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Add Bunnies to Cloned List

French researchers successfully produce four rabbits from adult cells

WEDNESDAY, April 3, 2002 (HealthDayNews) -- As if rabbits didn't reproduce fast enough on their own, a group of French scientists has announced the births of the first bunnies cloned from adult cells.

"Here's an example of another species to add to the goat, the pig, cattle, sheep, the cat and mice," says Robert H. Foote, professor emeritus of animal physiology at Cornell University.

Rabbits hold much promise as research animals for a number of reasons. They are genetically closer to primates than mice are, and rabbits are much easier to work with because of their size.

Cloning from adult cells also has advantages over cloning from embryonic cells. It's easier, for starters.

"There's lots of epithelial cells on the ear of the animal or any other place. You just take a few extra cells and don't disturb the animals," Foote says.

The main appeal of bunnies, though, is being able to replicate an animal scientists already know something about for research. "That's the real driving force," he says.

Rabbits had been cloned from embryonic cells in the late 1980s but, until the French breakthrough, cloning from adult cells had eluded scientists.

The French team, which published its results in the April issue of Nature Biotechnology, ended up using the same basic procedure that produced Dolly the sheep, but with some important modifications.

"We spent time to first characterize carefully, then take into account the physiology of early rabbit embryonic development," explains Jean-Paul Renard, one of the study authors and a professor at the Agronomical University of Paris.

Renard and his team first removed the nucleus from a female's egg, then fused it with an adult cell from a donor rabbit. The fused cells were then exposed to certain chemical agents needed to jump-start development. The time spent in the presence of these chemicals was minimized, and this turned out to be key to the success of the experiment.

The researchers also implanted the embryo into the foster mother within a narrowly defined window of time.

The cloning procedure has produced four surviving animals, which have since gone on to reproduce sexually. The oldest is now a year old.

The success of this method could hold hope for cloning other mammalian species.

"We feel that by paying attention to species differences in early reproductive traits, any of the species up to now considered as reluctant to be cloned could be used for somatic cloning," Renard says.

Unlike Dolly the cloned sheep and cc, the cloned cat, these rabbits do not have names. The researchers, anticipating the rabbits' future as laboratory animals, refrained from doing anything that might suggest they had pet status. Renard and his team did name their first cattle clone (born in 1998) and mouse clone (born in 1999).

"We, of course, feel very close to [the rabbits], and they are very friendly to us," Renard says. "[But] we have to consider them now as research animals and not pets."

This first generation of cloned rabbits is not yet being used for research, because adjustments need to be made. Eventually, scientists want to be able to use the rabbits to study several human illnesses, including cystic fibrosis and atherosclerosis.

What To Do

Check out this Cloning Fact Sheet from Oak Ridge National Laboratory.

View a diagram of the process used to create Dolly the sheep in Scientific American.

SOURCES: Jean-Paul Renard, Ph.D, professor, Agronomical University of Paris, France; Robert H. Foote, Ph.D, professor emeritus, animal physiology, Cornell University, Ithaca, N.Y.; April 2002 Nature Biotechnology
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