JAPANESE scientists say they have created a mouse from a dead cell frozen for 16 years, taking a step in the long impossible dream of bringing back extinct animals such as mammoths.

Scientists at the government-backed research institute, Riken, used the dead cell of a mouse that had been preserved at -20o Celsius -- a temperature similar to frozen ground.

They hope that the first-of-a-kind research will pave the way to restore extinct animals such as the mammoth.

The scientists extracted a cell nucleus from an organ of the dead mouse and planted it into an egg of another mouse which was alive, leading to the birth of the cloned mouse, researchers said.

"The newly developed technology of nucleus transfer greatly improved the possibility of reviving extinct animals," the team led by Teruhiko Wakayama said.
"Even though reviving extinct animals is often described in films and novels, such as in Michael Crichton's Jurassic Park, it had in reality been impossible," they said.

Cells from dead bodies have previously been useless as they are ruined in the freezing process. But Wakayama's team discovered a way to extract a nucleus intact from a frozen cell by grinding cell tissues into multiple pieces.

The cloned mouse was able to reproduce with a female mouse, it added.

But the researchers said tough challenges remain ahead in terms of how to restore extinct animals, which would require breeding with animals that are still alive.

To revive a mammoth, researchers would need to find a way to implant a cell nucleus of a mammoth into the egg of an elephant and then implant the embryo into an elephant's uterus, it said.The elephant is the closest modern relative of the mammoth, a huge woolly mammal believed to have died out with the Ice Age.

But Akira Iritani, a mammoth expert at Kinki University in Osaka, said it was only a matter of time before researchers could find a mammoth for a resurrection project.

"I have high hopes that we will be able to find a fine sample. It's said that there are more than 10,000 mammoths lying underneath Siberia."

Even if it is impossible to recreate a whole animal, the process could create cloned embryonic stem cells for extinct species, giving a boost to research on evolution and zoology, he said.

Cloning can be controversial in terms of both bioethics and, if the animals are eaten, food safety.

Earlier this year, a report by the European Union warned that cloning can threaten the health of livestock.

The South Korean Parliament has passed a law to regulate research into cloning, following a scandal in which a now-disgraced expert falsely claimed to have made the first human clone stem cells.