Signatures of selection acting on the innate immunity gene Toll-like receptor 2 (TLR2) during the evolutionary history of rodents

Patterns of selection acting on immune defence genes have recently been the focus of considerable interest. Yet, when it comes to vertebrates, studies have mainly focused on the acquired branch of the immune system. Consequently, the direction and strength of selection acting on genes of the vertebrate innate immune defence remain poorly understood. Here, we present a molecular analysis of selection on an important receptor of the innate immune system of vertebrates, the Toll-like receptor 2 (TLR2), across 17 rodent species. Although purifying selection was the prevalent evolutionary force acting on most parts of the rodent TLR2, we found that codons in close proximity to pathogen-binding and TLR2–TLR1 heterodimerization sites have been subject to positive selection. This indicates that parasite-mediated selection is not restricted to acquired immune system genes like the major histocompatibility complex, but also affects innate defence genes. To obtain a comprehensive understanding of ...

近年来，作用于免疫防御基因的选择模式已成为学界广泛关注的研究热点。然而针对脊椎动物而言，既往相关研究多聚焦于免疫系统的获得性免疫分支（acquired branch of the immune system）。故而，学界对于脊椎动物先天免疫防御（innate immune defence）基因所受选择的方向与强度仍缺乏清晰认知。本研究针对17个啮齿类物种体内的脊椎动物先天免疫系统重要受体——Toll样受体2（Toll-like receptor 2, TLR2）所受的选择压力开展了分子分析。尽管纯化选择（purifying selection）是驱动啮齿类TLR2绝大多数区域演化的主流进化力量，但我们发现，紧邻病原体结合位点与TLR2-TLR1异二聚化位点的密码子受到了正选择（positive selection）作用。这表明，寄生虫介导的选择压力并非仅局限于主要组织相容性复合体（major histocompatibility complex）这类获得性免疫系统基因，同样也会对先天防御基因产生影响。为全面了解……