Scientists Successfully Clone Cat

David Braun
National Geographic News
February 14, 2002
View Photo Gallery >>

Scientists in Texas have successfully cloned a cat, opening the way to replicating pets and other valued animals once the technique is perfected.

The kitten, called CC (the old typist's abbreviation for carbon copy) and now almost two months old, appears healthy and energetic, although she is completely unlike her tabby surrogate mother, Mark Westhusin and colleagues at Texas A&M University, College Station, announce in the February 21 issue of Nature.

The cat was cloned by transplanting DNA from Rainbow, a female three-colored (tortoiseshell or calico) cat into an egg cell whose nucleus had been removed, and then implanting this embryo into Allie, the surrogate mother.

"CC's coat color suggests that she is a clone, and a genetic match between CC and the donor mother confirms this," the researchers say.

She is not, however, identical to her DNA donor. The reason for this is that the pattern on cats' coats is only partly genetically determined—it also depends on other factors during development.

Out of 87 implanted cloned embryos, CC is the only one to survive—comparable to the success rate in sheep, mice, cows, goats, and pigs, the scientists say.

"If these odds can be shortened and CC remains in good health, pet cloning may one day be feasible," the scientists reported.

The technique used to clone the cat may not be readily extendable to other animals "if our understanding of their reproductive processes is limited or if there are species-specific obstacles," the scientists say.

In their first attempt, researchers obtained the cells used to make the clone from the skin cells of a "donor" cat. Eggs from other cats were used for the next step. Their chromosomes were removed and replaced with the DNA from the frozen cells, creating cloned embryos which were then transplanted into surrogate mothers.

"We carried out 188 such nuclear-transfer procedures, which resulted in 82 cloned embryos that were transferred into seven recipient females," the scientists said. Only one cat became pregnant, with a single embryo. But this pregnancy miscarried and the embryo was surgically removed after 44 days, when it was found to indeed be a cloned embryo.

In the next attempt the scientists tried using cells from ovarian tissue to receive the DNA from the cat to be cloned. Five cloned embryos made in this way were implanted into a single surrogate mother. Pregnancy was confirmed by ultrasound after 22 days and a kitten was delivered by C-section on December 22, 2001, 66 days after the embryo was transferred.

"The kitten was vigorous at birth and appears to be completely normal," the scientists say.

The announcement of the successful cat cloning was delayed until the animal had completed its shot series and its immune system was fully developed.

The work in Texas was funded in part by a company that hopes to use the technology to provide commercial cloning of companion animals for pet owners.

Endangered Species Could Benefit

The Texas A&M University announcement was greeted with a mixture of joy and disappointment by the Audubon Nature Institute in New Orleans, which has been trying hard to clone domestic cats so as to learn how to clone endangered felines. "It was only a matter of who was going to be the first to succeed in producing a cloned cat," said Philip Damiani, a staff scientist with the Institute. Damiani was involved in the first successful clone of an endangered species, a gaur (a kind of wild cattle) in January 2001.

The Audubon Nature Institute has been doing similar experiments to those of their colleagues in Texas. "The significance of their breakthrough is that it now allows us to take this technology and apply it for the preservation of endangered species," Damiani said. "It proves that cloning technology can be applied not only to livestock but also to companion animals. Ultimately it will also be used for endangered species."

There may be a significant demand for commercial cloning of pets, according to anecdotal evidence. Richard Denniston of Lazaron Biotechnologies said several hundred customers had "banked" the DNA of their animal companions with his company in the hope that some day they would be able to replicate them.

"We have banked lots and lots of cells of cats as well as dogs, cattle, goats, horses, you name it. There are quite a number of people who are interested in doing this."

Denniston said it was difficult to estimate when the cloning of dogs and cats might become commercially available. "Commercial cloning of cattle has been available for about a year now, and that was within a couple of years of the first bovine clone being born. Cloning of some species will be more successful than others, but there's still a lot of research that needs to be done," he said.

Humane Society Opposes Cloning

The Humane Society of the United States is opposed to the concept of cloning pets. "In the first place it is dangerous for the animals involved," said Brian Sodergren, who monitors the exploitation and abuse of companion animals for the society. "Take the cat that was cloned: The sheer amount of embryos it took is quite mind boggling.

"Secondly, cloning adds needlessly to the overpopulation of pets in the United States. There are millions of dogs and cats in shelters waiting to be adopted, looking for responsible owners and loving homes. About half of them will be euthanized because there are not enough homes for them."

Sodergren said he understood there was a close bond between people and their pets. "They do become a part of your life, and you grow up with them and learn to love their habits and ways. But to think that by cloning your pet you are going to get the same animal, that is a fallacy. You may get a cat that looks the same but the chances are it will not be the same animal socially because those things involve upbringing and environment."

© 1996-2008 National Geographic Society. All rights reserved.