Biologists Invent Better Method For Making Transgenic Animals

Using specially prepared HIV-derived viruses stripped of their disease-causing potential, California Institute of Technology biologist David Baltimore and his team have invented a new method of introducing foreign DNA into animals that could have wide-ranging applications in biotechnology and experimental biology.

The Baltimore team reports, on today's Science Express Web site, on their study of single-cell mouse embryos that have been virally infected in a manner that leaves a new gene from a jellyfish permanently deposited into their genomes. The mice, after they have been carried to term, carry at least one copy of the gene in 80 percent of the cases, and 90 percent of these show high levels of the jellyfish protein. Further, the study shows that the offspring of the mice inherit the genes and make the new protein. Thus the method makes transgenic mice that have new genetic potential.According to Baltimore, who is president of Caltech, the use of the HIV-like viruses could prove far superior to the current method of producing transgenic animals by pronuclear injection.

"It's surprising how well it works," says Baltimore, whose Nobel Prize-winning research on the genetic mechanisms of viruses 30 years ago is central to the new technique. "This technique is much easier and more efficient than the procedure now commonly in use, and the results suggest that it can be used to generate other transgenic animal species."The technique exploits features of HIV-like viruses known as lentiviruses, which can infect both dividing and non-dividing cells, as gene delivery vehicles. Unlike HIV, the lentivirus is rendered incapable of causing AIDS. The lentivirus carries new genes into the cell's existing genome. In this case, newly fertilized mouse eggs were engineered to carry the green fluorescent protein (GFP) derived from jellyfish.