CHICAGO Mice born without a key brain protein
developed obsessive compulsive symptoms that went away when
treated with anti-anxiety drugs, giving new clues about the
brain mechanism behind the disorder, researchers said on
They said mice who lacked the gene SAPAP3 -- which makes a
protein that helps nerves communicate -- groomed their faces
until they bled and developed an aversion for bright, open
"We think they cannot control themselves," said Guoping
Feng, a molecular geneticist at Duke University Medical Center
whose study appears in the journal Nature.
Feng said these behaviors resembled those of humans with
obsessive compulsive disorder, known as OCD.
The anxiety disorder is marked by intrusive thoughts and
repetitive compulsive behaviors, such as frequent hand washing,
that disrupt daily life. OCD affects up to 2 percent of the
Feng and colleagues had been focusing their research on the
function of the protein made by the gene SAPAP3. They bred mice
that lacked the gene.
Initially, these mice were normal but after four to six
weeks they developed raw patches on their faces. Videotapes
revealed compulsive grooming.
Further testing showed the mice were excessively anxious.
When placed in a dark box with a door leading to bright open
spaces, normal mice would venture out but mice who lacked the
protein remained inside the box.
"They feel the bright place is the riskier environment,"
Feng said in a telephone interview. "This is additional
evidence that they have increased anxiety."
When the researchers restored the missing gene, the mice
Fluoxetine, an anti-anxiety drug sold by Eli Lilly and Co.
under the brand name Prozac and used to treat OCD symptoms in
humans, also relieved the symptoms.
Feng said the study was the first to suggest that a defect
in the part of the brain called the striatum can cause OCD
SAPAP3 is part of a family of proteins that regulate the
neurotransmitter or message-carrying chemical glutamate. Feng
believes this neurotransmitter may be a useful target as
companies develop new drugs for anxiety disorders.