title: Sequencing of a second interleukin-10 gene in rainbow trout Oncorhynchus mykiss and comparative investigation of the expression and modulation of the paralogues in vitro and in vivo.
abstract: Interleukin-10 (IL-10) is a multifaceted cytokine that is produced by and effects a variety of cell populations, including macrophages, T, B and NK cells. The gene encoding for IL-10 has been isolated in mammals, birds, amphibians and recently in fish, with only single copy identified in each species. We report here a second IL-10 gene (tIL-10b) in rainbow trout that showed 92% identity in the coding region but only 50% identity in the 5'- and 3'-UTR to the known trout IL-10 paralogue, which we have now called tIL-10a. There is a short upstream open reading frame (uORF) within the 5'-untranslated region (UTR) of tIL-10a that may inhibit its translation, whilst in tIL-10b multiple mRNA instability motifs exist in the 3'-UTR, suggesting that the two IL-10 paralogues may have different mechanisms to regulate their expression post-transcriptionally. The expression of tIL-10a is generally higher than that of tIL-10b in most of the fourteen tissues examined and in the RTS-11, RTL and RTGill cell lines. However, the expression level of tIL-10b can exceed that of tIL-10a, as seen in vivo in the ovary of healthy fish and in the gills of Yersinia ruckeri challenged fish, and in vitro in head kidney (HK) leucocytes cultured for ≥ 8 h. The expression of the trout IL-10 paralogues can be up-regulated by LPS and polyIC in RTS-11 cells and by LPS, polyIC, PHA, PMA, calcium ionophore (CI) and IL-21 in head kidney leucocytes, as well as by Y. ruckeri infection, and can be modulated positively or negatively by IFN-γ. Synergistic effects on up-regulation of IL-10 expression were also seen between PHA and IL-21, as well as between PMA and CI. The expression kinetics of the IL-10 paralogues was also found to be different, suggesting that rainbow trout has evolved different pathways to regulate the expression of the two IL-10 paralogues at the transcriptional level.
authors.affiliation: Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB242TZ, UK.
authors.forename: Nor Omaima
authors.initials: NO
authors.lastname: Harun
authors.forename: Maria M
authors.initials: MM
authors.lastname: Costa
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Secombes
authors.forename: Tiehui
authors.initials: T
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D029941:Fish Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D020869:Gene Expression Profiling; D016753:Interleukin-10 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D015009:Yersinia Infections / Q000378:metabolism / Q000662:veterinary*; D044124:Yersinia ruckeri / Q000502:physiology*
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D016753:Interleukin-10