Meeting Abstract

6.3  Jan. 4  The evolution and possible function of cyclooxygenase in chordates HAVIRD, J. C.*; CHOE, K. P.; EVANS, D. H.; University of Florida; Vanderbilt University; University of Florida j_havird@hotmail.com

In mammals, prostaglandins (PGs) are involved in many physiological processes such as blood clotting, inflammation and regulation of vascular tone and osmoregulation. Cyclooxygenase (COX) is one of the major enzymes involved in PG synthesis. In mammals there are two COX subtypes, COX-1 and COX-2, but COX orthologues have been found in many chordates including the sea squirt (Ciona intestinalis). In the mammalian kidney, COX-2 generated PGs inhibit ion transport and support cell survival during salt loading and dehydration. Our lab has previously confirmed a COX-2 orthologue in the gills of the euryhaline killifish (Fundulus heteroclitus), and evidence suggests that COX-2 (and COX-1) generated PGs may influence ion and water balance in fishes. However, it is unknown whether ancestral chordates possess COX-1 and COX-2 or a precursor (COX-A and COX-B) as in found in the sea squirt. The goals of this project were to determine the COX cDNA sequence(s) from the following ancestral chordates: lancelet (Branchiostoma lanceolatum), hagfish (Myxine glutinosa), lamprey (Petromyzon marinus), and also the COX-1 sequence from the killifish and longhorn sculpin (Myoxocephalus octodecimspinosus); to determine the phylogenetic relationship between the chordate COXs and the osmoregulatory functions of COX in chordates. Using standard RT-PCR and cloning procedures, COX orthologues were found in all animals studied. Phylogenetic analysis suggests that lancelets, hagfish and lampreys have a COX precursor, and lack COX-1 and COX-2, as found in elasmobranchs, teleosts and mammals. Procedures such as qRT-PCR, tissue distribution analyses and immunohistochemistry suggest COX may play an omsmoregulatory role in most chordates.