Wnt9b permits the androgen action in promoting Wolffian duct

The Wolffian or mesonephric duct is the embryonic primordium that gives rise to the epididymis, vas deferens and seminal vesicle. The androgen action in the Wolffian duct mesenchyme during fetal development is the predominant driver for Wolffian duct maintenance which is critical for male fertility. However, the androgen’s capability of promoting Wolffian duct maintenance was completely lost in the absence of Wnt9b in mice. In this study, we followed up with this interesting phenomenon and elucidated cellular and molecular mechanisms whereby Wnt9b facilitates Wolffian duct maintenance in male embryos. Wnt9b belongs to the WNT family of secreted proteins and is expressed in the Wolffian duct epithelium. We found that the Wolffian duct degeneration in Wnt9b-/- male embryos was accompanied with decreased cell proliferation in the epithelium but not in the mesenchyme during sexual differentiation. Wnt9b deletion did not impair testicular androgen synthesis but altered expression pattern of mesenchymal androgen receptor. The percentage of androgen receptor positive cells in the mesenchyme was significantly reduced, which can be the cause of decreased epithelial proliferation. Wnt9b actions can be transduced by both β-catenin-dependent and β-catenin-independent pathways in the context of target cells. Transcriptomic analysis of E12.5 Wnt9b+/+ and Wnt9b-/- mesonephroi revealed that expression of multiple WNT/β-catenin-target genes was reduced in the absence of Wnt9b. Deletion of mesenchymal β-catenin led to caudal Wolffian duct degeneration and cystic formation in the cranial region. Taken together, our study uncovers the important WNT9B-AR signaling axis mediating the epithelial-mesenchymal interaction in Wolffian duct development.