MBE Advance Access published online on August 21, 2008
Molecular Biology and Evolution, doi:10.1093/molbev/msn183
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
Gene duplications and losses within the cyclooxygenase family of teleosts and other chordates
a Department of Zoology, University of Florida, Gainesville, FL 32611-8525, USA
b Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672, USA
c Departments of Anesthesiology, Pharmacology, and Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37240, USA
Correspondence: Justin C. Havird, Department of Zoology, University of Florida, Bartram 223, P.O. Box 118525, Gainesville, FL 32611-8525, (352) 392-1107, Fax (352) 392-3704, jhavird{at}zoology.ufl.edu
Received for publication May 29, 2008. Revision received July 16, 2008. Accepted for publication August 5, 2008.
Cyclooxygenase (COX) produces prostaglandins in animals via the oxidation and reduction of arachidonic acid. Different types and numbers of COX genes have been found in corals, sea squirts, fishes, and tetrapods, but no study has used a comparative phylogenetic approach to investigate the evolutionary history of this complex gene family. Therefore, to examine COX evolution in the teleosts and chordates, 9 novel COX sequences (possessing residues and domains critical to COX function) were acquired from the euryhaline killifish, longhorn sculpin, sea lamprey, Atlantic hagfish, and amphioxus using standard PCR and cloning methods. Phylogenetic analyses of these and other COX sequences show a complicated history of COX duplications and losses. There are 3 main lineages of COX in the chordates corresponding to the 3 subphyla in the phylum Chordata, with each lineage representing an independent COX duplication. Hagfish and lamprey most likely have traditional COX-1/2 genes, suggesting that these genes originated with the first round of genome duplication in the vertebrates according to the 2R hypothesis and are not exclusively present in the gnathostomes. All teleosts examined have three COX genes due to a teleost-specific genome duplication followed by variable loss of a COX-1 (in the zebrafish and rainbow trout) or COX-2 gene (in the derived teleosts). Future studies should examine the functional ramifications of these differential gene losses.
Key Words: cyclooxygenase • prostaglandins • 2R hypothesis • teleost genome • gene duplication • gene loss