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Progressive Retinal Atrophy (PRA) is a large group of genetic diseases in which the retina gradually degenerates over time, causing a progressive loss of vision.
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Specifications
| Breeds | |
|---|---|
| Gene | |
| Organ | |
| specimen | Swab, Blood EDTA, Blood Heparin, Semen, Tissue |
| Mode of Inheritance | |
| Chromosome | |
| Also known as | |
| Year Published |
General information
Progressive Retinal Atrophy (PRA) is a large group of genetic diseases in which the retina gradually degenerates over time, causing a progressive loss of vision. One form of PRA is cone-rod dystrophy 4 (crd4-PRA, also called cord1) that occurs in Miniature Longhaired Dachshund. It is caused by an autosomal recessive mutation in the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) gene.
This test detects a mutation in the microtubule-associated protein9 (MAP9) gene, which does not cause PRA on its own but acts as a modifier for the mutation in RPGRIP1. When present together with the RPGRIP1 mutation, the MAP9 mutation can accelerate disease onset, often leading to vision problems much earlier in life.
Clinical features
Dogs affected by crd4-PRA (cone-rod dystrophy type 4) experience a progressive degeneration of both cone and rod photoreceptor cells in the retina, leading to gradual vision loss. Early signs of visual impairment can appear as young as 10 to 12 weeks of age, especially in individuals carrying mutations in both RPGRIP1 and MAP9. Common symptoms include difficulty tracking moving objects, clumsiness, and night blindness. However, the age of onset and severity vary widely: some dogs may be blind by six months, while others retain functional vision well into their senior years. On average, signs of sight loss begin around five years of age. This variability is influenced by genetic modifiers such as MAP9, which can accelerate disease progression when present alongside RPGRIP1 mutation.
Additional information
The MAP9 variant is considered a modifier of age of onset, not a primary cause of PRA. Dogs that are homozygous for both RPGRIP1 and MAP9 mutations are at the highest risk of developing early-onset vision loss.
References
Pubmed ID: 27017229
Omia ID: 1432