Chemokines direct cell migration in development and immune defense, and bridge between innate and adaptive immune responses. The chemokine gene family has been rapidly evolving and has undergone species/lineage-specific expansion. Mammals possess inflammatory CXC chemokines CXCL1-8/15 and CXCL9-11 sub-groups, and homeostatic CXCL12-14, 16–17. Orthologues of mammalian CXCL12-14, three chemokines related to CXCL1-8/15 (CXCL8_L1-3), two chemokines related to CXC9-11 (CXCL11_L1-2), and five fish-specific chemokines (CXCL_F1-5) have been described in teleosts. In this study, we reported three novel CXC chemokines in Asian swamp eel Monopterus albus, a commercially important freshwater fish species in China. Two of them belong to the fish-specific CXCL_F2 group, named CXCL_F2a/b, that share 89.5% amino acid identity. The other (CXCL11_L3) belongs to a third CXCL11_L related to the mammalian CXCL9-11 subfamily found only in percomorph fish species, and is the only CXCL9-11 related molecules in this lineage. Mammalian CXCL9-11 attract Th1 cells, and block the migration of Th2 cells in an immune response. This study suggests that all major lineages of teleosts have a CXCL9-11 related chemokine that will aid future functional investigation of CXCL11_L in fish. Cxcl_f2a is highly expressed constitutively in the skin of swamp eels that may attract immune cells to protect the skin in the absence of scales. Cxcl11_l3 and cxcl_f2b are highly expressed in immune tissues/organs and are up-regulated by the viral mimic poly I:C, but not bacterial infection in vivo, suggesting their role in anti-viral defense. The two cxcl_f2 paralogues are differentially expressed and modulated, indicating sub- and/or neo-functionalization.
Yuan, H., Li, Y., Panpan Han, Tian, G., Zhang, W., Guo, H., … Wang, T. (2019). Identification and characterization of three CXC chemokines in Asian swamp eel (Monopterus albus) uncovers a third CXCL11_like group in fish. Developmental and Comparative Immunology, 101. https://doi.org/10.1016/j.dci.2019.103454