Trout CC chemokines: comparison of their sequences and expression patterns

Several thousand EST sequences were recently made available in the EMBL sequence database from the rainbow trout Oncorhynchus mykiss. BLAST based searches were utilised to identify sequences resembling mammalian CC chemokines within these ESTs. Fifteen new and unique CC chemokine-like sequences were identified for trout, bringing the total of known CC chemokine sequences in trout to 18 when including those already published. Some of these trout chemokines appeared highly related (in pairs) suggesting recent duplication events or tight evolutionary constraints. Phylogenetically, the trout chemokine sequences grouped with both inducible and constitutive mammalian CC chemokine subtypes, suggesting early divergence of these functional groups. Expression analyses on gill and head kidney show constitutive expression of many of these trout CC chemokines in these lymphoid-rich tissues. However, induction of some of the chemokines structurally related to 'inducible' CC chemokines was observed in a trout macrophage-like cell line (RTS-11) in response to stimulation with recombinant TNFalpha.