Biased distribution of single nucleotide polymorphisms (SNPs) in porcine Toll-like receptor 1 (TLR1), TLR2, TLR4, TLR5, and TLR6 genes

Toll-like receptors (TLRs) recognize various microbial components and induce immune responses. Polymorphisms in TLRs may influence their recognition of pathogen-derived molecules; swine TLRs are predicted to be associated with responses to infectious diseases such as pneumonia. In this study, we searched for single nucleotide polymorphisms (SNPs) in the coding sequences of porcine TLR1, TLR2, TLR4, TLR5, and TLR6 genes in 96 pigs from 11 breeds and elucidated 21, 11, 7, 13, and 11 SNPs, respectively, which caused amino acid substitutions in the respective TLRs. Distribution of these nonsynonymous SNPs was biased; many were located in the leucine-rich repeats, particularly in TLR1. These data demonstrated that the heterogeneity of TLR genes was preserved in various porcine breeds despite intensive breeding that was carried out for livestock improvement. It suggests that the heterogeneity in TLR genes is advantageous in increasing the possibility of survival in porcine populations.