Progressive retinal atrophy type 2 (GR-PRA 2 Golden Retriever)
Progressive retinal atrophy type II (GR-PRA 2) is caused by degeneration of the retinal photoreceptor cells and, in the course of the disease, the entire retina is destroyed. Affected animals go blind.
The hereditary disease is one of the three forms of PRA in the Golden Retriever. The inheritance is autosomal recessive.
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Symptoms
- Night blindness in the early stages
- Visual disorders
- Complete blindness
General Information
- Progressive retinal atrophy type I (GR-PRA 1) is caused by a degeneration of the photoreceptor cells (rods & cones).
- First, the rods responsible for light-dark vision lose their normal function.
- Later, the cones necessary for day and colour vision are also destroyed.
- The disease is progressive.
- In the course of the disease, the retina is completely destroyed.
- GR-PRA 2 is one of three forms of PRA in the Golden Retriever, GR-PRA 1 and prcd-PRA also occur.
Breeds affected
Labrador and Golden Retriever
Test Information
This mutation test detects a deletion (c.669delA) in exon 8 of the TTC8 gene.
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Genotype and Lab Report
Inheritance: autosomal recessive.
→ The hereditary disease only occurs if both alleles of the gene are affected by the mutation (pra2/pra2). Dogs that have only one allele with the causative mutation (N/pra2) are clinically healthy carriers.
Genotypes:
N/N = genetically normal
The dog has no predisposition for GR-PRA 2 and therefore cannot pass it on to its offspring.
N/pra2 = a carrier
The dog is a clinically healthy carrier. The variation is passed on 50% to the offspring, which are also carriers.
pra2/pra2 = affected
The variation is passed on 100% to the offspring. The offspring are carriers or affected.
Recommendations
- Carrier animals can be bred to normal animals (N/pra2 x N/N). Before using the offspring in breeding, it should be tested whether they are normal or carriers.
- Mating two carrier animals (N/pra2 x N/pra2) should be avoided because there is a 25% chance that the offspring will be affected.
- Affected animals (pra2/pra2) should be excluded from breeding.
Literature
- Downs, L.M., Aguirre, G.D.: FAM161A and TTC8 are Differentially Expressed in Non-Allelelic Early Onset Retinal Degeneration. Adv Exp Med Biol 854:201-7, 2016. Pubmed reference: 26427412. DOI: 10.1007/978-3-319-17121-0_27.
- Downs, L.M., Wallin-Håkansson, B., Bergström, T., Mellersh, C.S.: A novel mutation in TTC8 is associated with progressive retinal atrophy in the golden retriever. Canine Genet Epidemiol 1:4, 2014. Pubmed reference: 26401321. DOI: 10.1186/2052-6687-1-4.
- Further information is available at: Online Mendelian Inheritance in Animals.