Researchers funded by the National Institute of Child Health and Human Development (NICHD) and the National Center for Research Resources of the National Institutes of Health have completed the first successful effort to introduce a new gene into the unfertilized eggs of rhesus monkeys, a member of the family of mammals that includes human beings. The eggs were then fertilized, resulting in several pregnancies and the birth of three live monkeys. The gene was successfully incorporated into one monkey's DNA, making this the first genetically modified non-human primate. Previous gene transfer attempts in animals have been confined largely to rodents and agricultural animals.
The technology could lead to the development of a variety of animal models of diseases having a greater resemblance to the corresponding human conditions than do any animal models now in existence. The new accomplishment could also provide insights into human diseases and to techniques for treating a variety of human disorders, from cancer, to cystic fibrosis, to Alzheimer's disease, to birth defects, to heart disease, to AIDS. The finding, which appears in the current issue of Science, was reported by Gerald Schatten, Ph.D., and his coworkers at the Oregon Regional Primate Research Center at the Oregon Health Sciences University in Portland, Oregon.
"This research breaks a technical barrier," said NICHD Director Duane Alexander, M.D. "The technology paves the way for developing new models for testing treatments for a variety of diseases in a more relevant way than is currently possible."
Although scientists have often inserted genes into other animals, they have lacked the technical means to introduce new genes into primates. These researchers succeeded by adapting to rhesus monkeys a technology that previously was used for transferring genes to cattle. The Oregon group transferred a gene for green fluorescent protein (GFP) into the egg cells of rhesus monkeys. As its name implies, GFP fluoresces green, allowing researchers to observe and track the progress of the implanted gene.
The researchers began by adding the gene for GFP to some 224 rhesus monkey egg cells. Then, using a technique known as intracytoplasmic sperm injection (ICSI), they next injected a single rhesus sperm into each of the modified eggs. Of the fertilized eggs, 40 developed into embryos; after transfer to female monkeys, five developed into pregnancies. Two were stillborn; of the survivors, three male births resulted. Of these, only one carried the inserted DNA. This infant monkey was dubbed "ANDi," a reverse acronym for "inserted DNA." Two of the stillborn animals also carried the inserted DNA.