Cloning of the IL-1β3 gene and IL-1β4 pseudogene in salmonids uncovers a second type of IL-1β gene in teleost fish

To date two closely related interleukin-1 beta genes (IL-1 beta 1 and IL-beta 2) have been found in salmonids. The cloning of trout and salmon IL-1 beta 3, and a salmon IL-1 beta 4 pseudogene reveals that two types of IL-1 beta genes exist in teleost species. Type I teleost IL-1 beta genes, including salmonid IL-1 beta 3, share a similar 6 coding exon structure as in tetrapods. Type II teleost IL-1 beta genes, e.g. salmonid IL-1 beta 1-2, lack one or two coding exons at their 5'-end, and share higher identities within this subgroup than within the type I subgroup. Both types of IL-1 beta genes have been found in species of Salmoniformes, Perciformes and Beloniformes, suggesting the divergence occurred early in teleost evolution. Trout IL-1 beta 3 is highly expressed in ovary suggesting a role in reproduction. A relatively high constitutive expression in gills, spleen and kidney and the up-regulation by PAMPs, proinflammatory cytokines and viral infection suggests IL-1 beta 3 also has a role in inflammation and host defence. (C) 2012 Elsevier Ltd. All rights reserved.