PRA cord1
What is PRA:
Progressive Retinal Atrophy (PRA) is a group of inherited retinal diseases in dogs that result in blindness, and it is one of the most studied inherited disorders in canine genetics. PRA is caused by mutations that affect the photoreceptors in the retina, which are responsible for transforming light into electrical signals for the brain to process as vision. There are two types of photoreceptors: rods, which help with vision in low light, and cones, which are responsible for sharp, color vision in bright light. In PRA, mutations cause the degeneration of these photoreceptors, particularly the rods and cones, leading to blindness.
CORD-1 PRA is a specific form of PRA, also known by names like crd4, RPGRIP1-CRD, or simply cord1. It primarily affects the cone cells first, followed by the degeneration of the rod cells. One key characteristic of cord1-PRA is its variability—mutations in the RPGRIP1 gene, which were initially thought to be the main cause of the disease, do not always predict the onset or severity of PRA in dogs. Some dogs carrying two copies of the RPGRIP1 mutation (homozygotes) may never develop PRA, or may have a much later onset of the disease, especially in certain breeds.
History and Discoveries:
In 2006, researchers, led by Dr. Cathryn Mellersh, discovered a mutation in the RPGRIP1 gene in Miniature Longhaired Dachshunds (MLHDs), which was linked to PRA. This discovery led to the development of a genetic test for this mutation.
However, further research showed that not all dogs with the RPGRIP1 mutation developed PRA, and some dogs had different disease severities or ages of onset. This led to questions about whether other genetic factors influenced the disease.
Further Research (2016-Present):
In 2016, researchers identified a second gene mutation, MAP9, which, when present alongside the RPGRIP1 mutation, was strongly linked to early and severe PRA in Dachshunds. Dogs without the MAP9 mutation, but with two copies of RPGRIP1, showed less severe symptoms and often developed PRA after the age of six.
More recently, a third genetic factor, referred to as the L3 variant, has been identified as playing a role in the development of severe PRA when combined with both RPGRIP1 and MAP9 mutations.
Genetic Testing for Cord1-PRA:
Currently, there are genetic tests available for the RPGRIP1 mutation, which is a significant factor in cord1-PRA. However, tests for the MAP9 mutation and the L3 variant are not yet commercially available.
In summary, cord1-PRA is a complex disease with significant variability. While the RPGRIP1 mutation plays a central role, other genetic factors, including MAP9 and L3 variants, also contribute to its onset and severity.
Reference: https://mydogdna.com/blogs/news/the-saga-of-cord1-pra-testing-in-dogs
The researchers at Helsinki Yliopisto and Folkhälsan Institute found the RPGRIP1-gene mutation which causes PRA-type called CORD1 in Curly Coated Retrievers.
PRA is recessively inherited (affected dogs have got mutation from both parents) with low penetrance. Based on the results, the carrier frequency in the dog population in general as well as in Curly Coated Retrievers is quite high (Donner et al 2023). Using only genetically healthy dogs may lead to decrease of the breed’s gene pool and cause increase of some other inherited diseases. This is why carrier dogs as well as genetically affected dogs can be used for breeding with a genetically healthy dog. Additionally, taking into consideration of the current findings and the low penetrance of the RPGRIP1-mutation by it self, breeder may use discretion regarding the use of carriers.
You can find the results of some tested Curlies in the voluntary database as an attachment. In the dababase you can find the results from Finland, Germany, Australia, the Netherlands, Russia, Lithuania, Denmark, UK and so on. Please, fill the form for inclusion your dog’s results in the database.
Download the PRA-cord1 database
Download the PRA-cord1 list as pdf-file
A commercial gene test is offered for the breed trough MyDogDNA or VetGen.