Expression and localization of aromatase during fetal mouse testisdevelopment

Background: Both androgens and estrogens are necessary to ensure proper testisdevelopment and function. Studies on endocrine disruptors have highlightedthe importance of maintaining the balance between androgens and estrogensduring fetal development, when testis is highly sensitive to environmentaldisturbances. This balance is regulated mainly through an enzymatic cascadethat converts irreversibly androgens into estrogens. The most important andregulated component of this cascade is its terminal enzyme: the cytochromep450 19A1 (aromatase hereafter). This study was conducted to improve ourknowledge about its expression during mouse testis development.Findings: By RT-PCR and western blotting, we show that full-length aromatase isexpressed as early as 12.5 day post-coitum (dpc) with maximalexpression at 17.5 dpc. Two additional truncated transcripts were alsodetected by RT-PCR. Immunostaining of fetal testis sections and ofgonocyte-enriched cell cultures revealed that aromatase is stronglyexpressed in fetal Leydig cells and at variable levels in gonocytes.Conversely, it was not detected in Sertoli cells.Conclusions: This study shows for the first time that i) aromatase is expressed from theearly stages of fetal testis development, ii) it is expressed in mousegonocytes suggesting that fetal germ cells exert an endocrine function inthis species and that the ratio between estrogens and androgens may behigher inside gonocytes than in the interstitial fluid. Furthermore, weemphasized a species-specific cell localization. Indeed, previous worksfound that in the rat aromatase is expressed both in Sertoli and Leydigcells. We propose to take into account this species difference as a newconcept to better understand the changes in susceptibility to Endocrine Disruptors from one species to another. © 2013 Borday et al.; licensee BioMed Central Ltd.