Identification and expression analysis of two fish-specific IL-6 cytokine family members, the ciliary neurotrophic factor (CNTF)-like and M17 genes, in rainbow trout Oncorhynchus mykiss.
The mammalian interleukin (IL)-6 family of cytokines consist of eight class-I helical cytokines and are major players in hematopoiesis, as well as in neuroendocrine and immune systems, and have pro- and anti-inflammatory properties. We have identified a novel fish CNTF-like molecule, for the first time, as well as the trout M17 gene. The trout CNTF-like gene encodes a putative 191 amino acid peptide without a signal peptide, and shares high amino acid sequence identities (39-99%) within the fish CNTF-like molecules that we have identified, but only limited identities (21-24%) to higher vertebrate CNTF molecules among the IL-6 family members. The fish CNTF-like gene has two phase 0 introns in the coding region whilst the mammalian CNTF gene has only one phase 0 intron. The trout M17 encodes a peptide of 227 amino acid residues which has a predicted signal peptide of 35 aa and shares the highest identities (38-95%) to other fish M17 molecules, but limited homology to other IL-6 family members. Both of the fish CNTF-like and M17 proteins have four predicted helices and their tertiary structure could be stabilised by multiple conserved disulphide bonds. Phylogenetic analysis suggests that the fish CNTF-like and M17 genes may have arisen from ancestral genes that have given rise to mammalian LIF/OSM, and CNTF/CLC/CT-1/CT-2 of the IL-6 family. The trout CNTF-like gene is highly expressed in brain and muscle, whilst the M17 is highly expressed in immune tissues, including gills, spleen and head kidney. Furthermore, immune stimulation of a macrophage cell line and bacterial infection in vivo up-regulated M17 expression but had little effect on CNTF-like expression. These results suggest a major role of the CNTF-like molecule in fish nervous and muscular systems and of M17 in the immune system.
Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
Tiehui
T
Wang
Christopher J
CJ
Secombes
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020934:Ciliary Neurotrophic Factor / Q000235:genetics / Q000378:metabolism*; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000378:metabolism* / Q000382:microbiology; D010802:Phylogeny; D015009:Yersinia Infections / Q000378:metabolism
D020934:Ciliary Neurotrophic Factor; D015850:Interleukin-6