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Muñoz-Cueto JA, Zmora N, Paullada-Salmerón JA, Marvel M, Mañanos E, Zohar Y. The gonadotropin-releasing hormones: Lessons from fish. Gen Comp Endocrinol 2020; 291:113422. [PMID: 32032603 DOI: 10.1016/j.ygcen.2020.113422] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/02/2020] [Accepted: 02/03/2020] [Indexed: 12/26/2022]
Abstract
Fish have been of paramount importance to our understanding of vertebrate comparative neuroendocrinology and the mechanisms underlying the physiology and evolution of gonadotropin-releasing hormones (GnRH) and their genes. This review integrates past and recent knowledge on the Gnrh system in the fish model. Multiple Gnrh isoforms (two or three forms) are present in all teleosts, as well as multiple Gnrh receptors (up to five types), which differ in neuroanatomical localization, pattern of projections, ontogeny and functions. The role of the different Gnrh forms in reproduction seems to also differ in teleost models possessing two versus three Gnrh forms, Gnrh3 being the main hypophysiotropic hormone in the former and Gnrh1 in the latter. Functions of the non-hypothalamic Gnrh isoforms are still unclear, although under suboptimal physiological conditions (e.g. fasting), Gnrh2 may increase in the pituitary to ensure the integrity of reproduction under these conditions. Recent developments in transgenesis and mutagenesis in fish models have permitted the generation of fish lines expressing fluorophores in Gnrh neurons and to elucidate the dynamics of the elaborate innervations of the different neuronal populations, thus enabling a more accurate delineation of their reproductive roles and regulations. Moreover, in combination with neuronal electrophysiology, these lines have clarified the Gnrh mode of actions in modulating Lh and Fsh activities. While loss of function and genome editing studies had the premise to elucidate the exact roles of the multiple Gnrhs in reproduction and other processes, they have instead evoked an ongoing debate about these roles and opened new avenues of research that will no doubt lead to new discoveries regarding the not-yet-fully-understood Gnrh system.
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Affiliation(s)
- José A Muñoz-Cueto
- Department of Biology, Faculty of Marine and Environmental Sciences and INMAR, University of Cádiz, CEIMAR, The European University of the Seas (SEA-EU), Puerto Real (Cádiz), Spain.
| | - Nilli Zmora
- Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA
| | - José A Paullada-Salmerón
- Department of Biology, Faculty of Marine and Environmental Sciences and INMAR, University of Cádiz, CEIMAR, The European University of the Seas (SEA-EU), Puerto Real (Cádiz), Spain
| | - Miranda Marvel
- Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Evaristo Mañanos
- Institute of Aquaculture of Torre de la Sal, CSIC, Castellón, Spain
| | - Yonathan Zohar
- Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA.
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Chang JP, Pemberton JG. Comparative aspects of GnRH-Stimulated signal transduction in the vertebrate pituitary - Contributions from teleost model systems. Mol Cell Endocrinol 2018; 463:142-167. [PMID: 28587765 DOI: 10.1016/j.mce.2017.06.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/31/2017] [Accepted: 06/01/2017] [Indexed: 02/07/2023]
Abstract
Gonadotropin-releasing hormone (GnRH) is a major regulator of reproduction through actions on pituitary gonadotropin release and synthesis. Although it is often thought that pituitary cells are exposed to only one GnRH, multiple GnRH forms are delivered to the pituitary of teleost fishes; interestingly this can include the cGnRH-II form usually thought to be non-hypophysiotropic. GnRHs can regulate other pituitary cell-types, both directly as well as indirectly, and multiple GnRH receptors (GnRHRs) may also be expressed in the pituitary, and even within a single pituitary cell-type. Literature on the differential actions of native GnRH isoforms in primary pituitary cells is largely derived from teleost fishes. This review will outline the diversity and complexity of GnRH-GnRHR signal transduction found within vertebrate gonadotropes as well as extra-gonadotropic sites with special emphasis on comparative studies from fish models. The implications that GnRHR transduction mechanisms are GnRH isoform-, function-, and cell-specific are also discussed.
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Affiliation(s)
- John P Chang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Joshua G Pemberton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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Lumayno SDP, Ohga H, Selvaraj S, Nyuji M, Yamaguchi A, Matsuyama M. Molecular characterization and functional analysis of pituitary GnRH receptor in a commercial scombroid fish, chub mackerel (Scomber japonicus). Gen Comp Endocrinol 2017; 247:143-151. [PMID: 28153577 DOI: 10.1016/j.ygcen.2017.01.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 01/24/2017] [Accepted: 01/27/2017] [Indexed: 10/20/2022]
Abstract
The gonadotropin-releasing hormone (GnRH) is essential during pubertal onset, for its regulation of the synthesis and release of pituitary gonadotropins. Its action is mediated by GnRH receptors (GnRHRs) in the pituitary gonadotrophs. Our previous study demonstrated that the chub mackerel brain expresses three GnRH forms (gnrh1, gnrh2, and gnrh3), and that only GnRH1 neurons innervate anterior pituitary regions. Furthermore, chub mackerel gnrh1 mRNA exhibited a significant increase at pubertal onset. The present study aimed to isolate the functional GnRHR form involved in chub mackerel puberty. The open reading frame of our cloned receptor encodes 428 amino acids and contains seven transmembrane domains. Phylogenetic analysis also indicated clustering with other teleost-type IIB GnRHRs, mainly those involved in reproduction. Reporter gene assay results showed that all four synthetic peptides (GnRH1, GnRH2, GnRH3, and GnRH analogue) bind to the cloned receptor. Three deduced GnRH ligands stimulated luteinizing hormone (LH) release from cultured pituitary cells in vitro. Receptor gene expression was mainly detected in the pituitary and showed an increasing trend in the developing gonadal stages of both sexes during the pubertal process; this process was synchronous with previous studies of follicle-stimulating hormone beta (fshβ) and lhβ gene expression in chub mackerel. These results suggest that the cloned receptor is likely involved in the regulation of pubertal onset in this species. Therefore, we have designated the receptor cmGnRHR1.
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Affiliation(s)
| | - Hirofumi Ohga
- Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan
| | - Sethu Selvaraj
- Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan
| | - Mitsuo Nyuji
- Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan
| | - Akihiko Yamaguchi
- Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan
| | - Michiya Matsuyama
- Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan.
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Duan JR, Fang DA, Zhang MY, Liu K, Zhou YF, Xu DP, Xu P, Li DP. Changes of gonadotropin-releasing hormone receptor 2 during the anadromous spawning migration in Coilia nasus. BMC DEVELOPMENTAL BIOLOGY 2016; 16:42. [PMID: 27881074 PMCID: PMC5122156 DOI: 10.1186/s12861-016-0142-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 11/06/2016] [Indexed: 11/17/2022]
Abstract
Background An increase in the activity of the pituitary-gonad axis (PG-axis) and gonad development are essential for the onset of spawning migration in teleosts. In the fish Coilia nasus, gonad development and spawning migration up the Yangtze River occurs by the end of each summer. We hypothesized that gonadotropin releasing hormones receptor 2 (GnRH-R2), which together produce a signal that interacts with the PG-axis, may help to regulate spawning migration processes. Results In this regard, we (1) characterized the gonadosomatic index (GSI) in the anadromous fish C. nasus; (2) analyzed the GnRH-R2 mRNA expression levels in ovary and brain, and concentrations in the serum; and (3) identified the GnRH-R2 protein distribution in the brain and ovaries. We found strong relationships between all of these indices. Conclusions The results indicate that GnRH-R2 could act together to promote spawning during the anadromous migration. There is some evidence that the GnRH-R2 gene expression levels and protein distributions change in association with the migratory behavior.
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Affiliation(s)
- Jin-Rong Duan
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Di-An Fang
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Min-Ying Zhang
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Kai Liu
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Yan-Feng Zhou
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Dong-Po Xu
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China
| | - Pao Xu
- Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 9 Shanshui Road, Wuxi, 214128, China.
| | - Da-Peng Li
- Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, 430070, China.
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Williams BL, Akazome Y, Oka Y, Eisthen HL. Dynamic evolution of the GnRH receptor gene family in vertebrates. BMC Evol Biol 2014; 14:215. [PMID: 25344287 PMCID: PMC4232701 DOI: 10.1186/s12862-014-0215-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 09/25/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Elucidating the mechanisms underlying coevolution of ligands and receptors is an important challenge in molecular evolutionary biology. Peptide hormones and their receptors are excellent models for such efforts, given the relative ease of examining evolutionary changes in genes encoding for both molecules. Most vertebrates possess multiple genes for both the decapeptide gonadotropin releasing hormone (GnRH) and for the GnRH receptor. The evolutionary history of the receptor family, including ancestral copy number and timing of duplications and deletions, has been the subject of controversy. RESULTS We report here for the first time sequences of three distinct GnRH receptor genes in salamanders (axolotls, Ambystoma mexicanum), which are orthologous to three GnRH receptors from ranid frogs. To understand the origin of these genes within the larger evolutionary context of the gene family, we performed phylogenetic analyses and probabilistic protein homology searches of GnRH receptor genes in vertebrates and their near relatives. Our analyses revealed four points that alter previous views about the evolution of the GnRH receptor gene family. First, the "mammalian" pituitary type GnRH receptor, which is the sole GnRH receptor in humans and previously presumed to be highly derived because it lacks the cytoplasmic C-terminal domain typical of most G-protein coupled receptors, is actually an ancient gene that originated in the common ancestor of jawed vertebrates (Gnathostomata). Second, unlike previous studies, we classify vertebrate GnRH receptors into five subfamilies. Third, the order of subfamily origins is the inverse of previous proposed models. Fourth, the number of GnRH receptor genes has been dynamic in vertebrates and their ancestors, with multiple duplications and losses. CONCLUSION Our results provide a novel evolutionary framework for generating hypotheses concerning the functional importance of structural characteristics of vertebrate GnRH receptors. We show that five subfamilies of vertebrate GnRH receptors evolved early in the vertebrate phylogeny, followed by several independent instances of gene loss. Chief among cases of gene loss are humans, best described as degenerate with respect to GnRH receptors because we retain only a single, ancient gene.
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Bloch CL, Kedar N, Golan M, Gutnick MJ, Fleidervish IA, Levavi-Sivan B. Long-term GnRH-induced gonadotropin secretion in a novel hypothalamo-pituitary slice culture from tilapia brain. Gen Comp Endocrinol 2014; 207:21-7. [PMID: 24859253 DOI: 10.1016/j.ygcen.2014.05.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/29/2014] [Accepted: 05/01/2014] [Indexed: 12/19/2022]
Abstract
Organotypic cultures, prepared from hypothalamo-pituitary slices of tilapia, were developed to enable long-term study of secretory cells in the pituitary of a teleost. Values of membrane potential at rest were similar to those recorded from acute slices, and cells presented similar spontaneous spikes and spikelets. Some cells also exhibited slow spontaneous oscillations in membrane potential, which may be network-driven. Long-term (6days) continuous exposure to GnRH induced increases in LH and FSH secretion. FSH levels reached the highest levels after 24h of exposure to GnRH, and the highest secretion of LH was observed in days 4 and 5 of the experiment. Since slices were viable for several weeks in culture, maintaining the original cytoarchitecture, electrical membrane properties and the ability to secrete hormones in response to exogenous GnRH, this technique is ideal for studying the mechanisms regulating cell-to-cell communication under conditions resembling the in vivo tissue organization.
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Affiliation(s)
- Corinne L Bloch
- The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel; Koret School of Veterinary Medicine, Faculty of Agriculture, Food, and Environment, The Hebrew University, Rehovot 76100, Israel
| | - Noa Kedar
- Koret School of Veterinary Medicine, Faculty of Agriculture, Food, and Environment, The Hebrew University, Rehovot 76100, Israel
| | - Matan Golan
- The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Michael J Gutnick
- Koret School of Veterinary Medicine, Faculty of Agriculture, Food, and Environment, The Hebrew University, Rehovot 76100, Israel
| | - Ilya A Fleidervish
- Department of Physiology and Cell Biology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Berta Levavi-Sivan
- The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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Nocillado JN, Zohar Y, Biran J, Levavi-Sivan B, Elizur A. Chronic kisspeptin administration stimulated gonadal development in pre-pubertal male yellowtail kingfish (Seriola lalandi; Perciformes) during the breeding and non-breeding season. Gen Comp Endocrinol 2013; 191:168-76. [PMID: 23791760 DOI: 10.1016/j.ygcen.2013.06.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 05/13/2013] [Accepted: 06/03/2013] [Indexed: 01/24/2023]
Abstract
The kisspeptin system is now accepted as a key regulator of vertebrate reproductive function, particularly the onset of puberty. In teleosts, the stimulatory effect of exogenous kisspeptins has been demonstrated mainly at the hypothalamic and pituitary levels of the reproductive axis, with very limited information pertaining to gonadal response. We determined the effect of chronic peripheral administration of the conserved kisspeptin decapeptides (YNLNSFGLRY or Kiss1-10; and FNFNPFGLRF or Kiss2-10) on gonadal development of pre-pubertal yellowtail kingfish (Seriola lalandi), a Perciform teleost, during the breeding and non-breeding season. We utilized slow-release implants to chronically deliver the synthesized peptides, which were based on the yellowtail kingfish kiss1 and kiss2 cDNA sequences that we isolated. The expression level of kiss2r and gnrh1 in the brain or hypothalamus did not vary between treated and control groups. Pituitary expression of fshβ and lhβ was upregulated only with Kiss1-10 treatment regardless of the season. Based on histological evidence, gonadal development was stimulated in male fish with either Kiss1-10 or Kiss2-10, with Kiss2-10 being more effective during the non-breeding period. Overall, our results suggest that kisspeptins modulate the early gonadal development of male yellowtail kingfish, however that may vary with the breeding season.
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Affiliation(s)
- Josephine N Nocillado
- Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Queensland 4558, Australia
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Changes in Enzymes Activities of Clarias Gariepinus Brood Fish Exposed to Anaesthetics Metomidate. ACTA ACUST UNITED AC 2013. [DOI: 10.12691/aees-1-3-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Peñaranda DS, Mazzeo I, Hildahl J, Gallego V, Nourizadeh-Lillabadi R, Pérez L, Asturiano JF, Weltzien FA. Molecular characterization of three GnRH receptor paralogs in the European eel, Anguilla anguilla: tissue-distribution and changes in transcript abundance during artificially induced sexual development. Mol Cell Endocrinol 2013; 369:1-14. [PMID: 23416230 DOI: 10.1016/j.mce.2013.01.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 01/25/2013] [Accepted: 01/29/2013] [Indexed: 11/17/2022]
Abstract
Gonadotropin-releasing hormone receptor (GnRH-R) activation stimulates synthesis and release of gonadotropins in the vertebrate pituitary and also mediates other processes both in the brain and in peripheral tissues. To better understand the differential function of multiple GnRH-R paralogs, three GnRH-R genes (gnrhr1a, 1b, and 2) were isolated and characterized in the European eel. All three gnrhr genes were expressed in the brain and pituitary of pre-pubertal eels, and also in several peripheral tissues, notably gills and kidneys. During hormonally induced sexual maturation, pituitary expression of gnrhr1a (female) and gnrhr2 (male and female) was up-regulated in parallel with gonad development. In the brain, a clear regulation during maturation was seen only for gnrhr2 in the midbrain, with highest levels recorded during early vitellogenesis. These data suggest that GnRH-R2 is the likely hypophysiotropic GnRH-R in male eel, while both GnRH-R1a and GnRH-R2 seems to play this role in female eels.
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Affiliation(s)
- David S Peñaranda
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Valencia, Spain
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Gopurappilly R, Ogawa S, Parhar IS. Functional significance of GnRH and kisspeptin, and their cognate receptors in teleost reproduction. Front Endocrinol (Lausanne) 2013; 4:24. [PMID: 23482509 PMCID: PMC3591744 DOI: 10.3389/fendo.2013.00024] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 02/22/2013] [Indexed: 12/18/2022] Open
Abstract
Guanine nucleotide binding protein (G-protein)-coupled receptors (GPCRs) are eukaryotic transmembrane proteins found in all living organisms. Their versatility and roles in several physiological processes make them the single largest family of drug targets. Comparative genomic studies using various model organisms have provided useful information about target receptors. The similarity of the genetic makeup of teleosts to that of humans and other vertebrates aligns with the study of GPCRs. Gonadotropin-releasing hormone (GnRH) represents a critical step in the reproductive process through its cognate GnRH receptors (GnRHRs). Kisspeptin (Kiss1) and its cognate GPCR, GPR54 (=kisspeptin receptor, Kiss-R), have recently been identified as a critical signaling system in the control of reproduction. The Kiss1/Kiss-R system regulates GnRH release, which is vital to pubertal development and vertebrate reproduction. This review highlights the physiological role of kisspeptin-Kiss-R signaling in the reproductive neuroendocrine axis in teleosts through the modulation of GnRH release. Moreover, we also review the recent developments in GnRHR and Kiss-R with respect to their structural variants, signaling mechanisms, ligand interactions, and functional significance. Finally, we discuss the recent progress in identifying many teleost GnRH-GnRHR and kisspeptin-Kiss-R systems and consider their physiological significance in the control of reproduction.
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Affiliation(s)
- Renjitha Gopurappilly
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Sunway CampusSelangor, Malaysia
| | - Satoshi Ogawa
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Sunway CampusSelangor, Malaysia
| | - Ishwar S. Parhar
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Sunway CampusSelangor, Malaysia
- *Correspondence: Ishwar S. Parhar, Brain Research Institute, School of Medicine and Health Sciences, Monash University Sunway Campus, Petaling Jaya 46150, Selangor, Malaysia. e-mail:
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Hildahl J, Sandvik GK, Edvardsen RB, Norberg B, Haug TM, Weltzien FA. Four gonadotropin releasing hormone receptor genes in Atlantic cod are differentially expressed in the brain and pituitary during puberty. Gen Comp Endocrinol 2011; 173:333-45. [PMID: 21704626 DOI: 10.1016/j.ygcen.2011.06.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2010] [Revised: 03/01/2011] [Accepted: 06/06/2011] [Indexed: 01/27/2023]
Abstract
Gonadotropin releasing hormones (GnRH) are an important part of the brain-pituitary-gonad axis in vertebrates. GnRH binding to its receptors (GnRH-R) stimulates synthesis and release of gonadotropins in the pituitary. GnRH-Rs also mediate other processes in the central nervous system such as reproductive behavior and neuromodulation. As many as five GnRH-R genes have been identified in two teleost fish species, but the function and phylogenetic relationship of these receptors is not fully understood. To gain a better understanding of the functional relationship between multiple GnRH-Rs in an important aquaculture species, the Atlantic cod (Gadus morhua), we identified four GnRH-Rs (gmGnRH-R) by RT-PCR, followed by full-length cloning and sequencing. The deduced amino acid sequences were used for phylogenetic analysis to identify conserved functional motifs and to clarify the relationship of gmGnRH-Rs with other vertebrate GnRH-Rs. The function of GnRH-R variants was investigated by quantitative PCR gene expression analysis in the brain and pituitary of female cod during a full reproductive cycle and in various peripheral tissues in sexually mature fish. Phylogenetic analysis revealed two types of teleost GnRH-Rs: Type I including gmGnRH-R1b and Type II including gmGnRH-R2a, gmGnRH-R2b and gmGnRH-R2c. All four gmGnRH-Rs are expressed in the brain, and gmGnRH-R1b, gmGnRH-R2a and gmGnRH-R2c are expressed in the pituitary. The only GnRH-R differentially expressed in the pituitary during the reproductive cycle is gmGnRH-R2a such that its expression is significantly increased during spawning. These data suggest that gmGnRH-R2a is the most likely candidate to mediate the hypophysiotropic function of GnRH in Atlantic cod.
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Affiliation(s)
- Jon Hildahl
- Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, PO Box 8146 Dep, 0033 Oslo, Norway.
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van der Kraak G. Chapter 3 The GnRH System and the Neuroendocrine Regulation of Reproduction. FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(09)28003-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Signaling by G-protein-coupled receptor (GPCR): studies on the GnRH receptor. Front Neuroendocrinol 2009; 30:10-29. [PMID: 18708085 DOI: 10.1016/j.yfrne.2008.07.001] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Revised: 04/28/2008] [Accepted: 07/21/2008] [Indexed: 01/22/2023]
Abstract
Gonadotropin-releasing hormone (GnRH) is the first key hormone of reproduction. GnRH analogs are extensively used in in vitro fertilization, and treatment of sex hormone-dependent cancers, due to their ability to bring about 'chemical castration'. The interaction of GnRH with its cognate type I receptor (GnRHR) in pituitary gonadotropes results in the activation of Gq/G(11), phospholipase Cbeta (PLCbetaI), PLA(2), and PLD. Sequential activation of the phospholipases generates the second messengers inositol 1, 4, 5-trisphosphate (IP(3)), diacylglycerol (DAG), and arachidonic acid (AA), which are required for Ca(2+) mobilization, the activation of various protein kinase C isoforms (PKCs), and the production of prostaglandin (PG) and other metabolites of AA, respectively. PKC isoforms are the major mediators of the downstream activation of a number of mitogen-activated protein kinase (MAPK) cascades by GnRH, namely: extracellular signal-regulated kinase (ERK), jun-N-terminal kinase (JNK), and p38MAPK. The activated MAPKs phosphorylate both cytosolic and nuclear proteins to initiate the transcriptional activation of the gonadotropin subunit genes and the GnRHR. While Ca(2+) mobilization has been found to initiate rapid gonadotropin secretion, Ca(2+), together with various PKC isoforms, MAPKs and AA metabolites also serve as key nodes, in the GnRH-stimulated signaling network that enables the gonadotropes to decode GnRH pulse frequencies and translating that into differential gonadotropin synthesis and release. Even though pulsatility of GnRH is recognized as a major determinant for differential gonadotropin subunit gene expression and gonadotropin secretion very little is yet known about the signaling circuits governing GnRH action at the 'Systems Biology' level. Direct apoptotic and metastatic effects of GnRH analogs in gonadal steroid-dependent cancers expressing the GnRHR also seem to be mediated by the activation of the PKC/MAPK pathways. However, the mechanisms dictating life (pituitary) vs. death (cancer) decisions made by the same GnRHR remain elusive. Understanding these molecular mechanisms triggered by the GnRHR through biochemical and 'Systems Biology' approaches would provide the basis for the construction of the dynamic connectivity maps, which operate in the various cell types (endocrine, cancer, and immune system) targeted by GnRH. The connectivity maps will open a new vista for exploring the direct effects of GnRH analogs in tumors and the design of novel combined therapies for fertility control, reproductive disorders and cancers.
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Avitan A, Zelinger E, Levavi-Sivan B. Homologous desensitization and visualization of the tilapia GnRH type 3 receptor. Gen Comp Endocrinol 2007; 153:182-8. [PMID: 17507014 DOI: 10.1016/j.ygcen.2007.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 03/25/2007] [Accepted: 04/01/2007] [Indexed: 11/21/2022]
Abstract
Two types of gonadotropin-releasing hormone (GnRH) receptors were found in the pituitary of tilapia (t), named GnRHR type 3 (tGnRHR3) and GnRHR type 1, according to phylogenetic analysis. tGnRHR3 is highly expressed in the posterior part of the pituitary which contains LH and FSH cells. We characterized tGnRHR3 in terms of both LH release rate and receptor internalization rate in response to continuous exposure to GnRH. Constant exposure of tilapia pituitary fragments to salmon GnRH analog (sGnRHa) resulted in an increased secretion rate for 3h, followed by a gradual decline, taking 17-19h, to the basal secretion rate. A chimera between tGnRHR3 and green fluorescent protein (GFP) was created and used to observe the changes in receptor distribution and translocation, activated by agonist with time. The results suggested that the receptor is initially localized at the plasma membrane and upon activation by a homologous ligand (e.g. sGnRHa) undergoes relatively rapid endocytosis. In summary, the present work demonstrates that tGnRHR3 has already undergone endocytosis after 30min, while desensitization of LH release occurs only after 17-19h. It is concluded that for tGnRHR3, internalization of the receptor is not exclusively responsible for the desensitization of LH release.
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Affiliation(s)
- Ayelet Avitan
- Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, P.O. Box 12, Rehovot 76100, Israel
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Whitlock KE, Illing N, Brideau NJ, Smith KM, Twomey S. Development of GnRH cells: Setting the stage for puberty. Mol Cell Endocrinol 2006; 254-255:39-50. [PMID: 16777316 DOI: 10.1016/j.mce.2006.04.038] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Cells containing gonadotropin-releasing hormone (GnRH) are essential not only for reproduction but also for neuromodulatory functions in the adult animal. A variety of studies have hinted at multiple origins for GnRH-containing cells in the developing embryo. We have shown, using zebrafish as a model system, that GnRH cells originate from precursors lying outside the olfactory placode: the region of the anterior pituitary gives rise to hypothalamic GnRH cells and the cranial neural crest gives rise to the GnRH cells of the terminal nerve and midbrain. Cells of both the forming anterior pituitary and cranial neural crest are closely apposed to the precursors of the olfactory epithelium during early development. Disruption of kallmann gene function results in loss of the hypothalamic but not the terminal nerve GnRH cells during early development. The GnRH proteins are expressed early in development and this expression is mirrored by the onset of GnRH receptor (GnRH-R) expression during early development. Thus the signaling of the GnRH neuronal circuitry is set up early in development laying the foundation for the GnRH network that is activated at puberty leading to reproductive function in the mature animal.
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Affiliation(s)
- K E Whitlock
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, United States.
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Levavi-Sivan B, Biran J, Fireman E. Sex steroids are involved in the regulation of gonadotropin-releasing hormone and dopamine D2 receptors in female tilapia pituitary. Biol Reprod 2006; 75:642-50. [PMID: 16807382 DOI: 10.1095/biolreprod.106.051540] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Although molecular mechanisms underlying steroid effects on GnRH and dopamine receptors are well documented in mammals, little is known in fish. Herein, we describe the expression of pituitary GnRH and dopamine receptors relative to gonadotropin expression and release. We exposed female tilapia to graded doses of estradiol or 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP) in vitro, and of estradiol in vivo, and determined mRNA levels of gnrhr1, gnrhr3, drd2, lhb, and fshb by real-time PCR. We also determined gonadotropin levels using specific ELISAs. Exposure to low doses of estradiol caused increased gnrhr3 mRNA levels in vivo and in vitro, probably related to positive feedback on FSH release. Increasing concentrations of estradiol resulted in increased drd2 mRNA levels in vivo and in vitro, inhibition of LH and FSH release, and inhibition of lhb mRNA levels in vivo, possibly related to negative feedback. At high doses of estradiol, FSH release increased in preparation for a new generation of follicles. Exposure to nanomolar doses of DHP resulted in increased drd2 mRNA levels, probably related to negative feedback on LH release. A decrease in drd2 levels at the micromolar range of DHP (concomitant with increased gnrhr3 and fshb mRNA levels) may be related to the recruitment of a new generation of oocytes. Exposure to DHP also resulted in increased lhb mRNA levels toward final oocyte maturation. Salmon GnRH analog (sGnRHa) increased mRNA levels of gnrh1and gnrh3; when combined with DHP, sGnRHa synergistically increased expression of gnrh3 only. These results emphasize the role of sex steroids on positive and negative feedbacks controlling the reproductive cycle.
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Affiliation(s)
- Berta Levavi-Sivan
- Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University, Rehovot 76100, Israel.
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Levavi-Sivan B, Aizen J, Avitan A. Cloning, characterization and expression of the D2 dopamine receptor from the tilapia pituitary. Mol Cell Endocrinol 2005; 236:17-30. [PMID: 15876479 DOI: 10.1016/j.mce.2005.03.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 03/16/2005] [Accepted: 03/18/2005] [Indexed: 11/19/2022]
Abstract
A full-length cDNA encoding a dopamine receptor (DA-R) was obtained from the pituitary of tilapia (ta). This cDNA encodes a protein of 469 amino acids that exhibits the typical arrangement of GPCR. The taDA-R shows high similarity to the DA-Rs of mullet and fugu, and over 70% similarity to Xenopus, mouse and turkey D2 DA-Rs. Northern blot analysis revealed transcript for a single transcript in the pituitary, of approximately 3 kb. In a Southern analysis, the tilapia probe recognized specific bands in the genomic DNA of both mullet and catfish, suggesting high similarity between the corresponding genes. Phylogenetic analysis clearly aligned the taDA-D2-R with all vertebrate D2-like receptor sequences cloned to date, and it was therefore designated taDA-D2-R. taDA-D2-R was transiently expressed in COS-7 cells together with the reporter construct CRE-luciferase. Addition of the specific D2 dopamine agonists quinpirole or bromocriptine, in the presence of forskolin, led to a dose-dependent decrease in forskolin-induced cAMP levels. Both agonists yielded the same maximal inhibition (around 40%). However, the potency of taDA-D2-R for bromocriptine was higher than for quinpirole. As established for mammalian D2-like receptors, stimulation of the taDA-D2-R with quinpirole triggers pertussis-toxin-sensitive Gi/o-mediated, but not Gs-mediated signaling. In contrast to mammals, PCR analysis gave no evidence of alternative splicing in taDA-D2-R. Pharmacological and genetic manipulation of the taDA-D2-R should enable us to better define its physiological role and to further explore the usefulness of fish as a model system for understanding dopaminergic function in higher organisms.
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Affiliation(s)
- Berta Levavi-Sivan
- Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, P.O. Box 12, Rehovot 76100, Israel.
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