BAR HARBOR, Maine - Researchers at the University of Florida and The Jackson Laboratory in Maine say they used gene therapy to restore sight in mice with achromatopsia, a form of hereditary blindness that also strikes humans.

In a paper published online in Tuesday's edition of Nature Medicine, the Florida scientists working with Jackson research scientist Bo Chang describe their use of a harmless virus to deliver corrective genes to mice with a genetic impairment that deprives them of vision.

The discovery shows that it's possible to target and rescue cone cells, the most important cells for visual sharpness and color vision in people.

The mice used in the research had achromatopsia, which affects one in about 30,000 Americans by silencing cone photoreceptors in the retina. The disease results in nearly complete color blindness and very poor central vision.

"Cone vision defines whether someone is blind or not," said William Hauswirth, professor of ophthalmic molecular genetics and a member of the University of Florida Genetics Institute.

The ability to deliver a gene specifically to cone cells has implications for all blinding diseases, not just inherited ones, Hauswirth said. "Even in two very common types of blindness, age-related macular degeneration and diabetic retinopathy, if you can target cones you might be able to rescue that vision," he said.

Chang said the mouse with achromatopsia was found about three years ago while screening many strains of mice for vision problems as part of The Jackson Laboratory's program to develop new mouse models for human eye conditions.

Chang and Jackson colleagues then identified the genetic mutation that caused achromatopsia, while scientists elsewhere were zeroing in on the analogous human mutation.

Within two months of the gene therapy injection, scientists measured the electrical activity in the retinas. They found that 19 of the 21 treated eyes responded positively to therapy; 17 of those 19 had electrical readings from their retinas on par with those taken in normal mice.

Richard Weleber, professor of molecular and medical genetics at Oregon Health and Science University, said the Florida-Jackson Lab research is the first to his knowledge of a cone-targeted gene therapy that restores function in an animal model when cones are the primary defect.

"This validates the concept that it is possible to deliver a gene therapy targeting the cone system, and that is incredibly important for a number of degenerative diseases," said Weleber, who was not involved in the research.

The research was supported by grants from the National Institutes for Health, the Juvenile Diabetes Research Foundation and other organizations.