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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    • "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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