Toward more efficient cloning.

The burgeoning field of pharming--the practice of genetically engineering animals to produce pharmaceuticals for human use--got another boost last month with the arrival of a pair of spindly legged calves.

George and Charlie, genetically identical and carrying an introduced gene, are the brainchildren of James Robl and Steven Stice of the University of Massachusetts at Amherst. The method they used to clone the calves varied only slightly from the ones used by Scottish researchers to produce Dolly, Molly, and Polly (SN: 4/5/97, p. 214; 8/23/97, p. 127), but it turned out to be significantly more efficient.

The technology transfers nuclei from rapidly dividing fetal cells rather than from cells that have been induced to enter a temporarily nondividing state. The new method boasts roughly one full-term pregnancy for every 50 nuclear transfers, a success rate markedly higher than that achieved by the scientists who produced the cloned sheep, say the researchers. They announced their accomplishment on Jan. 20 at a meeting in Boston of the International Embryo Transfer Society.

George and Charlie are the products of a dry run--they carry a marker gene that is easily detected but produces no physiological effects. Next time, the scientists intend to clone female calves that will produce milk containing a human protein that enhances blood volume. Robl and Stice have focused on cloning cattle because cows produce large amounts of milk--and could thus chum out drugs in bulk.