Other companies such as Genzyme are currently engineering goats to produce milk that contains a protein that regulates blood clotting in humans. By combining cloning and transgenic technologies, scientists hope to quickly create large herds of transgenic goats, capable of producing commercial quantities of therapeutics. The PPL scientists introduced a gene in the chromosomes of livestock cells in culture. Before this advance experts could only add new genes to animals, but not replace or inactivate existing genes. It was also previously impossible to choose an exact site on the chromosome to add a gene.
Researchers have big plans for future applications of gene targeting.
Now that doctors have discovered a way to inactivate, or switch off specific genes, advances in organ transplants between species, also known as xenotransplantation, can be expected on the horizon. PPL staff are particularly interested in the inactivation of a specific gene that could lead to pig organs being more readily accepted by the human immune system when human organs are unavailable for transplant. Although the PPL advances are likely to aid in the development of human therapeutics through animals, there are also risks for both animals and humans, Overstrom cautioned. There are limits to which you can push a system. Genzyme received a patent similar to PPL's in Europe in 1996, but does not yet have one in the United States, according to company officials.