Back

Progressive Retinal Atrophy, Cone-Rod Dystrophy 4

Progressive Retinal Atrophy, Cone-Rod Dystrophy 4 (PRA-crd4) is an inherited eye disease that causes degeneration of both rod and cone photoreceptor cells in dogs, leading to progressive vision loss and eventual blindness.

Affected Genes: RPGRIP1

Inheritance: Autosomal Recessive With Incomplete Penetrance

Variant(canFam6):
chr15:18816423-18816424: 44 bp insertion (ins (A)29GGAAGCAACAGGATG) or 59 bp insertion (ins (A)44GGAAGCAACAGGATG)

Breed: American Bully
American Pit Bull Terrier
American Staffordshire Terrier
Australian Cobberdog
Australian Labradoodle*
Beagle
Boykin Spaniel
Carlin Pinscher
Chihuahua
Curly Coated Retriever
Dachshund
English Springer Spaniel
Field Spaniel
French Bulldog
Labradoodle*
Labrador Retriever
Miniature Longhaired Dachshund
Miniature Smooth Dachshund
Miniature Wirehaired Dachshund
Portuguese Podengo Pequeno
Service/Assistance Lab/Golden Retriever cross
Service/Assistance Labrador Retriever
Shorty Bull*
Standard Longhaired Dachshund
Standard Smooth Dachshund
Standard Wirehaired Dachshund
UK Breed Council Labrador Retriever

General Information: Progressive Retinal Atrophy, Cone-Rod Dystrophy 4 (PRA-crd4) is a genetic condition that affects both rod and cone photoreceptor cells in the retina, which are crucial for vision in low and bright light conditions, respectively. This disease typically manifests with symptoms of vision loss that can be detected by an ophthalmologic exam as early as 3 years of age, although the onset can vary dramatically from 1 to 15 years. Affected dogs experience a gradual decline in sight, with many progressing to complete blindness, particularly if the onset is early. The progression of PRA-crd4 is generally slow but inevitable, affecting the dog's ability to navigate their environment safely and confidently.

How to Read Your Dog's Test Results for this Genetic Variant:

Two Variants Detected: Dog Likely Affected

One Variant Detected: Dog Unlikely Affected

No Variants Detected: No Effect

Gene / Testing Information: Genetic testing for the RPGRIP1 gene is vital for determining whether a dog is a carrier of Progressive Retinal Atrophy, Cone-Rod Dystrophy 4 (PRA-crd4), which is inherited in an autosomal recessive manner. Dogs must inherit two copies of the mutated gene, one from each parent, to develop the disease, although it shows incomplete penetrance, meaning not all dogs with two copies will show symptoms. Carriers have one copy of the mutation and do not typically show any signs of the disease but can produce affected offspring if bred with another carrier. Each puppy from such a mating has a 25% chance of being affected by PRA-crd4 and a 50% chance of being a carrier. Responsible breeding practices, supported by reliable genetic testing, are crucial to prevent the breeding of carriers together, which helps to reduce the incidence of this disease in the population. Breeders are advised to test all breeding animals and use genetic information to avoid producing affected puppies, thereby maintaining the health and quality of life of future generations.

References:
Busse C, Barnett KC, Mellersh CS, Adams VJ. Ophthalmic and cone derived electrodiagnostic findings in outbred Miniature Long-haired Dachshunds homozygous for a RPGRIP1 mutation. Vet Ophthalmol. 2011 14(3):146-152.

Mellersh CS, Boursnell ME, Pettitt L, Ryder EJ, Holmes NG, Grafham D, Forman OP, Sampson J, Barnett KC, Blanton S, Binns MM, Vaudin M. Canine RPGRIP1 mutation establishes cone-rod dystrophy in miniature longhaired dachshunds as a homologue of human Leber congenital amaurosis. Genomics 2006 88(3):293-301.

Miyadera K, Kato K, Aguirre-Hernández J, Tokuriki T, Morimoto K, Busse C, Barnett K, Holmes N, Ogawa H, Sasaki N, Mellersh CS, Sargan DR. Phenotypic variation and genotype-phenotype discordance in canine cone-rod dystrophy with an RPGRIP1 mutation. Mol Vis. 2009 15:2287-2305.

Narfstrom K, Jeong M, Hyman J, Madsen RW, Bergstrom TF. Assessment of hereditary retinal degeneration in the English springer spaniel dog and disease relationship to an RPGRIP1 mutation. Stem Cells Int. 2012 2012:685901.