Functional Significance of the HIF1 Transcriptome in Granulosa Cells

描述（由申请人提供）：女性的生育能力需要控制卵母细胞、支持颗粒细胞（GCs）和构成卵泡的卵泡细胞的成熟。支持卵泡成熟的营养物质和激素来自于卵膜层的毛细血管；血管化在基膜处终止。因此，随着卵泡的生长，GCs暴露于越来越缺氧的条件下。卵泡生长是一个动态的过程，需要精细的调节。卵泡在胃窦前阶段受到抑制，直到它们受到垂体激素促卵泡激素（FSH）的刺激。在FSH的作用下，GCs产生类固醇、蛋白激素和生长因子，调节下丘脑/垂体轴和子宫容受性，促进卵母细胞成熟和卵泡发育至排卵前表型。我们已经证明，FSH促进了翻译的增强，导致转录因子缺氧诱导因子-1a （HIF1a）在GCs中积累。HIF1a在常氧条件下通常不存在，这是由于针对其蛋白体降解的氧依赖性翻译后修饰，并且仅在缺氧条件下积累。HIF1a与组成性表达的HIF1b形成异二聚体转录因子HIF1，激活一系列靶基因，使细胞在低氧浓度下存活。本应用的目的是验证一个总体假设，即适当的GC功能和卵泡成熟需要一个由FSH和缺氧优化调节的hif1响应转录组。我们的证据支持这些目标，fsh刺激的HIF1活性似乎是诱导多种靶基因的必要条件，包括血管内皮生长因子（Vegf）、抑制素-a（正式Inha）、黄体生成素/绒毛膜促性腺激素受体（正式Lhcgr）和蛋白激酶a调节亚基RIIb（正式Prkar2b）。除了Vegf外，这些在GCs中明显的HIF1靶点与这种普遍存在的转录激活因子的其他常见靶点不同。因此，阐明HIF1的功能作用不仅对胃癌成熟和生育很重要，而且可能有助于我们理解在许多表达高水平HIF1a的不同癌细胞中发现的Lhcgr等基因的错误调控。此外，了解FSH信号如何指导卵泡成熟可以转化为更安全，更有效的治疗不孕症和早期妊娠丢失以及避孕药物的新方法。

DESCRIPTION (provided by applicant): Fertility in females requires controlled maturation of the oocyte, supporting granulosa cells (GCs), and theca cells that comprise the ovarian follicle. Nutrients and hormones to support follicle maturation come from capillaries in the theca layer; vascularization terminates at the basement membrane. Thus, as follicles grow, GCs are exposed to increasingly hypoxic conditions. Follicle growth is a dynamic process that demands exquisite regulation. Follicles are restrained at the preantral stage until they are stimulated by the pituitary hormone follicle stimulating hormone (FSH). In response to FSH, GCs produce steroid and protein hormones and growth factors that regulate the hypothalamic/pituitary axis and uterine receptivity and promote oocyte maturation and development of the follicle to a preovulatory phenotype. We have shown that FSH promotes enhanced translation leading to an accumulation of the transcriptional factor hypoxia-inducible factor-1a (HIF1a) in GCs. HIF1a is normally absent under normoxia due to oxygen-dependent post-translational modifications that target it for proteosomal degradation, and accumulates only under hypoxic conditions. HIF1a, together with constitutively expressed HIF1b, form the heterodimeric transcriptional factor HIF1 that activates a hierarchy of target genes that permit cells to survive under reduced oxygen concentrations. The aims of this application test the overarching hypothesis that proper GC function and follicular maturation require a HIF1-responsive transcriptome optimally regulated by FSH and hypoxia. Support for these aims comes from our evidence that FSH-stimulated HIF1 activity appears to be necessary for induction of a diverse group of target genes that include vascular endothelial growth factor (Vegf), inhibin-a (officially Inha), luteinizing hormone/choriogonadotropin receptor (officially Lhcgr), and protein kinase A regulatory subunit RIIb (officially Prkar2b). With the exception of Vegf, these apparent HIF1 targets in GCs are distinct from other common targets of this ubiquitous transcriptional activator. Thus, elucidation of the functional role of HIF1 is important not only to GC maturation and fertility but may also contribute to our understanding of the misregulation of genes such as the Lhcgr seen in many different cancer cells that express high levels of HIF1a. Moreover, understanding how FSH signals to direct follicular maturation can translate into safer and more effective treatments of infertility and early pregnancy loss as well as new approaches for contraceptive drugs. PUBLIC HEALTH RELEVANCE: FSH signaling to mature follicles to the preovulatory phenotype is required for fertility. Understanding how FSH signals to direct follicular maturation can translate into safer and more effective treatments of infertility and early pregnancy loss as well as new approaches for contraceptive drugs.