Retinal atrophy, progressive, Type I (CNGB1 related)

 

Gene: CNGB1

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 and insertion, CNGB1 gene; c.2685 del.A, +c.2688 ins.6bp, p.(Y796S fs STOP 7 nt), exon25

Medical system: Ocular

Breeds: Brussels Griffon, Papillon / Continental Toy Spaniel, Phalène

Age of onset of symptoms: around 4 to 6 years

Progressive retinal atrophy refers to a group of genetic diseases affecting the retina and involving the progressive degeneration of the rod and cone light receptor cells.  Rod receptor cells detect weak light and are useful for night vision as well as for peripheral vision.  Cone receptor cells detect color vision and are useful for day vision.  PRA-type 1 of the Papillon and the Phalène is a genetic disease of the retina where clinical signs first appear around the age of 4 to 6 years.  Because the rod receptor cells are first to be affected, the dog that is double mutant will start to lose its night and peripheral vision.  The development of the disease is slow but progressive; eventually the cone receptor cells are affected and dogs now begin to lose its day vision.  An affected dog can retain limited day vision for up to several years, but the final outcome is usually blindness.  Changes in the retina can be identified during an ophthalmic examination.

 

References:

OMIA link : [2723-9615]

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]

Ahonen SJ, Arumilli M, Lohi H. (2013) A CNGB1 frameshift mutation in Papillon and Phalène dogs with progressive retinal atrophy. Plos One 8(8):e72122. [pubmed/24015210]