Science Behind Cloned Transgenic Calves Detailed in Leading Journal, "Science"
AMHERST, Mass. - The biotechnology techniques that enabled University of Massachusetts researchers to produce three cloned, transgenic calves last January will be published in the May 22 issue of the prestigious journal, Science. The research was conducted by James Robl, professor of veterinary and animal sciences at UMass, and Steven Stice, of Advanced Cell Technology (ACT) Inc., an adjunct faculty member at the University. The article includes new details on how researchers were able to extend the lifespan of certain cells, which may help scientists to introduce complex genetic modifications in cloned animals. Co-authors on the paper include recent UMass Ph.D. graduate Jose Cibelli, ACT research associates Paul Golueke, Jeff Kane, Joseph Jerry, Cathy Blackwell, and former UMass faculty member F. Abel Ponce de Leon, now at the University of Minnesota.
The scientists developed a reliable, efficient way to genetically modify and clone cattle. They used a technique called nuclear transfer, also used to produce the famous sheep clone, Dolly. Dolly was the first clone produced from adult body, or "somatic" cells, rather than from sperm and egg cells, called "germ" cells. The cloned bull calves George, Charlie, and Albert were the first calves to be produced from genetically altered, somatic cells, rather than germ or embryonic cells. The animals were created through a combination of cloning and genetic engineering (also called transgenics) developed by Robl and Stice, who conducted the research under the auspices of ACT, a biotechnology company with close ties to the University.
As an embryo develops, its cells become specialized, or differentiated, enabling the embryo to develop bones, muscles, and organs, for instance, Stice explained. Cells that are partially specialized are called fibroblast cells. The UMass researchers placed a "marker" gene into the nuclei of actively dividing bovine fetal fibroblast cells, Stice said. These cells are easily isolated, and grow well in a laboratory. The genetically tagged cells were then fused with cow eggs from which the nuclei, which contain the genetic coding, had been removed. The 28 engineered embryos were transferred to 11 recipient cows – essentially surrogate mothers – resulting in three healthy, identical, transgenic calves, a relatively high success rate compared with other cloning methods, researchers said.
Intriguingly, the process of transferring the nuclei extended the lifespan of older fibroblasts. The ability to extend the lifespan of these cells will be useful in introducing complex, multiple genetic changes in cattle, Stice said, because a significant number of cell divisions is necessary to correctly identify which cells have properly incorporated the new genes; the longer the fibroblasts live, the more cell divisions they undergo. Large-scale cloning of cattle has potential uses in agriculture, biotechnology, and human medicine, Stice said.