The new DNA test means there is no reason why another English Shepherd Dog ever needs to be born with progressive retinal atrophy, which causes total blindness. (Credit: University of Cambridge)
Researchers have identified a genetic mutation responsible for a blinding eye disease in dogs, specifically the English Shepherd breed. This discovery not only offers hope for preserving vision in these beloved canines but also sheds light on similar conditions in humans.
Progressive Retinal Atrophy (PRA) is a group of inherited eye diseases that affect over 100 dog breeds. The condition starts with night blindness and eventually leads to complete vision loss. Until now, the cause of PRA in English Shepherds was a mystery, leaving breeders and owners with limited options to prevent the disease.
A team of scientists from the University of Cambridge and Mars Petcare have pinpointed a tiny genetic change in a gene called FAM161A that’s linked to PRA in English Shepherds. This gene plays a crucial role in maintaining healthy photoreceptors – the light-sensing cells in the eye that allow us to see.
The mutation they found is fascinatingly small yet impactful. It’s called a SINE (Short Interspersed Nuclear Element) insertion, which is essentially a short piece of DNA that has inserted itself into the FAM161A gene. This seemingly minor change disrupts the gene’s normal function, leading to the gradual death of photoreceptor cells and, ultimately, blindness.
What makes this discovery particularly exciting is its potential impact on both canine and human health. The FAM161A gene is also associated with a form of retinitis pigmentosa in humans, a condition very similar to PRA in dogs. By understanding how this gene works (or doesn’t work) in dogs, researchers gain valuable insights that could lead to treatments for both species.
For English Shepherd owners and breeders, this breakthrough offers immediate practical benefits. The research team has developed a genetic test that can identify dogs carrying the PRA-causing mutation. This allows breeders to make informed decisions and reduce the likelihood of producing puppies that will develop the disease.
“Once the dog’s eyesight starts to fail there’s no treatment – it will end up totally blind,” says Katherine Stanbury, a researcher in the University of Cambridge’s Department of Veterinary Medicine and first author of the study, in a statement. “Now we have a DNA test, there’s no reason why another English Shepherd Dog ever needs to be born with this form of progressive retinal atrophy – it gives breeders a way of totally eliminating the disease.”
The study also highlights the value of dogs as models for human diseases. Dogs and humans share remarkably similar eye structures, making canine eye research particularly relevant to human medicine. As we unravel the genetic mysteries behind canine eye diseases, we simultaneously pave the way for advancements in human ophthalmology.
While there’s currently no cure for PRA, early detection through genetic testing can help manage the condition and improve the quality of life for affected dogs. It also opens the door for potential gene therapies in the future, which could one day restore or preserve vision in both dogs and humans with similar genetic eye disorders.
“An owner won’t necessarily notice their dog has got anything wrong with its eyes until it starts bumping into the furniture. Unlike humans who will speak up if their sight isn’t right, dogs just have to get on with things,” says Dr. Cathryn Mellersh, senior author of the study. “For the price of a decent bag of dog food people can now have their English Shepherd tested for Progressive Retinal Atrophy prior to breeding. It’s about prevention, rather than a cure, and it means a huge amount to the people who breed these dogs. They no longer need to worry about whether the puppies are going to be healthy or are going to develop this horrible disease in a few years’ time.”
This research serves as a poignant reminder of the intricate connection between genetics and health, and how a tiny change in our DNA can have profound effects on our well-being. It also underscores the importance of collaborative research between veterinary and human medicine, as insights gained from our four-legged friends continue to benefit both species.
Paper Summary
Methodology
The researchers used a combination of cutting-edge genetic techniques to zero in on the PRA-causing mutation. They started by sequencing the entire genomes of two affected English Shepherds. Think of this like reading every single word in a book, looking for a specific typo. They then compared these genomes to those of healthy dogs from various breeds.
To narrow down their search, they used a technique called homozygosity mapping. This is like finding a section of the book where the typo is most likely to occur. They looked at genetic markers in affected and unaffected dogs to identify regions that were consistently different in the PRA-affected dogs.
Finally, they closely examined the suspect region and found the SINE insertion in the FAM161A gene. They confirmed its presence in affected dogs and its absence in healthy ones using targeted DNA tests.
Results
The study found that all six PRA-affected English Shepherds had two copies of the mutated FAM161A gene (one from each parent). Healthy dogs either had no copies of the mutation or just one copy (making them carriers but not affected). This pattern is consistent with how recessive genetic traits are inherited.
The mutation they found extends a part of the FAM161A protein, likely disrupting its normal function in the eye. This explains why the photoreceptor cells gradually die off in dogs with PRA.
Limitations
While this study provides valuable insights, it’s important to note its limitations. The research focused on a small number of dogs, and more extensive studies would be needed to confirm these findings across the broader English Shepherd population. Additionally, while the genetic cause has been identified, the exact mechanism of how this mutation leads to vision loss still needs to be fully understood.
Discussion and Takeaways
The discovery of this PRA-causing mutation in English Shepherds is a significant step forward in canine genetics and ophthalmology. It provides a tool for breeders to reduce the incidence of PRA in the breed through genetic testing. Moreover, it contributes to our understanding of similar eye diseases in humans, potentially paving the way for new treatments.
The study also highlights the importance of investigating breed-specific genetic disorders, as each dog breed can have unique mutations causing similar diseases. This emphasizes the need for targeted genetic research in different breeds to develop comprehensive screening tools.
Funding and Disclosures
This research was supported by various organizations, including Dogs Trust, the Kennel Club Charitable Trust, and the University of Cambridge. One of the study authors is employed by a company that offers commercial genetic testing for dogs, and another manages a DNA testing service that now offers a test for this specific mutation. While these connections don’t invalidate the research, they’re important to note for transparency and to consider potential conflicts of interest.
This post was originally published on this site be sure to check out more of their content.
