Molecular cloning and tissue expression of the gonadotrophin-releasing hormone receptor in the tammar wallaby ( Macropus eugenii )

Gonadotrophin-releasing hormone (GnRH) plays a pivotal role in the endocrine control of both reproduction and embryonic development. This first study of the marsupial GnRH receptor (GnRH-R) gene in the tammar wallaby provides information on the complex molecular events that regulate hypothalamic-pituitary-gonadal function in marsupials, and allows a comparison with eutherian mammals. Two identical wallaby GnRH-R cDNA clones were obtained, one isolated from cDNA generated from the testis of a 79-day-old pouch young and the other from the pituitary of an adult. Wallaby GnRH-R is composed of 328 amino acid residues. Sequence analysis showed that wallaby GnRH-R contains 7 transmembrane domains and is a member of the G protein-coupled receptor family. A putative protein kinase A phosphorylation site and a putative protein kinase C (PKC) phosphorylation site were found in the first intracellular loop, and an additional PKC phosphorylation site was located in the third intracellular loop. Comparisons with the eutherian GnRH-Rs show a greater diversity in the N-terminal extracellular domain. Wallaby GnRH-R has approximately 80% amino acid sequence homology with eutherian GnRH-Rs and 93% homology with the brush-tail possum, another member of the Diprotodontia semiorder.