A mountain rescue dog whose duties ended after her eyesight failed has helped scientists create a test that could eradicate the genetic eye condition in her breed forever.
Shola the English shepherd has an inherited eye disease called progressive retinal atrophy (PRA) which causes the light-sensitive cells in the back of the eye to deteriorate, eventually leading to blindness.
PRA affects more than 100 dog breeds, can be caused by a number of different genetic variants, and has no treatment. For some types, symptoms do not appear until the dog is several years old, at which point they may have passed their genes on to puppies.
Katherine Stanbury, the first author of the research from the University of Cambridge, said Shola was four years old when she began to struggle with her vision in dim light.
“She was sent to a veterinary ophthalmologist and they confirmed that she had PRA,” Stanbury said. “And then it turned out that her brother also had PRA.”
Stanbury and colleagues not only identified the genetic variant responsible for the condition in English shepherds, but A £48 DNA test developed to reveal whether dogs have none, one or two copies of the variant.
While Stanbury said variants that cause PRA are typically breed-specific, the team will now screen any dog affected by an inherited eye disease for the new variant.
“If it does show up in another breed, we can monitor it,” she said.
The research began when Shola and her brother were brought to the team’s attention by their concerned breeder.
Write in the journal GenesStanbury and colleagues reported how they performed whole-genome sequencing on the siblings’ DNA, but found that none of them had genetic variants previously associated with PRA, suggesting that another variant was at play wash.
In a series of analyzes using these genomes, as well as data on the genetic makeup of two additional English shepherds with PRA and 22 free of eye disease, the team identified the responsible variant.
They hope the DNA test will enable owners to identify English Shepherds with PRA early and avoid using them for breeding, increasing the potential to eliminate PRA from the breed.
“You can still breed from a carrier [which has one copy of the variant]as long as you breed with a clear dog,” Stanbury said, adding that this is important for genetic variation as the breed is relatively rare, particularly in the UK.
She said the team tested the father of Shola’s offspring and revealed that the latter would not develop PRA.
“Two of her daughters have just completed their mountain rescue training with Mountain Rescue England,” said Stanbury. “And one of her sons is a therapy dog.”
Indeed, one of the rescue dogs recently saved a man’s life. “[The owners] know that none of those dogs are going to go blind and waste all that training,” Stanbury said.
