Just how many cloned mice does one lab need? Researchers in Japan announced today that they have succeeded in creating a total of 581 clones from 25 different rounds of cloning — all from the same original individual. A team led by Dr. Teruhiko Wakayama in Kobe, Japan first started the experiment in 2005.
The Kobe team used a technique that many other clone researchers have used, called somatic cell nuclear transfer (SCNT). The donor’s cell nucleus is inserted into a living egg that has had its own nucleus removed. When the egg starts to develop, it will now carry the genetic code of the clone instead of the original mother.
The technique is widely used to attempt to clone lab and valuable farm animals, but it has run into a problem. In the past, technicians have had a lot of trouble recloning individual mammals. Different researchers had experimented with cats, pigs, and, yes, mice, but they’d failed to reclone any mammals more than six times.
Dr, Wakayama’s team has discovered a chemical that can be added to the cell culture medium in order to stabilize the DNA and prevent errors from creeping in when they’re cloning animals. As a result, they have now recloned the mice 25 times — and the animals were healthy, fertile, gave birth to normal litters of their own, and even lived a normal lab mouse lifespan of around two years.
Cloning mice is not a very old science. The very first cloned mouse, Cumulina, was born at the University of Hawaii on Oct. 3, 1997. A first generation clone, she actually lived a longer-than-average lifespan, dying after two years and seven months, which researchers said was the equivalent of age 95 for humans.
That first clone was also created using the SCNT technique.
Now you may think that there doesn’t seem to be a crying need for a lot of cloned mice. However, identical rodents can be useful in lab studies, where you need a large group of similar test animals.
Wakayama’s team also has another purpose. In 2008, they proved that they could clone mice from bodies that had been kept frozen for 16 years. When both techniques are perfected, the cells of endangered animals could be kept on ice, so that scientists could clone new individuals as needed. Even if a species is wiped out, it might be possible to recreate the animals by using cells from a frozen zoo.
The world’s most famous clone, Dolly, was a sheep, not a mouse, and her story was a sad one. The first mammal to be cloned from an adult cell, instead of an embryonic cell, she died at a little more than half the normal expected lifespan of a sheep, with symptoms like arthritis of the hips which suggested that she had aged too fast.
If you followed Dolly’s story, you might have been surprised to learn that researchers are enjoying so much success with multiple generations of cloned mice.