Glycoprotein hormone in the pituitary of hagfish and its evolutionary implications
- 496 Downloads
The pituitary gland is present in all vertebrates, from agnathans (jawless vertebrates) to mammals, but not in invertebrates. Reproduction in gnathostomes (jawed vertebrates) is controlled by two pituitary gonadotropins (GTHs), luteinizing hormone and follicle-stimulating hormone, which are part of the pituitary glycoprotein hormone (GPH) family. Hagfishes, which lack both jaws and vertebrae, are considered the most primitive vertebrate known, living or extinct. Accordingly, they are of particular importance in understanding the evolution of the pituitary GPHs and their functions related to vertebrate reproduction. Nevertheless, key elements of the reproductive endocrine system in hagfish have yet to be elucidated. Our current report has revealed the first identification of a functional GPH composed of two subunits that possess gonadotropic action at the pituitary of brown hagfish. It seems most likely that an ancestral GPH gave rise to only one GTH in hagfish pituitary and that multiplicity of GPHs arose later during the early evolution of gnathostomes. This paper briefly summarizes the latest findings on the hagfish GPH from an evolutionary point of view.
KeywordsHagfish Pituitary gland Glycoprotein hormone Gonadotropin Reproduction Evolution
Glycoprotein alpha subunit
Glycoprotein beta subunit
- HPG axis
This work has been supported in part by Grant-in-Aid for Basic Research from the Ministry of Education, Japan, to K. U., S. M. and M. N. This work was also supported in part by Japanese Association for Marine Biology (JAMBIO, Project No. 23-38) from Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This work was also supported in part by National Science Foundation Grant NSF IOS-0849569 and NH AES Hatch 332 to S. A. S.
- Gorbman A (1983) Reproduction in cyclostome fishes and its regulation. In: Hoar WS, Randall DJ (eds) Fish physiology, vol IXA. Academic Press, New York, pp 1–28Google Scholar
- Hall BK (1998) Evolutionary developmental biology. Chapman & Hall, LondonGoogle Scholar
- Holmes RL, Ball JN (1974) The pituitary gland, a comparative account. Cambridge University Press, LondonGoogle Scholar
- Janvier P (1996) Early vertebrates. Clarendon Press, OxfordGoogle Scholar
- Miki M, Shimotani T, Uchida K, Hirano S, Nozaki M (2006) Immunohistochemical detection of gonadotropin-like material in the pituitary of brown hagfish (Paramyxine atami) correlated with their gonadal functions and effect of estrogen treatment. Gen Comp Endocrinol 148:15–21PubMedCrossRefGoogle Scholar
- Patzner RA, Ichikawa T (1977) Effect of hypophysectomy on the testis of the hagfish, Eptatretus burgeri, Girard (Cyclostomata). Zool Anz 199:371–380Google Scholar
- Powell ML, Kavanaugh SI, Sower SA (2004) Seasonal concentrations of reproductive steroids in the gonads of the Atlantic hagfish, Myxine glutinosa. J Exp Zool A 301:352–360Google Scholar
- Sudo S, Kuwabara Y, Park JI, Hsu SY, Hsueh AJ (2005) Heterodimeric fly glycoprotein hormone-alpha2 (GPA2) and glycoprotein hormone-beta5 (GPB5) activate fly leucine-rich repeat-containing G protein-coupled receptor-1 (DLGR1) and stimulation of human thyrotropin receptors by chimeric fly GPA2 and human GPB5. Endocrinology 146:3596–3604PubMedCrossRefGoogle Scholar