Hwang's team put together 1095 eggs containing the DNA of a three-year-old adult male Afghan, and transferred them into 123 surrogate mothers. Just three pregnancies resulted: one miscarried , and two others went to term. One of the clones died from pneumonia at 22 days old.
"Professor Hwang and his colleagues are to be congratulated on another great success," says Ian Wilmut, creator of Dolly the sheep, at the University of Edinburgh, UK.
Hwang's team used somatic cell nuclear transfer, the same technique used to create Dolly. To clone Snuppy, the researchers implanted nuclei from his father's ear cells into eggs from female dogs, having removed the eggs' nuclei. By passing a small electric shock to start development, the embryos were implanted into the uterus of a surrogate mother, which was a labrador dog. The team used DNA fingerprinting to confirm that Snuppy was genetically identical to his "father".
Successful nuclear transfer in dogs has been elusive until now because it is difficult to get egg cells to mature in the lab. Hwang used naturally ovulated egg cells, those which have naturally been released from the ovaries into the fallopian tubes. Snuppy is the latest mammal to be cloned after sheep, mice, cats, rats, cows, goats, pigs, horses, rabbits and a mule.
Inherited diseases such as malformed hip joints are a serious problem in purebred dogs which are due to both genetic and environmental factors, and having clones will be enable to have dogs without these problems.
Schatten, who was part of Hwang's team, says that the cloning of dogs is a step towards the cloning of canine stem cells. Stem cells can currently only be cloned in mice and human cells. "Once stem cells can be established it may be possible to learn about the genetic basis of traits by studying cells in a dish rather than in the dogs themselves," he says.
But despite Schatten's warning, many people are likely to immediately look to the possibility of cloning beloved pets. "I am sure that some people will think that it is worth spending money to have a puppy with a specific genotype," says Hinrichs.
Source: The New Scientist