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A Boston terrier which can suffer from a brain tumor similar to those in humans, running
Learning that Boston terriers and a few other dog breeds are susceptible to a brain tumor common in humans, neuro-oncologists have become interested in a possible link in the development and treatment of the problem for both people and dogs. (GettyImages)

Dogs and Humans Share 80 Percent of Their Genes — as Well as Many Genetic Disorders

By Maria Akhter on November 30, 2017

Our furry best friends are often our world, and when they fall ill, we feel their pain. That’s when we look for help from the veterinarians and researchers at the UC Davis School of Veterinary Medicine.

And what if studying diseases in our pets could also help us? Humans and dogs have a lot more in common than you may think. In fact, research has shown that dogs have greater than 80 percent genetic similarity to humans, versus only 67 percent for mice. Many of these same DNA sequences are grouped around developmental genes, ones that can lead to disorders if something goes wrong in translation.

Veterinary researchers at UC Davis have been exploring new study methods for diseases in their canine patients. They hope that the new findings can improve the lives of their animal patients and eventually translate into new methods to treat humans.

1. Short-legged dogs share a similar gene for dwarfism

3 Pekinese dogs running up the road toward the camera
Pekingese and other short-legged dogs can suffer from an intervertebral disc disease connected to a genetic mutation also found in humans. (GettyImages)

Sure, it’s entertaining to watch dachshunds race in the annual UC Davis Picnic Day Doxie Derby with their short legs, but those features might be causing them extreme pain in other areas.

Researchers have found that dachshunds, French bulldogs, Pekingese and other short-legged dogs are more likely to experience back pain and limb paralysis, unpleasant symptoms of an intervertebral disc disease.

Because treatment for the disease can be costly and risky, veterinarian researchers investigated its cause and discovered a genetic mutation that caused both the short legs and intervertebral disc disease.

They identified an important retrogene involved in the development of the dogs’ structure. This same retrogene is found in humans and when altered by the mutation, can lead to dwarfism in humans.

The discovery could affect how we study degenerative disc diseases in people.

2. Some brain tumors can be common to dogs and people

Bulldog laying down with head on floor
Bulldogs are among the breeds that are susceptible to a brain tumor similar to one found in humans. (GettyImages)

Boxers, bulldogs and Boston terriers have more in common than the first letter of their breed names. These breeds are more susceptible to developing a specific brain tumor, the glioma tumor, which causes a decline in brain functions. The tumor grows out of infected glial cells that provide nutrients and oxygen to neurons in the brain.

Veterinary geneticist Danika Bannasch and her research partner Peter Dickinson, a veterinary neurologist, investigated these tumors, asking why they’re so prevalent in only certain breeds of dogs.

They identified three gene candidates associated with glioma development and made a huge breakthrough in suggesting that humans and dogs share a common mechanism for how the glioma develops from cell to tumor.

Spontaneous gliomas are the most common form of malignant brain tumors in humans and occur at a similar frequency in canines, so neuro-oncologists are interested in a possible link in the development and treatment of gliomas in both people and dogs. 

“Cancer is cancer,” Dickinson says. “The big pathways altered in humans are likely to be altered in dogs as well.”

3. Veterinarians test immune therapy in clinical trial

Veterinary surgeons and nurses in the surgery room positioning a canine patient
Michael Kent (center) positions a dog for a CT scan at the UC Davis Veterinary Hospital. (Don Preisler/UC Davis)

Veterinarian and radiation oncologist Michael Kent and his research partner Arta Monjazeb, a fellow radiation oncologist, tested an immune therapy that shrinks lung cancer in dog patients, and they will soon be introducing the test to animal clinical trials. Kent also conducts stem cell research and has a new paper coming out soon on using a dog’s natural killer cells, immune cells that reject infections, to attack osteosarcoma, a bone cancer similarly found in humans.

“For a long time, we’ve looked at humans to see how to treat dogs,” Kent said. “We’re starting to do a little bit of the reverse now.”

It’s appropriate to use dogs as the comparison research animal because they’re often susceptible to the same carcinogenic environmental factors as humans and can get cancer spontaneously like humans do.

4. Cleft palate research for humans grows thanks to canine study

Nova Scotia duck tolling retriever
Nova Scotia duck tolling retrievers like this one are subject to cleft palate issues similar to those found in humans. (GettyImages)

Humans may not use their mouths to chew on bones the ways dogs do, but human and canine mouths are still similar enough to be subject to the same diseases. Cleft palate, a facial malfunction that splits open the upper lip, affects one in 1,500 human babies annually and is also found in the jaws of Nova Scotia duck tolling retrievers.

Researchers have identified the genetic mutation that causes the form of cleft palate found in dogs. As common as cleft palate is in humans, it isn’t completely understood, and veterinary researchers hope that their discovery can provide the first dog model for the facial defect.

Veterinary geneticist Danika Bannasch found the mutation by conducting a genome-wide study of the particular retrievers that have the naturally occurring cleft palate. The dogs had shortened lower jaws, similar to the humans who have Pierre Robin Sequence, a type of cleft palate.

“This discovery provides novel insight into the genetic cause of a form of cleft palate through the use of a less conventional animal model,” says Bannasch. “It also demonstrates that dogs have multiple genetic causes of cleft palate that we anticipate will aid in the identification of additional candidate genes relevant to human cleft palate.”

By studying the genetic similarities in animals, researchers can make important strides in understanding how diseases begin and how to cure them. Connect with the UC Davis School of Veterinary Medicine to read about more breakthroughs in animal research.

Maria Akhter ’18, an economics and comparative literature double major, is an intern for UC Davis Strategic Communications. She enjoys using writing to connect with her campus community.

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