Figure 7.

Before sex differentiation, the embryos possess primitive female and male reproductive tracts, known as Müllerian ducts (pink) and Wolffian ducts (blue). Expression of SRY and SOX9 in XY embryos induce the proliferation and differentiation of the Sertoli cells (SCs) in embryonic testes to produce AMH and DHH. DHH signaling recruit the fetal Leydig cells (FLCs) and induce differentiation to synthesize androgens. AMH and androgens retains the Wolffian ducts to form the male reproductive organs. On the other hand, absence, or very low levels or AMH and androgens in the XX embryos facilitate the growth of the Müllerian ducts to form female reproductive organs.