X-Linked Progressive Retinal Atrophy in GreyhoundsQuick Summary
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Phenotype: Affected dogs display retinal degeneration and vision impairment and are typically diagnosed with PRA in early adulthood.
Mode of Inheritance: X-linked
Alleles: N = Normal, PRA = Progressive retinal atrophy (Greyhound variant)
Breeds appropriate for testing: Greyhound
Explanation of results:
Males only have one X chromosome whereas females have two, therefore possible genotypes will differ by sex.
- Female dogs with N/N genotype and male dogs with N genotype will not have this inherited form of progressive retinal atrophy and cannot transmit this allele to their offspring.
- Female dogs with N/PRA genotype are being considered carriers, however work is ongoing to determine affection status of females with one copy. Careful consideration should be made when mating female dogs with this genotype. The PRA allele will be passed on to ~50% of her offspring and all males that inherit her affected allele will be affected by this X-linked PRA.
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Female dogs with PRA/PRA genotype and male dogs with PRA genotype will likely develop this form of progressive retinal atrophy. Female dogs with this genotype will transmit this allele to all of their offspring. Male dogs with this genotype will transmit this allele to all of their female 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 are thought to cause PRA in dogs. A deletion in the CACNA1F gene is a likely genetic cause for PRA in racing Greyhounds. When the scientific study that discovered this mutation is published, more details will be provided.
Scientific evidence suggests this particular form of PRA is inherited in an X-linked recessive manner. Typically, that means females, who normally have two X chromosomes, would require two copies to be affected. However, it is not yet known if females with one copy of this PRA allele are truly unaffected. Since male dogs only have one X chromosome, they only need one copy of this PRA allele to be affected. Affected dogs are typically diagnosed with PRA in early adulthood and typically display early vision impairment.
Testing recommendations: Testing for PRA assists owners and breeders in identifying affected and carrier dogs. Male dogs with one copy of this PRA allele will be affected and will pass on this PRA allele to all of their female offspring. Females with two copies of this PRA allele are affected and will pass on this allele to all of her offspring. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing dogs affected by this ocular disorder.