TGF-β3 exists in bony fish

A partial nucleotide sequence of transforming growth factor-β3 (TGF-β3) has been isolated from the Siberian sturgeon (Acipenser baeri), rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla), confirming a ubiquitous presence in the ray-finned (Actinopterygian) bony fish. The bony fish TGF-β3 is highly conserved, with some 83–84% nucleotide identity (coding region) and 90–95% predicted amino acid identity to known homeotherm TGF-β3’s. Far lower homologies are apparent with other known TGF-β isoforms in fish (e.g. 64–66% and 81–82% amino acid identity to trout TGF-β1/5 and carp TGF-β2 respectively). Phylogenetic tree analysis showed that the fish TGF-β3’s clustered with the known homeotherm TGF-β3’s. The relatively tight clustering of TGF-β1, TGF-β2 and TGF-β3 was in contrast to the TGF-β5’s, which are clearly a more heterogenous group.