After much patience and perseverance, dogs can now officially be added to the list of animals, including sheep, cats and horses, that have been successfully cloned. Researchers in South Korea led by Professor Woo Suk Hwang - the team that created the world's first cloned human embryos - have cloned an Afghan hound named 'Snuppy', named for Seoul National University puppy. As reported in this week's Nature, the puppy was born by Caesarean section to his surrogate mother - a yellow Labrador retriever - in a feat that had confounded all those who had tried before.
Like Dolly the sheep, the first mammal to be cloned, Snuppy was cloned using SCNT. In this case, genetic material was removed from skin cells taken from the ear of a three year-old male Afghan hound and inserted into a mature egg whose nucleus had been removed. The egg was treated chemically to jump start cell division and then transferred to the surrogate to develop into the genetically identical 'twin'.
What makes this study different from previous clonings is the difficulty with which it was accomplished. In the past, the dog's reproductive biology has posed an insurmountable challenge to other scientists. Dogs only ovulate once or twice a year, and there are no signs that indicate when they are about to begin. And unlike other animals, when they do, the eggs are immature. The scientists in South Korea had to collect mature eggs from the donors' oviduct, which is more difficult than extracting them from their ovaries. In addition, the Seoul team is the first to grow dog embryos in the lab. But even here, the efficiency is low. Out of 1,095 embryos transferred to 123 female dogs, only three pregnancies resulted and only two dogs were carried to full term (60 days). The second dog died of aspiration pneumonia after 22 days.
However small the results, it does bring researchers closer to cloning canine stem cells to study the causes and treatment of dog diseases and then of many human diseases, such as dementia, diabetes and blindness.
'We are not in the business of cloning pets,' said Gerald Schatten of the University of Pittsburgh School of Medicine who consulted with the research team in Seoul. 'This is to advance stem cell science and medicine, not to make dogs by this unnatural method', he added.
Though not the purpose, this accomplishment does raise questions on whether dogs can and should be cloned as pets or for competitive, prize-winning purposes. As it is, cat clones engineered at Genetic Savings and Clone in Sausalito, California can cost up to $50,000. Dogs would be more expensive because the process is more difficult.
In response to the cloning, Professor Ian Wilmut of the University of Edinburgh, emphasises the necessity for a global ban on human reproductive cloning, given this team has demonstrated the ability to clone one more mammalian species.