All-Male Batch of Mice Cloned
Scientists in Hawaii have cloned a trio of identical mice using ordinary cells rather than DNA extracted from the female reproductive system. This time, the cloned critters were male.
The clones grew using genetic material extracted from tail cells of adult male mice, but only one grew to adulthood, according to a study in the June issue of the journal Nature Genetics.
Researchers said their experiment demonstrates that cloning can be accomplished with the genetic material contained in the nucleus of somatic cells, or ordinary cells found throughout the body.
Previously, most cloning experiments ranging from mice to Dolly the Sheep used DNA extracted from female reproductive cells.
In July, the Hawaii team reported cloning more than 50 carbon-copy female mice extending at least three generations. The DNA used in that experiment was derived from cumulus cells, which surround developing eggs in the ovaries of female mice.
Scientists said somatic cells, such as tail cells, are more plentiful and large amounts of their genetic material could be frozen and stored for later use.
That would help to make cloning a more efficient procedure in agriculture and commercial laboratory operations. It also might help conservationists rescue endangered species by enabling them to stockpile more of the genes of rare animals for cloning.
Other scientists said the cloning of male mice from tail cells was not a remarkable achievement. For example, bulls have been cloned using DNA from ear samples.
But the problems the Hawaii team encountered with mice eventually could improve the cloning of a variety of animals, they said.
"Now we've got a beautiful model for looking at these defects and how we
might solve them," said geneticist James Robl of the [ University of Massachusetts ] .
In the mice experiment, researchers engineered 274 embryos by emptying eggs of their genetic material and adding the cloned DNA from the tail cells.
The embryos were implanted in female mice for development. In all but three cases, the resulting fetuses died. Two of the surviving mice died within an hour of birth.
The Hawaii researchers said the problems were the result of incomplete DNA communication between cells in the placenta and the fetus following the cloning procedure. Why the problem occurred has not been determined.
Robl said similar problems have complicated calf cloning experiments.
Other researchers said the Hawaii research is promising because it suggests that ordinary cells can be used in cloning, and identical animals of either sex can be commercially engineered.
Gina "Nanogirl" Miller
"Nanotechnology: solutions for the future."