Androgen-Dependent Rhox Homeobox Genes

描述（由申请人提供）：几十年来，人们一直知道精子发生依赖于雄激素，但其背后的分子机制在很大程度上仍然是难以捉摸的。甚至睾丸中响应雄激素而驱动精子发生的细胞类型也没有明确定义，直到最近的小鼠遗传学研究表明至少有一种参与者是支持细胞。这是合乎逻辑的，支持细胞将促进精子发生，以响应雄激素，因为它是在与发育中的生殖细胞密切接触，并表达高水平的雄激素受体（AR），一个核受体家族成员和转录因子，通常必须结合到雄激素激活其靶基因。支持细胞中大多数雄激素调节基因可能不是AR的直接靶点，而是受雄激素调节的转录因子调节。这些次级雄激素反应基因具有与雄激素调节的转录因子结合的顺式元件。迄今为止，没有转录因子调节这些二级雄激素反应基因在支持细胞已被明确确定。一个很好的候选者是Rhox同源框基因簇的创始成员Rhox 5（Pem），因为它是雄激素调节的，选择性地在支持细胞中表达，并且是正常精子发生所必需的。该提案的重点是Rhox同源框基因簇中的另外两个雄激素调节基因，Rhox 10和Rhox 11。每一个在睾丸中表达的峰值水平在出生后的时间点，对应于两个不同的AR依赖性事件在精子发生过程中：男性生殖细胞通过减数分裂I和后期圆形精子细胞的过渡到伸长精子细胞的进展。因此，我们假设Rhox 10和Rhox 11编码参与介导这两个AR依赖性事件的转录因子。本申请的具体目的是（i）鉴定雄激素调节的Rhox 10和Rhox 11基因在体内精子发生和精子成熟中的功能;（ii）区分雄激素调节的Rhox 5、Rhox 10和Rhox 11基因在雄性生殖中的独立和冗余作用;和（iii）通过鉴定雄激素调节的Rhox基因的基因靶点，开始阐明驱动精子发生的AR依赖性基因网络。通过为雄激素驱动的精子发生提供分子基础，拟议的工作最终可能导致某些男性不育症的治愈和新型男性避孕方法的开发。

DESCRIPTION (provided by applicant): Spermatogenesis has been known for decades to depend on androgens, but the molecular mechanism behind this has remained largely elusive. Even the cell types in the testis that drive spermatogenesis in response to androgens had not been clearly defined until recent mouse genetic studies demonstrated that at least one participant is the Sertoli cell. It is logical that the Sertoli cell would promote spermatogenesis in response to androgens, as it is in intimate contact with developing germ cells and expresses high levels of androgen receptor (AR), a nuclear hormone-receptor family member and transcription factor that must usually be bound to androgen to activate its target genes. Most androgen-regulated genes in Sertoli cells may not be direct targets of AR but instead may be regulated by androgen-regulated transcription factors. These secondary androgen-response genes have cis elements that bind to androgen-regulated transcription factors. To date, no transcription factors regulating these secondary androgen-response genes in Sertoli cells have been definitively identified. A good candidate is the founding member of the Rhox homeobox gene cluster, Rhox5 (Pem), as it is androgen regulated, selectively expressed in Sertoli cells, and necessary for normal spermatogenesis. This proposal focuses on two other androgen-regulated genes in the Rhox homeobox gene cluster, Rhox10 and Rhox11. Each is expressed at peak levels in the testes at postnatal time points that correspond to two distinct AR-dependent events during spermatogenesis: the progression of male germ cells through meiosis I and the transition of late-round spermatids into elongating spermatids. Thus, we hypothesize that Rhox10 and Rhox11 encode transcription factors that participate in mediating these two AR-dependent events. The Specific Aims of this application are (i) to identify the functions of the androgen-regulated Rhox10 and Rhox11 genes in spermatogenesis and sperm maturation in vivo; (ii) to distinguish the independent and redundant roles of the androgen-regulated Rhox5, Rhox10, and Rhox11 genes in male reproduction; and (iii) to begin to elucidate the AR-dependent gene networks that drive spermatogenesis by identifying gene targets of the androgen-regulated Rhox genes. By providing a molecular basis for androgen-driven spermatogenesis, the proposed work could ultimately lead to cures for some cases of male infertility and the development of novel male contraceptive methods.