DNA Therapy

By Christine Gorman

For years scientists doing gene therapy have had to rely on viruses to do their heavy lifting. Doctors would put whatever snatches of DNA they wanted to change into the viruses and then infect their patients with millions of them, hoping that some would hit the target. Unfortunately, the DNA patches would rarely land where they were supposed to, and even when they did, they usually fell out within weeks. A permanent genetic fix always seemed maddeningly out of reach.

Until now. Researchers led by Dr. Clifford Steer at the University of Minnesota Medical School report in the current Nature Medicine that they have eliminated the need for viruses by harnessing the body's own genetic repair processes. In a landmark proof-of-concept experiment, the Minnesota team permanently altered a blood-clotting gene in 40% of the liver cells in a group of rats. The researchers started by splicing their DNA patch into a slip of RNA. Then they encased the hybrid molecule in a protective coating, laced it with sugars that seek out liver cells and injected it into lab rats. True to plan, the hybrid molecules zeroed in on the targeted gene and lined up alongside it. An enzyme in the rats' own liver cells did the rest: whenever it spotted a mismatched DNA, it simply removed the offending DNA and stitched in a replacement. Now the trick is to show that it will work with other tissues--and other species.

--By Christine Gorman