Scientists at the University of Cambridge have developed a genetic test that could help identify progressive retinal atrophy — a type of hereditary blindness until now, without a cure — in English shepherd dogs and prevent the disease in their puppies. The news was reported in a study published this Monday (22) in the scientific journal Genes.
A progressive retinal atrophy also known as PRA, has no cure and causes progressive degeneration of the light-sensitive cells in the back of the eye. Dogs with the disease have normal vision at birth, but can become completely blind by the age of four or five.
Researchers have discovered a genetic mutation that causes PRA in English sheepdogs and have developed a genetic test for the disease. The scientists say the new test could help identify the condition in dogs before their vision begins to fail, providing a useful tool for owners to make breeding decisions so that the disease is not passed on to their puppies.
The team believes the discovery could help eliminate progressive retinal atrophy in future generations of English sheepdogs. This is because the genetic mutation identified can be passed on to puppies, even if the dog only has one copy of the mutated gene (an animal needs two copies of the mutation to develop the disease).
The risk to the puppy is even greater if both parents carry the genetic mutation — in this case, one in four puppies will be affected by PRA. Because dog breeds are often inbred, dogs are more likely to inherit genetic and hereditary diseases than humans.
“Once a dog’s vision starts to fail, there is no treatment – they will go completely blind,” Katherine Stanbury, a researcher at the University of Cambridge’s Department of Veterinary Medicine and first author of the report, said in a statement. “Now that we have a DNA test, there is no reason why another English Shepherd should be born with this form of progressive retinal atrophy – it gives breeders a way to eliminate the condition entirely.”
How was the study done?
The researchers began the study after being contacted by an English Shepherd owner who had recently been diagnosed with progressive retinal atrophy. The dog was a search and rescue dog, but had to stop working due to deteriorating vision, which resulted in total blindness.
From there, the scientists collected DNA samples from other dogs of the same breed: six of them had PRA and twenty others did not. Then, by sequencing the complete genome of these samples, the researchers identified the genetic mutation responsible for the disease.
As part of the discovery, they will offer a DNA test specifically for progressive retinal atrophy in English Shepherds. The test costs £48.
“An owner won’t necessarily notice that their dog has something wrong with its eyes until it starts bumping into furniture. Unlike humans, who will tell you if their vision isn’t right, dogs simply have to get on with things,” notes Cathryn Mellersh of the University of Cambridge’s Department of Veterinary Medicine, senior author of the study.
“For the price of a decent bag of dog food, people can now test their English Shepherds for Progressive Retinal Atrophy before breeding. It’s about prevention rather than cure and it means a lot to the people who breed these dogs. They no longer have to worry about whether their puppies will be healthy or whether they will develop this horrible disease in a few years’ time,” he adds.
Ultimately, the researchers believe the discovery could shed light on a similar disease that occurs in humans — called retinitis pigmentosa, which also causes blindness — and potentially help identify targets for gene therapy for the condition in the future.
Source: CNN Brasil
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