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First dog cloned

DOI: 10.1186/gb-spotlight-20050818-02

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The puppy–named Snuppy for the researchers' Seoul National University–was born by cesarean section on April 24 to a yellow Labrador surrogate mother and turned 100 days old yesterday (August 2). A second cloned dog lived just 22 days before succumbing to aspiration pneumonia. A postmortem analysis showed no signs of "any congenital defect due to cloning," said Woo Suk Hwang, the leader of the Korean team. A third pregnancy resulted in a miscarriage.Until now, somatic cell cloning in dogs has been hampered by limited success in maturing canine oocytes in vitro, said Hwang. Such maturation is necessary because unlike those of other domestic animals, canine oocytes aren't mature at ovulation. They're ovulated at prophase of the first meiotic division and undergo maturation in the distal part of the oviduct for at least 48 to 72 hours. The dog's opaque ova also make manipulation difficult.Hwang attributed his team's success to their ability to produce a nuclear transfer construct using in vivo matured oocytes, to transfer it into a surrogate mother at an early stage of development without in vitro embryo culture, and to optimize the conditions for transfer "through trial and error.""We were able to determine the exact ovulation and embryo transfer time," Hwang told The Scientist via E-mail. "Through hormonal and cellular analysis of vaginal smears, we made a database for prediction of ovulation time and for estrus synchronization. Thus, our team could obtain a good number of in vivo matured oocytes with good quality and find good surrogate mothers with an appropriate estrous cycle."Altogether, the researchers collected an average of 12 oocytes from 123 donor females to create nearly 1,500 successfully reconstructed embryos. Of those, 1,095 were transferred back into the same 123 surrogates. The researchers used "naturally collected eggs" rather than the hormone stimulation typical of in vitro fertilization, coauthor Gerald Schatten, of the University of Pittsburgh, note


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