Retinal atrophy, Rod-cone dysplasia 2 (RCD2)

Gene: RD3

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: Insertion, RD3 gene; ins.22pb, exon4

Medical system: Ocular

Breeds: Collie, Collie - Rough, Collie - Smooth

Age of onset of clinical signs: 6 weeks

Progressive retinal atrophy, RCD2 is one of a number of diseases involving progressive degeneration of the retinal. This involves degeneration of the cone and rod cells, the retinal photoreceptors that enable vision in daylight and darkness respectively. Very early in the puppy’s life, the affected animal shows a loss of vision in twilight, as the rod cells are affected more rapidly than the cone cells. By 6 months of age, the puppy is generally blind.

References:

OMIA link: [1260-9615]

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]

Kukekova AV, Goldstein O, Johnson JL, et al. (2009) Canine RD3 mutation establishes rod cone dysplasia type 2 (rcd2) as ortholog of human and murine rd3.  Mamm. Genome 20(2):109-123. [pubmed/19130129]