Scientists from the University of Idaho, US, have cloned the world's first animal from the horse family, it was reported last week in the journal Science. The mule, named Idaho Gem by his creators, was born on 5 May 2003 after a normal-length gestation.
Mules are usually the product of a male donkey and a female horse and are unable to reproduce naturally. Idaho Gem is therefore not only the first equine animal to be cloned, but the first sterile animal. It has taken many years of research to be able to clone an animal of the horse family. Gordon Woods, leader of the Idaho research team, said 'the horse system has been a difficult system' because it is more difficult to develop equine eggs and embryos in the laboratory as they do not 'respond well to chemicals routinely used in IVF and cloning'.
Another important difference between Idaho Gem and other cloned animals is that the researchers were careful not to clone from an adult cell. Some scientists believe that Dolly the sheep died prematurely at age six because she was cloned from an adult cell, so Woods' team decided to 'take the aging component out of the equation'. The scientists 're-bred' the parents of a world-champion racing mule named Taz and extracted a somatic cell from the resulting fetus at 45 days old. The DNA from the cell was put into an 'empty' horse egg, the resulting embryo being transferred to a surrogate mare. Two other mares are due to deliver cloned 'twins' of Idaho Gem in June and August 2003, and other scientists say they have cloned horse foals due to be born later this year.
Woods and his team believe that calcium levels are part of the reason why members of the horse family have proved difficult to clone in the past - in order to make the embryo grow, calcium levels in the solution in which the eggs were stored had to be increased. They also speculate that differences between horses and humans at the cellular level may help explain why horses are much less likely to die from cancer - especially prostate cancer - than humans. Approximately 24 per cent of human cancers are fatal, compared to just 8 per cent of horse cancers, none of which are prostate cancer. It is hoped that this development in cloning - funded by Taz's owner and the racing industry - may help research into human cancers, as well as breeding of new race winners.