SOUTH Korea鈥檚 king of cloning has done it again. Woo Suk Hwang has successfully produced the world鈥檚 first cloned dog, an Afghan hound.
The breakthrough is bound to lead to excitement among dog lovers who long to clone their dead pets, but team-member Gerald Schatten, of the University of Pittsburgh School of Medicine, has stern words. 鈥淲e are not in the business of cloning pets,鈥� he says. 鈥淲e perform nuclear transfer for medical research.鈥�
Producing 鈥淪nuppy鈥�, or Seoul National University puppy, was not easy. Hwang鈥檚 team made 1095 eggs containing the DNA of a 3-year-old male Afghan, and transferred them into 123 surrogate mothers. Just three pregnancies resulted: one miscarried, and two others went to term. One of the clone dogs died from pneumonia aged 22 days (Nature vol 436, p 641).
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The team used somatic cell nuclear transfer, the same technique that created Dolly the sheep. To clone Snuppy, the researchers implanted nuclei from his father鈥檚 ear cells into eggs from female dogs that had had their nuclei removed. After being zapped with a small electric shock to start development, the embryos were implanted into the uterus of a surrogate mother 鈥� in Snuppy鈥檚 case, a labrador. The team confirmed that Snuppy was genetically identical to his 鈥渇ather鈥� using DNA fingerprinting.
Successful nuclear transfer in dogs had been hindered by difficulties in getting egg cells to mature in the lab. Hwang got round the problem by using egg cells released naturally from the ovaries into the Fallopian tubes. Snuppy is the latest mammal species to be cloned after sheep, mice, cats, rats, cows, goats, pigs, horses, rabbits and a mule.
There are many research applications for cloning in dogs, says Katrin Hinrichs, of the College of Veterinary Medicine at Texas A&M University, who was the first to clone a horse in the US. 鈥淭here are human diseases for which we have dog models,鈥� she says. 鈥淚t would be of great benefit to have multiple genetically identical animals to study the pathogenesis and treatment of these diseases.鈥�
Inherited diseases, for example, are a serious problem in pure-bred dogs. Many, such as malformed hip joints, are influenced by both genes and the environment, and having clones will enable scientists to tease these factors apart.
Schatten says that cloning dogs is also a step towards cloning canine stem cells. Stem cells can currently only be cloned in mice and humans. With dog stem cell lines, it could be possible to work out the genetic basis of animal traits in cells grown in a dish rather than in the dogs themselves, says Schatten.
Why did they choose an Afghan? 鈥淗aving a distinctive dog means that if we鈥檇 got a dachshund we鈥檇 know that something funny had happened,鈥� he adds.
