Gene-mutation discovery could help humans, cats with eye disease

Columbia, Mo.

-- A veterinary ophthalmologist at the University of Missouri identified a genetic link between cats and humans for two forms of retinitis pigmentosa (RP), a discovery that could lead to gene-based therapies benefiting cats and humans.

About one person in 3,500 is afflicted with RP, a progressive deterioration of the retina's visual cells that eventually leads to blindness. It starts with night blindness, then loss of peripheral vision and finally central vision, and there are no therapies currently available.

"The same genetic mutations that cause retinal blindness in humans also cause retinal blindness in cats," says Kristina Narfstrom, the Ruth M. Kraeuchi-Missouri professor in veterinary ophthalmology in MU's College of Veterinary Medicine.

"Now, cats with these mutations can be used as important animal models to evaluate the efficiency of gene therapy. The eye is an ideal organ to use as we examine the potential of gene-replacement therapy because it offers an accessible and confined environment," Narfstrom explains.

Her team of researchers examined the genetic mutations in two groups of cats - one with a congenital form of RP and another with a late-onset form and could identify the genes responsible for both in cats. They found that cats with the late-onset form have the same gene mutation found in humans that cause changes in the function and structure of photoreceptor nerve cells, leading to cell death and blindness.

Narfstrom works primarily with Abyssinian cats with hereditary retinal blinding disease; she discovered the feline version of RP in her native Sweden.

In 2007, she implanted silicon chips in partially blind cats to determine if they can replace or possibly repair diseased retinas in humans. The chips implanted in the back of a cat's eye are covered with light-sensitive diodes that send electric signals along the optic nerve to the brain. Studies at the time suggested the currents might help regenerate damaged photoreceptors around the implants. Narfstrom said it would take about two years to know whether the implants actually encourage retinal cells in the cats to grow.