Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic.
RG Animal Immunogenomics, CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic.
Vet Res Commun. 2024 Apr;48(2):725-741. doi: 10.1007/s11259-023-10245-4. Epub 2023 Oct 24.
Toll-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 analyzed TLR genes in the order Perissodactyla with a focus on the family Equidae. Twelve TLRs 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 of TLR11 and TLR12 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 of Equus caballus and Equus hemionus kulan (1.34%) in the TLR3, and Equus africanus somaliensis and Equus quagga antiquorum (2.1%) in the TLR1 protein. In each TLR gene, there were haplotypes shared between equid species, most extensively in TLR3 and TLR9 CDS, and TLR6 amino acid sequence. All twelve TLR genes were under strong negative overall selection. Signatures of diversifying selection in specific codon sites were detected in all TLRs except TLR8. Differences in the selection patterns between virus-sensing and non-viral TLRs were observed.
Toll 样受体 (TLRs) 是先天免疫系统的重要组成部分。虽然人类和鼠类 TLRs 已经得到了深入研究，但对非模式物种的 TLRs 知之甚少。奇蹄目包括各种自由生活和家养物种，它们生活在不同的栖息地，面临着不同的病原体，因此适合分析与免疫相关基因的多样性和进化。我们通过对在线基因组资源的生物信息学分析，研究了奇蹄目动物的 TLR 基因，重点关注马科。通过对 9 个物种的基因组 DNA 重新测序，在马科中通过生物信息学分析鉴定了 12 个 TLRs；其序列得到了确认。通过 cDNA 测序，我们在马属动物中证实了 TLR11 和 TLR12 的表达。奇蹄目 TLR 基因家族的系统发育重建确定了 6 个亚家族。TLR4 与 TLR5 聚在一起；TLR1-6-10 亚家族显示出高度的序列同一性。在所研究的 12 个 TLR 中，所有 12 个 TLR 的平均估计进化分歧度在马科中为 0.3%；TLR3 中 TLR3 和 TLR10 最具差异性的 CDS 为 Equus caballus 和 Equus hemionus kulan（1.34%），TLR1 蛋白中 TLR1 最具差异性的 CDS 为 Equus africanus somaliensis 和 Equus quagga antiquorum（2.1%）。在每个 TLR 基因中，马科物种之间都有单倍型共享，TLR3 和 TLR9 CDS 以及 TLR6 氨基酸序列中共享最广泛。所有 12 个 TLR 基因都受到强烈的负向整体选择。除了 TLR8 之外，在所有 TLR 中都检测到了特定密码子位点的多样化选择信号。在病毒感应 TLR 和非病毒 TLR 之间观察到了选择模式的差异。
