Retinal atrophy, progressive (GR_PRA2)

 

Gene: TTC8

Transmission: Autosomal recessive

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Deletion, TTC8 gene; c.699 del.A, p.(K223R fs STOP 15 nt), exon8

Medical system: Oculaire

Breeds: Akita, American Staffordshire Terrier/Amstaff, English Bulldog, Golden Retriever, Labrador Retriever, Poodle - Miniature (Dwarf), Poodle - Standard

Age of onset of symptoms: Around the age of 4 to 5 years

Progressive retinal atrophy (PRA) is a family of genetic diseases that affect the vision of many dog breeds.  GR_PRA2 refers to Golden Retriever progressive retinal atrophy 2, which is a recessive, autosomal version of retinal atrophy seen in Golden Retrievers.  Clinical signs of GR_PRA2 start with night blindness due to degeneration of rod photoreceptor cells within the retina, followed by day blindness due to the degeneration of cone photoreceptor cells within the retina.  The progression of the disease is characteristically slow.  Pathological changes can be observed in the retina of affected dogs during a clinical exam by a veterinary ophthalmologist.

 

References:

OMIA link: [1984-9615]

Donner J, Freyer J, Davison S, et al. (2023) Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs.  PLoS Genet. 19(2):e1010651. [pubmed/36848397]

Trecenti-Santana AS, Guiraldelli GG, Albertino LG, et al. (2022) Allele frequency of SLC4A3 (PRA1), TTC8 (PRA2), and PRA-prcd mutations in golden retrievers in Brazil. Front Vet Sci 9:973854.  [pubmed/36325094]

Genetics Committee of the American College of Veterinary Ophthalmologists. (2021) The Blue Book: Ocular disorders presumed to be inherited in purebred dogs. 13th Edition.  [https://ofa.org/wp-content/uploads/2022/10/ACVO-Blue-Book-2021.pdf]

Palanova A. (2016) The genetics of inherited retinal disorders in dogs: implications for diagnosis and management.  Vet Med (Auckl). 7:41-51. [pubmed/30050836]

Downs LM, Aguirre GD. (2016) FAM161A and TTC8 are Differentially Expressed in Non-Allelelic Early Onset Retinal Degeneration. Adv Exp Med Biol 854:201-7. [pubmed/26427412]

Downs LM, Hitti R, Pregnolato S, Mellersh CS. (2014) Genetic screening for PRA-associated mutations in multiple dog breeds shows that PRA is heterogeneous within and between breeds. Vet Ophthalmol. 17(2):126-30. [pubmed/24255994]