offer an answer.

For that reason, said Kate Snider of the American Mule Racing Association, "cloning a brother to Taz is a very big deal."

Jacklin said there are more 200 members of the mule racing organization and that 70 to 80 mules race each year on a circuit of tracks in California and Nevada.

Woods said to clone the mule, he and his researchers bathed the horse eggs in different concentrations of calcium. He said the calcium ratio that has been used for cloning other mammals produced only two pregnancies out of 132 attempts and no births. Higher calcium concentrations had better luck, leading to Idaho Gem and two other full-term pregnancies.

Also, unlike other researchers, the Idaho team placed the manipulated eggs into the womb without allowing the embryo to grow in a laboratory dish.

Experts applauded Woods' success.

"This is the first cloned equine, so it is a very important advance," said Katrin Hinrichs, a professor at Texas A&M and the leader of a group of horse cloning researchers.

"What is encouraging about this Idaho report is that the foal was born normally and had no problems," said Hinrichs. "Some species, such as cattle, seem to have problems with cloning."

Hinrichs said the result was particularly encouraging because her team is also attempting to clone an equine.

She said they used a technique different from Woods, allowing the cloned embryo to grow to a later stage in development before implanting in the womb. Hinrichs said that out of five manipulated eggs, her team has produced one long-term pregnancy and expects a mare to give birth to a cloned horse in November.

Hinrichs said she has been told that another group of researchers may clone a horse even sooner. A mare carrying a cloned fetus is expected to deliver in Italy this summer, she said.

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On the Net

  • Science: www.sciencemag.org


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