U.S. Team Produces First Mule Clone

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But in 2001, the team began to focus on the calcium levels in the fluid surrounding the eggs. After they raised those levels, "the results were impressive and immediate," said Woods. The team established 14 pregnancies in 113 attempts. Eight of the pregnancies continued to at least the 40-day stage when heartbeats were detected.

Cancer Causes

The understanding of cellular biology in horses may offer new insights into cancer research.

The mortality rate for horses with metastatic cancer is eight percent for all cancers and zero percent for prostate cancer. By comparison, the mortality rate in humans is approximately 24 percent for all cancers, and 13 percent for prostate cancer.

"We believe there is a chemical explanation for this," said Woods. Calcium may be the key. Horses have a lower amount of intracellular calcium than humans and correspondingly a slower rate of cell activity. Their metabolism is slow compared to humans. Researchers believe the difference in cellular activity might play a role in cancer development and reproduction.

When Woods and his team increased calcium levels, putting them at a level closer to that of humans, they also increased the pregnancy success rate.

"Horses can be used as a key to understanding humans," said Woods. "It's important to understand what's regulating calcium activity. If there is a way to manipulate it, we could lower the risk of cancer in humans."

The Perfect Stallion

The discovery could also have a major impact on mule racing.

The main sponsor of the cloning project was Don Jacklin, an Idaho businessman with a passion for mule racing. The cloned foal is the full brother of Taz, Jacklin's best racer. Mule racing is gaining popularity in some parts of the country. But because mules are sterile, breeding new champions is difficult. Cloning is the only feasible way for a mule to reproduce.

Preliminary testing showed that the method developed by the researchers to successfully clone a mule should also work with a horse. But the Jockey Club, which regulates American thoroughbred racing, bans cloning.

Too bad, say some horsebreeders. They would love to clone Funny Cide, the remarkable thoroughbred that has collected wins at the Kentucky Derby and Preakness this year and could complete the Triple Crown with a win at the Belmont Stakes next month. Funny Cide is a gelding, a castrated male that is now a genetic dead end.

A summary of the research appears in the current issue of the journal Science.

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