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Feline Progressive Retinal Atrophy (rdy-PRA)
| Acronym: | rdy-PRA, PRA-rdy |
| Gene: | CRX |
| Mutation: | c.546delC |
| Inheritance: | Autosomal dominant |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Feline Progressive Retinal Atrophy (rdy-PRA) is an eye disorder or simply a form of blindness. It belongs to a group of inherited blinding feline diseases (PRA)that affect the retina of the eye. The retina is located at the back of the eye and contains rods and cones, which are specialized cells that are essential for vision. PRA is seen in many pure breeds, although the exact genetic cause is known for only a few. An early-onset rod-cone dysplasia (Rdy) was first described in a domestic cat of the Abyssinian breed in the United Kingdom. The disorder also affects Somali and Ocicat breeds.
In feline progressive retinal atrophy (rdy-PRA) abnormal photoreceptor development is observed first at 22 days of age, with older individuals displaying more advanced photoreceptor degeneration and thinning of the neural retina. Rdy-affected cats display retarded development of the photoreceptor cells, followed by degeneration when these cells initiate functional differentiation. The disease causes loss of vision by the time a cat reaches 12-16 months of age.
Feline progressive retinal atrophy (rdy-PRA) is caused by a mutation in the CRX gene. The CRX gene is a member of the protein family that is requisite for mammalian eye development. The disorder is inherited in an autosomal dominant manner. That means that both cats carrying one copy of the mutated gene (heterozygous cats) and cats carrying two copies of the mutated gene (homozygotes for the mutation) show signs of the disease. With a DNA test for feline progressive retinal atrophy (rdy-PRA) affected heterozygotes can be differentiated from affected homozygotes which is important for future breeding and preventing of spreading the mutation in the population.
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. |
AFFECTED HETEROZYGOTE |
Tested mutation was detected in animal with „affected heterozygote“ result. Animal tested as affected heterozygote has one wild-type and one mutation allele, it is in heterozygous state. It is likely to 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.
**Penetrance of tested mutation, and potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Menotti-Raymond, M., Deckman, K.H., David, V., Myrkalo, J., O’Brien, S.J., and Narfström, K. (2010). Mutation discovered in a feline model of human congenital retinal blinding disease. Invest