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Laboratoire Estrogènes et Reproduction, EA 2608-USC INRA 2006, Université de Caen, Esplanade de la Paix, 14032 Caen Cedex, France
1 INRA, UMR1245, INSERM U 418 Hopital Debrousse, 29 rue Sœur Bouvier, 69322 Lyon Cedex 05, France
(Requests for offprints should be addressed to S Carreau; Email: serge.carreau{at}unicaen.fr)
D Silandre is a recipient of a fellowship from Région Basse Normandie
Aromatase is the key enzyme responsible for the irreversible transformation of androgens into estrogens. It is encoded by the cyp19 gene and is expressed in the mammalian testis under the control of the proximal promoter PII. Since both somatic and germ cells contain a biologically active aromatase, we looked for the existence of other promoters that may direct the expression of aromatase in adult rat germ cells. Besides the promoter II, we have shown the presence of transcripts derived from the brain promoter PI.f in spermatogonia–preleptotene spermatocytes (G–PL), pachytene spermatocytes (PS), and round spermatids (RS). A new aromatase cDNA has been isolated by 5'-rapid amplification of cDNA ends that we named I.tr (testis rat). The I.tr transcripts are found in all the testicular cell populations studied with a greater expression in PS. Because of the utilization of these three promoters in the adult rat testis, we studied their putative involvement according to the age. At 10 days, aromatase expression was very low and then strongly increased between 10 and 20 days, with a preferential activation of PII and PI.tr. Transcripts coming from PI.f were found starting from 20 days onwards. The new promoter PI.tr, localized between promoters PI.f and PII, is devoid of a TATA box but contains a transcriptional initiator (Inr) and putative regulatory sequences. Therefore, the identification of the specific trans-activating factors should bring some enlightenments to understand the regulation of these three promoters in germ cells especially according to their stage of development.
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