Etude des récepteurs des oestrogènes et des androgènes chez l'amphibien "Pleurodeles waltl." : Intérêts pour la différenciation du sexe et l'impact des perturbateurs endocriniens

Abstract : Steroids are important for sex differentiation in amphibian species Pleurodeles waltl. Besides, sex reversal can be induced by different factors, like the rearing temperature or exogenous steroids. This study has a double objective: to analyze effects of estrogen mimic chemicals and to characterize expression of estrogens and androgens receptors. The sex reversal in larvae of genotype male is induced by ethynylestradiol. This chemical is also more efficient than oestradiol. At the concentration, which could be found in the nature, the development of mullerian duct is induced. Thus, oviduct differentiation in male larvae could be a good marker of endocrine potentiql of estrogen mimic chemicals. The estrogen receptor alpha and androgen receptor were isolated. In adult, ERalpha mRNA is present specifically in reproductive tissues. In larvae, higher level of ERalpha mRNA was observed in female gonads than in male ones; but such a difference appears after the increase of aromatase expression. ERalpha expression is inhibited in female larvae reared at 32°C, and the difference of expression between male and female was not observed. Steroids do not affect ERalpha expression in gonad, but treatments of testosterone and of DHT provoke a huge increase of ERalpha expression in mesonephros interrenal organ. In adult, a polyclonal antibody of androgens receptor reveals the presence of AR protein in testis, overy, brain, spleen and oviduct. Nevertheless, the level of AR mRNA is higher in female larvae than in male ones during the sex differentiation. A promoter region of ERalpha was also isolated. Site directed mutagenesis reveals a fixation element of factor TCTFL/BORIS, which is susceptible to regulate ERalpha expression. These studies confirm the importance of estrogenic signaling in ovary differentiation, they also demonstrate the capacity of certains estrogen mimic chemicals in oviduct differentiation induction even in male versus female sex reversal.
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Chia-I Ko. Etude des récepteurs des oestrogènes et des androgènes chez l'amphibien "Pleurodeles waltl." : Intérêts pour la différenciation du sexe et l'impact des perturbateurs endocriniens. Sciences agricoles. Université Henri Poincaré - Nancy 1, 2008. Français. ⟨NNT : 2008NAN10110⟩. ⟨tel-01748522⟩

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