Advances in equine cloning may aid insight into human diseases

02/05/04

SEATTLE, WA On May 4, 2003, scientists cloned the first mule, an animal otherwise unable to reproduce, using a cell from a mule fetus and an egg from a horse. Today at the 2004 AAAS (Triple-A-S) Annual Meeting, researcher Gordon L. Woods will discuss the relative healthiness of equine clones as opposed to the health of other cloned animals, asserting that "mules bridge the gap of science" since they are usually born sterile. AAAS is the American Association for the Advancement of Science.

Since Idaho Gem, the research team has seen the birth of two other cloned mules in 2003: Utah Pioneer, born June 9, and Idaho Star, born July 27. The project was a joint scientific effort by researchers Drs. Gordon Woods and Dirk Vanderwall of the University of Idaho and Dr. Kenneth White of Utah State University. All three cloned mule foals will be present at the exhibit hall in the Seattle Convention Center on Sunday, 15 February starting at noon.

While researchers have cloned a variety of other animals, they had been unable to clone horses or their "equine" relatives until Idaho Gem. The research promised potential 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.)

With the successful birth of Idaho Gem, Gordon Woods and colleagues found that increasing the calcium concentrations in the media containing the oocytes -- cells from which an egg or ovum develops by meiosis -- in the cloned embryos may have contributed to the success of their cloning efforts. The authors implanted 305 oocytes in surrogate mares. Each of the three mule clones resulted from embryos exposed to higher calcium concentrations.

Consequently, the successful birth and development of these foals offered new opportunities to explore an alternate method of calcium regulation in equines that may aid understanding of human disease.

Calcium concentrations in equine red blood cells differ from those in humans both within and outside the cells. Equine red blood cells contain calcium concentrations 2.3 times less than in human red blood cells, even though calcium concentrations outside of the cells are 1.5 times higher in the equine than in humans. Woods' team found that increasing calcium concentrations in the fluid holding cloned embryos helped increase calcium within the cells and elevated pregnancy rates seven-fold.

The positive cloning that ensued from manipulating calcium levels in the mule clones provides insight into calcium's role in cell signaling, possibly leading to greater insight into human diseases. As some human cancers and age-onset diseases develop, calcium concentrations escalate in cells. The mule cloning demonstrated that equine cell activation and division rates can be accelerated by exposure to calcium, "suggesting the use of equines as valuable animal models to study human disease," said Woods.

He reported that all three mule foals are healthy and vigorous and are growing and behaving normally. After prototypical pregnancies for equines, the births of the foals in May, June and July last year were normal and unassisted and the each foal stood within 20 minutes of birth.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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