Androgen-Dependent Rhox Homeobox Genes

描述(申请人提供)：几十年来，精子发生一直被认为依赖于雄激素，但其背后的分子机制在很大程度上仍然难以捉摸。直到最近的小鼠遗传学研究表明，至少有一个参与者是Sertoli细胞，甚至睾丸中驱动雄激素反应精子生成的细胞类型也没有明确的定义。支持细胞在雄激素作用下促进精子发生是合乎逻辑的，因为它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)，这是一个核激素受体家族成员和转录因子，通常必须与雄激素结合才能激活其靶基因。Sertoli细胞中大多数雄激素调控基因可能不是AR的直接靶点，而可能受雄激素调控转录因子的调控。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。到目前为止，还没有明确的转录因子在支持细胞中调节这些次级雄激素反应基因。一个很好的候选者是Rhox Homeobox基因簇Rhox5(Pem)的创始成员，因为它是雄激素调节的，在Sertoli细胞中选择性表达，是正常精子发生所必需的。这项建议集中在Rhox Homeobox基因簇中的另外两个受雄激素调节的基因，Rhox10和Rhox11。在出生后的时间点，它们在睾丸中的表达水平达到峰值，对应于精子发生过程中两个不同的AR依赖事件：男性生殖细胞通过减数分裂I的进展和晚一轮精子细胞向伸长精子细胞的转变。因此，我们假设Rhox10和Rhox11编码参与调节这两个AR依赖事件的转录因子。本应用的具体目的是(I)鉴定雄激素调控的Rhox10和Rhox11基因在体内精子发生和精子成熟中的功能；(Ii)区分雄激素调控的Rhox5、Rhox10和Rhox11基因在男性生殖中的独立和冗余作用；以及(Iii)通过识别雄激素调控的Rhox基因的基因靶点，开始阐明驱动精子发生的AR依赖的基因网络。通过为雄激素驱动的精子发生提供分子基础，这项拟议的工作最终可能导致治愈一些男性不育病例，并开发新的男性避孕方法。

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.