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


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 order to discuss the physiological role of kisspeptin systems identified by studies on different animals and fish species, the nomenclature referred to in Tena-sempre et al., 2012 has been adopted throughout this manuscript. The existence of kisspeptin system in fish was demonstrated by the molecular cloning of kiss1r first in Nile tilapia, Oreochromis niloticus (Parhar et al., 2004), and subsequently in grey mullet, Mugil cephalus (Nocillado et al., 2007), cobia, Rachycentron canadum (Mohamed et al., 2007) and fathead minnow, Pimephales promelas (Filby et al., 2008). In most mammals, it was reported only one kisspeptin gene (Kiss1), with the exception of the platypus, a mammalian monotreme, in which two kisspeptin genes (kiss1 and kiss2) were reported (Lee et al., 2009). "
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    ABSTRACT: Kisspeptin is an important regulator of reproduction in mammals and presumably non-mammalian species. In the Indian subcontinent, rohu (Labeo rohita) is a commercially important seasonal breeder freshwater fish species, but till date, the expression of kisspeptin gene during different phases of annual reproductive cycle has not been investigated. To address this, we cloned and characterized kiss1 and kiss2 full-length cDNA by RACE (rapid amplification of cDNA ends), and analyzed their expressions in brain-pituitary-gonad (BPG) axis by quantitative real time PCR (qRT-PCR) assay at various gonadal developmental stages of the annual reproductive cycle. Full-length rohu kiss1 and kiss2 cDNA encodes 116 and 125 amino acids respectively, and in the adult fish, they were widely expressed in brain, pituitary, gonad, liver, muscle, kidney, intestine and eye. In male, kiss1 mRNA in brain and testis showed highest level of expression during meiosis division of the gonad. The kiss2 mRNA revealed highest expression during recrudescence stages in the brain, spermiation stages in pituitary and post-spawning stages in testes. In females, significantly (p<0.05) higher level of kiss1 transcript was expressed in brain and ovary, in the full grown oocyte stages, whereas during pre-vitellogenic and vitellogenic stages in pituitary. The kiss2 gene expression was almost similar at various gonadal developmental stages in the brain and ovary, but, highest expression was detected in full grown oocyte stages in the pituitary. These results together may suggest the involvement of two kiss genes in the control of seasonal gonadal development in rohu.
    Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 10/2015; 191. DOI:10.1016/j.cbpb.2015.10.008 · 1.55 Impact Factor
    • "Therefore, to rule out possible issues with our assays, each RT-qPCR assay was tested on pooled ovary, testis, and brain cDNA samples (i.e., the primary sites of kisspeptin gene expression in the tissue distribution) which were serially diluted and analyzed in triplicate. Similar to Nocillado et al. (2007), the reliability of each assay was determined by examining standard curves (i.e., PCR efficiencies ) of each assay, the y-intercept cycle threshold (Ct) value of best-fit lines, and R 2 values across tissues (Table 3). "
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    ABSTRACT: The kisspeptin system plays pivotal roles in the regulation of vertebrate reproduction. Classically, kisspeptin produced in the brain stimulates brain gonadotropin-releasing hormone signaling, which in turn activates the pituitary-gonad axis. Expression of the kisspeptin system has also been documented in peripheral tissues, including gonads of mammals and fishes. However, the fish gonadal kisspeptin system remained uncharacterized. Herein we report identification and characterization of four kisspeptin system mRNAs (kisspeptin 1 (kiss1), kiss2, and G protein-coupled receptor 54-1 (gpr54-1) and gpr54-2) in sablefish, Anoplopoma fimbria. Sablefish predicted protein sequences were highly similar to those of other marine teleosts, but less so to freshwater teleosts. Tissue distribution analyses revealed that all four kisspeptin-system transcripts were expressed in both brain and gonad. However, kiss2 was the predominant transcript in the gonads and the only transcript detected in ovulated eggs. Ontogenetic analysis of kiss2 expression in juvenile sablefish gonads demonstrated that levels were low during sex differentiation but increased with fish size and gonadal development. Dramatic increases in kiss2 mRNA occurred during primary oocyte growth, while levels remained relatively low in testes. In situ hybridization revealed that kiss2 mRNA was localized to cytoplasm of perinucleolus stage oocytes, suggesting it could play a local role in oogenesis or could be synthesized and stored within oocytes as maternal mRNA. This represents the first study to focus on the gonadal kisspeptin system in fishes and provides important tools for further investigation of both the gonadal and brain kisspeptin systems in sablefish.
    General and Comparative Endocrinology 09/2015; DOI:10.1016/j.ygcen.2015.07.015 · 2.47 Impact Factor
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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.
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