Retinal atrophy, Cone-rod dystrophy 3 (CRD3)

Gene: ADAM9

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, ADAM9 gene; c.1592_1881 del. >23Kb, exons 15-16

Medical system: Ocular

Breeds : Glen of Imaal Terrier

Age of onset of clinical signs: 3 to 5 years

Cone-rod dystrophy 3 (CRD3) is an inherited eye disease of adult dogs.  It involves degeneration of the photoreceptors in the retina: cones for colour and day vision, and rods for dark (night) and peripheral vision.  A veterinary examination can detect the disease as early as 3 years of age, through visible changes in the tapetum lucidum, the structure behind the retina.  Affected dogs first show a loss of vision in the dark, followed by a loss of peripheral vision.  The disease progresses slowly, but gradually leads to complete blindness, sometimes taking several years.

References:

OMIA link: [1520-9615]

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]

Goldstein O, Mezey JG, Boyko AR, et al. (2010) An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9.  Molecular Vision 16:1549-1569. [pubmed/20806078]

Kropatsch R, Petrasch-Parwez E, Seelow D, et al. (2010) Generalized progressive retinal atrophy in the Irish Glen of Imaal Terrier is associated with a deletion in the ADAM9 gene. Mol Cell Probes. 24(6):357-63. [pubmed/20691256]