26 January 2009
ByAppeared in BioNews 492
A new multinational study, published in Nature Genetics has identified a gene mutation which may dramatically increase the risk of developing certain types of heart disease for 60 million South Asians. The study - led by Kumarasamy Thangaraj of the Centre for Cellular and Molecular Biology in Hyderabad, India - showed that a mutation causing the loss of 25 'letters' in the genetic code for the gene MYBPC3 increased the risk of developing cardiomyopathy by over five-fold.
Heart disease is the primary cause of death in the world, linked to 17.5m deaths a year. The World Health Organisation (WHO) estimates that by 2010, 60 per cent of heart disease patients will be Indian. The new research demonstrated that carriers of the MYBPC3 gene mutation were statistically more likely to develop cardiomyopathy, a condition which causes heart muscle to become thickened, stiff and scarred. Along with other contributing factors such as high blood pressure, angina and valve diseases, it can eventually result in heart failure.
In the study, the researchers initially examined 800 patients with cardiomyopathy and matched them with 704 people without the disease who were of similar age and ethnicity, as a control. They found that the mutation increased the risk of the disease by 5.3 fold. They then looked at over 6,000 people across India, and 2,085 people from 63 other countries. The mutation was also detected in people from Pakistan, Sri Lanka, Indonesia and Malaysia, but not anywhere else. Approximately four per cent of South Asians possess the defective gene.
Cell culture studies on rats show that the defect results in a dysfunctional protein found in heart muscle. According to Mr Thangaraj, 'Young people can degrade the abnormal protein and remain healthy, but as they get older it builds up and eventually results in the symptoms that we see'.
The findings may explain why there is such a high incidence of heart disease in South Asian populations, although the research did not look at other contributing factors in such as poor diet or smoking.
'What we expect to find are common mutations with very small effects or rare mutations with big effects. The combination of big effects and high frequency is surprising', said study author Chris Tyler-Smith, a senior investigator at the Wellcome Trust Sanger Institute, Hinxton, UK.
It is possible that people could be screened for the mutation during infancy, so that they can be prepared as soon as possible to adopt a suitable lifestyle to reduce the serious risk of heart disease occurring.