Temporal expression of G-protein-coupled receptor 54 (GPR54), gonadotropin-releasing-hormones (GnRH), and dopamine receptor D2 (drd2) in pubertal female grey Mullet, Mugil cephalus

Department of Primary Industries and Fisheries, Bribie Island Aquaculture Research Centre, 144 North Street, Woorim 4507, Qld, Australia.
General and Comparative Endocrinology (Impact Factor: 2.47). 02/2007; 150(2):278-87. DOI: 10.1016/j.ygcen.2006.09.008
Source: PubMed

ABSTRACT The G-protein-coupled receptor 54 (muGPR54) cDNA was cloned from the brain of the grey mullet, and its expression level, as well as those of the gonadotropin-releasing hormones (GnRH1, GnRH2, GnRH3) and dopamine receptor D2 (drd2), in the brain, pituitary and ovary of pubertal fish (early, intermediate, advanced) were determined by real-time quantitative RT-PCR (QPCR). The muGPR54 cDNA has an open reading frame of 1140 bp with a predicted 380 amino acid peptide, containing seven putative transmembrane domains and putative N-glycosylation and protein kinase C phosphorylation sites. QPCR results showed that the early stage of puberty in grey mullet is characterized by significantly high levels of expression of GPR54, GnRH and drd2 in the brain relative to the intermediate and advanced stages, except for GnRH1 that increased at the advanced stage of puberty. In the pituitary, drd2 expression declined significantly at the advanced stage relative to levels at the intermediate stage. Ovarian expression of GPR54 significantly increased from the intermediate stage of puberty relative to the early stage while that of GnRH1 acutely increased at the advanced stage of puberty. The ovarian expression of drd2 decreased as puberty progressed, but the changes were not significant. The results suggest the possible role of GPR54 and GnRH in positively regulating pubertal development in grey mullet and the dopaminergic inhibition of reproductive function mediated by drd2.

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Available from: Berta Sivan, Nov 24, 2014
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    • "In the zebrafish, the mRNA levels of kisspeptins (Kiss1 and Kiss2) are increased significantly at the start of the pubertal phase together with hypothalamic GnRH (GnRH3) mRNAs (Kitahashi et al., 2009). The levels of kissR mRNAs in the brain, which are expressed in GnRH neurons (Parhar et al., 2004), are also higher at the start of puberty compared to the pre-or post-pubertal stages in the cobia (Mohamed et al., 2007), grey mullet (Nocillado et al., 2007), fathead minnow (Filby et al., 2008), and the tilapia (Martinez-Chavez et al., 2008). These results indicate that fish kisspeptins most likely control the onset of puberty by stimulating GnRH release, as in mammals (Dungan et al., 2006; Seminara, 2005). "
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    ABSTRACT: Fish reproduction is regulated by the hypothalamus-pituitary-gonadal (HPG) axis. Within the HPG axis, gonadotropin-releasing hormone (GnRH) has been well recognized as the master molecule of reproduction, which regulates synthesis and release of gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), from the pituitary. In recent years, new molecules such as kisspeptins and gonadotropin-inhibitory hormone (GnIH) in the HPG axis have become the focus of research in reproductive neuroendocrinology. Each of them is considered to play an important role in the control of the HPG axis, in particular in the positive and negative feedback actions. In this chapter, we summarize the old and new molecules in the HPG axis from anatomical and physiological points of view.
    Sexual Plasticity and Gametogenesis in Fishes, Edited by Balasubramanian Senthilkumaran, 10/2013: chapter Hypothalamic Regulation of Pituitary Gonadotropins: pages 153-182; Nova Biomedical., ISBN: 978-1-62618-848-8
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    • "Expression levels of the kissr2 mRNA in the brain was correlated with pubertal development in cobia (Rachycentron canadum) (Mohamed et al., 2007), grey mullet (Mugil cephalus) (Nocillado et al., 2007), zebrafish (Biran et al., 2008), fathead minnow (Pimephales promelas) (Filby et al., 2008), Nile tilapia (Martinez-Chavez et al., 2008), Senegalese sole (Solea senegalensis) (Mechaly et al., 2009), and Atlantic halibut (Hippoglossus hippoglossus) (Mechaly et al., 2010). In the brain of Nile tilapia, kissr2 was expressed in a significantly higher percentage of GnRH neurons in mature males compared with immature males (Parhar et al., 2004). "
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    ABSTRACT: The kisspeptin receptor (Kiss1R) is a cognate receptor for kisspeptin (Kiss), and this Kiss-Kiss1R system has been shown to regulate seasonal reproduction in vertebrates. Our previous study found the chub mackerel (Scomber japonicus) brain expresses both kiss1 and kiss2 and exhibits sexually dimorphic changes during the seasonal reproductive cycle. The present study cloned two subtypes of kissr from the chub mackerel brain, and their signal transduction pathways to Kiss1 and Kiss2 were characterized in a mammalian cell line. Results of identification showed that kissr1 and kissr2 mRNAs encode 369 and 378 deduced amino acids, respectively, and share 52% similarity in amino acid sequences. In vitro functional analysis revealed that chub mackerel Kiss receptor signals are also preferentially transduced via the protein kinase C (PKC) rather than protein kinase A (PKA) pathway. Synthetic chub mackerel Kiss1-15 and Kiss2-12 peptides showed the highest potency for the activation of KissR1 and KissR2, respectively, stronger than their corresponding Kiss-10 peptides. Tissue distribution analyses indicated that both genes are highly expressed in the brain and that only kissr2 mRNA is expressed in the pituitary of both sexes. Unexpectedly, both kissr1 and kissr2 mRNAs were detected only in the testes. Seasonal expression changes showed higher expression levels of both kissr1 and kissr2 mRNAs in the brain of females during the early vitellogenic period; however, no significant differences were found in the brain of males. Pituitary kissr2 mRNA levels showed no significant variations. In the testes, the kissr1 mRNA expression level increased dramatically at spermiation compared with the immature and post-spawning periods. However, kissr2 mRNA levels in the testes did not vary significantly at different testicular stages. These results suggest that both kissr1 and kissr2 likely participate in the seasonal ovarian development of females, and thus in males, we propose a paracrine or autocrine role for kissr1 in testicular development.
    General and Comparative Endocrinology 08/2013; 193. DOI:10.1016/j.ygcen.2013.07.016 · 2.47 Impact Factor
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    • "P234 administration also reduced GnRH pulses from pubertal female rhesus monkeys (Roseweir et al., 2009). Evidence that the kisspeptin system exists in fish was demonstrated by the molecular cloning of the kiss1r ortholog first in Nile tilapia (Oreochromis niloticus) (Parhar et al., 2004), and subsequently in grey mullet (Mugil cephalus) (Nocillado et al., 2007b), cobia (Rachycentron canadum) (Mohamed et al., 2007) and fathead minnow (Pimephales promelas) (Filby et al., 2008). Since then, the complexity of the kisspeptin system in fish has been unraveled (Elizur, 2009; Tena-Sempere et al., 2012; Pasquier et al., 2012). "
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    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.
    General and Comparative Endocrinology 06/2013; 191. DOI:10.1016/j.ygcen.2013.06.005 · 2.47 Impact Factor
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