Retinal atrophy, progressive, adult onset (SAG related)

Gene: SAG

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: Substitution, SAG gene; c.1216 T>C, p.(STOP405R, extension, STOP 25 nt), exon16

Medical system: Ocular

Breeds: Basenji

Age at onset of clinical signs: 5-7 years

Adult onset progressive retinal atrophy in the Basenji is a hereditary disease affecting adult dogs that involves thinning of the retinal blood vessels and eventual blindness.  By the age of 5 years, a veterinary ophthalmological examination can detect changes in the tapetum lucidum, a structure at the back of the retina of an affected dog.  By 6 years of age of life the disease results in a clinical reduction in peripheral and low-light vision due to degeneration of the retinal rod receptors.  Progression of the disease is variable but will often result in complete blindness. Some dogs, however, maintain acceptable daylight vision throughout their lives.

References:

OMIA link: [1876-9615]

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]

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]

Bunel M, Chaudieu G, Hamel C, Lagoutte L, et al. (2019) Natural Models for Retinitis Pigmentosa: Progressive Retinal Atrophy in Dog Breeds.  Hum Genet. 138(5):441-453. [pubmed/30904946]

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

Goldstein O, Jordan JA, Aguirre GD, Acland GM. (2013) A non-stop S-antigen gene mutation is associated with late onset hereditary retinal degeneration in dogs.  Mol Vis 19:1871-1874. [pubmed/24019744]