U.S. Scientists Look to Cloned Sheep for Inspiration

Article excerpt

Government researchers are counting on Dolly to reverse a decade of genetic engineering setbacks that yielded diabetic sheep, arthritic pigs and none of the "super animals" they were trying to produce.

Scottish researcher Ian Wilmut, who cloned Dolly from the cells of an adult sheep, is scheduled to visit the Agriculture Research Service in Beltsville on Wednesday to talk about his methods.

Soon, U.S. government scientists hope to deploy the cloning methods that Wilmut used to shock the world. Caird E. Rexroad Jr, research supervisor at the Agriculture Department's Gene Evaluation and Mapping Lab at Beltsville, said researchers hope to begin their own experiments within months. He said in an interview last week: "This is wonderful for us. We needed the stimulation from this as well as the opportunities it presents." The Beltsville scientists intend to use Wilmut's method but in a different way. Rather than using adult cells,a the U.S. scientists plan to use fetal cells for cloning. And instead of sheep, the scientists at Beltsville are hoping to use Wilmut's methods on cattle. But they want to use cloning to study genes for the purpose of producing bigger, leaner and faster-growing farm animals that need less food and produce less waste.ts Rather than cloning - creating a new animal from a single cell of an existing animal - researchers at Beltsville have been using a related genetic engineering method of transferring genes from other animals. And humans. In long-running experimentation that began in the mid-1980s, the Agriculture Department researchers transferred genes that control growth from humans and other mammals into farm animals. These genes - obtained by cloning - were injected into fertilized eggs that were implanted into farm animals in Beltsville. Growth Hormones Part of the experiment was successful: The genetic makeup of the pigs, sheep and other animals was changed, and the animals passed along the changes to their offspring. As a result of the new gene, many of the transgenic animals, as they are called, produced the growth hormone from their pituitary glands. But the problem that the government scientists have not been able to overcome is controlling the growth hormone produced by the experimental animals. The hormone caused diabetes and other ill effects in sheep. While some of the pigs were better muscled, many of them had health problems such as arthritis, pneumonia and lethargy that prevented breeding. "If you can't avoid the health problems, you can't go on," said Vernon G. Pursel, swine researcher at the Beltsville labs, explaining why he stopped most of that research several years ago. In his latest experiments, Pursel has been producing pigs implanted with genetic material called IGF1 (Insulin-like Growth Factor) in an effor t to avoid the unpredictable effects of growth hormone. …