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: 2.67). 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.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: In recent years, brain kisspeptin system has been shown to be involved in diverse reproductive function, including sexual differentiation in vertebrates. Our previous reports demonstrated that the chub mackerel (Scomber japonicus) brain expresses two kisspeptin (kiss1, kiss2), two kisspeptin receptor (kissr1, kissr2) and three gonadotropin-releasing hormone (gnrh1, gnrh2, gnrh3) genes. In the present study, using quantitative real-time PCR (qRT-PCR) assays, we analysed expression changes of these genes during early development (0-30dphs) and gonadal sex differentiation periods (37-60dphs). Absolute expression level of kiss-kissr-gnrh in the whole head was higher between 0 and 15dphs, in comparison to later developmental periods. Histological analyses revealed presence of sexually differentiated males and females with testicular and ovarian features at 37, 45, and 60dphs. In both males and females, kiss2, kissr1, and kissr2 levels were higher at 37dph, in comparison to 45 and 60dphs, with kiss1 showing no significant differences. Levels of all three gnrh mRNAs were higher at 45dph, in comparison to 60dph. Changes in the expression levels of kiss-kissr-gnrh mRNAs in different brain regions of sexually differentiated males and females indicated differences in their regional distribution. These results suggest possible involvement of Kiss-KissR-GnRH systems during early development and gonadal sex differentiation in the chub mackerel.
    General and Comparative Endocrinology 10/2014; DOI:10.1016/j.ygcen.2014.09.019 · 2.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Kisspeptin (Kiss) and its cognate receptor (Kiss1R or GPR54), implicated in the neuroendocrine control of gonadotropin-releasing hormone (GnRH) secretion in mammals, have been proposed to be key factors in reproduction, with a special role during puberty. However, the mechanisms underlying the initiation of puberty in fish are poorly understood. The chub mackerel Scomber japonicus possesses two forms of Kiss (kiss1 and kiss2) and two Kiss receptor (kissr1 and kissr2) genes in the brain, which exhibit sexually dimorphic changes during the seasonal reproductive cycle. This indicates that the kisspeptin system plays an important role in gonadal recrudescence of chub mackerel; however, the involvement of kisspeptin system in the pubertal process has not been identified in this species. In the present study, we examined temporal patterns of kiss1, kiss2, kissr1, kissr2, and gnrh1 (hypophysiotropic GnRH form in this species) mRNA expression in chub mackerel brain during the pubertal process. In male fish, kiss2, kissr1 and kissr2 expression levels increased significantly at 14 weeks post-hatch (wph), synchronously with an increase in type A spermatogonial populations in the testis; kiss2 and gnrh1 expression levels significantly increased at 22 wph, just before the onset of meiosis in the testes. In female fish, kiss2 increased significantly at 14 wph, synchronously with an increase in number of perinucleolar oocytes in the ovary; kiss1 and kiss2 levels significantly increased concomitantly with an increase in the kissr1, kissr2, and gnrh1 levels at 24 wph, just before the onset of vitellogenesis in oocytes. The present results suggest positive involvement of the kisspeptin–GnRH system in the pubertal process in both chub mackerel sexes, as in mammals.
    Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 09/2014; DOI:10.1016/j.cbpa.2014.09.012 · 2.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) play central roles in regulating gametogenesis and the production of gonadal hormones, in fish as in other vertebrates. Pituitary gonadotropins are composed of two non-covalently associated polypeptide subunits, which must be glycosylated, folded, and assembled as a heterodimer to be biologically active. Since biotechnology for the production of recombinant proteins has been greatly advanced, it is possible that fish FSH and LH are produced biotechnologically as an alternative way for various manipulations in modern aquaculture. This review discusses different platforms currently being applied for recombinant piscine gonadotropin production.


Available from
Nov 24, 2014