Researchers make progress in studying genetic traits of India-born populations

Los Angeles, Calif., Dec. 21, 2006 -- Despite the fact that the people of India constitute more than one-sixth of the world's entire population, they have been underrepresented in studies related to genetic diseases. And with the growth of modernization, complex genetic diseases associated with urban and western lifestyles have risen to near-epidemic proportions, making genetic cataloging and association studies of particular importance.

In response to this dearth of information, a team of researchers, including Pragna I. Patel, professor of biochemistry and molecular biology at the Keck School of Medicine of the University of Southern California (USC), and Noah Rosenberg, assistant professor in the department of Human Genetics at the University of Michigan, have conducted genetic analysis of India-born individuals in the U.S. Through their studies, they have begun to shed light on the genetic variations of the diverse population of India.

In a study to be published Dec. 22 online in the journal PLoS Genetics, a peer-reviewed journal published by the Public Library of Science (PLoS), Patel and colleagues analyzed 1,200 genome-wide polymorphisms collected from 432 individuals representing 15 different Indian populations.

This study represents the largest study of Indian genetic variation performed to date, in terms of the total number of sites in the human genome that were surveyed.

The researchers found that populations from India, and more generally, South Asia, make up one of the major human ancestry groups, with relatively little genetic differentiation among the Indian populations. Although the study used participants that may not reflect a random sample from India, these results still suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world.

"We were struck both by the low level of diversity amongst people spanning such a large geographical region, and by the fact that people of the Indian sub-continent constituted a distinct group when compared to populations from other parts of the world," says Patel.

Her group is using this study as a foundation for future studies on the genetic basis of various common diseases in Asian Indians-such as heart disease, which is highly prevalent in this population. Individuals interested in participating in this study may see details at www.usc.edu/RICADIA.

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The research group also includes other researchers from the USC Institute for Genetic Medicine at the Keck School of Medicine, the University of Michigan, the departments of neurology and molecular and human genetics at Baylor College of Medicine in Houston, Texas, and the Center for Medical Genetics at the Marshfield Medical Research Foundation, Marshfield, Wisconsin.

The study was funded by a Burroughs Wellcome Fund Career Award in the Biomedical Sciences (Rosenberg), an Alfred P. Sloan Research Fellowship (Rosenberg) and a grant from the University of Southern California. The National Heart, Lung and Blood Institute provided additional support for genotyping.

Noah A. Rosenberg, Saurabh Mahajan, Catalina Gonzalez-Quevedo, Michael G. B. Blum, Laura Nino-Rosales, Vasiliki Ninis, Parimal Das, Madhuri Hegde, Laura Molinari, Gladys Zapata, James L. Weber, John W. Belmont and Pragna I. Patel, "Low levels of genetic divergence across geographically and linguistically diverse populations of India." PLoS Genetics, Dec. 22: Vol. 2, No. 12. www.plosgenetics.org.


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