Ocicat and Progressive Retinal Atrophy (PRA-rdAc / CEP290): What the DNA Test Really Tells You

The short answer: The Ocicat is a wholly American-created breed (Michigan, 1964), and like several cat breeds it can carry rdAc, an autosomal-recessive variant in the CEP290 gene (c.7584+9T>G) that causes a late-onset progressive retinal atrophy. Because it is recessive, only cats with two copies degenerate; carriers stay clinically normal but pass it on. A DNA test reports clear / carrier / affected — genetic risk and breeding information, not a diagnosis, and it cannot say how far any degeneration has progressed.

What rdAc and CEP290 are (and why Rdy is different)

SamAn old college roommate’s Ocicat got an “rdAc carrier” result and he’s convinced the cat’s going blind.

Elena MarshAlmost certainly not from this gene: rdAc is autosomal recessive, so a one-copy carrier stays clinically normal — the variant was first mapped in cats by Menotti-Raymond et al. (2007, J Hered; PMID 17507457).

The rdAc form of feline progressive retinal atrophy is caused by a splice variant in the CEP290 gene — the legacy name is IVS50+9T>G, and the current HGVS designation is c.7584+9T>G (OMIA:001244-9685). It is autosomal recessive and late-onset. CEP290 builds the “gatekeeper” at the photoreceptor connecting cilium — the narrow bridge between the cell’s protein-making inner segment and its light-sensing outer segment. The splice mutation truncates the protein, so opsins can no longer be transported across the cilium, the outer segments can’t be built or maintained, and the rods degenerate first, followed by the cones. One important distinction: a separate Abyssinian PRA called Rdy exists — that one is in a different gene (CRX), is autosomal dominant, and is early-onset. Rdy is not the same disease as rdAc, and this article is about the recessive rdAc/CEP290 form.

How common rdAc is in Ocicats and other breeds

SamSo is rdAc actually common in Ocicats?

Elena MarshIt’s relatively low in Ocicats — the 43-breed survey of Menotti-Raymond et al. (2009, Vet J; PMID 19747862) put the Ocicat rdAc allele frequency at 0.083, versus roughly 0.27 in Siamese.

Because the Ocicat descends from Siamese and Abyssinian lines — both of which carry rdAc — it is not surprising that the variant appears in the breed, but at a comparatively modest frequency. In the Menotti-Raymond 2009 survey, the Ocicat sample (N=18) contained 15 clear, 3 carriers and 0 affected cats, giving an allele frequency of 0.083. The same survey found much higher frequencies in the Siamese and Oriental families. The table below reports those figures directly; note that the Peterbald estimate rests on a very small sample and should be read with caution.

Symptoms and late-onset progression

SamIf a cat were affected, when would anyone even notice?

Elena MarshNot early — rdAc is genuinely late-onset, with ERG and clinical changes appearing around 1.5–2 years, which is exactly what Narfström et al. (2009, Vet Ophthalmol; PMID 19751487) documented in genotype–phenotype work.

The reason rdAc is so easy to miss is its timing. An affected cat typically sees normally through its first year and beyond. The connecting-cilium defect gradually starves the outer segments, so the rods — responsible for dim-light and night vision — break down first, and the earliest signs are subtle: hesitation in low light, or bumping objects at dusk. Measurable changes on electroretinography (ERG) and clinical fundus exam tend to appear around 1.5–2 years of age, with blindness developing over the subsequent years as the cones follow the rods. Because this is a slow, progressive rod-cone degeneration rather than a congenital condition, owners often notice nothing until the cat is well into adulthood.

Clear, carrier, affected — and the breeding math

SamMy roommate wants a litter someday. Does “carrier” rule that out?

Elena MarshNo — because rdAc needs two mutant copies to cause disease, a carrier × clear mating produces zero affected kittens, exactly as the autosomal-recessive model predicts.

A DNA test reports one of three results for this variant: clear (two normal copies), carrier (one copy — clinically normal, and never goes blind from rdAc), or affected (two copies, at risk of developing rdAc degeneration). UC Davis’s Veterinary Genetics Laboratory frames its rdAc test in exactly these clear / carrier / affected terms. Because the disease is recessive, the breeding math is simple and reassuring:

• carrier × carrier → on average 25% affected, 50% carrier, 25% clear.
• carrier × clear → no affected kittens (50% carrier, 50% clear).

The responsible goal is therefore not to purge carriers from a small gene pool, but to avoid pairing a carrier with an affected or carrier mate. Bred to a clear cat, a carrier produces zero affected offspring while preserving genetic diversity — which matters in a breed with a modest founding population.

What the test can and cannot tell you

SamSo if the test says “affected,” does that mean the cat is already blind?

Elena MarshNo — the test only reads the CEP290 c.7584+9T>G genotype (OMIA:001244-9685); it cannot say how far any degeneration has progressed, which is what an ophthalmologist’s fundus exam and ERG are for.

An rdAc DNA test is genetic risk and breeding information for one specific variant — not a clinical diagnosis. It tells you whether the cat carries zero, one, or two copies of CEP290 c.7584+9T>G, and nothing more. It does not reveal how far degeneration has advanced, and because rdAc is late-onset, an “affected” genotype in a young cat does not mean it is blind today. A clinical diagnosis is made by a veterinary ophthalmologist through a fundus (retinal) examination and, where needed, electroretinography (ERG). No treatment reverses rdAc, so the real value of the DNA test is early awareness and responsible breeding — it complements an eye exam and never replaces one.

FAQ — Frequently Asked Questions

Q. My Ocicat tested “carrier” for rdAc. Will it go blind?
Not from this gene. rdAc is autosomal recessive, so a carrier has only one copy, stays clinically normal, and never develops rdAc-related blindness. Two copies (affected) are needed to be at risk.

Q. Is rdAc the same as the Abyssinian Rdy disease?
No. Rdy is in a different gene (CRX), is autosomal dominant, and is early-onset. rdAc/CEP290 is recessive and late-onset. They are distinct conditions and should not be conflated.

Q. Can I still breed a carrier Ocicat?
Yes. Bred to a clear mate, a carrier produces no affected kittens (only carriers and clears). Testing lets you avoid carrier × carrier or carrier × affected pairings rather than removing carriers from a small gene pool.

Q. Does an “affected” result tell me how bad my cat’s vision is?
No. The DNA test reports genotype only; it cannot measure how far degeneration has progressed. Because rdAc is late-onset, a diagnosis and staging require a veterinary ophthalmologist using a fundus exam and ERG.

References

• CFA — The Ocicat (breed article): https://cfa.org/ocicat-article/
• CFA — Ocicat breed page: https://cfa.org/breed/ocicat/
• OMIA:001244-9685 (CEP290, rdAc, Felis catus): https://www.omia.org/OMIA001244/9685/
• Menotti-Raymond M, et al. 2007, J Hered 98(3):211 (PMID 17507457): https://pubmed.ncbi.nlm.nih.gov/17507457/
• Menotti-Raymond M, et al. 2009/2010, Vet J 186(1):32 (PMID 19747862): https://pmc.ncbi.nlm.nih.gov/articles/PMC6984347/
• Narfström K, et al. 2009, Vet Ophthalmol (PMID 19751487): https://pubmed.ncbi.nlm.nih.gov/19751487/
• UC Davis VGL — PRA (rdAc) test: https://vgl.ucdavis.edu/test/pra-rdac

About the author

Elena Marsh

Editor & writer (not a veterinarian)

A writer with a molecular-biology background and a lifelong dog and cat owner. Not a veterinarian — she translates peer-reviewed genetics research and primary data into plain language, always as information rather than diagnosis.