Scientists Spot Possible OCD Gene
In Lab Tests, Mice Lacking the SAPAP3 Gene Groom Themselves Compulsively
Aug. 22, 2007 -- Obsessive-compulsive disorder (OCD) may be affected by a
gene called SAPAP3, new research shows.
OCD is an anxiety disorder marked by recurrent, unwanted thoughts
(obsessions) and/or repetitive behaviors (compulsions) such as washing hands,
counting, checking, or cleaning, which are often performed with the hope of
preventing or getting rid of obsessive thoughts, according to background
information from the National Institute of Mental Health (NIMH).
The new OCD study, published in tomorrow's edition of the journal
Nature, is based on mice bred without the SAPAP3 gene and other mice
with a normal SAPAP3 gene.
When the mice were pups, they all behaved normally. But by the time the mice
were four to six months old, those lacking the SAPAP3 gene compulsively groomed
themselves to the point of self-injury and acted more anxious than normal
"We obviously cannot talk to mice to find out what they are thinking,
but these mutant mice clearly did things that looked like OCD," Feng says
in a Duke University Medical Center news release.
The scientists tried two strategies to relieve the OCD-like behavior and
anxiety in the mice lacking the SAPAP3 gene.
First, they gave some of those mice a daily injection of fluoxetine (the
active ingredient in the antidepressant Prozac) for six days. That eased the
mice's excessive grooming and anxiety.
The researchers' second strategy involved injecting a bit of DNA, including
the SAPAP3 gene, directly into the brains of other mice lacking the SAPAP3
gene. That reduced the mice's anxious and OCD-like symptoms.
The researchers conclude that the SAPAP3 gene may be involved in
obsessive-compulsive behavior. But that doesn't rule out other genetic or
The findings "sharpen our focus" on certain brain chemistry circuits
involved in OCD, writes Harvard Medical School neurobiology professor Steven
Hyman, MD, in a Nature editorial.
But Hyman cautions that studies in mice can't fully mimic OCD.
"In OCD patients, the main cause of anxiety is the unwanted intrusive
thoughts. The sufferers are anxious because they cannot be certain that the
door is locked, the gas has been turned off, or that they are free of dread
microbes. The anxiety-like behaviors observed in these mice may also resemble
OCD, but this requires a stretch of the imagination," writes Hyman.