Sequence characterization and expression pattern analysis of six kinds of IL-17 family genes in the Asian swamp eel (Monopterus albus)

• Published in: Fish & shellfish immunology Vol. 89; pp. 257 - 270
• Main Authors: Tang, Dongdong, Wu, Shipei, Luo, Kai, Yuan, Hanwen, Gao, Weihua, Zhu, Dashi, Zhang, Wenbing, Xu, Qiaoqing
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2019
• Subjects: Aeromonas veronii; antiviral properties; Asian swamp eel; exons; Expression; fish; gene expression; genomics; humans; immune response; inflammation; Inflammatory response; Interleukin-17; introns; kidney cells; kidneys; loci; messenger RNA; Monopterus albus; pathogens; peptide elongation factors; phylogeny; polyinosinic-polycytidylic acid; quantitative polymerase chain reaction; Reference gene; reverse transcriptase polymerase chain reaction; sequence analysis; signal peptide; Asian swamp eel; Inflammatory response; Reference gene; Interleukin-17; Expression
• ISSN: 1050-4648; 1095-9947; 1095-9947
• DOI: 10.1016/j.fsi.2019.03.050

Interleukin-17 (IL-17) is an important cytokine that plays a critical role in the inflammatory response and host defense against extracellular pathogens. In the present study, six novel IL-17 family genes (MaIL-17) were identified by analyzing Asian swamp eel (Monopterus albus) genome. Sequence analysis revealed that the MaIL-17 family genes shared similar features, comprising a signal peptide, an IL-17 superfamily region, and four conserved cysteines. Phylogenetic analysis showed that the MaIL-17 genes were clustered together with their corresponding IL-17 genes from other species. The similarity and identity of all IL-17 family genes indicated that the MaIL-17 genes are conserved among teleosts, while Ma-IL-17D is more conserved than the other Ma-IL-17s. Except for MaIL-17A/F3 and MaIL-17D, all MaIL-17s shared the same genomic structure as the genes from other fish, namely three exons and two introns. The MaIL-17s showed conserved synteny among fish, and we found that the MaIL-17D locus has a more conserved syntenic relationship with the loci from other fish and humans. These results demonstrated that MaIL-17D and human IL-17D might have evolved from a common ancestral gene and subsequently diverged. The analysis of swamp eel reference genes revealed that EEF1A1 (encoding eukaryotic translation elongation factor 1 alpha 1) was an ideal reference gene for accurate real-time qRT-PCR normalization in the swamp eel. The MaIL-17 genes are widely distributed throughout tissues, suggesting that MaIL-17s carry out their biological functions in immune and non-immune tissues compartments. The transcript of Ma-IL17s exhibited different fold changes in head kidney cells in response to Aeromonas veronii phorbol 12-myristate 13-acetate (PMA) and polyinosinic:polycytidylic acid (poly I:C) challenge, showing that MaIL-17A/F1 has stronger antiviral activities compared with other MaIL-17 family genes, and that MaIL-17A/F3 and MaIL-17A/F2 possess stronger effects against extracellular pathogens compared with the others; however, MaIL-17C2 and MaIL-17D may play vital roles during pathogen infection. The differential immune responses of these genes to Aeromonas veronii, PMA and poly I:C implied distinct mechanisms of host defense against extracellular pathogens. •EEF1A1 was suitable as an ideal swamp eel reference gene.•MaIL-17D is the most conserved among all the MaIL-17s.•MaIL-17s carry out different biological functions in immune and non-immune tissues.•MaIL-17s play diverse roles in host defense against extracellular pathogens.