 Well-frozen mammoths are the extinct animals that scientists are most likely to clone.
November 4, 2008 10:38 PM
By Maggie Fox
WASHINGTON - Japanese scientists have cloned mice whose bodies were frozen for as long 16 years and said on Monday it may be possible to use the technique to resurrect mammoths and other extinct species.
Mouse cloning expert Teruhiko Wakayama and colleagues at the Center for Developmental Biology, at Japan's RIKEN research institute in Yokohama, managed to clone the mice even though their cells had burst.
"Thus, nuclear transfer techniques could be used to 'resurrect' animals or maintain valuable genomic stocks from tissues frozen for prolonged periods without any cryopreservation," they wrote in the Proceedings of the National Academy of Sciences.
Wakayama's team used the classic nuclear transfer technique to make their mouse clones. This involves taking the nucleus out of an egg cell and replacing it with the nucleus of an ordinary cell from the animal to be cloned.
When done with the right chemical or electric trigger, this starts the egg dividing as if it had been fertilised by a sperm.
"Cloning animals by nuclear transfer provides an opportunity to preserve endangered mammalian species," they wrote.
"However, it has been suggested that the 'resurrection' of frozen extinct species (such as the woolly mammoth) is impracticable, as no live cells are available, and the genomic material that remains is inevitably degraded," they said.
DIGGING INTO FREEZERS
Wakayama's team dug out some mice that had been
kept frozen for years and whose cells were indisputably
damaged. Freezing causes cells to burst and can damage
the DNA inside. Chemicals called cryoprotectants can
prevent this but they must be used before the cells are
frozen.
They tried using cells from several places and discovered
that the brains worked best. This is a bit of a mystery, as
no one has yet cloned any living mouse from a brain cell.
Many animals have been cloned, starting with sheep,
and including pigs, cattle, mice and dogs. Livestock
breeders want to use cloning to start elite herds of
desirable animals, and doctors want to use cloning
technology in human medicine.
"There is hope in bringing Ted Williams back, after all,"
cloning and stem cell expert John Gearhart of the University
of Pennsylvania saidin an e-mail. The family of Williams, the
Boston Red Sox hitter, had his body frozen by cryogenics
firm Alcor after he died in 2002.
Gearhart was only half-joking and said the study "may
now stimulate the small industry of freezing parts of us
before we die to bring us back in the future."
Mammoths may be the extinct animals that scientists
would be most likely to try to clone, as many of the
animals have been found preserved in ice.
In July 2007 Russian scientists discovered the body of a
baby mammoth frozen in the Arctic Yamalo-Nenetsk region
for as long as 40,000 years.
"It remains to be shown whether nuclei can be collected
from whole bodies frozen without cryoprotectants and
whether they will be viable for use in generating offspring
following nuclear transfer," Wakayama's team wrote.
|
