Gene therapy used to treat total color blindness in dogs

By Jacques Von Lunen, Special to The Oregon...
April 22, 2010, 12:37PM

Researchers at the University of Pennsylvania have successfully used gene therapy to treat a congenital eye disease that affects dogs and people.

The disease, achromatopsia, also called total color blindness, affects the function of the small cones in the retina that receive light. Proper function of the cones is essential for color and daytime vision. About one in 30,000-50,000 humans is afflicted with the disease.

Although achromatopsia is quite rare, its treatment is thought to function as a model for other, more common, diseases that affect the retinal cones.

The observed results of the study suggest the dogs' retinal cells and visual pathways were able to process the input from the restored cones.

This video filmed by the researchers shows how dogs with the disease could easily make their way through a darkened obstacle course, but had significant trouble navigating the same course in bright light. Dogs treated with the gene therapy walked the course with the same speed as healthy dogs.

The gene therapy targets mutations of a gene known as CNGB3, the most common cause of achromatopsia in humans. Dogs are the only large animal with CNGB3-achromatopsia.

The treatment cured young dogs and was effective for the 33 months of the study, which led researchers to believe that it is permanent. The success rate for dogs 54 weeks or older was lower than that for younger dogs.

Many vision-impairing disorders in humans result from genetic defects. So far, mutations have been identified in approximately 150 genes. This wealth of genetic information and the development of gene-transfer technologies make successful treatment of these disorders a real possibility for the first time.

-- Jacques Von Lunen