Study links genetic traits to bipolar disorder
By Will Dunham, ReutersWASHINGTON -- Two genes that influence the activity of nerve cells in the brain may play a key role in a person’s risk for bipolar disorder, marked by dramatic swings from depression to manic behavior, researchers said on Sunday.
August 19, 2008, 12:00 am TWN
The findings are not expected to lead to a genetic test for the risk of the condition but could help unravel the mystery of how it arises and lead to better treatments, they reported in the journal Nature Genetics.
An international team of scientists examined the genomes of 10,596 people mainly from Britain and the United States, including 4,387 with bipolar disorder, also sometimes known as manic-depression.
The researchers found those with bipolar disorder more likely to have certain variants of the ANK3 and CACNA1C genes. Proteins made by the two genes help govern the flow of sodium and calcium ions into and out of neurons in the brain, influencing the activity of these nerve cells.
“The key importance of this is that it gives us a clear idea of the sorts of chemicals and mechanisms in the brain that are involved in bipolar disorder,” Nick Craddock of Britain’s Cardiff University, who helped lead the study, said in a telephone interview.
“Over a number of years, that will help researchers to develop better approaches to diagnosis and treatment.”
Because it tends to run in families, scientists have been trying to pinpoint genes involved in bipolar disorder. This was the largest genetic analysis of its kind on the disease, which affects an estimated 1 percent to 3 percent of adults worldwide, Craddock said.
The brain disorder causes extreme shifts in mood, energy and ability to function. It is marked by high periods of elation or irritability and low periods of sadness and hopelessness that can last months.
The proper function of brain neurons depends on a delicate equilibrium between sodium and calcium, the researchers said.
“The brain operates according to how quickly calcium and sodium are going in and out of cells and how much of it goes in and out,” Craddock said.
The findings suggest that bipolar disorder may stem at least in part from malfunctions in the flow of these ions, which are electrically charged versions of the chemicals.