They searched for regions that looked different between sick and healthy dogs. They also searched for genes that looked the same in all of the Dobermans but that differed between that breed and others.
When they had zeroed in on several suspicious areas of the genome, the researchers compared the suspect Doberman genes with genes from a sample of bull terriers, Shetland sheepdogs and German shepherds -- three other breeds that also suffer higher-than-usual rates of OCD.
Those analyses pinpointed four genes that have unusually high rates of mutations in dogs with obsessive and compulsive behaviors, the team reported Sunday in the journal Genome Biology. The researchers also found OCD-linked mutations in a tiny piece of the genome more than million bases away from any gene that likely plays a role in regulating the genes that play into the disease.
The genes implicated in the new study play roles in pathways that have also been connected to human OCD, Karlsson said, suggesting that dogs could provide a helpful model system for developing better treatments for people.
The new study is "another hard-won rung of the ladder toward unraveling the OCD mystery," said Janice Kloer-Matznick, an animal behaviorist and dog-origins researcher in Central Point, Oregon. But there is still a long way to go towards truly understanding the disease.
"It sounds like there is more to discover, such as interaction of alleles that result in the abnormal behavior, with no single 'smoking gun,' she added. "That's too bad as it means a simple gene test will probably not be developed, one breeders could use to screen out affected dogs and avoid breeding two carriers."