Researchers study a rare dog breed with a mutation that causes blindness
Dogs' eyes are similar in many ways to humans' eyes, anatomically and genetically
Finding mutations in dog genes may lead to understanding of what causes human blindness
In a mural from the year A.D. 79, a dog leads a blind man across a marketplace in Pompeii.
Dogs have lent their eyesight to people who need it, perhaps since the friendship between human and beast began. And now, mapping the genes of blind dogs could lead to treatments for the visually impaired.
By uncovering canine eye mutations, veterinary researchers are coming closer to understanding two of the most common diseases that cause blindness: glaucoma and retinitis pigmentosa.
It turns out that dogs’ eyes are similar to humans’, the veterinary researchers say, and what goes for theirs often goes for ours, too. So much so, that a U.S. foundation for research into blindness has funded some of their work.
A random phone call
Andras Komaromy’s research journey began 10 years ago with a phone call from a breeder, who was watching dogs slowly go blind from a strange retinal disease.
“I drove more than 500 miles from Philadelphia to Michigan to examine the affected dogs,” the research veterinarian said in a statement. He eventually moved there and researched the disease at Michigan State University.
The dogs were all of the same breed, Swedish Vallhunds. The hereditary disease appeared to be relatively new. Scandinavian veterinary eye examiners began seeing it in late 1990s.
The Swedish Vallhund is small, stocky and pointy-eared, with thick gray to red fur in a pattern resembling that of a German shepherd. Despite its compact size, it’s tough and fearless, the American Kennel Club says – a “big dog in a small body.”
It’s an athletic herder and a friendly family dog. It impresses in show competitions – dashing through “flyball” obstacle courses or walking through obedience drills.
It’s also called a Viking dog, because its ancestors go back at least to those times, and the breed almost died out during World War II in Sweden until a nobleman intervened. Swedish Vallhunds are still not found in many places.
Search for Viking dogs
So, Komaromy hit the road to dog shows in Scandinavia and North America to examine the Viking dogs. And he found colleagues Hannes Lohi and Paivi Vanhapelto doing similar research in Finland.
They covered seven countries on three continents to examine 324 dogs, and with the dog owners’ permission and supervision by an animal ethics group, they tested blood samples from the dogs to study their genomes.
The researchers nailed the degenerative retinal disease down to a mutational defect on a gene designated as MERTK (c-mer proto-oncogene tyrosine kinase). They published the results in a study last month.
Problems with the gene are already associated with incurable retinal blindness in humans. When things go wrong with the gene, tissue in the retina can slowly atrophy.
By marking the gene, they can help breeders avoid spreading the hereditary disease, but they will also work to develop a treatment that inhibits the mutated gene to put the brakes on the disease.
The researchers hope it will lead to similar possibilities in humans stricken with retinal disease, since not only the anatomy of a dog’s eye is similar to a human’s, but how genes shape them is as well.
“Canine retinal disease models contribute significantly to our understanding of retinal disease mechanisms and the development of new therapies for human patients,” they said.
’National dog of Norway’
Studies on blindness in another dog, also believed to be of Viking origin, has led the same research team to make advances in the fight against glaucoma, a much more widespread cause of blindness in humans.
It affects roughly 66 million people worldwide, the researchers said.
The Norwegian elkhound is sometimes called the “national dog of Norway.” It and the Vallhund look like they could be cousins.
It’s also stocky but not as slight as the Swede and more of a hunter and guard dog than a herder. It has similar markings but is silver-gray, the AKC says. It has a low-key temperament but gets very attached to its family and has a hard time being away from it.
Human glaucoma is caused by multiple factors, the scientists said in a study.
But they found that a major form of glaucoma in the elkhound is associated with a mutation on the so-called ADAMTS10 gene.
Here, too, their work makes it possible to develop a genetic test to help breeders stop passing on the hereditary disease. And Komaromy’s laboratory is working on a treatment for the blindness it causes.
The San Francisco-based Glaucoma Research Foundation has supported his work with a grant.