Genetic diversity within 5′upstream region of Toll-like receptor 8 gene reveals differentiation of riverine and swamp buffaloes☆

In this study the nucleotide diversity in the 5'untranslated region (UTR) of TLR8 gene in riverine as well as swamp buffaloes has been described. Analysis of the 5'UTR of TLR8 gene showed presence of two SNPs in this region, g.-139G>T and g.-128A>G. A PCR-RFLP assay designed for genotyping of g.-139G>T SNP across 667 samples from 2 buffalo populations revealed a striking difference in allele frequency distribution across the swamp and riverine buffaloes. The frequency of T allele was higher in swamp buffalo as compared to riverine buffalo, ranging from 0.71 to 1. The G allele on the other hand exhibited a higher frequency across all the Indian riverine buffalo breeds/populations. The principal component analysis revealed separate clusters for the riverine and swamp buffaloes, as expected; however, the riverine type Assamese buffalo population of eastern India formed a distinct cluster. Since most of the buffalo populations in the eastern region are swamp type, this demarcation may be related to the difference in immune response in riverine and swamp buffaloes. These preliminary results indicate that the genetic variation observed in 5'upstream region of TLR8 gene, which differentiates swamp and riverine buffalo, needs to be further explored for association with disease susceptibility in buffalo, an important dairy and meat animal of Southeast Asia.