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In dog genes, we may find clues to human behavior

Some conditions, such as obsessive-compulsive disorder and aggression, may be easier to study in animals.

October 08, 2007|Judy Foreman | Special to The Times

For months, Dr. Nicholas Dodman, head of the animal behavior clinic at the Cummings School of Veterinary Medicine at Tufts University, has been in doggie heaven.

Using brand-new genetic "chip" technology developed by researchers at the Broad Institute of Harvard and MIT, where the entire dog genome was sequenced a couple of years ago, Dodman is finally poised to do the experiments he's been waiting years to do -- exploring the genetics of complex psychiatric problems in dogs.

The "chips" are silica wafers containing thousands of different pieces of dog DNA whose precise sequence is known. Researchers can take a sample of DNA from a particular dog and process it chemically so that they can visualize it (using a fluorescent "tag"). From the spots on the chip that light up, they can determine exactly where the DNA from the dog they are studying varies from the standard DNA.

Dodman will first compare DNA from Doberman pinschers that suck fanatically on their own flanks with DNA from normal Dobermans to see precisely where the genes for this compulsive disorder lie. Then, he will do the same DNA comparisons of normal bull terriers and abnormal ones with another compulsive behavior, tail-chasing. Dodman and other scientists also hope to use the latest techniques to find the genetic roots of rage in springer spaniels, which in theory might help explain some human aggression.

"This is absolutely revolutionary," Dodman said recently.

Until new MIT chip technology came along, the Tufts team was looking gene by gene to try to unravel the genetic origin of compulsive behavior in dogs. Now they can search for multiple genes at once, knowledge that should also shed light on aggression and obsessive-compulsive disorders, or OCD, in people.

"It's like the difference between searching house by house for insurgents in Iraq and looking at the whole of Baghdad at once," he said.

These diseases can be easier to study in dogs than humans.

"The genetics of obsessive-compulsive disorder and other mental illnesses are likely to be very complex -- and very difficult to study in humans," said Dr. Francis Collins, director of the National Human Genome Research Institute at the National Institutes of Health. "With their selective breeding and well-characterized behaviors, purebred dogs may provide a powerful system for untangling the genetic roots of these disorders."

Incessant tail-chasing, for instance, is very breed-specific in dogs, said Alice Moon-Fanelli, a Tufts behavioral geneticist who works with Dodman. But not all researchers think studying dogs for insights into human behavior is a good idea. For OCD, for instance, human subjects make more sense, according to Dr. Michael Jenike, a professor of psychiatry at Harvard Medical School, because people can describe what they're thinking -- and a dog, obviously, cannot. Jenike thinks his current research, searching for genetic markers in people with the disorder, will yield better scientific results about a disease that affects 6 million Americans and is characterized by intrusive, repetitive thoughts and ritualistic behaviors like excessive hand-washing.

Linking research on animal aggression with human behavior used to be controversial, but now people are more accepting of the idea that genetics can influence human behavior, said Dr. Frederick Goodwin, a psychiatrist and director of a center of neuroscience, medical progress and society at George Washington University Medical Center. The genetics of human aggression are still unclear.

In dogs, though breeders hate to hear it, 27% of springer spaniels bite people -- usually their owners -- said Cornell University veterinarian and animal behaviorist Katherine Houpt. Houpt and other dog geneticists are working to unravel the roots of this aggression. Researchers in her lab found lower levels of two key neurotransmitters -- serotonin and dopamine -- in the more aggressive dogs.

Houpt's lab is now working with Elaine Ostrander, chief of the comparative genetics branch at the National Human Genome Research Institute to look for "candidate" genes that may underlie aggression.

After that, said Ostrander, who knows what dog researchers will be looking for. But she's sure of one thing. "People would love to understand the genetics of affection or blind adoration."

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