What Dogs Can Teach Us About OCD and Cancer
WHY YOU SHOULD CARE
Because dogs are doctors’ best friends too.
Doberman pinscher puppies clumsily shuffle around a white-walled enclosure, getting tripped up by their oversize paws. Then, without warning, one of the pups slumps over, catatonic. Although Dobermans have a reputation as fierce guard dogs, they also succumb to a particularly strange kind of kryptonite: narcolepsy.
It may be entertaining for the scientists who ring the pen to watch narcoleptic pups fall asleep mid-romp, but there’s a serious reason why the dogs have captured the attention of geneticists. By studying the DNA of Doberman puppies, Emmanuel Mignot of the Stanford Center for Sleep Sciences and Medicine and other specialists were able to isolate the gene that causes the neurological sleep disorder, which also afflicts humans. Mignot’s 1999 discovery led him and others to identify the gene in human DNA and make progress toward treatments.
Scientists from Arizona to Massachusetts are researching a slew of medical conditions by looking at the DNA of greyhounds, rottweilers, Irish wolfhounds and other breeds.
As it turns out, we can learn a lot about human diseases and potential cures by studying our canine friends. Locating disease-causing genes is much simpler in dogs than in humans because dogs have fewer genetic variations for scientists to sift through. Human DNA contains approximately 1 million genetic markers; a dog breed contains about 170,000. This difference means that researchers need 400 to 600 dogs for a genetic study of a canine disease. That same study in humans would require 100 times more barkers. Selective breeding also means there’s greater uniformity in dog DNA, so it’s relatively straightforward for geneticists to locate aberrations.
Armed with these insights, scientists from Arizona to Massachusetts are researching a slew of medical conditions — rare bone cancers, obsessive-compulsive disorder, Alzheimer’s disease, deafness, autism, even obesity — by looking at the DNA of greyhounds, rottweilers, Irish wolfhounds and other breeds. Some diseases are known to be more prevalent in certain breeds, such as cancer in golden retrievers, epilepsy in beagles and autoimmune disorders in Siberian huskies, which helps narrow the search area for mutated genes even further.
As the field expands, so does support and research money. There’s “absolutely growing interest” and “acceptance” that studying diseases in dogs can “help us understand human disease,” says Will Hendricks, an assistant professor in the Integrated Cancer Genomics Division of the Translational Genomics Research Institute, in Phoenix. Earlier this year, the National Advisory Council for the Dog and Human Precision Medicine Initiative “helped stimulate a coming sea change,” Hendricks says. First-time NIH grant opportunities are becoming available, and a growing number of for-profit companies are jumping on the bandwagon.
The growing interest in canine genetics is hardly surprising, considering Americans are famously obsessed with their pets. Nearly 45 percent of American households have at least one dog, according to the Humane Society. The estimated pet dog population: a staggering 77.8 million animals. To scientists, that’s a giant untapped pool of potential research subjects that already live in relatively controlled environments. “One of the wonderful things about dogs is that every dog lives with a human who watches it all the time,” says Elinor Karlsson, a postdoctoral scientist at the Broad Institute of MIT and Harvard who specializes in evolutionary genomics. “It’s this incredible resource for science.”
Humans know what and how much dogs eat, their patterns of movement and whether they are acting lethargic or displaying strange behaviors like incessant tail chasing or flank sucking. That’s why dog geneticists are harnessing citizen science to crowdsource dog DNA. Darwin’s Dogs, part of the Broad Institute’s research effort, posted a series of 10-question surveys on its website in October 2015, hoping to get responses and DNA samples from 5,000 dog owners within a few years. By June, dog owners had answered more than 616,000 questions and volunteered nearly 7,000 pets for the project. Put simply: It’s a scientific trifecta — a win for scientists, pet lovers and their animals, all of which will benefit from new health insights.
Certainly, some researchers remain more comfortable working with rats and mice than canines. For them, the home of even the fussiest anal-retentive is an uncontrolled environment. Hendricks acknowledges that “the naturally occurring cancer model is in a unique space between a highly artificial model and a human model.” For other naysayers, there is a mental block. Humans are special; how could we possibly gain insights about OCD, say, from mangy mutts? On the other hand, Nicholas Dodman, a professor at the Cummings School of Veterinary Medicine at Tufts University, notes, “Some psychiatrists don’t think you can learn anything from dogs, which is kind of ironic since everything we know about humans comes from mice.”