169. SERTOLI CELL-SPECIFIC DISRUPTION OF THE ANDROGEN RECEPTOR DNA-BINDING DOMAIN REVEALS DIFFERENTIAL TEMPORAL CONTROL OF DISTINCT ANDROGEN-REGULATED GENES

Abstract

Androgen receptor (AR) actions are vital for spermatogenesis. However, in postnatal development male germ cells do not express AR, highlighting its key role in testicular somatic cells. We recently used a Cre-loxP strategy to determine the in vivo requirement of AR DNA-binding in Sertoli cell (SC) function. Transgenic (Tg) mice with Cre expression targeted by SC-specific AMH or Abp promoters were crossed with floxed-Ar (Ar^flox) mice for Cre-loxP inframe deletion of Ar exon 3, which encodes a zinc finger essential for the DNA-binding domain (DBD). SC-specific mutated AR^Δex3 (SCAR^Δex3) produced infertile AMH.SCAR^Δex3 and Abp.SCAR^Δex3 males. Testes from adult homozygous TgCre^(+/+) AMH.SCAR^Δex3 or Abp.SCAR^Δex3 males were 30% of normal size and exhibited meiotic arrest, whereas testes from hemizygous TgCre^(+/–) Abp.SCAR^Δex3 males were larger (47% normal) with more postmeiotic germ cell development. Despite marked Leydig cell hypertrophy, testicular expression of the adult Leydig marker Hsd3b6 (RT-PCR) and normal intratesticular testosterone levels (LC-MS/MS) in SCAR^Δex3 males indicated the presence of morphologically distinct but functional adult Leydig cells. SC-specific mutated AR ^Δex3 was predicted to disrupt classical AR-regulated pathways via loss of direct DNA interaction. Androgen-repressed testicular Ngfr expression (known to be via non-classical AR pathways) was not upregulated in SCAR^Δex3 testes, suggesting maintenance of a non-classical mechanism independent of AR-DBD. In contrast, SC-specific Rhox5 and Eppin transcription, regulated by divergent or classical androgen-response elements respectively, were both decreased in postnatal SCAR^Δex3 vs. control testes, demonstrating SC-specific AR function as early as postnatal day 5. However, Rhox5 expression declined dose-dependently, whereas Eppin expression increased, in adult TgCre^(+/−) and TgCre^(+/+) SCAR^Δex3 testes, revealing differential temporal control for distinct AR-regulated transcripts. Thus, our SCAR^Δex3 paradigm displayed dose-dependent TgCre-disruption of meiotic competence and post-meiotic development as well as gene expression, and represents a unique model to selectively differentiate AR-regulated genes.