Transcriptional Determinants of Cell Differentiation

描述(由申请者提供)：精子是高度专业化的细胞，表达许多细胞特异性的mRNAs，是其正常发育和功能所必需的。其中许多mRNAs是由生殖细胞特有的基因或启动子产生的，许多转录因子在生精细胞中具有独特的丰度。然而，目前对单个转录因子在男性生殖细胞分化中的作用知之甚少，包括它们调控的特定基因靶点以及它们之间的相互转录相互作用。这项建议的长期目标是阐明负责精化生精分化计划的转录网络。一个特别的重点是鉴定减数分裂精母细胞和单倍体精子细胞分化所需的生精细胞特异性转录因子。我们最近发现了一种独特的、雄性生殖细胞丰富的转录因子SREBP2，它是体细胞中胆固醇和能量代谢所必需的。这种名为SREBP2gc的因子具有几个细胞特异性的特性，表明在精子发生过程中具有新的、阶段依赖的功能。我们的假设是，生精细胞已经适应了普遍表达的SREBP2转录因子，以调节一组完全不同的新的、细胞特异性的靶基因，这些基因对生殖细胞分化非常重要。最近的发现表明，SREBP2gc调控生殖细胞特异性的顶体酶原基因启动子。这项建议的目的是：1)确定SREBP2gc功能受扰对精子形成和功能以及生殖细胞特异性基因表达的影响；2)进一步表征SREBP2gc与小鼠顶体蛋白原启动子之间的转录相互作用；以及3)建立表达表位标记的SREBP2gc的转基因小鼠。这些小鼠将被用来进一步检测精子发生过程中SREBP2gc的直接靶基因。这些研究将极大地促进我们对精子形成的转录程序的理解，并可能揭示在男性不育和男性避孕药发展中重要的潜在机制。

DESCRIPTION (provided by applicant): Sperm are highly specialized cells and express numerous cell-specific mRNAs required for their proper development and function. Many of these mRNAs are generated from germ cell-specific genes or promoters, and numerous transcription factors are uniquely enriched in spermatogenic cells. However, extremely little is currently known about the role of individual transcription factors in directing male germ cell differentiation, including the specific gene targets they regulate and their mutual transcriptional interactions. The long-term goal of this proposal is to elucidate the transcriptional network responsible for elaboration of the spermatogenic differentiation program. A particular emphasis is the identification of spermatogenic cell-specific transcription factors required for the differentiation of meiotic spermatocytes and haploid spermatids. We recently identified a unique, male germ cell-enriched form of the transcription factor, SREBP2, which is required for cholesterol and energy metabolism in somatic cells. This factor, SREBP2gc, possesses several cell-specific properties which suggest novel, stage-dependent functions during spermatogenesis. It is our hypothesis that spermatogenic cells have adapted the ubiquitously expressed SREBP2 transcription factor to regulate a totally distinct set of novel, cell-specific target genes that are important for germ cell differentiation. Recent findings now demonstrate that SREBP2gc regulates the germ cell-specific proacrosin gene promoter. The aims of this proposal are: 1) to determine the impact of perturbing SREBP2gc function on sperm formation and function as well as on germ cell-specific gene expression; 2) further characterize the transcriptional interactions between SREBP2gc and the mouse proacrosin promoter; and 3) generate transgenic mice expressing epitope-tagged SREBP2gc. These mice will be used to further examine direct target genes for SREBP2gc during spermatogenesis. These studies will greatly advance our understanding of the transcriptional program underlying the formation of sperm, and may reveal underlying mechanisms important in male infertility and for the development of male contraceptives.