Essential functions of androgen signaling emerged through the developmental analysis of vertebrate sex characteristics

Androgen-androgen receptor (AR) signaling plays key roles in the development of sex characteristics for vertebrates. The essential role of androgen-AR signaling can be analyzed by interdisciplinary approaches including molecular and evolutionary analyses. Recent evolutionally analyses of AR gene revealed that the most ancient AR appeared in cartilaginous fish, the common ancestor of all the extant, jawed vertebrates. Sexual differentiation is a remarkably complex process, which depends on the orchestration of the signaling network. Recent molecular analyses of reproductive organ development indicate the presence of putative effectors for growth factor signaling that can potentially interact with hormonal signaling. The Wnt/β-catenin pathway is an indispensable masculinizing factor for the external genitalia development of mice. Sonic hedgehog pathway, with expression induced by androgen is involved in the copulatory organ outgrowth in teleosts. This review focuses on the interaction of androgen and growth factor pathways that promote the sexual differentiation of reproductive organs in vertebrates.