The first successful cloning of a mule has unexpectedly shed light on human cancers and other age-related diseases, as well as making possible the cloning of champion horses.

The announcement, in today's issue of the journal Science, makes it now scientifically feasible to clone valuable horses - including studs and racetrack stars, according to U.S. researchers led by Professor Gordon Woods of the University of Idaho.

"We should be able to make genetically identical copies of champion racehorses," Woods told ABC Science Online. "To produce many exact copies, the efficiency of the procedures will need to improve. I am confident the increased efficiency can occur."

Woods believes a new understanding of the biochemistry needed for horse cloning - especially the low calcium levels in horse red blood cells - may offer significant new insights into cell growth, cancer development and ageing in humans.

He notes that stallions do not develop prostate cancer, and that abnormally high intracellular calcium is a root cause of abnormally high cell activity in aged people.

"Embryo cell division and cancer cell division have electrifying similarities with multiple age-onset diseases in humans being characterised by abnormally high levels of intracellular calcium," he said. "The mortality rate for horses … is 8% for all cancers and zero for prostate cancer. By comparison, the mortality rate in humans is approximately 24% for all cancers, of which 13 to 14% are for prostate cancer."

The apparently healthy cloned mule, named Idaho Gem, was born on 5 May 2003 after a normal 346-day gestation in the womb of a surrogate mare.

A mule usually cannot reproduce - it is an infertile hybrid sired by a donkey and borne by a mare - so this one has the further distinction of being the first sterile animal to be cloned. Two further copies of Idaho Gem are in gestation in other mares. Other research teams in Texas and Italy are reportedly expecting the first cloned horses to be born in coming weeks.

Idaho Gem's birth has also raised hopes as well that cloning may become an option to aid the conservation of rare and endangered species, such as Prezwalski's horses and Somali wild asses, both of which have breeding problems.

Woods's team fused a body cell taken from a 45-day-old mule foetus - from the same parents as a champion racing mule known as Taz - with the egg of a horse that had had its nucleus removed.

They overcame earlier difficulties in the in-vitro fertilisation and cloning of equine animals when they realised that calcium levels in their red blood cells were low relative to other mammals, such as cows and humans, and that this might be inhibiting embryo growth.

When the scientists boosted calcium concentrations in the media containing the cloned mule embryos, they began to thrive. In all, 305 embryos were implanted into surrogate mares, resulting in just three successful ongoing pregnancies.

"We've identified a suppressor of intracellular calcium and believe its deficiency is the root cause of abnormally high intracellular calcium," Woods said. He is now working toward critical testing of the effects of deficiencies in the suppressor in human clinical trials.

Mules now join a growing list of cloned animals, including sheep, cows, pigs, rabbits, cats and mice.

The day when clones of Phar Lap - Australia's greatest champion racehorse - might fill a field may still be some time away. And while cloned horses, if and when they eventuate, may be denied the registration necessary to compete in professional sports, some prominent competitions are open to unregistered breeds - including the Olympic Games.

Source of the given news and the copyrights belong to a ABC Online News

Back