Retinal atrophy, Rod-cone dysplasia 3 (RCD3)

Gene: PDE6A

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, PDE6A gene; c.1940 del.A, p.(N616T fs STOP 29 nt), exon16

Medical system: Ocular

Breeds : Cardigan Welsh Corgi, Chihuahua, Chinese Crested, Pembroke Welsh Corgi, Pomeranian, Poodle - Standard

Age at onset of clinical signs: around 4 weeks of age

Progressive retinal atrophy refers to a group of diseases affecting the retina, including cone and rod cell degeneration. RCD3 in the Chinese Crested Dog and Cardigan Welsh Corgi is a retinal disease that begins at around 4 weeks of age. Changes in the tapetum can be seen on ophthalmic examination between 6 and 16 weeks of age.  As the rod cells (receptors for faint light) are the first cells to be affected, double mutant animals will first begin to loose night and peripheral vision. The disease gradually progresses to affect the cone cells (colour receptors), and the animal eventually loses daylight vision before one year of age.  Progression is variable and some affected dogs can retain very limited vision until the age of 3 or 4 years.

References :

OMIA link: [1314-9615]

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]

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, 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 Ophthalmology 17(2):126-130. [pubmed/24255994]

Tuntivanich N, Pittler SJ, Fischer AJ, et al. (2009) Characterization of a canine model of autosomal recessive retinitis pigmentosa due to a PDE6A mutation. Invest Ophthalmol Vis Sci 50:801-813. [pubmed/18775863]

Petersen-Jones SM, Entz DD, Sargan DR. (1999) cGMP phosphodiesterase-alpha mutation causes progressive retinal atrophy in the Cardigan Welsh Corgi dog.  Invest Ophthal. Visual Science 40(8):1637-1644. [pubmed/10393029]