First Mule Cloned

Scientists have cloned the first mule, an animal otherwise unable to reproduce. While researchers have cloned a variety of other animals, they have been unable to clone horses or their "equine" relatives until now. The new research, appearing in the 30 May 2003 issue of the journal Science, may thus offer insights into cloning other species that have difficulty reproducing on their own, including many endangered species.

Mules are created by breeding a male donkey with a female horse, producing an animal with 63 chromosomes. (Donkeys have 62 and horses have 64.) Initial observations indicated that equine reproduction may involve unusually high levels of intracellular calcium. Gordon L. Woods and colleagues found that increasing the calcium concentrations in the media containing the oocytes and the cloned embryos may have contributed to the success of their cloning efforts.

The authors implanted 305 oocytes in surrogate mares. Two additional mares were still carrying fetuses when the first foal was born on May 4, 2003. The foal is named Idaho Gem, and has thus far developed normally, according to the authors.

Support for this work was provided by the Idaho Equine Education Bill and by D. W. Jackson and the Jackson Family Foundation, Inc. This work is part of the Idaho Agricultural Experimental Station Series, A3A03. G.L.Woods, K.L.White, and D.K. Vanderwall are principals of ClonE2, a company involved in equine cloning, and CancEr2, a company focused on human cancer.

—Kathy Wren

2 June 2003