'New vision on blindness' with illustration of dog dancing on top, saying 'I can see!'
POSTED 14 FEB 2002
  RELATED WHY FILES:
New body parts!

Diet and blindness.

Spare parts via cloning?

Fixing spinal cords?

Genetics of species restoration.

Human Genome Project.

 

 

 

 

 

 

 

 

 

 

 

 

 


Light brown and white collie poses for picture.
Cody the Collie.
Courtesy Robert Olson

 

 

 

 

 

 

 

 

 

 

 

 

illustration of dog wagging it's tail,looking to play

 

 

Three blind dogs,Three blind dogs,Blind's a bat you see,Blind's a bat you see,They each got virus in the eye,Fixed their genes oh my oh my,They never saw nuttin' Now they goin' struttin',Three blind dogsThree blind dogs

As those highly bred dogs prance and strut at the Westminster Kennel Club, The Why Files got to thinking about the downside of inbreeding: genetic defects. Inbreeding reduces genetic diversity, and concentrates defective genes in the offspring, leading to genetic disease.

Briard stands with woman while judge gives ribbon.Mon Ami, a champion Briard.
Courtesy Mon Jovis Briards.

Many dog breeds are known for hip problems, largely due to the continual inbreeding required by kennel-club regulations. But blindness may be even worse: Irish setters, Norwegian elkhounds and collies, among others, suffer congenital blindness.

Even a little-known sheepdog called a Briard suffers inbred blindness, in the form of LCA, or Leber congenital amaurosis. LCA in patients -- whether canine or human -- may lack a gene for a protein that transports a chemical called a retinoid in the retina. This vitamin A-like compound plays an essential role in the first stage of vision -- the transformation of photons of light into chemical energy in the eye's retina.

It's as simple as this: No transformation, no vision.

Can genes be fixed?
Long before The Why Files got obsessed with harmful inbreeding, a group of researchers at University of Pennsylvania, Cornell University and the University of Florida got interested in curing the genetic defect of LCA. Last May, they reported that they had restored vision to three Briards that were born blind.

Nearly white, light brown and black long-haired dogs.

Briards, similar to the three pictured here, are prone to blindness.
Courtesy Mon Jovis Briards.

Jean Bennett, an author of the study who is a researcher at the F.M. Kirby Center for Molecular Ophthalmology at Penn State's Scheie Eye Institute, said researchers had previously reversed genetic blindness in rodents, but this was the first success with a larger animal. "The results are spectacular -- in fact, they are the sort of findings that a scientist usually only hopes to, but rarely does, see, in the course of a career," Bennett explained in the press release.

"This study takes a great stride forward in demonstrating that gene therapy does not just slow down a retinal degenerative disease, but can actually provide recovery of vision to an animal that was previously blind," Bennett said.

The success could set the stage for a similar experiment in humans, but since that's several years down the pike, let's see how the dog's sight was restored.

Diagram of eye with retina, iris, cornea, pupil, lens, and optical nerve labeled. Diagram of the human eye.
National Institutes of Health.

The researchers genetically engineered a virus that frequently infects people but does not cause disease to carry the RPE65 gene, which was lacking in the dogs (and in the 2,000 Americans born each year with LCA, who go blind soon after birth). Then they injected the virus beneath the retina in the dogs, waited a few months, and performed electrical tests to see whether the dogs could see.

And they could -- but only in the eye that had gotten the virus carrying the gene. In fact, the eyes not only responded on electrophysiological tests of retinal function. The dogs could also navigate mazes and dodge obstacles -- unless they were on the left side (only the right eye had been fixed). Even 18 months after the dogs got their new genes, they continue to see, Bennett told The Why Files, and one has even made two Congressional appearances -- without pleading the Fifth Amendment, by the way...

illustration of dog scratching When, oh when?
Gene therapy has been suggested as a cure for dozens of genetic defects, but so far, all human trials have essentially failed, apparently because of failures to really insert the corrective genes into the cells. Now, the dog study shows one technique that seems to work. Conceivably, Bennett said, gene therapy could be used to treat many other blinding diseases that have a genetic component.

"We have worked hard for many, many years to develop a treatment for retinal degeneration, and this is the biggest leap forward yet," states Bennett. "However, we are nowhere near the introduction of the missing protein in humans to restore sight."

The first human tests are about years away, she says, and will start by testing the safety, not the effectiveness, of gene therapy.
-- David Tenenbaumillustration of dog wagging it's tail, sniffing David Tenenbaum's name

     


BIBLIOGRAPHY
Gene Therapy Restores Vision in a Canine Model of Childhood Blindness, Gregory Acland et al, Nature Genetics, May, 2001.

University of Pennsylvania press release.

Canine Diversity Project

The Truth About Dogs, Stephen Budiansky, The Atlantic Monthly, July, 1999.

 
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