Genetic link
eyed in dogs' troubled ways
By Judy Foreman
September 3,
2007
All summer,
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.
First,
he'll compare the DNA he has collected from Doberman
pinschers who 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, endless 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 last week.
Until the
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." 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. When people bring
their pets in for excessive tail chasing, "nine
times out of 10, it's a bull terrier or a German
shepherd."
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 the testing is easy
- just a blood test - and people can describe what
they're thinking, which 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 people nowadays are
generally 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, although it's
obvious that "having been hit by your dad makes
aggressiveness even worse," he said.
In dogs,
though breeders hate to hear it, 27 percent 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. This fits, Houpt noted, with
some human data linking low serotonin levels to an
increased risk of suicide, which many researchers
consider a form of self-aggression.
Houpt's lab
has collected DNA samples from both aggressive and
non-aggressive dogs and is now working with Elaine
Ostrander, chief of the comparative genetics branch
at the National Human Genome Research Institute
(part of the National Institutes of Health) 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."
