Compulsive behavior in mice cured by bone marrow transplant

The mice shown here both had a mutant gene named Hoxb8 that originated in bone marrow and caused the mice to groom themselves pathologically, pulling out their hair. The mouse on the left displays hair loss on its chest and flank. After receiving a bone marrow transplant from a normal mouse three months earlier, the mouse at right fully recovered from the pathological grooming mutation and regrew its lost hair. University of Utah geneticist and Nobel Laureate Mario Capecchi says the study is the first to show and direct cause-and-effect link between an immune system defect and a psychiatric disorder. (Credit: Shau-Kwaun Chen, University of Utah)

This is one of those periodic discoveries that totally changes the way we think about behavior and mental illness. Wow.