Rainbow trout cytokine and cytokine receptor genes.

Transforming growth factor-beta (TGF-beta) and interleukin-1 beta (IL-1 beta) have been cloned from rainbow trout (Oncorhynchus mykiss) in our laboratory. The trout TGF-beta is typical of members of the cysteine knot cytokine family, and has highest homology to TGF-beta 1, TGF-beta 4 and TGF-beta 5. The gene organisation is different to other TGF-beta genes despite the presence of seven exons. Trout IL-1 beta has less homology to known IL-1 beta s (49-56% amino acid similarity) but shows clear conservation of the secondary structure of the "mature peptide". An interleukin-converting enzyme cut site is not apparent however, and it remains to be determined whether fish IL-1 beta must be cleaved for biological activity. The trout IL-1 beta gene consists of six exons, one less than in mammals, with the missing exon at the 5' end of the gene. Two trout chemokine receptors have also been isolated in our laboratory, having high homology to CXC-R4 and CC-R7 (67% and 56% nucleotide identity respectively). With a view to studying the biological effects of fish cytokines we have also cloned the inducible nitric oxide (iNOS) and cyclooxygenase (COX-2) genes in trout. Both have high homology to known mammalian and chicken genes, and have been shown to be inducible in trout.