20 Years Since 'Dolly'
It was 20 years ago this week that scientists announced the first successful cloning of a mammal — the now-famous sheep Dolly — from a cell taken from an adult animal. [Full story: 20 Years After Dolly the Sheep, What Have We Learned About Cloning?]
The cloning of Dolly by the team at The Roslin Institute, at the University of Edinburgh in Scotland, paved the way for researchers to try cloning a number of other mammals. Prior to Dolly, scientists had been able to clone mammals only by splitting growing embryos.
Since the announcement of Dolly's birth, dozens of other species have been cloned from adult body cells, including many mammals. Here are eight of the mammals that have been cloned in this manner since Dolly:
In 2000, PPL Therapeutics, the same company that worked with The Roslin Institute to clone Dolly the sheep, announced that it had cloned five female piglets from adult pig cells. The piglets were named Millie, Christa, Carrel, Dotcom and Alexis. The findings were published in a 2000 paper (opens in new tab)in the journal Nature.
In 2001, researchers at Texas A&M University cloned a cuddlier animal: a cat. The kitten was born Dec. 22, 2001, to a surrogate mother, according to the findings, which were published in a 2002 (opens in new tab)paper in Nature.
Though the kitten — nicknamed CC, short for Carbon Copy — was genetically identical to the cat Rainbow, the patterns on her fur looked different, likely due to developmental, rather than genetic, factors, the study said. CC had her own kittens a few years later.
Researchers at Texas A&M also cloned a white-tailed deer, nicknamed Dewey, in 2003. Dewey was born to a surrogate mother named Sweet Pea on May 23, 2003, and was cloned from skin cells taken from a deceased white-tailed buck, according to a statementat the time from Texas A&M University. Dewey is still alive today.
In 2003, researchers in Italy cloned a female horse, which they named Prometea. Interestingly, the female that gave birth to Prometea was also the donor of the genetic material, according to the study. The authors noted that the successful cloning of Prometea helped dispel notions that it might be unsafe (for immune-related reasons) for a mother to carry a fetus that was genetically identical to herself to term. Their results were published in Nature in 2003 (opens in new tab).
Researchers in South Korea cloned a dog, according to their results published in Nature in 2005 (opens in new tab). The puppy, named Snuppy, was born April 24, 2005. He was cloned from adult skin cells taken from an Afghan hound, according to the study. Snuppy was the lone survivor after 1,095 dog embryos were implanted into 123 surrogate mother dogs, leading to just two births (the other puppy died a few weeks later), according to the article. In 2008, Snuppy fathered his own puppies, the article said.
In 2008, researchers in Japan announced that they had cloned mice using cells that had been frozen at minus 4 degrees Fahrenheit (minus 20 degrees Celsius) for 16 years. After thawing these cells, researchers found that all of them had ruptured, but the scientists were still able to extract the DNA required to produce healthy cloned mice, according to the study, published in 2008in the journal Proceedings of the National Academy of Sciences. The scientists wrote that they hoped that this might indicate that it would be possible, in future, to "resurrect," certain animals or keep stocks of frozen tissue to use later, the study said.
In 2009, resurrection science got another boost: Scientists reported that, for the first time, they had cloned an extinct mammal, the bucardo (a type of wild goat also called a Pyrenean ibex). The group of researchers, with members from Spain, France and Belgium, used cells from preserved samples from a bucardo captured in 1999 to produce the cloned animal, according to the study. However, the young goat died only minutes after its birth because of defects in her lungs. The research was published in 2009in the journal Theriogenology.
In 2005, South Korean researchers cloned the endangered gray wolf, producing two young pups: Snuwolf and Snuwolffy. One pup was born Oct. 18, 2005, and the other was born Oct. 26, 2005. The two cloned wolves were produced from genetic material taken from the ear cells of a female gray wolf. However, researchers used eggs from dogs to host the genetic material in order to bring the cloned animals to term, because it was difficult to obtain this material from gray wolves in the wild, the study said. Dogs were also used as the surrogates for the wolf pups, according to the study, which was published in the journal Cloning and Stem Cells in 2009.
Originally published on Live Science.