What is PRA-CRD4/CORD1?

Progressive retinal atrophy, cone-rod dystrophy 4/cord1 (PRA-crd4/cord1) is an inherited eye disease affecting numerous breeds. The disease is associated with a mutation in the RPGRIP1 gene. PRA-crd4/cord1 occurs as a result of degeneration of both rod and cone type cells of the retina. Affected dogs can show symptoms of vision loss or have signs of retinal disease on veterinary ophthalmologic exam by 3 years of age. However, age of onset and disease severity varies significantly among PRA-crd4/cord1 affected dogs, and not all dogs with that are genetically at risk will develop noticeable visual impairment. Mutations in the RPGRIP1 gene show incomplete penetrance meaning that only some dogs inheriting two copies of the mutation develop clinical disease.  A report from the laboratory of Dr. Keiko Miyadera at the University of Pennsylvania indicates that whether dogs with the RPGRIP1 mutation develop appreciable visual impairment and the severity of the impairment is influenced by the presence or absence of two genetic modifiers.  Among dogs with two copies of the RPGRIP1risk variant, the odds of developing significant visual impairment is dependent on whether the dog has one or both of the modifying mutations.

Breeds affected: 

The RPGRIP1 mutation has been identified in over 25 dog breeds, so this mutation is a potential cause of progressive retinal degeneration in almost any breed. In a large multibreed survey, the incidence of the RPGRIP1 risk variant was over 5% in the following breeds:  American Staffordshire Terrier, Barbet, Beagle, Bedlington Terrier, Bloodhound, Clumber Spaniel, Dachshund, Field Spaniel, French Bulldog, Kai Ken, Rottweiler, Standard Schnauzer, Silky Terrier, and Weimaraner.

Explanation of Test Results

PRA-crd4/cord1 is an autosomal recessive disease with incomplete penetrance.

Normal/Clear
This dog has tested normal/clear for the RPGRIP1 mutation associated with PRA-crd4/cord1. It can only transmit a normal gene to its offspring, and can be bred to a dog with any test result with no risk of producing affected offspring.

Carrier
This dog has tested as a carrier for the RPGRIP1mutation associated with PRA-crd4/cord1. There is no evidence that carriers develop clinical signs of the disease. It may transmit either a normal or mutated gene to potential offspring. Carriers may be bred to normal/clear dogs with no risk of producing affected offspring. However, those offspring should be tested to determine their possible carrier status.

Affected
This dog is homozygous for the RPGRIP1 mutation associated with PRA-crd4/cord1. It is at risk for developing the disease and will pass on one copy of the risk variant to any offspring. However, not every dog that tests at risk will develop clinical PRA.  It appears that in breeds other than in Miniature Longhaired Dachshunds and English Springer Spaniels the risk of developing clinical PRA associated with homozygosity for the RPGRIP1 variant is low.

Tests are ordered online through the secure area of the OFA website. Payment is accepted by credit card (MasterCard and VISA). The OFA administers all order handling. Upon receipt of an order, the OFA will send out the test kit which will include a buccal (cheek) swab for DNA sample collection, along with sample collection instructions. Owners can safely collect DNA samples at home. The collection process is non-invasive, and no veterinary appointment is necessary.

Samples are then sent to the University of Missouri College of Veterinary Medicine where the samples will be processed by the Small Animal Molecular Genetics Lab. Results will be forwarded to the OFA, and the OFA will issue the resulting report to the owner.

The fee for each test includes the test kit, laboratory processing, and subsequent registration in the OFA databases.