Étude des gènes de la sexualisation de la gonade chez Pleurodeles waltl

Abstract : ln the urodele amphibian Pleurodeles waltl, the genetic sex detennination is influenced by temperature : genetically female larvae develop in fertile males when bred at 32°C during the thennosensitive period (stages 42-54). Aromatase, the estrogens enzyme synthesising, plays a key role in female gonadal differentiation. Our initial goal was to detennine if the rise of aromatase activity observed at the onset of sexual differentiation (stage 52) was related to an up regulation of expression. The cDNA of aromatase was isolated. Its expression is more important in control females than in males or in heated females. However, compared to enzyme activity, this difference is weak and is delayed (stage 54). Thus, post-transcriptionnal modifications could be involved in addition to transcritional regulation. Genes that are supposed to act upstream of aromatase were then studied. The cDNA of SfI, Dmrtl and Sox9 were isolated. Their expression in the complexes gonads-mesonephros is detected as early as stage 42. At stage 55, sn is overexpressed in female gonads. So these changes appear after those affecting aromatase expression, suggesting a regulation of SfI by estrogens. Dmrtl is alternatively spliced at larval stages and its expression is stronger in female gonads at stage 55. ln juvenile larvae, the expression stops in ovary and becomes testis-specific. Sox9 does not present any differential expression during gonad development. ln addition, analyses of SfI and aromatase expression in brain disagree with a role of central nervous system as a relay during gonadal differentiation.
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Sandra Kuntz. Étude des gènes de la sexualisation de la gonade chez Pleurodeles waltl. Sciences agricoles. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL036N⟩. ⟨tel-01749692⟩

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