Sequence-Based Structural and Evolution of Polymorphisms in Bovine Toll-Like Receptor2 Gene in Dhanni and Jersey Cattle Breeds. Genetic polymorphisms in bovine TLR2.

Host defense against infectious disease is a tormenting task considering not only the enormous pathogens diversity, but also their rapid genome replication and mutation rates. Front line and anti-microbial defense is accomplished by the innate immune system with the help of pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) in prompt pathogens detection. In this study, distribution of single nucleotide polymorphisms (SNPs) in TLR2 gene was studied in two cattle breeds Dhanni and locally adapted exotic Jersey. The complete sequences of TLR2 gene composed of 5'UTR 136 bp, coding sequence 2355 bp and 3'UTR 1316 bp. Phylogenetic analysis revealed clustering of Dhanni with Bos indicus and Jersey with Bos taurus as the nearest neighbor. Sequencing of TLR2 in Dhanni cattle showed the occurrence of 35 variable sites within coding region including 37% non-synonymous and 63% synonymous, while in Jersey cattle, 21 SNPs were identified within coding region including 48% non-synonymous and 52% synonymous. Mostly SNPs fell within the leucine-rich repeats (LRR) of extracellular domain, regions responsible for ligand recognition. The ratio of dS/dN substitutions was <1 at polymorphic-sites indicating purifying selection. The SNPs at position 681 (p.Leu227Phe in Jersey) and 521(p.Thr174Ile in Dhanni) were presumed to have possible damaging or functional altering effect. The predicted bovine TLR2 is a solenoid-like (coil-like) built from 20 LRRs bend into a horseshoe shaped structure. The polymorphisms in TLR2 can be useful in future research exploring its role in immunity and may be used as markers for disease resistance under selective breeding. [ABSTRACT FROM AUTHOR]