A group of Taiwan scientists has identified four genes associated with bipolar I disorder in people of Chinese ethnicity.

"This study marks important progress in the identification of disease genes for bipolar I disorder. It is the only large scale bipolar I disorder study ever done on Han Chinese or on any Asian population," said the team's leader, Andrew Tai-Ann Cheng, a distinguished research fellow in Academia Sinica's Institute of Biomedical Sciences.

Bipolar I disorder is a mood disorder defined by the presence of recurrent episodes of abnormally elevated mood (mania), according to the research team.

Some patients who experience manic episodes also experience depressive episodes, or mixed episodes in which features of both mania and depression are present at the same time.

The affliction, which affects approximately 1 percent of the world's population, often interferes with patients' personal lives and affects their ability to function socially.

The scientists said the heritability of bipolar I disorder has been estimated to be around 80 percent and is passed down through multiple genes, but the exact cause of the disease remains unclear.

In the study researchers analyzed the genes of 1409 patients with bipolar I disorder and 1000 normal individuals using high density genotyping technology.

They linked four genes - SP8, ST8SIA2, CACNB2 and KCTD12 - to bipolar I disorder in ethnic Chinese people, and three of them (SP8, CACNB2 and KCTD12) were identified for the first time.

Because SP8 and ST8SIA2 influence the development of the brain, the scientists said their study supports a model attributing the development of bipolar I disorder to the growth of the brain or central nervous system.

CACNB2 and KCTD12 are genes regulating calcium and potassium ion channels, which also suggested that disorders of the ion channels - proteins that regulate the flow of ions across cell membranes - contribute to the development of bipolar I disorder.

"The genes identified in this study pave the way for researchers to elucidate pathogenic mechanisms for bipolar disorder and perhaps new drug targets for the disease," Cheng said.

With the combined effort of public health and medical centers, Cheng hopes that in the future genetic factors associated with the pharmacological effects of mood stabilizers can also be identified, leading to advances in health care, personalized medication, and the prevention of bipolar disorder and suicide.

The study was published online in the international scientific journal Molecular Psychiatry on April 13.

China Daily/CNA

(HK Edition 04/15/2010 page3)