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First Horse Cloned Successfully in North America

America has its first cloned horse.

Texas A&M University researchers, who teamed up with French scientist Eric Palmer, Ph.D., of Cryozootech, announced this week that a 6-week-old colt was successfully cloned using skin cells from a performance horse in Europe. The colt, named "Paris Texas," is active, healthy and steadily growing at TAMU.

"He's bay with a big white blaze, beautiful eyes, and four white stockings. He's real forward, a real nice foal. Everything is completely normal about him,” said Katrin Hinrichs, D.V.M., Ph.D., professor in the College of Veterinary Medicine at TAMU, who led the cloning team on the project.

"Dr. Palmer took a small piece of skin from the donor animal and grew the cells up in culture and froze them, and he shipped them to us. We did the cloning procedure here, cultured the embryo, and transferred it to one of our recipient mares, who foaled here in the hospital."

Paris Texas is the fourth equine clone to be born in North America, but he is the first horse foal (the other three were mules) and the first to be cloned from adult cells in North America. The mule clones were produced from cells from a fetus.

The TAMU team does all of its cloning work in vitro, or in the laboratory. Rather than getting oocytes (eggs) from mares right before they ovulate (the procedure used to produce the mule clones), TAMU researchers harvest oocytes from mares at other points in the cycle and mature them in an incubator. The scientists then perform nuclear transfers, in which they remove the nucleus from an egg cell (containing the cell's genetic material) and place a donor cell into the enucleated egg. The eggs are then activated, or stimulated to start dividing to form an embryo. Resulting cloned embryos are cultured in the laboratory for seven days, and once they are deemed ready, the scientists transfer them nonsurgically into the recipient mare's uterus just as they would in normal embryo transfer procedures.

About 400 oocytes were cultured during the TAMU project, and the cloning process produced six embryos. Only one pregnancy resulted, and this was carried to term. The grade mare that carried the clone (Greta) has been a part of the reproduction herd at TAMU for about four years.

The colt will be used as breeding stock in Europe, but is unlikely to be a competitor.

"We're looking for a way to save valuable genetics," Hinrichs said. "This horse, genetics-wise, should produce exactly the same sperm and should be able to sire foals with the same genetic makeup as the donor animal."

TAMU has several pregnancies from cloned embryos that are currently gestating and due for arrival in 2006. All were produced using donor cells from American horses.

"We're so excited about what we're learning about the horse oocyte,” Hinrichs said. “We're looking at different methods for treating the donor cells before the nuclear transfer procedure and activating the egg afterward, looking at more ways to build on our results of the study that produced Paris Texas."