Scientists discover manic depression gene

Elizabeth Gosch – AUSTRALIAN scientists have become the first in the world to identify the gene that makes people vulnerable to manic depression. People with a particular form of the so-called FAT gene are twice as likely to develop bipolar disorder – also known as manic depression — according to a joint team of scientists from the Garvan Institute of Medical Research in Sydney and the University of NSW.

Lead author Ian Blair said the team was the first in the world to take a multi-faceted approach to identifying a gene that increases the risk of bipolar disorder. “We used a number of families, unrelated patients and mice treated with the current medications,” Dr Blair said. “Each of these three lines of investigation led us to a gene called FAT. “We know that the FAT gene codes for a protein that is involved in connecting brain cells together. What we need to do now is find out exactly how it contributes to the increased risk of bipolar disorder. “Once we understand what the FAT gene does, we will be able to develop better diagnostic tests for bipolar disorder.”

While previous studies have identified genes that indicate a susceptibility to bipolar disorder, none have been replicated. The Australian study drew evidence from four independent study groups – one in Australia, two in Britain and one in Bulgaria. Bipolar disorder is a major psychiatric illness affecting about one person in 50. About one in six people with the condition will commit suicide.

People with bipolar disorder suffer aberrant mood swings resulting in periods of mania and depression, reverting to stable behaviour between episodes. Symptoms of a manic episode include overactivity and talkativeness, hypersexuality, reduced need to sleep and inflated self-esteem. A depressive episode is marked by tearfulness, fatigue, loss of appetite, insomnia and poor concentration.

Lithium has long been used to help control bipolar disorder by stabilising moods. Unfortunately, it has several severe side effects, including tremors and weight gain. “In the future, we hope our research will lead to new, targeted medicines specifically for bipolar disorder that don’t have the unpleasant side effects that lithium has,” Dr Blair said.

The study, published in the medical journal Molecular Psychiatry, is a culmination of 20 years of research.