Abstract
Ongoing modernization in India has elevated the prevalence of many complex genetic diseases associated with a western lifestyle and diet to near-epidemic proportions. However, although India comprises more than one sixth of the world's human population, it has largely been omitted from genomic surveys that provide the backdrop for association studies of genetic disease. Here, by genotyping India-born individuals sampled in the United States, we carry out an extensive study of Indian genetic variation. We analyze 1,200 genome-wide polymorphisms in 432 individuals from 15 Indian populations. We find that populations from India, and populations from South Asia more generally, constitute one of the major human subgroups with increased similarity of genetic ancestry. However, only a relatively small amount of genetic differentiation exists among the Indian populations. Although caution is warranted due to the fact that United States–sampled Indian populations do not represent a random sample from India, these results suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world and that the effects of population heterogeneity on the production of false positives in association studies may be smaller in Indians (and particularly in Indian-Americans) than might be expected for such a geographically and linguistically diverse subset of the human population.
Highlights
In addition to its use in understanding human evolutionary history, investigation of human genetic variation and population structure is important for the design and analysis of studies that map disease-susceptibility loci
In examining genetic variants for disease association, knowledge of population structure is important for evading the spurious associations that can be produced by heterogeneity in the ancestry of sampled individuals [4,5,6,7]
During the last few decades, the prevalence in India of complex genetic diseases associated with increased life span and with an urban and western lifestyle—including coronary artery disease, non-insulin-dependent diabetes, and metabolic syndrome—has risen considerably and is greater than in most other populations [8,9,10,11,12]
Summary
India comprises more than one sixth of the world’s human population, it has largely been omitted from genomic surveys that provide the backdrop for association studies of genetic disease. By genotyping India-born individuals sampled in the United States, we carry out an extensive study of Indian genetic variation. Caution is warranted due to the fact that United States–sampled Indian populations do not represent a random sample from India, these results suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world and that the effects of population heterogeneity on the production of false positives in association studies may be smaller in Indians (and in Indian-Americans) than might be expected for such a geographically and linguistically diverse subset of the human population
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