FREAMAT, M.*; SOWER, S.A.; University of New Hampshire, Durham; University of New Hampshire, Durham: A Putative Gonadotropin Hormone Receptor from Sea Lamprey (Petromyzon marinus) Testes.

The sea lamprey (Petromyzon marinus) is the only Agnathan in which the existence of an endocrine hypothalamo-pituitary-gonadal (HPG) axis has been clearly established. Knowledge of the HPG axis in lamprey is important for our understanding of the evolution of endocrine controls of reproduction in later evolved vertebrates. Results of extensive studies clearly support the hypothesis of existence of a gonadotropin hormone similar in function with the gonadotropin hormones from other vertebrates (follicle stimulating hormone FSH and luteinizing hormone LH). However, concerted efforts for identification, cloning and characterization of a lamprey gonadotropin homologous to FSH and LH have not yet provided definitive results. Therefore, the objective of this study was to clone and characterize the receptor for the putative lamprey gonadotropin(s) under the same hypothesis of homology with the gonadotropin receptors from gnathostomes. The cDNA encoding the full sequence of a glycoprotein hormone receptor highly similar to gonadotropin receptor homologs has been isolated from lamprey testes by RT-PCR with degenerate primers derived from the PRINTS/GLYCHORMONER protein signature followed by RACE. The corresponding gene shows its highest level of expression in testes. The change in its expression level in response to lGnRH-III treatment indicates a functional relationship between these two molecules. These results as well as the molecular phylogenetic relationships of the protein sequence with the known gonadotropin hormone receptors support the hypothesis of a common evolutionary origin of the lamprey and gnathostome gonadotropins. Supported by NSF Grant 0090852 to S.A. Sower.