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Progressive Retinal Atrophy (Discovered in the Golden Retriever - GR-PRA 2 variant)

Progressive Retinal Atrophy (PRA) is an inherited disorder that results in degeneration of the light sensing retina at the back of the eye, leading to progressive vision loss and eventual blindness. Golden Retriever PRA, Type 2 (GR-PRA2) is a late onset form, with the average age of diagnosis being 6 years old. The associated genetic variant has been identified in the Golden Retriever.

Key Signs

Progressive vision loss, Night blindness, Blindness

Age of Onset

3 to 7 yrs

Adult to mature onset

Inheritance

Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

Moderate-high likelihood

At risk dogs are likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with GR-PRA2

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about GR-PRA2

Progressive Retinal Atrophy, Type 2 (or GR-PRA2) is one type of genetically inherited retinal dystrophy in the Golden Retriever. Similar to GR-PRA1, GR-PRA2 is characterized by a late-onset, slowly progressive degeneration of retinal photoreceptors, leading to vision loss and eventual blindness. Initial clinical signs usually correspond with the loss of vision in dim light (night blindness) caused by degeneration of rod photoreceptor cells in both eyes. Over time, there is a slow, gradual progression to total blindness as the cone photoreceptor cells of the retina also degenerate. The age of onset varies among affected dogs, with the average age being 6 to 7 years old when owners tend to first observe signs. Please note, affected dogs may develop the first signs of vision loss several years earlier or several years later than this average.

Although this condition results in gradual vision loss, and eventual blindness, many dogs adapt remarkably well to the loss of vision. While the progression is slow, owners should be advised that the dog may need assistance in unfamiliar surroundings as clinical signs progress. Owners may find that it is helpful to keep the dog's main environment as stable as possible (avoid moving furniture, etc.) to help them navigate as their vision declines. Precautions to protect the dog from threats they cannot visually detect (such as stairs, pools, etc.) should also be taken.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disorder is autosomal recessive, meaning two copies of the variant are needed for a dog to be at an elevated risk for being diagnosed with the condition. A carrier dog with one copy of the Progressive Retinal Atrophy, GR-PRA2 variant can be safely bred with a clear dog with no copies of the Progressive Retinal Atrophy, GR-PRA2 variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. Furthermore, a dog with two copies of the GR-PRA2 variant can be safely bred with a clear dog. The resulting puppies will all be carriers. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disorder signs similar to the ones associated with this GR-PRA2 variant could develop due to a different genetic or clinical cause.

Technical Details

Gene TTC8
Variant Deletion
Chromosome 8
Coordinate 60,090,185

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Downs, L. M., Wallin-Håkansson, B., Bergström, T., & Mellersh, C. S. (2014). A novel mutation in TTC8 is associated with progressive retinal atrophy in the golden retriever. Canine Genetics and Epidemiology, 1(1), 4. View the article