Haplotype diversity and linkage disequilibrium at DRD2 locus--a study on four population groups of Andhra Pradesh, India.

Dopamine receptor D2 (DRD2) is expressed in the central nervous system and has a high affinity for many antipsychotic drugs. Besides several epidemiological investigations on association of DRD2 locus polymorphism(s) with neuropsychiatric problems and addictive behavior, a few polymorphisms in this locus have also been used to understand genomic diversity and population migratory histories globally. The present study attempts to understand the genomic diversity/affinity among four endogamous groups of Andhra Pradesh (India) against the backdrop of diversity studies from other parts of India and the rest of the world, with special reference to DRD2 locus. The four population groups from Adilabad District of Andhra Pradesh, namely, Brahmin (n=50), Nayakpod (n=49), Thoti (n=52), and Kolam (n=53), were included in the study. The DRD2 markers typed for the present study are three biallelic restriction fragments, that is, TaqI A (rs1800497), TaqI B (rs1079597), and TaqI D (rs1800498). Scoring of DRD2 haplotypes with respect to the three TaqI sites shows that five out of eight possible haplotypes are shared by the four populations. Ancestral haplotype B2D2A1 is most frequent among Thotis (0.359). The results of the present study indicate a differential gene flow into South India followed by certain important demographic events resulting in diversified peopling of India.