Quick Summary
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Phenotype: Affected dogs are typically diagnosed in adulthood and may display vision loss, especially in low light conditions. Additional ophthalmoscopic findings include pale optic nerve heads in both eyes, extremely narrow retinal vessels and hyperreflectivity of the tapetum lucidum.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, PRA = Progressive retinal atrophy (Shetland Sheepdog variant)
Breeds appropriate for testing: Shetland Sheepdog
Explanation of results:
• Dogs with N/N genotype will not have this inherited form of progressive retinal atrophy and cannot transmit this allele to their offspring.
• Dogs with N/PRA genotype will not be affected by this inherited form of progressive retinal atrophy but are carriers. They may transmit this allele to 50% of their offspring. Matings between two carriers are predicted to produce 25% of affected puppies.
• Dogs with PRA/PRA genotype will likely develop this form of progressive retinal atrophy and will transmit this allele to all of their offspring.
Sample Collection
Dog DNA tests are carried out using cells brushed from your dog's cheeks and gums. The preferred cytology brushes are sent to you by mail, or you may provide your own brushes. For accepted alternative brushes, click here
We recommend waiting until puppies are at least three weeks old before testing.
Step-By-Step:
- Make sure the dog has not had anything to eat or drink for at least 1 hour prior to collecting sample.
- When swabbing puppies, isolate each puppy from the mother, littermates and any shared toys for 1 hour prior to swabbing. Puppies should not have nursed or eaten for 1 hour prior to collecting sample.
- If collecting samples from more than one dog, make sure to sample one dog at a time and wash your hands before swabbing another dog.
- Label brush sleeve with name or ID of dog to be sampled.
- Open brush sleeve by arrow and remove one brush by its handle.
- Place bristle head between the dog’s gums and cheek and press lightly on the outside of the cheek while rubbing or rotating the brush back and forth for 15 seconds.
- Wave the brush in the air for 20 seconds to air dry.
- Insert brush back into sleeve.
- Repeat steps 5 - 8 for each unused brush in sleeve on a fresh area of cheek and gums. Make sure to use and return all brushes sent by the VGL. In most cases, it will be 3 brushes per dog. If using interdental gum brushes, please note that the VGL requires 4 brushes per dog and only moderate or wide interdental gum brushes are accepted.
- Do not seal brushes in sleeve.
- Place all samples in an envelope and return to the address provided.
ATTENTION:
- Do not collect saliva/drool – the key to obtaining a good sample is getting cheek cells on the swab
- Do not rub swab on the dog’s tongue or teeth – this will result in poor quality sample
- Do not collect a sample from a puppy that has recently nursed – the mother’s genetic material can rub off on the puppy’s mouth and contaminate the sample
Progressive retinal atrophy (PRA) is a term used to describe a group of inherited disorders of the retina, characterized by progressive retinal degeneration and consequent blindness. More than 20 mutations in various genes have been associated with PRA in dogs. A 4 base pair deletion in the CNGA1 gene is associated with one form of PRA in the Shetland Sheepdog. This mutation causes a frameshift and premature termination of a protein that is found in the outer portion of rod photoreceptors in the retina.
This PRA disorder is inherited in an autosomal recessive manner, meaning that a dog must have two copies of this PRA variant to be affected. Affected dogs are typically diagnosed in adulthood and may display vision loss, especially in low light conditions. Additional ophthalmoscopic findings include pale optic nerve heads in both eyes, extremely narrow retinal vessels and hyperreflectivity of the tapetum lucidum.
Testing recommendations: Testing for PRA assists owners and breeders in identifying affected and carrier dogs. Dogs with one copy of the PRA allele are normal but are carriers. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing dogs affected by this ocular disorder.
