Tuesday, 04 Nov, 2008 Science

Japanese Researchers Cloned Mice Frozen for 16 Years


Researchers from Japan managed to clone mice, whose bodies had been frozen for about 16 years at a temperature of -20C.

To be able to clone frozen mice, scientists applied classic nuclear transfer method: they took the nucleus out of an egg cell and then replaced it with another nucleus taken from a simple cell of the animal that was to be cloned.

Scientists consider that it would be possible to apply their new technique to revive many extinct species, such as, for example, mammoths.

In the Proceedings of the National Academy of Science the team of scientists wrote that the process of cloning species using nuclear transfer could be useful for preserving extinct animals. They added that their technique will be able replace cryopreservation in terms of maintaining valuable genomic stocks.

Together with his colleagues from the Center for Developmental Biology, at RIKEN research institute located in Yokohama, Dr Teruhiko Wakayama was able to clone mice despite the fact that their cells disintegrated, ABC News reports.

Scientists wrote that the so-called resurrection of frozen extinct species is impractical because there are no live cells. They say that the genomic material that is left is "inevitably degraded."

It is worth mentioning that freezing might damage the DNA inside, but such chemicals as cryoprotectants are able to prevent the burst of cells. However, these chemicals must be used prior to the freezing of cells. Researchers used cells from different places and found that brain cells are the most suitable.

It is possible that mammoths will be cloned first. Last summer Russian scientists found the body of a baby mammoth. The frozen body was discovered in the Arctic Yamalo-Nenetsk region and presumable has over 40,000 years.

"In dead specimens frozen in natural conditions such as permafrost tundra, the cells of tissue will presumably bind strongly to each other and freeze gradually after death due to the large body size," the team wrote.

They wrote that they still need to discover whether nuclei can be gathered from whole bodies of frozen specimens without cryoprotectants. In addition, researchers have to demonstrate that the frozen bodies could be used to produce offspring after the nuclear transfer.

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