Distribution of the Val108/158 Met Polymorphism of COMT Gene in the Khasi, Garo, Jaintia Populations of Northeast India

Catechol-O-methyltransferase (COMT) transfers methyl group from S-adenosylmethionine to hydroxyl group on dopamine and norepinephrine, thereby, inactivates catecholamine. It has two isoforms S-COMT and MB-COMT. The polymorphism of COMT (rs4680) changes valine to methionine at amino acid position 108 in S-COMT and 158 in MB-COMT. In Met108/158 Met polymorphism COMT enzyme activity is reduced by one-fourth compared to the Val108/158Val. This rs4680 polymorphism is associated with various cognitive disorders, and its frequency differs in populations. The present study determined COMT Val108/158Met polymorphism frequency in Khasi, Garo and Jaintia tribes of Northeast India. We recruited 93 healthy volunteers from these tribes and using their genomic DNA amplified COMT polymorphic site and sequenced the DNA. We observed frequent Valine allele ranged from 53% (Jaintia) to 56% (Khasi). Additionally, we analyzed Val108/158Met polymorphism frequency in various ethnic populations of HapMap 1000 genome project and compared that with Khasi, Garo and Jaintia tribes. Interestingly, we found that Val108/158Met genotype and allele frequencies of Jaintia population were significantly different from African, Asian and Caucasian, including Guajarati but not different from Italians of Tuscan. However, Khasi and Garo populations showed significant difference in Val108/158Met polymorphism compared to African and Asian populations but not to Caucasian, including Gujarati.