Fig. 2.

Steroidogenic enzyme expression in human fetal tissue from the major period of sexual differentiation and their proposed role(s) in alternative pathway synthesis. (A and B) mRNA expression (mean ± SEM) in human fetal tissues collected at 6 to 10 wpc as measured by qPCR in female adrenals (n = 1), gonads (n = 2), genital skin (n = 2), and corresponding male tissues (≥3 biological replicates for adrenals, gonads, and genital skin). (C) Fetal genital skin mRNA expression of all enzymes potentially capable of converting 5α-androstanediol to 5α-dihydrotestosterone. Expression data were normalized to ribosomal 18S. (D) Schematic summary of the proposed distinct roles of the identified enzymes in the classic androgen pathway (dark blue) and the alternative androgen synthesis pathway (light blue), both resulting in the synthesis of potent 5α-dihydrotestosterone. Arrows indicate observed conversions in the fetal organ explant cultures; dotted arrows represent reactions only rarely observed.