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.