Twelve toll-like receptor (TLR) genes in the family Equidae – comparative genomics, selection and evolution

AbstractToll-like receptors (TLRs) represent an important part of the innate immune system. While human and murine TLRs have been intensively studied, little is known about TLRs in non-model species. The order Perissodactyla comprises a variety of free-living and domesticated species exposed to different pathogens in different habitats and is therefore suitable for analyzing the diversity and evolution of immunity-related genes. We analyzedTLR genes in the order Perissodactyla with a focus on the family Equidae. TwelveTLRs were identified by bioinformatic analyses of online genomic resources; their sequences were confirmed in equids by genomic DNA re-sequencing of a panel of nine species. The expression ofTLR11 andTLR12 was confirmed in the domestic horse by cDNA sequencing. Phylogenetic reconstruction of the TLR gene family in Perissodactyla identified six sub-families. TLR4 clustered together with TLR5; the TLR1-6-10 subfamily showed a high degree of sequence identity. The average estimated evolutionary divergence of all twelve TLRs studied was 0.3% among the Equidae; the most divergent CDS were those ofEquus caballus andEquus hemionus kulan (1.34%) in theTLR3, andEquus africanus somaliensis andEquus quagga antiquorum (2.1%) in the TLR1 protein. In eachTLR gene, there were haplotypes shared between equid species, most extensively inTLR3 andTLR9 CDS, and TLR6 amino acid sequence. All twelveTLR genes were under strong negative overall selection. Signatures of diversifying sel...
Source: Veterinary Research Communications - Category: Veterinary Research Source Type: research