Three dogs with congenital blindness can now see, thanks to gene therapy. By injecting each dog behind one of its retinas with a virus carrying replacement DNA, researchers have reversed the effects of a mutation in the RPE65 gene. A mutation in this gene also causes human blindness. Those with the condition are blind from birth.
Ten months after treatment, the dogs can see up to 40 percent as well in the treated eye as normal dogs do, the researchers report in the May Nature Genetics.
The rare form of blindness, called Leber congenital amauosis, stems from mutations in any of three genes. RPE65 normally encodes a protein needed to translate images into nerve impulses that the brain can process.
"We're all very excited about this, cautiously excited," says study coauthor Jean Bennett of the University of Pennsylvania in Philadelphia. Before testing the therapy in people, the researchers need to determine wheth