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Testosterone regulates FGF-2 expression during testis maturation by an IRES-dependent translational mechanism.

Abstract : Spermatogenesis is a complex process involving cell proliferation, differentiation, and apoptosis. Fibroblast growth factor 2 (FGF-2) is involved in testicular function, but its role in spermatogenesis has not been fully documented. The control of FGF-2 expression particularly occurs at the translational level, by an internal ribosome entry site (IRES)-dependent mechanism driving the use of alternative initiation codons. To study IRES activity regulation in vivo, we have developed transgenic mice expressing a bicistronic construct coding for two luciferase genes. Here, we show that the FGF-2 IRES is age-dependently activated in mouse testis, whereas EMCV and c-myc IRESs are not. Real-time PCR confirms that this regulation is translational. By using immunohistological techniques, we demonstrate that FGF-2 IRES stimulation occurs in adult, but not in immature, type-A spermatogonias. This is correlated with activation of endogenous FGF-2 expression in spermatogonia; whereas FGF-2 mRNA transcription is known to decrease in adult testis. Interestingly, the FGF-2 IRES activation is triggered by testosterone and is partially inhibited by siRNA directed against the androgen receptor. Two-dimensional analysis of proteins bound to the FGF-2 mRNA 5'UTR after UV cross-linking reveals that testosterone treatment correlates with the binding of several proteins. These data suggest a paracrine loop where IRES-dependent FGF-2 expression, stimulated by Sertoli cells in response to testosterone produced by Leydig cells, would in turn activate Leydig function and testosterone production. In addition, nuclear FGF-2 isoforms could be involved in an intracrine function of FGF-2 in the start of spermatogenesis, mitosis, or meiosis initiation. This report demonstrates that mRNA translation regulation by an IRES-dependent mechanism participates in a physiological process.
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Contributor : Annick Harel-Bellan <>
Submitted on : Wednesday, September 6, 2006 - 5:12:18 PM
Last modification on : Friday, January 10, 2020 - 9:09:03 PM

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Irma Gonzalez-Herrera, Leonel Prado-Lourenco, Frédéric Pileur, Caroline Conte, Aurélie Morin, et al.. Testosterone regulates FGF-2 expression during testis maturation by an IRES-dependent translational mechanism.. FASEB Journal, Federation of American Society of Experimental Biology, 2006, 20, pp.476-8. ⟨10.1096/fj.04-3314fje⟩. ⟨inserm-00091607⟩



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