Figure 8.

DHH regulation of male gonadal development. The fetal testis is composed of testis cords that contain the developing germ cells and Sertoli cells (SCs), as well as vascular networks. These structures are surrounded by an interstitial tissues compartment containing Leydig cells (LCs). DHH secreted by the SCs signals through PTCH1 and GLI1 in the LCs to regulate their development and overall organization of the testis cord. DHH signaling also induces the expression of SF1 in LCs, which upregulates the expression of steroidogenic enzymes. On the other hand, SHH is expressed in the Wolffian duct epithelium, and the cells in mesonephric mesenchyme express PTCH1, SMO, and GLI1. Thus, the two HH signaling pathways may take part into the epithelial–mesenchymal communication during the male reproductive tract development.