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1 May 2013 Characterization, Localization, and Stage-Dependent Gene Expression of Gonadotropin Receptors in Chub Mackerel (Scomber japonicus) Ovarian Follicles
Mitsuo Nyuji, Hajime Kitano, Akio Shimizu, Jae Man Lee, Takahiro Kusakabe, Akihiko Yamaguchi, Michiya Matsuyama
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Abstract

The pituitary gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are key regulators of gametogenesis in teleosts. However, little is known about the physiological mechanisms by which GtHs regulate asynchronous oocyte development in multiple-spawning marine fishes. We cloned cDNAs encoding GtH receptors (FSHR and LHR) from chub mackerel (Scomber japonicus). FSH and LH were purified by anion-exchange chromatography, gel filtration, and concanavalinA-agarose. When expressed in mammalian cells, FSHR and LHR responded strongly to their own ligands. By separating LH into two subunits by the use of reverse-phase chromatography, we found that the beta-subunit is responsible for signal transduction and the alpha-subunit may be important for holding hormone-receptor complex. In situ hybridization showed that only fshr was expressed in prefollicle and granulosa cells in oocytes at the perinucleolus and cortical alveolus stages, suggesting that FSH is involved in the primary and early secondary growth of oocytes. In ovarian follicles during vitellogenesis, both fshr and lhr were expressed in granulosa and thecal cells, and lhr was strongly expressed during germinal vesicle migration (GVM). Real-time PCR analysis of stage-dependent fshr and lhr expression showed that fshr expression was high in ovarian follicles throughout vitellogenesis and decreased during GVM, whereas lhr expression was low in early vitellogenesis, but increased markedly in the late phase of vitellogenesis, remaining high during GVM. These findings suggest that switching of the expression of FSHR to LHR controls the effects of FSH and/or LH on vitellogenesis and final oocyte maturation via steroid production in granulosa and thecal cells.

Mitsuo Nyuji, Hajime Kitano, Akio Shimizu, Jae Man Lee, Takahiro Kusakabe, Akihiko Yamaguchi, and Michiya Matsuyama "Characterization, Localization, and Stage-Dependent Gene Expression of Gonadotropin Receptors in Chub Mackerel (Scomber japonicus) Ovarian Follicles," Biology of Reproduction 88(6), (1 May 2013). https://doi.org/10.1095/biolreprod.112.107292
Received: 26 December 2012; Accepted: 1 April 2013; Published: 1 May 2013
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KEYWORDS
chub mackerel
follicle-stimulating hormone receptor
gonadotropin
luteinizing hormone receptor
oogenesis
ovarian follicle
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