Kundu Samit, Faulkes Christopher G
School of Biological Sciences, Queen Mary, University of London, UK.
Proc Biol Sci. 2004 Feb 7;271(1536):273-8. doi: 10.1098/rspb.2003.2584.
African mole-rats are a family of rodents exhibiting an eclectic range of social behaviour and occupying a variety of habitat types. These differences are likely to impact upon the risk of parasite transmission and virulence, with increasing sociality predicted to correspond to an increased risk of transmission. We investigate these factors by analysing the major histocompatibility complex (MHC), a set of genes responsible for encoding highly variable intermediaries of the vertebrate adaptive immune response. To this end we assessed selection at exons 2 and 3 of the MHC class II DQalpha1 gene of four African mole-rat species representing a range of social behaviours. We demonstrate that: (i) the overall pattern of selection at these exons differentiates according to the predicted function of different regions, with the presence of positive selection indicating the likely influence of host-parasite coevolution; and (ii) contrary to the often observed and predicted positive correspondence between sociality and the risk of parasite transmission, two highly social African mole-rat species in fact appear to have comparatively weak positive selection, suggesting diminished host immunity and thus a low overall risk of parasite transmission.
非洲鼹形鼠是一类啮齿动物，表现出多样的社会行为，栖息于多种栖息地类型。这些差异可能会影响寄生虫传播风险和毒力，预计社交性增强会导致传播风险增加。我们通过分析主要组织相容性复合体（MHC）来研究这些因素，MHC是一组负责编码脊椎动物适应性免疫反应中高度可变中间产物的基因。为此，我们评估了代表一系列社会行为的四种非洲鼹形鼠物种的MHC II类DQalpha1基因外显子2和3的选择情况。我们证明：（i）这些外显子的总体选择模式根据不同区域的预测功能而有所不同，正选择的存在表明宿主 - 寄生虫协同进化的可能影响；（ii）与通常观察到的以及预测的社交性与寄生虫传播风险之间的正相关相反，实际上两种高度群居的非洲鼹形鼠物种似乎具有相对较弱的正选择，这表明宿主免疫力下降，因此寄生虫传播的总体风险较低。
