Expression of Cyp21a1 and Cyp11b1 in the fetal mouse testis

Abstract

Fetal Leydig cells and fetal adrenocortical cells may share a common progenitor cell. Both cell types show several similarities, particularly in relation to their primary steroidogenic function. Differences in steroid secretion are largely due to the expression of 21-hydroxylase (CYP21A1) and 11β-hydroxylase (CYP11B1) activity in the adrenal. To determine whether expression of these enzymes defines a clear difference between adrenocortical and Leydig cells, or is further evidence of a link between the cell types, we have measuredCyp21a1andCyp11b1expression and related enzyme activity in the fetal testis. Expression of bothCyp21a1andCyp11b1was clearly detectable in the fetal testis by RT-PCR and Southern blotting. Real-time PCR studies showed thatCyp11b1was expressed only in the fetal/neonatal testis with no expression in the pubertal or post-pubertal animal.Cyp21a1was also predominantly expressed in the fetal testis although some lower expression was also seen in the adult. Expression ofCyp21a1andCyp11b1in neonatal testicular cells was unaffected by incubationin vitrowith human chorionic gonadotrophin or ACTH. Using immunohistochemistry, CYP21A1 was localised to a subset of interstitial steroidogenic cells in the fetal testis although CYP11B1 was not detectable. Incubation studies showed that 21-hydroxylase activity was present in the tissue although 11β-hydroxylase activity could not be detected. Results indicate that a subpopulation of steroidogenic cells in the fetal testis expressCyp21a1and show 21-hydroxylase activity. This may provide further evidence of a link between fetal Leydig cells and adrenocortical cells but does not discount the possibility that these steroidogenic cells represent ‘ectopic’ adrenal cells.