Article

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: 1.68). 11/2011; 38(3):883-97. DOI: 10.1007/s10695-011-9576-y
Source: PubMed

ABSTRACT 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
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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.
    Neuroscience Letters 01/2014; DOI:10.1016/j.neulet.2013.12.072 · 2.06 Impact Factor
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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.
    Reproductive Biology and Endocrinology 09/2012; 10(1):71. DOI:10.1186/1477-7827-10-71 · 2.41 Impact Factor
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    • "Real-time PCR analysis of chub mackerel GPα, FSHβ, and LHβ (GenBank Accession Nos. JF495131, JF495132, and JF495133, respectively) were performed using a Stratagene Mx3000P system with the Brilliant II Fast SYBR Green QPCR master mix (Stratagene) as described previously (Nyuji et al., 2012). In brief, the pituitary was fixed in RNAlater (QIAGEN), and total RNA was isolated using Isogen (Nippon Gene) and digested by DNase I (Invitrogen). "
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    ABSTRACT: The gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are heterodimers composed of a common α subunit (GPα) and a unique β subunit (FSHβ or LHβ); they are synthesized in and secreted from gonadotrophs (FSH and LH cells) in the pituitary. Little is known about the roles of FSH and LH during spermatogenesis in perciform fishes. In this study, we examined immunoreactive changes in FSH and LH cells, and changes in the gene expression of the three gonadotropin subunits in the pituitary of male chub mackerel Scomber japonicus during testicular development. FSHβ-immunoreactive (ir) and LHβ-ir cell area were measured immuno-histochemically based on the FSH and LH cell-occupying area in the proximal pars distalis. The FSHβ-ir cell area increased significantly during spermiation, while FSHβ mRNA levels, already high at the beginning of spermatogenesis, increased further, peaking during spermiation. In contrast, LHβ-ir cell area and LHβ mRNA levels, which were low at the beginning of spermatogenesis, increased significantly during late spermatogenesis, peaking during spermiation. For both FSH and LH, GtHβ-ir cell area and GtHβ mRNA levels decreased until gonadal resting. GPα mRNA levels showed similar changes to LHβ mRNA levels. These results suggest that in the chub mackerel, FSH may play an important role in the early and late phases of spermatogenesis, and that LH may play a role during late spermatogenesis and spermiation. Moreover, our results demonstrate that changes in GtHβ-ir cell area were accompanied by similar changes in the expression of the FSHβ and LHβ genes, both of which increased during testicular development.
    ZOOLOGICAL SCIENCE 09/2012; 29(9):623-9. DOI:10.2108/zsj.29.623 · 0.88 Impact Factor
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