A team of US researchers has identified a genetic change that could trigger bipolar disorder, a type of mental illness commonly known as manic depression. Alterations in the GRK3 gene could be involved in up to 10 per cent of cases, claim the scientists, who are based at the University of California, San Diego. Their findings, published in the journal Molecular Psychiatry, show that the changes occur in the gene's 'on-off' switch. 'One of the major limitations in bipolar treatment is the lack of new molecular targets for drugs' said lead author John Kelsoe. 'Our hope is that the discovery of genetic defects that cause bipolar disorder will lead to drugs that can be directed to those specific genes'.
Manic depression is characterised by alternating bouts of depression and mania, during which the patient becomes agitated and euphoric. The symptoms are thought to be caused by an imbalance in the levels of brain chemicals involved in mood, including dopamine. GRK3 controls the brain's sensitivity to dopamine, and it could be that alterations in the control region of the gene affect a person's response to the chemical. 'We believe that a defect in GRK3 may make one super-sensitive to dopamin, somewhat like being born on cocaine' said Kelsoe.
The researchers found an association between the altered gene and the disorder in one group of 153 families, and a second group of 275. They also found that rats with a mania-type condition showed unusual patterns of GRK3 gene activity. But Kelsoe stresses that more research is needed to confirm the association, and also says that there are probably 'dozens' more genes involved in the illness. Amanda Harris, of the UK Manic Depression Fellowship, said that better treatments for the condition were badly needed. 'Manic depression probably has several underpinning reasons, and at the moment treatment is very hit and miss' she said.