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Does Dog DNA Hold Clue to Parkinson’s?

Tibetan terriers may hold the key to a debilitating disease

When Topper was 5 years old, he started behaving strangely. The Tibetan terrier became increasingly shy. Then he developed physical symptoms, including seizures that his person, Lynn Steinhaus described as “just terrible.” Finally, Topper had to be euthanized.

What happened to Topper is not unusual among Tibetan terriers. It turns out that many of them carry a particular mutated gene that makes them prone to a condition called NCL – adult-onset neuronal ceroid-lipofuscinosis. And a simple cheek swab can be used to identify whether a puppy is carrying the mutated gene.

This is good news for people who breed Tibetan terriers and want to avoid passing the mutation along to new generations. It also turns out to be good news for doctors and researchers who are looking for help for people with Parkinson’s disease.

That’s because the two conditions have some remarkable similarities. And the results of a 10-year study that began with Topper have now been published in an important medical journal.

Findings of this study show that within the eyes and brains of the affected dogs, cells that should be carried away are not properly “recycled” and begin to interfere with cells that contribute to visual clarity and coordination. That’s why the dogs begin to exhibit the early signs of dementia, loss of vision and coordination and then develop seizures.

And the DNA samples showed a gene that is also known to cause a hereditary form of Parkinson’s in humans.

“Dogs and people suffer from the same diseases, and it’s much easier to discover gene issues in dogs because of the unique genetics of pure-bred dogs,” said Dennis OBrien, a professor in the veterinary medicine and surgery department.

Another veterinarian, Dr. Martin Katz, helped isolate the particular gene. “Looking through samples collected from hundreds of dogs over many years, we got to the point where we’re able to say this is a disease caused by the mutation of one gene,” he said. “Finding that gene was like finding a single house in a very large city – but we had the dog family history and the tools to look through the city in a systematic way to locate address of the mutation responsible for the disease.”

Next step, according to the researchers, is to establish whether, and to what extent, something similar is going on in humans.

“Maybe what’s going on in patients with Parkinson’s is that the recycling process is messing up when you’re getting old,” O’Brien said.