Japanese scientists use clone 581 copies of the same mouse

Scientists in Japan have created nearly 600 cloned mice after 25 rounds of cloning Scientists in Japan have created nearly 600 exact genetic copies of one mouse after 25 rounds of cloning.The perfectly cloned mice could pave the way for milk and meat from 'super' animals created in the lab, scientists say. Experts successfully cloned the successive generations of mice using the same techniques used to create Dolly the sheep.
The rodents live a normal lifespan and the process can be carried on indefinitely through successive generations.The cloned mice showed no signs of growing old prematurely and appeared mentally and physically perfect.
Dr Teruhiko Wakayama said: 'This technique could be very useful for the large scale production of superior quality animals, for farming or conservation purposes.'
In an experiment that began eight years ago, the researchers used 'somatic cell nuclear transfer' (SNCT) to produce almost six hundred mice from one original 'donor' after twenty five consecutive rounds of cloning.
The technique shot to fame in 1997 when Dolly the sheep, the first mammal to be cloned from an adult cell, was unveiled to the world.
It creates an embryo by taking the nucleus, which houses the genetic material of a cell, from one cell and putting it into an unfertilised egg that has had its own genetic material removed.
The resulting embryo is then an exact genetic copy of the cell from the animal or person that donated the nucleus.
It has been used successfully in laboratory and farm animals but, until now, scientists had not overcome the limitations of low success rates and the few times mammals could be recloned.
Attempts at recloning cats, pigs and mice more than two to six times had failed.
Dr Wakayama, of the Riken Centre for Developmental Biology, Kobe, Japan, said: 'One possible explanation for this limit on the number of recloning attempts is an accumulation of genetic or epigenetic abnormalities over successive generations.'
An animal inherits its genetic code from its parents along with the machinery for unlocking it, a process known as epigenetics.
The epigenetic changes in the cell control what parts of its DNA are expressed and how.
It is the method by which a liver or skin cell knows its specific function because of the genes that are switched on or off.
So to prevent these potentially devastating alterations the researchers added a naturally occurring chemical called trichostatin.
This increased cloning efficiency up to sixfold, according to the findings published in the journal Cell Stem Cell.
By improving each step of the procedure, they were able to clone the mice repeatedly without seeing a reduction in the success rate.
The 581 healthy mice obtained in this way were all fertile, gave birth to healthy pups and lived for about two years, similar to mice conceived in the normal way.
The researchers said: 'Our results show there were no accumulations of epigenetic or genetic abnormalities in the mice, even after repeated cloning.'
Dr Wakayama's work hit the headlines in 2008 when his team created clones from the bodies of mice that had been frozen for sixteen years, again using SNCT.