The Evolutionary Studies Of CCL20 And CCR6 Genes In Marinae

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.