Their research was published in the Science journal in the middle of this month.

"Discovery of this disease-causing gene not only sheds new light on the disease's mechanism, but may have an impact in the clinic area and drug innovation," said Chen Yihan, chief scientist of the Institute of Medical Genetics at Tongji University and Xu Shijie of Chinese National Human Genome Center in Shanghai, who led the research.

The discovery may also lead to new methods in diagnosing the cardiac disorder at an early stage for a certain group of patients.

As a common cardiac disease, atrial fibrillation hits more than 5 per cent of people aged over 65 in the world and the strike rate increases with age.

It often leads to stroke, heart failure and other serious consequences. But present medical treatments are either very poor or have serious side effects due to a limited understanding of the disease's mechanism.

It has been observed that the disease can occur in several family members, suggesting it may partly be a hereditary disease caused by genetic mutation.

Scientists, therefore, have hoped to understand its genetic mechanism before creating effective drugs to treat it.

The Shanghai-based Chinese scientists started the genome research program in 1998.

A year earlier, a foreign research group reported a hereditary atrial fibrillation link in three families after discovering a locus on chromosome 10.

The inspired Chinese research group started with a large four-generation family with hereditary atrial fibrillation history in East China's Shandong Province and focused on chromosome 11.

They found a mutation in a gene called KCNQ1 in all of the atrial fibrillation-suffering members of the family.

KCNQ1 is a gene that had already been found to be associated with another disease called Long QT syndrome, a heart disease that has been a common cause of sudden death. But its association with atrial fibrillation was previously unknown.

The newly found mutation, called S140G, was not discovered in all the healthy family members except one as well as in another 188 healthy individuals used as a control group.

It was presumed that there might be a link between the mutation and the occurrence of atrial fibrillation in the family.

Further studies revealed the S140G mutation, in combination with another two genes, plays a critical role in initiating and maintaining atrial fibrillation in family members.

The discovery of the mutation's function opens the door for the creation of medicine in the future that can assist some atrial fibrillation sufferers. But the researchers stressed that atrial fibrillation may very likely have more than one genetic cause.

There is the possibility that another mutation in a yet unidentified gene in the same critical region on chromosome 11 may also cause atrial fibrillation, they said.

"The gene may be just one of the genes leading to atrial fibrillation, but the discovery suggests new approaches to devising therapies for both inherited and other forms of atrial fibrillation," Chen and Xu added.

Prior to the discovery, Chinese scientists had reported discoveries of gene mutations that caused a certain type of deafness and a hereditary dental disease.

The discoveries largely depended on the availability of the genetic information of families with a history of a particular type of hereditary disease.

(China Daily January 29, 2003)