Changes in the expression of pituitary gonadotropin subunits during reproductive cycle of multiple spawning female chub mackerel Scomber japonicus

Laboratory of Marine Biology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
Fish Physiology and Biochemistry (Impact Factor: 1.62). 11/2011; 38(3):883-97. DOI: 10.1007/s10695-011-9576-y
Source: PubMed


The endocrine regulation of reproduction in a multiple spawning fish with an asynchronous-type ovary remains largely unknown. The objectives of this study were to monitor changes in the mRNA expression of three gonadotropin (GtH) subunits (GPα, FSHβ, and LHβ) during the reproductive cycle of the female chub mackerel Scomber japonicus. Cloning and subsequent sequence analysis revealed that the cDNAs of chub mackerel GPα, FSHβ, and LHβ were 658, 535, and 599 nucleotides in length and encoded 117, 115, and 147 amino acids, respectively. We applied a quantitative real-time PCR assay to quantify the mRNA expression levels of these GtH subunits. During the seasonal reproductive cycle, FSHβ mRNA levels remained high during the vitellogenic stages, while GPα and LHβ mRNA levels peaked at the end of vitellogenesis. The expression of all three GtH subunits decreased during the post-spawning period. These results suggest that follicle-stimulating hormone (FSH) is involved in vitellogenesis, while luteinizing hormone (LH) functions during final oocyte maturation (FOM). Both GPα and FSHβ mRNA levels remained high during the FOM stages of the spawning cycle and increased further just after spawning. Thus, FSH synthesis may be strongly activated just after spawning to accelerate vitellogenesis in preparation for the next spawning. Alternatively, LHβ mRNA levels declined during hydration and then increased after ovulation. This study demonstrates that chub mackerel are a good model for investigating GtH functions in multiple spawning fish.

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Available from: Mitsuo Nyuji, Mar 21, 2014
    • "First-strand cDNA was synthesized using a Transcriptor First Strand cDNA Synthesis Kit (Roche Diagnostics, Mannheim, Germany) or Superscript III reverse transcriptase (Invitrogen, Carlsbad, CA) with oligo-dT and random hexamer primers . The complete nucleotide sequences for Fshb, Lhb, Gpa, Fshr and Lhr were determined using basic molecular cloning techniques as previously described for other perciform species (Nyuji et al., 2012, 2013). Pairwise amino acid sequence identities of Gth subunits and ECDs of Gthrs were calculated using the BioEdit program ( "
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    ABSTRACT: To understand the endocrine regulation of ovarian development in a multiple spawning fish, the relationship between gonadotropins (Gths; follicle-stimulating hormone [Fsh] and luteinizing hormone [Lh]) and their receptors (Gthrs; Fshr and Lhr) were investigated in greater amberjack (Seriola dumerili). cDNAs encoding the Gth subunits (Fshβ, Lhβ, and glycoprotein α [Gpα]) and Gthrs were cloned. The in vitro reporter gene assay using recombinant hormones revealed that greater amberjack Fshr and Lhr responded strongly to their own ligands. Competitive enzyme-linked immunosorbent assays (ELISAs) were developed for measuring greater amberjack Fsh and Lh. Anti-Fsh and anti-Lh antibodies were raised against recombinant chimeric single-chain Gths consisting of greater amberjack Fshβ (or Lhβ) with rabbit Gpα. The validation study showed that the ELISAs were precise (intra- and inter-assay coefficient of variation, <10%) and sensitive (detection limit of 0.2 ng/ml for Fsh and 0.8 ng/ml for Lh) with low cross-reactivity. A good parallelism between the standard curve and serial dilutions of greater amberjack plasma and pituitary extract were obtained. In female greater amberjack, pituitary fshb, ovarian fshr, and plasma E2 gradually increased during ovarian development, and plasma Fsh significantly increased during the post-spawning period. This suggests that Fsh plays a role throughout ovarian development and during the post-spawning period. Pituitary lhb, ovarian lhr, and plasma Lh were high during the spawning period, suggesting that the synthesis and secretion of Lh, and Lhr expression are upregulated to induce final oocyte maturation and ovulation.
    No preview · Article · Oct 2015 · General and Comparative Endocrinology
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    • "These studies suggest that the two forms of kisspeptins may play different biological roles in fish species. We have previously identified the key molecular elements of the chub mackerel (Scomber japonicus) BPG axis; namely, kisspeptins [27], kisspeptin receptors [22], GnRHs [28], GtHs [17] [21], and GtH receptors [18]. The chub mackerel brain expresses two kiss and receptor genes and shows sexually dimorphic changes during the seasonal gonadal cycle [22] [27]. "
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    ABSTRACT: In vertebrates (including teleosts), the pivotal hierarchical factor in the control of gonadotropin secretion is the hypothalamic gonadotropin-releasing hormone (GnRH) decapeptide, which regulates the release of pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Recently, kisspeptins encoded by the Kiss1 gene have been shown to act as upstream endogenous regulators of GnRH neurons in mammals. The chub mackerel (Scomber japonicus) brain expresses two kiss genes (kiss1 and kiss2) that show sexually dimorphic expression profiles during the seasonal gonadal cycle. In the present study, we evaluated the biological potency of kisspeptin peptides to induce transcriptional changes in gnrh1 (hypophysiotropic GnRH form in this species), fshβ and lhβ during the immature stage of adult chub mackerel (2+ years old). Synthetic Kiss1 pentadecapeptide (Kiss1-15) or Kiss2 dodecapeptide (Kiss2-12) at a dose of 100ng were administered into the intracerebroventricular (ICV) region, and brains were sampled at 6 and 12h post-injection. In female fish, gnrh1 levels decreased in the presence of both kisspeptin peptides at 12h post-injection. No significant variation was observed in male fish. In contrast, ICV administration of Kiss2-12 (but not Kiss1-15) significantly increased fshβ and lhβ mRNAs at 12h post-injection compared to a saline injected control in both sexes. These results suggested that synthetic Kiss2-12 could induce transcriptional changes in gnrh1 and gths.
    Full-text · Article · Jan 2014 · Neuroscience Letters
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    • "In the Western blot analysis, the purified cmFSHβ and cmLHβ subunits reacted specifically to the 003 and 299 antisera, respectively (Figure 2B and 2C). The α subunits of cmGtHs showed N-terminal amino acid sequences (PNVD) which corresponded to those deduced from chub mackerel GPα cDNA data [23]. In the native-PAGE, cohesive 3 bands were observed for both cmFSH and cmLH and the other bands were not ascertained (Figure 2D). "
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    ABSTRACT: Background The gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the pituitary gland and regulates gametogenesis through production of gonadal steroids. However, respective roles of two GtHs in the teleosts are still incompletely characterized due to technical difficulties in the purification of native GtHs. Methods Native FSH and LH were purified from the pituitaries of adult chub mackerel, Scomber japonicus by anion-exchange chromatography and immunoblotting using specific antisera. The steroidogenic potency of the intact chub mackerel FSH (cmFSH) and LH (cmLH) were evaluated in mid- and late-vitellogenic stage follicles by measuring the level of gonadal steroids, estradiol-17beta (Ε2) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P). In addition, we evaluated the maturation-inducing potency of the GtHs on same stage follicles. Results Both cmFSH and cmLH significantly stimulated E2 production in mid-vitellogenic stage follicles. In contrast, only LH significantly stimulated the production of 17,20beta-P in late-vitellogenic stage follicles. Similarly, cmLH induced final oocyte maturation (FOM) in late-vitellogenic stage follicles. Conclusions Present results indicate that both FSH and LH may regulate vitellogenic processes, whereas only LH initiates FOM in chub mackerel.
    Full-text · Article · Sep 2012 · Reproductive Biology and Endocrinology
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