HYDERABAD: An international team of researchers, including from the city-based Centre for Cellular and Molecular Biology CCMB ) has decoded the genetic secrets behind certain rare diseases present in people living in India and other parts of South Asia.The research study was published in the latest issue of the prestigious scientific journal, Nature Genetics. The scientists described how the 1.5 billion people of South Asia are particularly vulnerable to rare genetic diseases. The study provides an extraordinary opportunity to identify mutations that are responsible for population-specific disease and to test for and decrease the burden of recessive genetic diseases in South Asia.According to the researchers, each person in the world – not only in South Asia – carries several mutations that, if they occurred in two copies, would leads to serious “recessive” diseases. In South Asia, “founder events” in which small numbers of ancestors carrying such mutations gave rise to large numbers of descendants – combined with endogamy leading to marriage only within groups – causes these mutations to often be carried in two copies, leading to a far higher rate of populations-specific diseases than elsewhere in the world.The researchers said South Asia is inhabited by about 5,000 anthropologically well-defined populations, many of which are endogamous (marrying within a population) communities with significant barriers to gene flow due to sociological, linguistic and cultural factors that restrict inter-population marriage. Several diseases that are specific to populations of South Asia have been identified in the past. However, the genetic causes for the vast majority of population-specific disease are largely unknown.CCMB director Dr Rakesh Mishra said the study will help in accelerating predictive and personalized medicine.From the CCMB the study was led by senior scientist Dr Kumarasamy Thangaraj . The team identified that about a third of populations in South Asia have had strong founder events/population bottlenecks, which are responsible for a high rate of population-specific disease in the region.“We have analysed samples from more than 2,800 individuals from over 275 distinct South Asian populations who belongs to various social and linguistic groups from India, Pakistan, Nepal, Sri Lanka, and Bangladesh using about 600,000 genome-wide markers”, said Dr Thangaraj.As an example of founder event disease gene mapping in South Asia, the authors highlighted the case of the Vysya community. The Vysya have an approximately 100-fold higher rate of butyrylcholinesterase deficiency than other groups, and Vysya ancestry is a known counter-indication for the use of muscle relaxants such as succinylcholine or mivacurium that are given prior to surgery.