Human origin, health and disease in India: genetic perspectives

ABSTRACT:
India represents one of the largest sources of human diversity, comprising of more than four and half thousand anthropologically well-defined populations. Since most of the Indian populations maintaining very strict endogamy marriage practices, for the last thousands of years, genetic mutations introduced in every population remains populations-specific. Hence we have studied the genetic variation among large number of Indian populations to get insight about their complex origin, health and genetic disease. Using the complete mitochondrial DNA (mtDNA) sequence information, we have demonstrated that the India inhabited by the descendents of the very first modern humans, who migrated out-of-Africa about 60,000 years ago. Subsequently using about a million SNPs, we have shown relatively small group of ancestors founded most Indian groups, which then remained largely isolated with limited gene flow for long periods of time. We also identified two main ancestral groups in India: an "Ancestral North Indian (ANI)", which is distantly related to those in the Middle East, Central Asia, and Europe, and an "Ancestral South Indian (ASI)", not related to groups outside India. Groups with only ASI ancestry may no longer exist in mainland India. Our results show that genetic patterns in Indian populations have been shaped by a long history of genetic isolation between different groups that predates the caste system in place in India during colonialism. Allele frequency differences between groups in India are larger than in Europe, reflecting strong founder effects whose signatures have been maintained for thousands of years owing to endogamy. We, therefore, predict that there will be an excess of recessive and complex diseases in India. During the presentation, I would focus on how the Indian genetics is different from rest of the world and what would be its implications in health and disease.

References:
1.	Science, 2005
2.	Nature, 2009
3.	Nature Genetics, 2009
4.	American Journal of Human Genetics, 2011 (2)