Mouse Spermatogenesis Requires Classical and Nonclassical Testosterone Signaling.

Area of Science:

• Reproductive Biology
• Endocrinology
• Molecular Cell Biology

Background:

• Testosterone is crucial for male fertility and spermatogenesis, acting via the androgen receptor in Sertoli cells.
• The precise molecular mechanisms of testosterone action, including classical and nonclassical signaling pathways, remain incompletely understood.

Purpose of the Study:

• To investigate the in vivo relevance of nonclassical testosterone signaling in Sertoli cells.
• To elucidate the distinct and overlapping roles of classical and nonclassical testosterone signaling in spermatogenesis and male fertility.

Main Methods:

• Investigated MAP kinase cascade activation in rat Sertoli cells following increased testosterone levels.
• Utilized testis explants to study testosterone-mediated gene expression (Rhox5, Zbtb16, c-Kit) under classical and nonclassical pathway activation.
• Administered pathway-specific inhibitors in mouse models to assess effects on the blood-testis barrier, meiosis, and germ cell populations.

Main Results:

• Demonstrated in vivo activation of the MAP kinase cascade in Sertoli cells, confirming nonclassical testosterone signaling.
• Showed that both classical and nonclassical pathways regulate Rhox5 gene expression, with differential effects on Zbtb16 and c-Kit.
• Inhibitors of either pathway disrupted the blood-testis barrier; nonclassical pathway inhibition blocked meiosis and caused germ cell loss, while classical pathway inhibition led to premature germ cell release.

Conclusions:

• Classical and nonclassical testosterone signaling pathways are essential for maintaining spermatogenesis and male fertility.
• These pathways regulate both overlapping and distinct functions critical for germ cell development and the integrity of the testis.