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Feline Progressive Retinal Atrophy (PRA-rdAc)
| Acronym: | PRA-rdAc |
| Gene: | CEP290 |
| Mutation: | c.7584+9T>G |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Feline progressive retinal atrophy is a hereditary eye disorder in cats, which belongs to a wider group of disorders, the progressive retinal atrophies. Progressive retinal atrophy (PRA) includes autosomal recessively inherited diseases that lead to degeneration of retinal photoreceptor cells in cats, dogs, and other pets. Feline Progressive Retinal Atrophy (PRA-rdAc) is an equivalent to retinitis pigmentosa (RP), an inherited eye disorder affecting human beings. In cats, there are two main forms of PRA, ”rdAc” and ”Rdy”. PRA-rdAc is characterized by progressive degeneration of the photoreceptors in the retina, while ”Rdy” is a different form of blindness called ”rode cone dysplasia”. There are two types of photoreceptors in the eye, rods and cones. Rods have an important role in vision in dim light and also night vision. The photoreceptors are localized in the retina, an important part of the eye that takes the light and converts it into electrical nerve signals which are sent to the brain. PRA affects the retina in a way that it causes rode degeneration. This way PRA leads to night blindness.
In PRA affected, photoreceptors develop after the kitten’s birth, but as the cat ages, the receptor degenerate. Loss of retinal function is recorded by 8 months of age with early funduscopic changes detectable at 1 to 2 years of age. First symptom is night blindness, which with time progresses to complete blindness. Complete visual impairment onsets by 5 to 6 months of age. The eye of an affected cat may seem red, squinty, and with excessive tearing. Night blindness can be observed through behavioral changes, such as the cat’s refusal to go downstairs or down a dark hallway. With the disease’s progression, pupils will appear as dilated and reflection of light from the back of the eye may be noticed. Sometimes, the lens of the eye of an affected animal will become cloudy. In an affected cat, PRA can be diagnosed through an ophthalmic examination of characteristic changes in the retina. Another way of diagnostics is via electroretinography. Due to the later onset and progressive nature of the disorder, PRA in cats may be unobserved for years.
Feline Progressive Retinal Atrophy (PRA-rdAc) is an inherited autosomal recessive disease. It is caused by a mutation in the CEP290 gene. The allele shows widespread distribution and has been documented in 37% cat breeds, with high frequency in North American and European Siamese populations. A cat can be clear, carrier, or affected. Carriers of the gene are heterozygous and do not develop the disease’s symptoms. When mating two carrier cats, each future kitten has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Menotti-Raymond M, David VA, Schäffer AA, Stephens R, Wells D, Kumar-Singh R, O’Brien SJ, Narfström K. Mutation in CEP290 discovered for cat model of human retinal degeneration. J. Hered. 2007 May-Jun; 98(3):211-20. Epub 2007 May 16. PubMed PMID: 17507457.
Menotti-Raymond M, Deckman KH, David V, Myrkalo J, O’Brien SJ, Narfström K. Mutation discovered in a feline model of human congenital retinal blinding disease. Invest Ophthalmol Vis Sci. 2010 Jun; 51(6):2852-9. Epub 2010 Jan 6. PubMed PMID: 20053974.
Menotti-Raymond M, David VA, Pflueger S, Roelke ME, Kehler J, O’Brien SJ, Narfström K. Widespread retinal degenerative disease mutation (rdAc) discovered among a large number of popular cat breeds. Vet J. 2009 Sep 9. [Epub ahead of print] PubMed PMID: 19747862.