AGNATHA AND AVIAN: EVOLUTIONARY RECRUITMENT OF GNRH SYSTEMS
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1
University of Guelph, Canada
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2
MRC Human Reproductive Sciences Unit, United Kingdom
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3
The Roslin Institute, United Kingdom
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4
University of New Hampshire, United States
Gonadotropin releasing hormone (GnRH) plays a pivitol role in the regulation of reproductive function through activation of its corresponding receptor (GnRH-R). Loss of a GnRH ligand and receptor isoforms may be correlated with the evolution of complexity of reproductive physiology. With the identification of two novel type III GnRH-Rs in the lamprey and the previously identified lGnRH-R-1, the total number of identified GnRH-Rs in the lamprey is three, which coincides with three endogenous lamprey GnRH ligands. In the chicken, two GnRH-R subtypes (type I and III) coincide with two endogenous chicken GnRH ligands. A comparison of the GnRH systems in a basal vertebrate and an avian species provides a unique insight into the recruitment of GnRH systems in these two divergent species and the evident plasticity in utilization of specific GnRH receptors in particular tissues. We have examined expression profiles, ligand specificity and activation of intracellular signaling in lamprey and chicken GnRH-Rs. Our latest findings describe which GnRH-R is the probable major mediator of pituitary gonadotrope function in each species and demonstrate that evolutionary recruitment of specific ligand-receptor pairing for particular physiological processes does not necessarily correlate with ligand–binding affinity or potency of second messenger activation. We propose that type I and III GnRH-Rs are more prevalent than type II GnRH-Rs and the gene duplication event from which type II and III GnRH-Rs emerged may have occurred before the split of the tetrapods and teleosts lineages. The retention of type II and III GnRH ligands may correlate with diverse endocrine functions for GnRH, including intra-gonadal functions and coincides with a diffusional hypothalamic-pitutary system in lampreys, whereas the loss of the type III ligand coincides with a developed hypothalamic portal system in chickens.
Acknowledgements
Supported by NSF IOS-0849569, NH AES Hatch 332 to SAS and BBSRC scholarship to NJ.
Keywords:
Agnatha,
avian,
chicken,
evolution,
GnRH,
GnRH receptor,
Lamprey,
Pharmacology
Conference:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011.
Presentation Type:
Invited Symposium
Topic:
Neuroendocrine control of reproduction
Citation:
Joseph
NT,
Morgan
K,
Millar
R,
Dunn
I,
Bedecarrats
G and
Sower
S
(2011). AGNATHA AND AVIAN: EVOLUTIONARY RECRUITMENT OF GNRH SYSTEMS.
Front. Endocrinol.
Conference Abstract:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology.
doi: 10.3389/conf.fendo.2011.04.00149
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Received:
21 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Dr. Nerine T Joseph, University of Guelph, Guelph, Canada, nerine.joseph@gmail.com