Molecular insights into androgen actions in male and female reproductive function from androgen receptor knockout models

Androgens and the androgen receptor (AR) have well known roles in male reproduction, and recent genetic mouse models inactivating the Ar gene have conclusively defined a role for androgens in female reproduction. In males, AR gene inactivation severely disrupts spermatogenesis by interrupting completion of meiosis, thereby eliminating production of mature sperm leading to male sterility. These effects have overshadowed the study of additional post-meiotic androgen effects required for the production of fully functional spermatozoa, as well as the production of females with complete androgen insensitivity which cannot be produced by natural breeding. However, these limitations have been overcome by the creation of global and cell-specific AR knockout (ARKO) mouse models using Cre-LoxP genetic engineering. Pubmed searches were carried out using the following search terms: androgen receptor, knockout mouse and fertility. Articles published before the end of November 2009 were included. These experimental models have identified cell-specific AR-mediated androgen actions in testis and androgen actions in sex accessory glands independent of testicular effects which are crucial for sperm maturation, motion and fertilizing ability. The ability to produce homozygous ARKO females has revealed that AR-mediated androgen actions are important for normal female fertility. AR function is required for full functionality in follicle health, development and ovulation through both intra-ovarian and neuroendocrine mechanisms. ARKO mouse models provide valuable tools to unravel novel roles of AR-mediated actions in male and female reproductive function, and new insights into the role of androgens in human reproductive function.