Sertoli Cell Androgen Receptor DNA Binding Domain Is Essential for the Completion of Spermatogenesis

Abstract

We examined the biological importance of Sertoli cell androgen receptor (AR) genomic interaction, using a Cre-loxP approach to selectively disrupt the AR DNA-binding domain (AR-DBD). Sertoli cell (SC)-specific transgenic Abpa or AMH promoters targeted Cre-mediated inframe excision of mouse Ar exon-3, encoding the AR-DBD second zinc-finger (ZF2), generating SC-specific mutant AR ZF2 lines designated Abp.SCAR ZF2 and AMH.SCAR ZF2 , respectively. Both SCAR ZF2 lines produced infertile males exhibiting spermatogenic arrest, despite normal SC numbers and immunolocalized SC nuclear AR. Adult homozygous TgCre (/) SCAR ZF2 or double-TgCre (/) Abp/ AMH.SCAR ZF2 males displayed equivalent small testes 30% of normal size, representing maximal Cre-loxP-disruption of Sertoli AR function. Hemizygous TgCre (/) vs. homozygous TgCre (/) Abp.SCAR ZF2 testes were larger (47% normal size) with more postmeiotic development, indicating dose-dependent Cre-mediated disruption of SC-specific AR-DBD activity. SCAR ZF2 males exhibited adult Leydig cell hypertrophy but normal serum testosterone levels. Sertoli cell-specific Rhox5 and Spinlw1 transcription, regulated by divergent or classical androgen-response elements, respectively, were both decreased in postnatal SCAR ZF2 vs. control testes, demonstrating SCspecific AR-DBD function as early as postnatal d 5. However, Rhox5 expression declined dosedependently, whereas Spinlw1 expression increased, in adult TgCre (/) and TgCre (/) SCAR ZF2 testes, revealing differential temporal control for distinct AR-regulated transcripts. Androgenrepressed Ngfr was not up-regulated in SCAR ZF2 testes, suggesting maintenance of a nonclassical mechanism independent of AR-DBD. Thus, our unique SCAR ZF2 paradigm provided dose-dependent Cre-mediated disruption of testicular development and gene expression revealing that the AR-DBD is essential for SC function and postmeiotic spermatogenesis. Nongenomic or AR-DBDindependent pathways appear secondary or play no major independent role in SC function.