In a feat never before accomplished in mammals, scientists have found a way to turn a laboratory dish full of cells into hundreds of genetically identical sheep.
Scientists in Scotland took cells from an embryo, grew thousands of copies in the lab and then used copies to produce sheep from ewes.
Experts said if the technique can be perfected, it will be a major gain in the ability to make genetic changes in livestock for research and to quickly produce animals that give more or better milk or meat, resist diseases or display other desirable traits.
“It is a great achievement,” commented Robert H. Foote, professor emeritus of animal physiology at Cornell University in Ithaca, N.Y.
The work was reported in today’s issue of the journal Nature by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute near Edinburgh, Scotland. The institute does agricultural research on animals, with government and industry funding.
Currently, scientists can produce genetically identical farm animals by such techniques as breaking a single embryo into pieces and implanting each piece in a womb to form a new animal. But that approach yields fewer than 20 copies, rather than hundreds.
Scientists can already plant genes into farm animals by injecting the genetic material into fertilized eggs. But the new technique can generate thousands of cells to receive genes, giving scientists many more chances to achieve successful gene transfers.
As a result, scientists would be able to insert genes more precisely, swap new genes for old or inactivate particular genes in an animal, said animal gene expert Caird Rexroad Jr.
That would offer major advantages for studying farm animal genetics and eventually producing better barnyard stock, said Rexroad, research leader at the Gene Evaluation and Mapping Laboratory at the U.S. Department of Agriculture’s Agricultural Research Service in Beltsville, Md.
The new work has “put us a step closer to doing that,” he said.
Mass-producing hundreds of animals is still years away, Wilmut said, because the technique is currently much too inefficient. The Nature paper reports the birth of only five lambs from hundreds of attempts.
Wilmut said he believes the technique could also be used eventually for cattle. For other species, like pigs, goats and poultry, the prospects are less clear because of differences in the biology of early development.
Wilmut also said he doesn’t know if it would work in people, adding that many scientists would consider this application unethical.