ABSTRACT

Spermatogenesis and male fertility is dependent on testosterone signaling. In the testis, testosterone acts via the androgen receptor (AR) in Sertoli, Leydig, peritubular myoid, and other somatic cells to support spermatogenesis. Testosterone is required for processes that are essential for completing spermatogenesis including maintenance of the blood-testis barrier, transit through meiosis, adhesion of haploid spermatids, and the release of mature sperm. Only recently have we begun to understand how testosterone signals are translated into the cellular responses that support these processes. In this chapter, the molecular mechanisms of testosterone action including direct regulation of testosterone-mediated gene expression by AR (the classical testosterone signaling pathway) and the activation of kinase cascades (the nonclassical testosterone pathway) are described. The methods by which testosterone supports each stage of germ cell development are outlined. As well, the regulation of gene expression via testosterone and AR in whole testis and individual cell types are reviewed. Additional remaining challenges are discussed including the need to develop an understanding of how testosterone-mediated signals are delivered between somatic cells and from somatic cells to germ cells.