Retinal atrophy – rod and cone dysplasia

Progressive retinal atrophy is a disease of the retina in cats leading to early and progressive degeneration of photoreceptors. Clinically, the disease manifests itself in the first weeks of life with reduced pupillary reflexes, dilated pupils, nystagmus, patchy changes in the retina, hyperreflectivity of the tapetal part of the eye fundus, and gradual development of blindness during the first months.

The disease occurs in Abyssinian and Somali cats and is caused by a c.546del mutation in the CRX gene, which encodes a transcription factor specifically expressed in retinal
photoreceptor cells.

The mutation is inherited in an autosomal incomplete dominant pattern. This means that one copy of the mutated gene inherited from one parent is sufficient for the symptoms of the disease to manifest. However, the affected homozygote will differ from the heterozygote in the severity of the symptoms. Genetic testing can clearly reveal the genotype of an animal and is a useful tool for breeders to prevent the unintentional breeding of kittens with this disease.

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References:

Menotti-Raymond, M., Deckman, KH., David, VA., Myrkalo, J., O'Brien, SJ., Narfstrom, K. : Mutation discovered in a feline model of human congenital retinal blinding disease. Invest Ophthalmol Vis Sci 51:2852-2859, 2010. Pubmed reference: 20053974