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Fujimori C, Sugimoto K, Ishida M, Yang C, Kayo D, Tomihara S, Sano K, Akazome Y, Oka Y, Kanda S. Long-lasting redundant gnrh1/3 expression in GnRH neurons enabled apparent switching of paralog usage during evolution. iScience 2024; 27:109304. [PMID: 38464591 PMCID: PMC10924128 DOI: 10.1016/j.isci.2024.109304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 12/08/2023] [Accepted: 02/16/2024] [Indexed: 03/12/2024] Open
Abstract
Expressed subtype of paralogous genes in functionally homologous cells sometimes show differences across species, the reasons for which have not been explained. The present study examined hypophysiotropic gonadotropin-releasing hormone (GnRH) neurons in vertebrates to investigate this mechanism. These neurons express either gnrh1 or gnrh3 paralogs, depending on the species, and apparent switching of the expressed paralogs in them occurred at least four times in vertebrate evolution. First, we found redundant expression of gnrh1 and gnrh3 in a single neuron in piranha and hypothesized that it may represent an ancestral GnRH system. Moreover, the gnrh1/gnrh3 enhancer of piranha induced reporter RFP/GFP co-expression in a single hypophysiotropic GnRH neuron in both zebrafish and medaka, whose GnRH neurons only express either gnrh3 or gnrh1. Thus, we propose that redundant expression of gnrh1/3 of relatively recent common ancestors may be the key to apparent switching of the paralog usage among present-day species.
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Affiliation(s)
- Chika Fujimori
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
- Optics and Imaging Facility, National Institute for Basic Biology, Okazaki, Aichi, Japan
| | - Kohei Sugimoto
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Mio Ishida
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Christopher Yang
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Daichi Kayo
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan
| | - Soma Tomihara
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
- Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan
| | - Kaori Sano
- Department of Chemistry, Faculty of Science, Josai University, Sakado, Saitama, Japan
| | - Yasuhisa Akazome
- Department of Anatomy, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan
| | - Yoshitaka Oka
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shinji Kanda
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
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2
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Soloperto S, Olivier S, Poret A, Minier C, Halm-Lemeille MP, Jozet-Alves C, Aroua S. Effects of 17α-ethinylestradiol on the neuroendocrine gonadotropic system and behavior of European sea bass larvae ( Dicentrarchus labrax). JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2023; 86:198-215. [PMID: 36803253 DOI: 10.1080/15287394.2023.2177781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The widespread use of 17α-ethinylestradiol (EE2), and other estrogenic endocrine disruptors, results in a continuous release of estrogenic compounds into aquatic environments. Xenoestrogens may interfere with the neuroendocrine system of aquatic organisms and may produce various adverse effects. The aim of the present study was to expose European sea bass larvae (Dicentrarchus labrax) to EE2 (0.5 and 50 nM) for 8 d and determine the expression levels of brain aromatase (cyp19a1b), gonadotropin-releasing hormones (gnrh1, gnrh2, gnrh3), kisspeptins (kiss1, kiss2) and estrogen receptors (esr1, esr2a, esr2b, gpera, gperb). Growth and behavior of larvae as evidenced by locomotor activity and anxiety-like behaviors were measured 8 d after EE2 treatment and a depuration period of 20 d. Exposure to 0.5 nM EE2 induced a significant increase in cyp19a1b expression levels, while upregulation of gnrh2, kiss1, and cyp19a1b expression was noted after 8 d at 50 nM EE2. Standard length at the end of the exposure phase was significantly lower in larvae exposed to 50 nM EE2 than in control; however, this effect was no longer observed after the depuration phase. The upregulation of gnrh2, kiss1, and cyp19a1b expression levels was found in conjunction with elevation in locomotor activity and anxiety-like behaviors in larvae. Behavioral alterations were still detected at the end of the depuration phase. Evidence indicates that the long-lasting effects of EE2 on behavior might impact normal development and subsequent fitness of exposed fish.
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Affiliation(s)
- S Soloperto
- Normandie Univ, UNIHAVRE, Le Havre Cedex, France
| | - S Olivier
- Normandie Univ, UNIHAVRE, Le Havre Cedex, France
| | - A Poret
- Normandie Univ, UNIHAVRE, Le Havre Cedex, France
| | - C Minier
- Normandie Univ, UNIHAVRE, Le Havre Cedex, France
| | - M P Halm-Lemeille
- Ifremer Port-en-Bessin, LaboratoireEnvironnement Ressources de Normandie, Port-en-Bessin, France
| | - C Jozet-Alves
- Normandie Univ, Unicaen, CNRS, Caen, France
- Univ Rennes, CNRS, Rennes, France
| | - S Aroua
- Normandie Univ, UNIHAVRE, Le Havre Cedex, France
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Chaube R, Rawat A, Sharma S, Senthilkumaran B, Bhat SG, Joy KP. Molecular cloning and characterization of a gonadotropin-releasing hormone 2 precursor cDNA in the catfish Heteropneustes fossilis: Expression profile and regulation by ovarian steroids. Gen Comp Endocrinol 2019; 280:134-146. [PMID: 31015009 DOI: 10.1016/j.ygcen.2019.04.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 04/10/2019] [Accepted: 04/16/2019] [Indexed: 01/26/2023]
Abstract
Gonadotropin-releasing hormone 2 (Gnrh2) is one of the three classes of Gnrh distributed in vertebrates and is highly conserved. In the present study, the cDNA encoding Gnrh2 was isolated and characterized in the ostariophysan catfish Heteropneustes fossilis (hf). The cDNA is 611 bp long with an open reading frame (ORF) of 261 bp that encodes a highly conserved protein of 86 amino acids. The deduced Gnrh2 precursor protein clustered with the vertebrate Gnrh2 type. The sequence identity of hfgnrh2 is 94% with African catfish (Clarias gariepinus) gnrh2 mRNA (accession no. X78047). The hfgnrh2 transcripts were expressed only in the brain and gonads with a higher expression in the female brain and ovary in both resting and prespawning phases. The expression was higher in the prespawning phase than the resting phase. The gnrh2 expression in the brain and ovary showed significant seasonal variations but with opposite patterns. In the brain, the expression was the highest in the preparatory phase, decreased progressively to low levels in the postspawning and resting phases. In the ovary, the transcript level was low in the resting and preparatory phases, increased sharply in the prespawning phase reaching the peak level in the spawning phase and declined sharply in the postspawning phase. The gnrh2 mRNA showed the highest expression in the hind brain-medulla oblongata and moderate to low expression in forebrain regions and pituitary. Ovariectomy resulted in a duration-dependent inhibition of hfgnrh2 mRNA levels in the resting and prespawning phases. Steroid (E2, testosterone and progesterone) replacement treatments (0.5 μg/g body weight) in the 3- week ovariectomized fish restored the inhibition due to ovariectomy, elevated the expression over and above the sham level in the resting phase (E2 group), and raised the levels almost to that of the sham group (testosterone and progesterone groups) in the prespawning phase. In the sham control groups, the steroid replacement resulted in a significant reduction in the mRNA levels. The expression of the gnrh2 mRNA in the brain-pituitary-gonadal axis and its regulation by gonadal steroids suggest that Gnrh2 may have a reproductive role in the catfish.
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Affiliation(s)
- R Chaube
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - A Rawat
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - S Sharma
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - B Senthilkumaran
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, Telangana, Hyderabad 500046, India
| | - S G Bhat
- Department of Biotechnology, Cochin University of Science and Technology, Kochi 682022, India
| | - K P Joy
- Department of Biotechnology, Cochin University of Science and Technology, Kochi 682022, India.
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Whitlock KE, Postlethwait J, Ewer J. Neuroendocrinology of reproduction: Is gonadotropin-releasing hormone (GnRH) dispensable? Front Neuroendocrinol 2019; 53:100738. [PMID: 30797802 PMCID: PMC7216701 DOI: 10.1016/j.yfrne.2019.02.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 02/12/2019] [Accepted: 02/14/2019] [Indexed: 02/06/2023]
Abstract
Gonadotropin releasing hormone (GnRH) is a highly conserved neuroendocrine decapeptide that is essential for the onset of puberty and the maintenance of the reproductive state. First identified in mammals, the GnRH signaling pathway is found in all classes of vertebrates; homologues of GnRH have also been identified in invertebrates. In addition to its role as a hypothalamic releasing hormone, GnRH has multiple functions including modulating neural activity within specific regions of the brain. These various functions are mediated by multiple isoforms, which are expressed at diverse locations within the central nervous system. Here we discuss the GnRH signaling pathways in light of new reports that reveal that some vertebrate genomes lack GnRH1. Not only do other isoforms of GnRH not compensate for this gene loss, but elements upstream of GnRH1, including kisspeptins, appear to also be dispensable. We discuss routes that may compensate for the loss of the GnRH1 pathway.
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Affiliation(s)
- Kathleen E Whitlock
- Centro Interdisciplinario de Neurociencia de Valparaiso (CINV), Instituto de Neurociencia, Universidad de Valparaiso, Avenida Gran Bretaña 1111, Valparaiso, Chile.
| | - John Postlethwait
- Institute of Neuroscience, 324 Huestis Hall, 1254 University of Oregon, Eugene, OR 97403-1254, USA
| | - John Ewer
- Centro Interdisciplinario de Neurociencia de Valparaiso (CINV), Instituto de Neurociencia, Universidad de Valparaiso, Avenida Gran Bretaña 1111, Valparaiso, Chile
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5
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Li L, Wojtowicz JL, Malin JH, Huang T, Lee EB, Chen Z. GnRH-mediated olfactory and visual inputs promote mating-like behaviors in male zebrafish. PLoS One 2017; 12:e0174143. [PMID: 28329004 PMCID: PMC5362193 DOI: 10.1371/journal.pone.0174143] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 03/03/2017] [Indexed: 01/13/2023] Open
Abstract
The engagement of sexual behaviors is regulated by a number of factors which include gene expression, hormone circulation, and multi-sensory information integration. In zebrafish, when a male and a female are placed in the same container, they show mating-like behaviors regardless of whether they are kept together or separated by a net. No mating-like behaviors are observed when same-sex animals are put together. Through the olfacto-visual centrifugal pathway, activation of the terminalis nerve in the olfactory bulb increases GnRH signaling in the brain and triggers mating-like behaviors between males. In zebrafish mutants or wild-type fish in which the olfacto-visual centrifugal pathway is impaired or chemically ablated, in response to odor stimulation the mating-like behaviors between males are no longer evident. Together, the data suggest that the combination of olfactory and visual signals alter male zebrafish's mating-like behaviors via GnRH signaling.
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Affiliation(s)
- Lei Li
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States of America
- * E-mail:
| | - Jennifer L. Wojtowicz
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States of America
| | - John H. Malin
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States of America
| | - Tao Huang
- Center for Reproductive Medicine, Shandong University, Jinan,China
| | - Eric B. Lee
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States of America
| | - Zijiang Chen
- Center for Reproductive Medicine, Shandong University, Jinan,China
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Yu M, Zhang X, Guo L, Tian H, Wang W, Ru S. Anti-estrogenic effect of semicarbazide in female zebrafish (Danio rerio) and its potential mechanisms. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 170:262-270. [PMID: 26688189 DOI: 10.1016/j.aquatox.2015.11.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 11/25/2015] [Accepted: 11/26/2015] [Indexed: 06/05/2023]
Abstract
Semicarbazide (SMC), a member of the hydrazine family, has various toxic effects and has been detected in organisms, aquatic environments, and food. SMC exposure inhibited the transcription of hepatic vitellogenin and estrogen receptors in female zebrafish (Danio rerio), suggesting that it had anti-estrogenic properties. In order to elucidate the mechanisms underlying these, we exposed female zebrafish to SMC and used enzyme-linked immunosorbent assays to examine plasma 17β-estradiol (E2) and testosterone (T) levels. Gonad histology was analyzed and the mRNA expression of genes involved in the reproductive axis, the gamma-aminobutyric acid (GABA) shunt, and leptin was quantified by real-time PCR. Zebrafish were exposed to 1, 10, 100, or 1000μg/L SMC in a semi-static system for 96hours or 28 days. Plasma E2 levels were significantly decreased and ovarian maturation was inhibited by SMC, suggesting that its anti-estrogenic effect was exerted by reducing endogenous E2 levels. This was likely due to the SMC-mediated inhibition of cytochrome P450 (CYP) 19A mRNA levels, because this enzyme catalyzes the conversion of T to E2 in the gonads. In addition, down-regulation of the mRNA expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase, steroidogenic acute regulatory protein, CYP17, and 17beta-hydroxysteroid dehydrogenase was observed; this was predicted to reduce T concentrations and further contribute to the reduced E2 levels. SMC-induced changes in the expression of these steroidogenic genes correlated with decreased transcription of gonadotropic hormones (follicle-stimulating hormone and luteinizing hormone) and significantly elevated leptin expression. Furthermore, SMC also altered expression of the key enzyme in gamma-aminobutyric acid (GABA) synthesis, GABA receptors, and salmon gonadotropin-releasing hormone, thus affecting gonadotropin expression. Overall, SMC acted at multiple sites related to reproduction to reduce plasma E2 levels, consequently exerting an anti-estrogenic effect in female zebrafish. These effects were observed at environmentally relevant concentrations and highlight the importance of controlling SMC contamination.
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Affiliation(s)
- Miao Yu
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Xiaona Zhang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Linlin Guo
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Hua Tian
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Wei Wang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Shaoguo Ru
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
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Pfister D, Yu C, Kim DS, Li J, Drewing A, Li L. Zebrafish Olfacto-Retinal Centrifugal Axon Projection and Distribution: Effects of Gonadotropin-Releasing Hormone and Dopaminergic Signaling. Dev Neurosci 2015; 38:27-33. [PMID: 26505192 DOI: 10.1159/000439524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 08/19/2015] [Indexed: 11/19/2022] Open
Abstract
The terminalis neurons (TNs) have been described in teleost species. In zebrafish, the TNs are located in the olfactory bulb. The TNs synthesize and release gonadotropin-releasing hormone (GnRH) as one of the major neurotransmitters. The TNs project axons to many brain areas, which include the neural retina. In the retina, the TN axons synapse with dopaminergic interplexiform cells (DA-IPCs) and retinal ganglion cells (RGCs). In this research, we examine the role of GnRH and dopaminergic signaling in TN axon projection to the retina using the transgenic zebrafish Tg(GnRH-3::GFP). While the TNs developed at 34 h postfertilization (hpf), the first TN axons were not detected in the retina until 48-50 hpf, when the first DA-IPCs were differentiated. In developing embryos, inhibition of retinal GnRH signaling pathways severely interrupted the projection of TN axons to the retina. However, inhibition of retinal dopaminergic signaling produced little effect on TN axon projection. In adult retinas, inactivation of GnRH receptors disrupted the patterns of TN axon distribution, and depletion of DA-IPCs abolished the TN axons. When DA-IPCs regenerated, the TN axons reappeared. Together, the data suggest that in developing zebrafish retinas GnRH signaling is required for TN axon projection, whereas in adult retinas activation of GnRH and dopaminergic signaling transduction is required for normal distribution of the TN axons.
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Affiliation(s)
- Delaney Pfister
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Ind., USA
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Huang W, Zhang J, Liao Z, Lv Z, Wu H, Zhu A, Wu C. Genomic structure and promoter functional analysis of GnRH3 gene in large yellow croaker (Larimichthys crocea). Gene 2015; 576:458-65. [PMID: 26519998 DOI: 10.1016/j.gene.2015.10.063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Revised: 10/09/2015] [Accepted: 10/24/2015] [Indexed: 01/30/2023]
Abstract
Gonadotropin-releasing hormone III (GnRH3) is considered to be a key neurohormone in fish reproduction control. In the present study, the cDNA and genomic sequences of GnRH3 were cloned and characterized from large yellow croaker Larimichthys crocea. The cDNA encoded a protein of 99 amino acids with four functional motifs. The full-length genome sequence was composed of 3797 nucleotides, including four exons and three introns. Higher identities of amino acid sequences and conserved exon-intron organizations were found between LcGnRH3 and other GnRH3 genes. In addition, some special features of the sequences were detected in partial species. For example, two specific residues (V and A) were found in the family Sciaenidae, and the unique 75-72 bp type of the open reading frame 2 and 3 existed in the family Cyprinidae. Analysis of the 2576 bp promoter fragment of LcGnRH3 showed a number of transcription factor binding sites, such as AP1, CREB, GATA-1, HSF, FOXA2, and FOXL1. Promoter functional analysis using an EGFP reporter fusion in zebrafish larvae presented positive signals in the brain, including the olfactory region, the terminal nerve ganglion, the telencephalon, and the hypothalamus. The expression pattern was generally consistent with the endogenous GnRH3 GFP-expressing transgenic zebrafish lines, but the details were different. These results indicate that the structure and function of LcGnRH3 are generally similar to the other teleost GnRH3 genes, but there exist some distinctions among them.
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Affiliation(s)
- Wei Huang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Jianshe Zhang
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Zhi Liao
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Zhenming Lv
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Huifei Wu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Aiyi Zhu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
| | - Changwen Wu
- National Engineering Research Center of Marine Facilities Aquaculture, College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, PR China
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Cortés-Campos C, Letelier J, Ceriani R, Whitlock KE. Zebrafish adult-derived hypothalamic neurospheres generate gonadotropin-releasing hormone (GnRH) neurons. Biol Open 2015. [PMID: 26209533 PMCID: PMC4582115 DOI: 10.1242/bio.010447] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) is a hypothalamic decapeptide essential for fertility in vertebrates. Human male patients lacking GnRH and treated with hormone therapy can remain fertile after cessation of treatment suggesting that new GnRH neurons can be generated during adult life. We used zebrafish to investigate the neurogenic potential of the adult hypothalamus. Previously we have characterized the development of GnRH cells in the zebrafish linking genetic pathways to the differentiation of neuromodulatory and endocrine GnRH cells in specific regions of the brain. Here, we developed a new method to obtain neural progenitors from the adult hypothalamus in vitro. Using this system, we show that neurospheres derived from the adult hypothalamus can be maintained in culture and subsequently differentiate glia and neurons. Importantly, the adult derived progenitors differentiate into neurons containing GnRH and the number of cells is increased through exposure to either testosterone or GnRH, hormones used in therapeutic treatment in humans. Finally, we show in vivo that a neurogenic niche in the hypothalamus contains GnRH positive neurons. Thus, we demonstrated for the first time that neurospheres can be derived from the hypothalamus of the adult zebrafish and that these neural progenitors are capable of producing GnRH containing neurons.
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Affiliation(s)
- Christian Cortés-Campos
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2340000, Chile Whitehead Institute for Biomedical Research (WIBR), 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Joaquín Letelier
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2340000, Chile Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, Carretera de Utera km 1, Sevilla 41013, España
| | - Ricardo Ceriani
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2340000, Chile
| | - Kathleen E Whitlock
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 269, Valparaíso 2340000, Chile
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10
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Zhou X, Yi Q, Zhong Q, Li C, Muhammad S, Wang X, Wang Z, Qi J, Yu H, Zhang Q. Molecular cloning, tissue distribution, and ontogeny of gonadotropin-releasing hormone III gene (GnRH-III) in half-smooth tongue sole (Cynoglossus semilaevis). Comp Biochem Physiol B Biochem Mol Biol 2012; 163:59-64. [PMID: 22580269 DOI: 10.1016/j.cbpb.2012.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 03/14/2012] [Accepted: 04/28/2012] [Indexed: 10/28/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is a neuropeptide that plays a vital role in hypothalamus-pituitary-gonad (HPG) axis. In the present study, the GnRH-III gene was isolated from half-smooth tongue sole (Cynoglossus semilaevis). In the 1160 bp genomic sequence, four exons, three introns, and 5'-/3'-flanking sequences were identified. The putative peptide was 92 residues long, including a putative signal peptide containing 23 amino acids, the GnRH decapeptide, a proteolytic cleavage site of three amino acids and a GnRH associated peptide of 56 amino acids. The overall amino acid sequence of C. semilaevis GnRH-III (csGnRH-III) was highly conserved with other teleost GnRH-III genes. Phylogenetic analysis showed the evolutionary relationships of csGnRH-III with other known GnRH genes. A 320 bp promoter sequence of the csGnRH-III was also analyzed, and several potential regulatory motifs were identified which were conserved in the GnRH promoters of other teleosts. Quantitative real-time PCR analysis indicated csGnRH-III was expressed only in brain and gonads. In C. semilaevis, the csGnRH-III transcript was maternally deposited and appeared to be developmentally regulated during embryogenesis and early larval development. Comparing sequence and expression patterns of csGnRH-III with other teleosts GnRH-IIIs suggested that the main function of GnRH-III might be conserved in teleosts.
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Affiliation(s)
- Xiaosu Zhou
- College of Marine Life Science, Ocean University of China, Key Laboratory of Marine Genetics and Breeding, Ministry of Education, #5 Yushan Road, Qingdao 266003, PR China
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11
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Nishiguchi R, Azuma M, Yokobori E, Uchiyama M, Matsuda K. Gonadotropin-releasing hormone 2 suppresses food intake in the zebrafish, Danio rerio. Front Endocrinol (Lausanne) 2012; 3:122. [PMID: 23087673 PMCID: PMC3473230 DOI: 10.3389/fendo.2012.00122] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 09/30/2012] [Indexed: 12/14/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) is an evolutionarily conserved neuropeptide with 10 amino acid residues, of which several structural variants exist. A molecular form known as GnRH2 ([His(5) Trp(7) Tyr(8)]GnRH, also known as chicken GnRH II) is widely distributed in vertebrates except for rodents, and has recently been implicated in the regulation of feeding behavior in goldfish. However, the influence of GnRH2 on feeding behavior in other fish has not yet been studied. In the present study, therefore, we investigated the role of GnRH2 in the regulation of feeding behavior in a zebrafish model, and examined its involvement in food intake after intracerebroventricular (ICV) administration. ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding. Cumulative food intake was significantly decreased by ICV injection of GnRH2 at 1 pmol/g BW during the 30-min post-treatment observation period. The anorexigenic action of GnRH2 was completely blocked by treatment with the GnRH type I receptor antagonist Antide at 25 pmol/g BW. We also examined the effect of feeding condition on the expression level of the GnRH2 transcript in the hypothalamus. Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally. These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.
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Affiliation(s)
- Ryo Nishiguchi
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
| | - Morio Azuma
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
| | - Eri Yokobori
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
| | - Minoru Uchiyama
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
| | - Kouhei Matsuda
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
- Laboratory of Regulatory Biology, Graduate School of Innovative Life Science, University of ToyamaToyama, Japan
- *Correspondence: Kouhei Matsuda, Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan. e-mail:
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Han XB, Lei ENY, Lam MHW, Wu RSS. A whole life cycle assessment on effects of waterborne PBDEs on gene expression profile along the brain-pituitary-gonad axis and in the liver of zebrafish. MARINE POLLUTION BULLETIN 2011; 63:160-165. [PMID: 21549400 DOI: 10.1016/j.marpolbul.2011.04.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 04/01/2011] [Accepted: 04/04/2011] [Indexed: 05/30/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are now found ubiquitously in the aquatic environment and biota, and there is a growing concern that PBDEs may disrupt endocrine systems, leading to reproductive impairments of aquatic animals. In our study, zebrafish (Danio rerio) were exposed to the 5 ng/L, 1 μg/L and 50 μg/L of DE-71 for the duration of the whole life cycle (120 days, from eggs to adults). The expression of selected genes along the brain-pituitary-gonadal (BPG) axis and liver, and the levels of plasma sex hormones were examined. In male fish, up-regulation of GnRH in brain, FSHβ and LHβ in pituitary, FSH-receptor, LH-receptor, and CYP19a in testis was clearly evident, while down-regulation of CYP11a and 3β-HSD was found in testis. In female fish, a 2.4-fold up-regulation of 3β-HSD was found in ovary upon exposure to 50 μg/L of DE-71. GnRH in brain, FSHβ and LHβ in pituitary were also up-regulated, while ERβ, TH and TPH in brain and GnRH-receptor in pituitary were significantly down-regulated. Hepatic ERα, AR and VTG in males were all down-regulated, while hepatic ERα and AR in female were up-regulated. Serum estradiol (E2) was reduced in both male and female upon exposure to DE-71, while significant increases in serum testosterone (T) and 11-keto-testosterone (11-KT) were only found in male but not female fish. The ratio of T/E2 as well as the ratio of 11-KT/E2 in male fish increased in a dose-dependent manner upon exposure to DE-71. Our overall results showed that whole life exposure of DE-71 altered the expression of regulatory genes and receptors at all three levels of the BPG axis in zebrafish, and the responses are sex dependent. The observed disruption of GnRH and GtHs can be further related to the subsequent disruption in both levels and balance sex steroid hormones.
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Affiliation(s)
- X B Han
- Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, Hong Kong.
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13
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Wang X, Huang L, Li Y, Li X, Li P, Ray J, Li L. Characterization of GFP-tagged GnRH-containing terminalis neurons in transgenic zebrafish. J Cell Physiol 2011; 226:608-15. [PMID: 20717967 DOI: 10.1002/jcp.22369] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The terminalis nerve (TN) has been described in all vertebrate species, in which it plays important roles in animal behavior and physiology. In teleost fish, the TN is located in the olfactory bulb and in its nerve tract. Here, we report a study on the characterization of the TN cell development, axon projection and physiology in zebrafish (Danio rerio). We have generated several lines of transgenic zebrafish [Tg (GnRH-3::GFP)] that express GFP in the TN cells. The transgenes are expressed under the transcriptional control of the zebrafish GnRH-3 promoter. During development, the first GFP-positive TN cell was identified at approximately 34 h post-fertilization (hpf). By 38 hpf, several clusters of TN cells were identified in the olfactory bulb and olfactory nerve tract. In the olfactory bulb, the TN cells projected axons caudally. In the forebrain, some of the TN axons extended caudally, but most crossed the midline of the brain at the commissural anterior. In the midbrain, some of the TN axons extended dorsally towards the tectum, whereas other axons extended caudally, or extended ventrally to the optic nerve where they entered the neural retina. We also examined the cell membrane property of the TN cells. Using patch-clamp techniques, we recorded spontaneous and evoked action potentials from isolated TN cells. We examined the expression of glutamate receptors in the TN cells. The data shed light on the mechanisms of TN function in the nervous system and in the regulation of animal physiology.
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Affiliation(s)
- Xiaokai Wang
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA
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14
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Huang L, Li L. Characterization of voltage-activated ionic currents in the GnRH-containing terminalis nerve in transgenic zebrafish. Brain Res 2010; 1367:43-9. [PMID: 20951681 DOI: 10.1016/j.brainres.2010.10.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 10/06/2010] [Accepted: 10/07/2010] [Indexed: 12/29/2022]
Abstract
The terminalis nerve (TN) is in a class of cranial nerves that plays important roles in animal development, physiology and behavior. Here, we report a study on the characterization of voltage-activated ionic currents in GnRH-containing TN cells in zebrafish. The experiments were performed using acutely dissociated TN cells from the transgenic zebrafish Tg (GnRH-3::GFP). In the transgenic zebrafish, the TN cells express GFP under the transcriptional control of the zebrafish GnRH-3 promoter. In all of the GnRH-containing TN cells examined, we recorded both low-voltage-activated (LVA) and high-voltage-activated (HVA) calcium current (I(Ca)). The characteristics of the I(Ca) were similar to those described in other zebrafish cell types. However, the distribution patterns of the currents in the GnRH-containing TN cells were different in comparison to the distribution of the currents in other cell types. In addition, we characterized TTX-sensitive sodium current (I(Na)) and 4AP-sensitive and TEA-resistant potassium current (I(K)). The characteristics of voltage-activated I(Na) and I(K) in the GnRH-containing TN cells were similar to those described in other zebrafish cell types. Together, the data from this study revealed the electrophysiological properties of the GnRH-containing TN cells, thereby providing insight on the regulatory mechanisms of TN-signaling in animal physiology.
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Affiliation(s)
- Luoxiu Huang
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
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15
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Selvaraj S, Kitano H, Fujinaga Y, Amano M, Takahashi A, Shimizu A, Yoneda M, Yamaguchi A, Matsuyama M. Immunological characterization and distribution of three GnRH forms in the brain and pituitary gland of chub mackerel (Scomber japonicus). Zoolog Sci 2010; 26:828-39. [PMID: 19968470 DOI: 10.2108/zsj.26.828] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The presence of three gonadotropin-releasing hormone (GnRH) forms in the brain of the chub mackerel, Scomber japonicus, namely, salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II), and seabream GnRH (sbGnRH), was confirmed by combined high performance liquid chromatography (HPLC) and time-resolved fluoroimmunoassay (TR-FIA). Immunocytochemical localization of the three GnRH forms in the brain was Investigated by using specific antisera, to elucidate possible roles of each GnRH form in reproduction in this species, and double immunolabeling was used to localize GnRH-ir (immunoreactive) fibers Innervating the pituitary. sGnRH-ir neurons were localized in the ventral olfactory bulb and terminal nerve ganglion region. Further, sGnRH-ir fibers were found in different regions of the brain, with prominent fibers running in parallel in the preoptic area (POA) without entering the pituitary. cGnRH-II-ir cell bodies were observed only in the midbrain tegmentum region, with a wide distribution of fibers, which were dense in the midbrain tegmentum and spinal cord. SbGnRH-ir cell bodies were localized in the nucleus preopticus of the POA, with fibers in the olfactory bulb, POA, and hypothalamus. Among the three GnRH forms, only SbGnRH-ir fibers innervated the pituitary gland from the preoptic-hypothalamic region, targeting follicle stimulating hormone (FSH) and luteinizing hormone (LH)-producing cells in the proximal pars distalis, as demonstrated by double immunocytochemistry. The localization of the GnRH-ir system was similar in male and female fish. These results demonstrate that multiple GnRH forms exist in the brain of the chub mackerel and suggest that they serve different functions, with SbGnRH having a significant role in reproduction in stimulating FSH- and LH-producing cells, and sGnRH and cGnRH-II serving as neurotransmitters or neuromodulators.
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Affiliation(s)
- Sethu Selvaraj
- Laboratory of Marine Biology, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan
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16
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17
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Abraham E, Palevitch O, Gothilf Y, Zohar Y. Targeted gonadotropin-releasing hormone-3 neuron ablation in zebrafish: effects on neurogenesis, neuronal migration, and reproduction. Endocrinology 2010; 151:332-40. [PMID: 19861502 DOI: 10.1210/en.2009-0548] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hypophysiotropic GnRH neurons are located in the preoptic area and ventral hypothalamus of sexually mature vertebrates. In several species, the embryonic origin of hypophysiotropic GnRH neurons remains unclear. Using the Tg(GnRH3:EGFP) zebrafish line, in which GnRH3 neurons express EGFP, GnRH3 neurons in the olfactory region were specifically and individually ablated during early development using laser pulses. After ablation, the olfactory region maintained the capacity to regenerate GnRH3 neurons. However, this capacity was time-limited. When ablation of GnRH3 cells was conducted at 2 d after fertilization, high regeneration rates were observed, but regeneration capacity significantly decreased when ablation was performed at 4 or 6 d after fertilization. Unilateral GnRH3 neuron ablation results in unilateral soma presence. These unilateral somata are capable of projecting fiber extensions bilaterally. Successful bilateral GnRH3 soma ablation during development resulted in complete lack of olfactory, terminal nerve, preoptic area, and hypothalamic GnRH3 neurons and fibers in 12-wk-old animals. Mature animals lacking GnRH3 neurons exhibited arrested oocyte development and reduced average oocyte diameter. Animals in which GnRH3 neurons were partially ablated exhibited normal oocyte development; however, their fecundity was significantly reduced. These findings demonstrate that the hypophysiotropic GnRH3 populations in zebrafish consist of neurons that originate in the olfactory region during early development. The presence of GnRH3 neurons of olfactory region origin in reproductively mature zebrafish is a prerequisite for normal oocyte development and reproduction.
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Affiliation(s)
- Eytan Abraham
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA
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18
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Clelland E, Peng C. Endocrine/paracrine control of zebrafish ovarian development. Mol Cell Endocrinol 2009; 312:42-52. [PMID: 19406202 DOI: 10.1016/j.mce.2009.04.009] [Citation(s) in RCA: 186] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 04/16/2009] [Accepted: 04/17/2009] [Indexed: 12/11/2022]
Abstract
Ovarian differentiation and the processes of follicle development, oocyte maturation and ovulation are complex events, requiring the coordinated action of regulatory molecules. In zebrafish, ovarian development is initiated at 10 days after hatching and fish become sexually mature at 3 months. Adult zebrafish have asynchronous ovaries, which contain follicles of all stages of development. Eggs are spawned daily under proper environmental conditions in a population of zebrafish, with individual females spawning irregularly every 4-7 days in mixed sex conditions. Maximal embryo viability is achieved when sexually isolated females are bred in 10-day intervals [Niimi, A.J., LaHam, Q.N., 1974. Influence of breeding time interval on egg number, mortality, and hatching of the zebra fish Brachydanio verio. Can. J. Zool. 52, 515-517]. Similar to other vertebrates, hormones from the hypothalamus-pituitary-gonadal axis play important roles in regulating follicle development. Follicle stimulating hormone (FSH) stimulates estradiol production, which in turn, promotes viteollogenesis. Luteinizing hormone (LH) stimulates the production of 17,20beta-dihydroxy-4-pregnen-3-one (17,20betaP) or maturation inducing hormone (MIH) which acts through membrane progestin receptors to activate maturation promoting factor, leading to oocyte maturation. Recent studies in zebrafish have also provided novel insights into the functions of ovary-derived growth factors in follicle development and oocyte maturation. The present review summarizes the current knowledge on how endocrine and paracrine factors regulate ovarian development in zebrafish. Special emphasis is placed on how follicle development and oocyte maturation in adult females is regulated by gonadotropins, ovarian steroids and growth factors produced by the ovary.
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Affiliation(s)
- Eric Clelland
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
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Abraham E, Palevitch O, Gothilf Y, Zohar Y. The zebrafish as a model system for forebrain GnRH neuronal development. Gen Comp Endocrinol 2009; 164:151-60. [PMID: 19523393 DOI: 10.1016/j.ygcen.2009.01.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 12/31/2008] [Accepted: 01/20/2009] [Indexed: 01/18/2023]
Abstract
Development and function of the forebrain gonadotropin-releasing hormone (GnRH) neuronal system has long been the focus of study in various vertebrate species. This system is crucial for reproduction and an important model for studying tangential neuronal migration. In addition, the finding that multiple forms of GnRH exist in the CNS as well as in non-CNS tissues, coupled with the fact that GnRH fibers project to many CNS regions, implies that GnRH has a variety of functions in addition to its classic reproductive role. The study of the GnRH system and its functions is, however, limited by available model systems and methodologies. The transgenic (Tg) GnRH3:EGFP zebrafish line, in which GnRH3 neurons express EGFP, allows in vivo study of the GnRH3 system in the context of the entire animal. Coupling the use of this line with the attributes and molecular tools available in zebrafish has expanded our ability to study the forebrain GnRH system. Herein, we discuss the use of the Tg(GnRH3:EGFP) zebrafish line as a model for studying forebrain GnRH neurons, both in developing larvae and in sexually mature animals. We also discuss the potential use of this line to study regulation of GnRH3 system development.
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Affiliation(s)
- Eytan Abraham
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, MD, USA
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20
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Lin SW, Ge W. Differential regulation of gonadotropins (FSH and LH) and growth hormone (GH) by neuroendocrine, endocrine, and paracrine factors in the zebrafish--an in vitro approach. Gen Comp Endocrinol 2009; 160:183-93. [PMID: 19063890 DOI: 10.1016/j.ygcen.2008.11.020] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 11/18/2008] [Accepted: 11/20/2008] [Indexed: 10/21/2022]
Abstract
Recently, zebrafish has quickly risen as a model species for functional analysis of the brain-pituitary-gonad axis. However, one of the hurdles for such work in this popular model organism is the small size of its pituitary gland, which makes it difficult to investigate the regulation of pituitary hormone expression and secretion in vitro. To provide a solution to this problem and demonstrate the value of zebrafish in reproductive endocrinology, the present study was undertaken to establish a primary pituitary cell culture followed by investigating the regulation of FSHbeta (fshb), LHbeta (lhb), and GH (gh) expression by a variety of neuroendocrine, endocrine, and paracrine factors. All the factors examined influenced the expression of fshb, lhb, and ghin vitro except epidermal growth factor (EGF) despite the expression of its receptor egfr in the pituitary. Acting in a similar manner, gonadal steroids (estradiol and testosterone) stimulated both fshb and lhb, but had no effect on gh. In contrast, all other factors tested (gonadotropin-releasing hormone, GnRH; pituitary adenylate cyclase-activating polypeptide, PACAP; activin/follistatin, and insulin-like growth factor I, IGF-I) exhibited distinct effects on the expression of the three target genes studied, suggesting roles for these factors in the differential regulation of two gonadotropins and growth hormone and therefore the gonadotrophic and somatotrophic axes.
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Affiliation(s)
- Sze-Wah Lin
- Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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21
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Palevitch O, Abraham E, Borodovsky N, Levkowitz G, Zohar Y, Gothilf Y. Nasal embryonic LHRH factor plays a role in the developmental migration and projection of gonadotropin-releasing hormone 3 neurons in zebrafish. Dev Dyn 2009; 238:66-75. [DOI: 10.1002/dvdy.21823] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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22
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Hu SY, Chen MHC, Lin YC, Lin GH, Gong HY, Yang TH, Wu JL. Cloning and functional analysis of the proximal promoter region of the three GnRH genes from the silver sea bream (Sparus sarba). Comp Biochem Physiol B Biochem Mol Biol 2008; 151:373-80. [DOI: 10.1016/j.cbpb.2008.06.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 06/14/2008] [Accepted: 06/18/2008] [Indexed: 11/24/2022]
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23
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Tello JA, Wu S, Rivier JE, Sherwood NM. Four functional GnRH receptors in zebrafish: analysis of structure, signaling, synteny and phylogeny. Integr Comp Biol 2008; 48:570-87. [DOI: 10.1093/icb/icn070] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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24
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Wong AC, Van Eenennaam AL. Gonadotropin hormone and receptor sequences from model teleost species. Zebrafish 2008; 1:203-21. [PMID: 18248232 DOI: 10.1089/zeb.2004.1.203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Fish offer some advantages for the study of vertebrate reproductive physiology. Only a few of the genes encoding the components of the hypothalamic-pituitary-gonadal axis have been identified from model teleosts. This study describes a combination of database searching and molecular approaches to identify the FSH and LH gonadotropin beta-subunits (fshb and lhb, respectively), and the LH receptor (lhr) from two model teleost species: zebrafish (Danio rerio) and Fugu (Takifugu rubripes). Sequence and phylogenetic analyses were used to examine the relationships that exist between gonadotropins and their receptors from species representing several piscine orders. The gonadotropin alpha-subunit (Cga) is highly conserved among teleosts and tetrapods. The presence of a genomic pseudogene (cgap) was also noted in zebrafish. Generally, teleostean FSHbeta protein sequences share less identity with each other than do LHbeta protein sequences, supporting the hypothesis that FSHbeta diverged more rapidly during teleost evolution. Interestingly, and uniquely, zebrafish Fshb lacked two highly conserved cysteine residues in the "determinant loop" which is thought to contribute towards receptor binding and specificity. Teleost gonadotropin receptor sequences clearly diverged into two distinct groups, FSHR and LHR. As has been seen with mammalian gonadotropin receptor transcripts, splice variants of zebrafish lhr were also observed.
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Affiliation(s)
- Andrew C Wong
- Department of Animal Science, University of California, Davis, California 95616, USA
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25
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Guilgur LG, Ortí G, Strobl-Mazzulla PH, Fernandino JI, Miranda LA, Somoza GM. Characterization of the cDNAs encoding three GnRH forms in the pejerrey fish Odontesthes bonariensis (Atheriniformes) and the evolution of GnRH precursors. J Mol Evol 2007; 64:614-27. [PMID: 17557168 DOI: 10.1007/s00239-006-0125-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Accepted: 02/12/2007] [Indexed: 01/11/2023]
Abstract
Most vertebrates express two gonadotropin releasing hormone (GnRH) variants in brain tissue but there is an increasing number of fish species for which a third GnRH form has been detected. We characterized the precursors (cDNAs) of all three forms expressed in the brain of the pejerrey (silverside) fish, Odontesthes bonariensis (Atheriniformes): type I (GnRH-I; 440 bp), type II (GnRH-II; 529 bp), and type III (GnRH-III; 515 bp). The expression of these GnRHs precursors was also observed in peripheral tissues related to reproduction (gonads), visual and chemical senses (eye and olfactory epithelium), and osmoregulation (gill), suggesting that in teleost fish and possibly other vertebrates GnRH mediates directly or indirectly many other functions besides reproduction. We also present a comprehensive phylogenetic analysis including representatives of all chordate GnRH precursors characterized to date that supports the idea of two main paralogous GnRH lineages with different function. A "forebrain lineage" separates evolutionarily from the "midbrain lineage" as a result of an ancient duplication (ca. 600 million years ago). A third, fish-only clade of GnRH genes seems to have originated before the divergence of fish and tetrapods but retained only in fish. Phylogenetic analyses of GnRH precursors (DNA and protein sequences) under different optimality criteria converge on this result. Although alternative scenarios could not be statistically rejected in this study due to the relatively short size of the analyzed molecules, this hypothesis also receives support from chromosomal studies of synteny around the GnRH genes in vertebrates.
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Affiliation(s)
- Leonardo G Guilgur
- Laboratorio de Ictiofisiología y Acuicultura, Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico de Chascomús CONICET-UNSAM, C.C. 164 B7130IWA, Chascomús, Provincia de Buenos Aires, Argentina
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26
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Alvarez MC, Béjar J, Chen S, Hong Y. Fish ES cells and applications to biotechnology. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2007; 9:117-27. [PMID: 17089084 DOI: 10.1007/s10126-006-6034-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 06/27/2006] [Indexed: 05/12/2023]
Abstract
ES cells provide a promising tool for the generation of transgenic animals with site-directed mutations. When ES cells colonize germ cells in chimeras, transgenic animals with modified phenotypes are generated and used either for functional genomics studies or for improving productivity in commercial settings. Although the ES cell approach has been limited to mice, there is strong interest for developing the technology in fish. We describe the step-by-step procedure for developing ES cells in fish. Key aspects include avoiding cell differentiation, specific in vitro traits of pluripotency, and, most importantly, testing for production of chimeric animals as the main evidence of pluripotency. The entire process focuses on two model species, zebrafish and medaka, in which most work has been done. The achievements attained in these species, as well as their applicability to other commercial fish, are discussed. Because of the difficulties relating to germ line competence, mostly of long-term fish ES cells, alternative cell-based approaches such as primordial germ cells and nuclear transfer need to be considered. Although progress to date has been slow, there are promising achievements in homologous recombination and alternative avenues yet to be explored that can bring ES technology in fish to fruition.
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Affiliation(s)
- M Carmen Alvarez
- Department of Cell Biology and Genetics, Faculty of Sciences, University of Málaga, 29071, Málaga, Spain.
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27
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Palevitch O, Kight K, Abraham E, Wray S, Zohar Y, Gothilf Y. Ontogeny of the GnRH systems in zebrafish brain: in situ hybridization and promoter-reporter expression analyses in intact animals. Cell Tissue Res 2006; 327:313-22. [PMID: 17036230 DOI: 10.1007/s00441-006-0279-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Accepted: 06/09/2006] [Indexed: 10/24/2022]
Abstract
The ontogeny of two gonadotropin-releasing-hormone (GnRH) systems, salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), was investigated in zebrafish (Danio rerio). In situ hybridization (ISH) first detected sGnRH mRNA-expressing cells at 1 day post-fertilization (pf) anterior to the developing olfactory organs. Subsequently, cells were seen along the ventral olfactory organs and the olfactory bulbs, reaching the terminal nerve (TN) ganglion at 5-6 days pf. Some cells were detected passing posteriorly through the ventral telencephalon (10-25 days pf), and by 25-30 days pf, sGnRH cells were found in the hypothalamic/preoptic area. Continuous documentation in live zebrafish was achieved by a promoter-reporter expression system. The expression of enhanced green fluorescent protein (EGFP) driven by the sGnRH promoter allowed the earlier detection of cells and projections and the migration of sGnRH neurons. This expression system revealed that long leading processes, presumably axons, preceded the migration of the sGnRH neuron somata. cGnRH-II mRNA expressing cells were initially detected (1 day pf) by ISH analysis at lateral aspects of the midbrain and later on (starting at 5 days pf) at the midline of the midbrain tegmentum. Detection of red fluorescent protein (DsRed) driven by the cGnRH-II promoter confirmed the midbrain expression domain and identified specific hindbrain and forebrain cGnRH-II-cells that were not identified by ISH. The forebrain DsRed-expressing cells seemed to emerge from the same site as the sGnRH-EGFP-expressing cells, as revealed by co-injection of both constructs. These studies indicate that zebrafish TN and hypothalamic sGnRH cell populations share a common embryonic origin and migratory path, and that midbrain cGnRH-II cells originate within the midbrain.
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Affiliation(s)
- Ori Palevitch
- Department of Zoology, George S Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel
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Wu S, Page L, Sherwood NM. A role for GnRH in early brain regionalization and eye development in zebrafish. Mol Cell Endocrinol 2006; 257-258:47-64. [PMID: 16934393 DOI: 10.1016/j.mce.2006.06.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 06/12/2006] [Accepted: 06/23/2006] [Indexed: 11/22/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is a highly conserved peptide that is expressed early in brain development in vertebrates. In zebrafish, we detected GnRH mRNA within 2h post fertilization by RT-PCR. To determine if GnRH is involved in development, we used gene knockdown techniques to block translation of gnrh2 or gnrh3 mRNA after which the expression patterns for gene markers were examined at 24h post fertilization with in situ hybridization. First, loss of either GnRH2 or GnRH3 affected regionalization of the brain as shown by a change in expression of fgf8 or pax2.1 genes in the midbrain-hindbrain boundary or diencephalon-midbrain boundary. Second, lack of GnRH2 and/or GnRH3 altered gene markers expressed in the formation of the eye cup (pax2.1, pax6.1, mab21l2 and meis1.1) or eye stalk (fgf8 and pax2.1). Third, knockdown of GnRH2 affected the size and shape of the midbrain and expression of gene markers therein. Results from assays with the TUNEL method and caspase-3 and -9 activity showed the brain and eye changes were unlikely to result from secondary apoptotic cell death before 24h post fertilization. These experiments suggest that GnRH loss-of-function affects early brain and eye formation during development.
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Affiliation(s)
- Sheng Wu
- Department of Biology, University of Victoria, Victoria, BC, Canada
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Guilgur LG, Moncaut NP, Canário AVM, Somoza GM. Evolution of GnRH ligands and receptors in gnathostomata. Comp Biochem Physiol A Mol Integr Physiol 2006; 144:272-83. [PMID: 16716622 DOI: 10.1016/j.cbpa.2006.02.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 01/19/2006] [Accepted: 02/14/2006] [Indexed: 10/24/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is the final common signaling molecule used by the brain to regulate reproduction in all vertebrates. Until now, a total of 24 GnRH structural variants have been characterized from vertebrate, protochordate and invertebrate nervous tissue. Almost all vertebrates already investigated have at least two GnRH forms coexisting in the central nervous system. Furthermore, it is now well accepted that three GnRH forms are present both in early and late evolved teleostean fishes. The number and taxonomic distribution of the different GnRH variants also raise questions about the phylogenetic relationships between them. Most of the GnRH phylogenetic analyses are in agreement with the widely accepted idea that the GnRH family can be divided into three main groups. However, the examination of the gnathostome GnRH phylogenetic relationships clearly shows the existence of two main paralogous GnRH lineages: the ''midbrain GnRH" group and the "forebrain GnRH" group. The first one, represented by chicken GnRH-II forms, and the second one composed of two paralogous lineages, the salmon GnRH cluster (only represented in teleostean fish species) and the hypophysotropic GnRH cluster, also present in tetrapods. This analysis suggests that the two forebrain clades share a common precursor and reinforces the idea that the salmon GnRH branch has originated from a duplication of the hypophysotropic lineage. GnRH ligands exert their activity through G protein-coupled receptors of the rhodopsin-like family. As with the ligands, multiple GnRHRs are expressed in individual vertebrate species and phylogenetic analyses have revealed that all vertebrate GnRHRs cluster into three main receptor types. However, new data and a new phylogenetic analysis propose a two GnRHR type model, in which different rounds of gene duplications may have occurred in different groups within each lineage.
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Affiliation(s)
- Leonardo G Guilgur
- Laboratorio de Ictiofisiología y Acuicultura, IIB-INTECH, CONICET-Universidad Nacional de General San Martín, IIB-INTECH, Camino de Circunvalación Laguna Km. 6, CC 164, B7130IWA, Chascomús, Provincia de Buenos Aires, Argentina
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30
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Whitlock KE, Smith KM, Kim H, Harden MV. A role forfoxd3andsox10in the differentiation of gonadotropin-releasing hormone (GnRH) cells in the zebrafishDanio rerio. Development 2005; 132:5491-502. [PMID: 16291787 DOI: 10.1242/dev.02158] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is found in a wide range of vertebrate tissues, including the nervous system. In general, GnRH has two functions: endocrine, acting as a releasing hormone; and neuromodulatory,affecting neural activity in the peripheral and central nervous system. The best understood population of GnRH cells is that of the hypothalamus, which is essential for reproduction. Less well understood are the populations of GnRH cells found in the terminal nerve and midbrain, which appear to be neuromodulatory in function. The GnRH-containing cells of the midbrain are proposed to arise from the mesencephalic region of the neural tube. Previously, we showed that neuromodulatory GnRH cells of the terminal nerve arise from cranial neural crest. To test the hypothesis that neuromodulatory GnRH cells of the midbrain also arise from neural crest, we used gene knockdown experiments in zebrafish to disrupt neural crest development. We demonstrate that decrement of the function of foxd3 and/or sox10, two genes important for the development and specification of neural crest, resulted in a reduction and/or loss of GnRH cells of the midbrain, as well as a reduction in the number of terminal nerve GnRH cells. Therefore, our data support a neural crest origin for midbrain GnRH cells. Additionally, we demonstrate that knockdown of kallmann gene function resulted in the loss of endocrine GnRH cells of the hypothalamus, but not of neuromodulatory GnRH cells of the midbrain and terminal nerve, thus providing additional evidence for separate pathways controlling the development of neuromodulatory and endocrine GnRH cells.
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Affiliation(s)
- Kathleen E Whitlock
- Department of Molecular Biology and Genetics, 445 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
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31
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Kuo MW, Lou SW, Postlethwait J, Chung BC. Chromosomal Organization, Evolutionary Relationship, and Expression of Zebrafish GnRH Family Members. J Biomed Sci 2005; 12:629-39. [PMID: 16132106 DOI: 10.1007/s11373-005-7457-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Accepted: 05/17/2005] [Indexed: 11/24/2022] Open
Abstract
Multiple forms of gonadotropin-releasing hormone (GnRH) are found in different vertebrates. In this study, we have cloned cDNA encoding the full-length gnrh3 and gnrh2 from zebrafish brain and characterized their structure and expression patterns. We performed phylogenetic analysis and compared conserved syntenies in the region surrounding the GnRH genes from human, chicken, pufferfish, and zebrafish genores. The gnrh3 and gnrh2 genes were mapped to LG17 and LG21, respectively. The zebrafish genome appears to lack an ortholog to human GNRH1, and the human genome appears to lack an ortholog of gnrh3. Expression of gnrh3 began in the olfactory pit at 24-26 h postfertilization and expanded to the olfactory bulb during early larval stage. Expression of gnrh2 is always in the midbrain. In addition, GnRH is also expressed in boundary cells surrounding seminiferous cysts of the testis. Thus, this detailed phylogenetic, chromosomal comparison, and expression study defines the identity and the evolutionary relationship of two zebrafish gnrh genes. We propose a model describing the evolution of gnrh genes involving ancestral duplication of the genes followed by selective loss of one gene in some teleosts.
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Affiliation(s)
- Ming-Wei Kuo
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road Section 2, Nankang, Taipei, Taiwan
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32
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Sherwood NM, Wu S. Developmental role of GnRH and PACAP in a zebrafish model. Gen Comp Endocrinol 2005; 142:74-80. [PMID: 15862551 DOI: 10.1016/j.ygcen.2005.02.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2004] [Revised: 02/08/2005] [Accepted: 02/09/2005] [Indexed: 11/28/2022]
Abstract
GnRH is expressed early in development long before reproduction begins. To determine whether GnRH has a role in development, gene knockdown with morpholinos was used in one-cell zebrafish embryos to block translation of gnrh mRNA into protein. Gene knockdown of gnrh2, gnrh3 or both at the one-cell stage resulted in a high percentage of embryos at 24-48 h with a defective mid-hindbrain boundary and underdeveloped eyes; a small percentage of embryos at 72 h had a defective heart. In similar studies on GHRH-PACAP, gene knockdown resulted in a smaller brain and eyes, but a normal-appearing heart. The evidence supports a role for the three neuropeptides in early development.
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Affiliation(s)
- Nancy M Sherwood
- Department of Biology, University of Victoria, Victoria, BC, Canada V8W 3N5.
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Morgan K, Millar RP. Evolution of GnRH ligand precursors and GnRH receptors in protochordate and vertebrate species. Gen Comp Endocrinol 2004; 139:191-7. [PMID: 15560865 DOI: 10.1016/j.ygcen.2004.09.015] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Revised: 08/19/2004] [Accepted: 09/15/2004] [Indexed: 11/25/2022]
Abstract
Primary structure relationships between GnRH precursors or GnRH receptors have received significant attention recently due to rapid DNA sequence determination of gene fragments and cDNAs from diverse species. Concepts concerning the evolutionary history of the GnRH system and its function in mammals, including humans, are likely to be modified as more complete sequence information becomes available. Current evidence suggests occurrence of fewer GnRH ligand and GnRH receptor genes in mammals compared to protochordates, fish and amphibians. Whilst several sequence-related GnRH decapeptide precursors and 2 or 3 separate GnRH receptors are encoded within the genomes of protochordates, fish and amphibians, only two types of GnRH (GnRH-I and GnRH-II) and two GnRH receptors occur in mammals. In addition, fish and mammalian genomes both retain inactive remnants of GnRH ligand or GnRH receptor genes. The number of distinct GnRH receptor genes in teleosts (at least five complete genes in pufferfish and three in zebrafish) partly reflects whole genome duplication during the evolution of this order of animals. Three GnRH receptor genes occur in certain frog species, consistent with the occurrence of up to three types of prepro-GnRH in amphibians. In contrast, only one functional GnRH receptor gene (the type I GnRH receptor) has been identified in humans and chimpanzees and a gene encoding a second receptor, homologous to a functional monkey receptor (the type II GnRH receptor), is either partially or completely silenced in a range of mammalian species (human, chimpanzee, sheep, cow, rat, and mouse). Further work is required to determine the significance of species-specific differences in the GnRH system to reproductive biology. For instance, recent data show that even species as closely related as humans and chimpanzees exhibit important organisational changes in the genes comprising the GnRH system.
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Affiliation(s)
- Kevin Morgan
- MRC Human Reproductive Sciences Unit, Old Dalkeith Road, Edinburgh EH16 4SB, UK.
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Gopinath A, Andrew Tseng L, Whitlock KE. Temporal and spatial expression of gonadotropin releasing hormone (GnRH) in the brain of developing zebrafish (Danio rerio). Gene Expr Patterns 2004; 4:65-70. [PMID: 14678830 DOI: 10.1016/s1567-133x(03)00149-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Gonadotropin releasing hormone (GnRH) is a neuroendocrine decapeptide found in all vertebrate animals. The best understood function of GnRH is its endocrine function as a releasing hormone acting on the pituitary. But GnRH also functions as a neuromodulator within the nervous system. In a given species, GnRH occurs in a variety of forms that fall into three general categories based on pattern of protein/gene expression in the brain and amino acid sequence. The salmon GnRH (sGnRH), is found in the terminal nerve, where it has a neuromodulatory function. The sGnRH form is also the hypothalamic form in many fishes, although some fishes have a species specific form in the hypothalamus. Finally, chicken-GnRH-II (cGnRH-II), the most highly conserved form, is found in the midbrain where its function remains unclear. Here we have cloned the sGnRH and cGnRH-II cDNAs from zebrafish. By conducting stage specific in situ hybridization in developing zebrafish embryos, we provide a description of the spatial and temporal expression patterns of these genes. The location of sGnRH and cGnRH-II expressing cells is in agreement with previous reports of GnRH in the brains of adult fishes. Our results provide the first developmental description of GnRH gene expression where cGnRH-II and sGnRH are initially expressed at the onset of the first day after fertilization. Unlike what has been reported in many adult fishes, we did not find sGnRH expressed in the hypothalamic population during development.
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Affiliation(s)
- Ashok Gopinath
- Field of Genetics and Development/Neurobiology and Behavior, Department of Molecular Biology and Genetics, 445 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA
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Vickers ED, Laberge F, Adams BA, Hara TJ, Sherwood NM. Cloning and localization of three forms of gonadotropin-releasing hormone, including the novel whitefish form, in a salmonid, Coregonus clupeaformis. Biol Reprod 2003; 70:1136-46. [PMID: 14668205 DOI: 10.1095/biolreprod.103.023846] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Cells containing different GnRH peptides currently are thought to have distinct locations and functions in the brain. Lake whitefish is the first salmonid species to have three forms of GnRH peptide in contrast to later-evolving salmonids (salmon and trout) in which only two forms have been identified. Our objective was to isolate the cDNAs that code for these transcripts and to localize the transcripts for the three forms of GnRH in adult lake whitefish brain. Also, we provide phylogenetic analysis of these three whitefish genes based on their preprohormone sequence. From whitefish we isolated cDNAs encoding chicken (c)GnRH-II, salmon (s)GnRH, and the novel whitefish (wf)GnRH. The three cDNAs each encode only one GnRH and are placed in separate groups with phylogenetic analysis. A combination of in situ hybridization and immunocytochemistry with two antisera revealed neurons that expressed protein and/or mRNA for cGnRH-II in the midbrain and hindbrain; sGnRH in the olfactory nerve and bulb, ventral telencephalon, and preoptic area; and wfGnRH in the same latter two brain regions and the hypothalamus. Thus, in the anterior brain, cells containing sGnRH and wfGnRH were in the same brain areas but not at identical locations in the ventral telencephalon and preoptic area. Based on our results, we speculate that both sGnRH and wfGnRH have gonadotropin-releasing roles in the lake whitefish brain.
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Affiliation(s)
- Elaine D Vickers
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 3N5
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Steven C, Lehnen N, Kight K, Ijiri S, Klenke U, Harris WA, Zohar Y. Molecular characterization of the GnRH system in zebrafish (Danio rerio): cloning of chicken GnRH-II, adult brain expression patterns and pituitary content of salmon GnRH and chicken GnRH-II. Gen Comp Endocrinol 2003; 133:27-37. [PMID: 12899844 DOI: 10.1016/s0016-6480(03)00144-8] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The zebrafish has proven to be a model system with unparalleled utility in vertebrate genetic and developmental studies. Substantially less attention has been paid to the potential role that zebrafish can play in answering important questions of vertebrate reproductive endocrinology. As an initial step towards exploiting the advantages that the zebrafish model offers, we have characterized their gonadotropin-releasing hormone (GnRH) system at the molecular level. GnRHs comprise a family of highly conserved decapeptide neurohormones widely recognized to orchestrate the hormonal control of reproduction in all vertebrates. We have isolated the gene and cDNA encoding chicken GnRH-II (cGnRH-II) from zebrafish, as well as several kilobases of upstream promoter sequence for this gene. As the gene encoding salmon GnRH (sGnRH) has been previously isolated (Torgersen et al, 2002), this is the second GnRH gene isolated from zebrafish to date. We have localized expression of these two genes in the brains of reproductively mature zebrafish using in situ hybridization. sGnRH is localized to the olfactory bulb-terminal nerve region (OB-TN), the ventral telencephalon-preoptic area (VT-POA) and, as we report here for the first time in any teleost species, the hindbrain. cGnRH-II is expressed exclusively in the midbrain, as has been found in all other jawed vertebrate species examined. Finally, the levels of both GnRH peptides in pituitaries of reproductively mature zebrafish were quantified using specific ELISAs. sGnRH pituitary peptide levels were shown to be 3- to 4-fold higher than cGnRH-II pituitary peptide. The cumulative results of these experiments allow us to conclude that zebrafish express just two forms of GnRH in a site-specific manner within the brain, and that sGnRH is the hypophysiotropic GnRH form. This work lays the foundation for further research into the control of reproduction in zebrafish, such as the functional significance of multiple GnRHs in vertebrates, and the molecular mechanisms controlling tissue-specific GnRH expression.
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Affiliation(s)
- Colin Steven
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 E Pratt Street, Baltimore, MD 21202, USA
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