【作者】 李波；

【导师】 李岩；

【作者基本信息】 四川农业大学 ， 动物学， 2015， 硕士

【摘要】 免疫反应中,趋化因子(chemokines)能够活化特定的趋化因子受体,引起炎症性和非炎症性细胞迁移至感染或受损的位点,从而导致一系列的生理生化反应。其中,趋化因子CCL20与其七跨膜域受体CCR6能发生特异性结合并诱导未成熟树突状细胞(dendritic cell, DC)、效应T细胞或记忆T细胞及B细胞的化学趋向性,且在内稳态、炎症及病理状态下的皮肤和黏膜表面起重要作用。目前,针对CCL20及CCR6的结构和功能,仍有诸多问题有待深入的探讨。免疫相关基因的进化历程和进化机制为我们研究其结构特征及在免疫反应中的功能提供了重要信息。鉴于模式动物,如大鼠和小鼠等在免疫相关研究领域的广泛应用,通过对这些模式动物及其近缘物种中趋化因子CCL20及其受体CCR6的遗传与进化的研究,将有助于我们更为深入的认识其结构与功能的特点。为清晰刻画趋化因子CCL20及其受体CCR6在鼠科动物中的进化历程,本研究测定了鼠亚科(Marinae)动物中多个物种,包括黑线姬鼠(Apodemus agrarius)、中华姬鼠（A. draco)/田鼷鼠(Mus caroli)、锡金小鼠(M. pahari)、黑尾鼠(Niviventer cremoriventer)、波利尼西亚鼠(Rattus exulans)、沼泽鼠(R.fuscipes)、黑鼠(R. rattus)、亚洲家鼠(R. tanezumi), CCL20及CCR6基因编码区序列。结合公共数据库Ensembl中已有的小家鼠(M. musculus)和褐家鼠(R. norvegicus)相应的基因序列,我们系统分析了鼠亚科动物CCL20及CCR6基因的进化情况。主要结果如下：1)鼠亚科9个物种中CCL20及CCR6基因的全长编码序列分别约为290bp和1100bp。CCL20及CCR6基因在鼠亚科以及灵长类动物中保持了较保守的基因结构。2)CCL20基因在鼠亚科中经历适应性进化,共有12个氨基酸位点受到正选择的影响：CCR6基因在这一进化过程中则受到较强的负选择的影响。3)上述正选择位点中有8个位点位于CCL20可能与受体CCR6特异性结合的结构域。该结果提示这些位点可能影响或者参与CCL20蛋白与CCR6的结合。这一重要信息为深入探讨CCL20与其复杂的七次跨膜域受体相互作用的分子机理,及其在免疫反应的调控机理提供了重要信息。本研究基于分子进化角度,对鼠亚科物种中免疫相关基因CCL20及CCR6的进化进行了系统的研究,深入探讨了其进化特征及其影响因素。将有助于我们更好的认识其结构与功能的特点,并为揭示其在免疫反应中的作用提供重要的信息。更多还原

【Abstract】 Chemokines could activate specific chemokine receptors, causing a series of physiological and biochemical reaction, such as the migration of inflammatory and non-inflammatory cells to the site of infection or damage in the immune response. Chemokine CCL20 play an important role in homeostasis, inflammation, and pathological responses of skin or mucosa,by specifically binding to the seven-transmembrane receptor CCR6 on immature dendritic cells, effector T cells, memory T cells, and B cells. Despite the progress in elucidating the structure and function of CCL20 and CCR6, the details of these information are, to some extent, deficient. In view of animal models such as rats and mice widely used in the field of immune-related research, further research of evolution, genetics, structures and functions on chemokines and their receptors in these models and their closely related species will be of important to shed insight into their roles in the immune response.Pathogens have evolved a range of anti-immune molecular mechanisms to overcome both innate and adaptive immunity, determining the evolution of immune related genes may be valuable in exploring the structural and functional nature of these genes and strategies by which hosts and pathogens compete in the arms race. In order to chart the evolutionary history of Chemokines CCL20 and its receptor CCR6 in Marinae,we sequenced the complete coding region of CCL20 and CCR6 genes within 9 species, including Apodemus agrariu, A. draco, Mus caroli, M. pahari, Niviventer cremoriventer, Rattus exulans, R. fuscipes, R. rattus, R. tanezumi. Combined with the gene sequences of M. musculus and R. norvegicus in public databases Ensembl, we systematically analyzed the evolution of CCL20 and CCR6 genes. The main results are as follows:1) The entire CCL20 and CCR6 coding regions of all samples were amplified from genomic DNA. The sequences share the similar gene structures as CCL20 and CCR6 in M. musculus, R. norvegicus, and primates.2) CCR6 gene has been influences by purifying selection while CCL20 gene has experienced rapid diversity in Murinae. Further, we observed that twelve positive selection sites within CCL20 subjected to adaptive selection.3) Eight of twelve adaptively selected amino acids that subjected to adaptive selection are distributed on the putative contact region between CCL20 and CCR6. The evolutionary pattern of CCL20 and the distribution of selected sites increase our understanding of the molecular determinants of CCL20 and seven-transmembrane receptor CCR6 with regard to recognizing signature and the relevant regulation in immune response.In this study, we used molecular evolutionary approaches and population genetics analyses to describe the evolution of CCL20 and CCR6 in Murinae lineages. The insights on the evolution of these genes in Murinae could be important to understand the physiological function of these immune related molecules and their critical mechanisms in immune response.更多还原