Two unsuspecting farm animals have helped to demonstrate the increasing accuracy of genetic engineering techniques. The first is a cow that produced hypoallergenic milk after researchers used RNA interference to block the production of an allergy-inducing protein, as reported today (October 2) in PNAS. The second, reported in another paper in the same issue, is a pig that could be a model for atherosclerosis after researchers used an enzyme called TALEN to silence a gene that usually helps to remove cholesterol.
Researchers have long struggled to remove cow milk's allergy-inducing protein, beta-lactoglobulin, which can cause diarrhoea and vomiting in children. They were previously unable to introduce foreign genes precisely enough, however, so they could never quite successfully replace the gene that codes for beta-lactoglobulin with a defective form.
But scientists at AgResearch in Hamilton, New Zealand, worked with molecules that interfere with messenger RNA (mRNA), which...
Another technique could speed up the process. TALENs are enzymes that target and cut out a specific DNA sequence from the genome. As the break is repaired, mutations are introduced that scramble the targeted gene, leaving it unable to function.
“The TALEN technology is staggeringly easy, quick, and leaves no mark in the genome,” researcher Bruce Whitelaw, told Nature. Whitelaw, a molecular biologist at the Roslin Institute near Edinburgh, UK, and colleagues at Recombinetics, a livestock genetics company in Minneapolis, Minnesota, used TALENs to disrupt genes encoding low-density lipoprotein (LDL) receptors in pigs. Without those receptors, which remove LDL from the blood, the pigs develop atherosclerotic arteries. Such pigs could be reliable models for biomedical researchers studying human atherosclerosis.
Clarification (October 8): Bruce Whitelaw worked as part of a team to produce the GM pigs mentioned in this story. The Scientist has added that information and regrets the omission.