Regulation of Reproduction

该项目的长期目标是彻底了解类固醇激素合成如何以发育和组织特异性方式进行调节，以及调节异常如何导致生殖疾病，如多囊卵巢综合征（PCOS）。 类固醇生成酶的基因在几个水平上受到转录调控：发育、组织特异性和生殖。 这种调节具有共同的特征，但在类固醇生成酶的各种基因和各种哺乳动物之间也存在差异。 P450 c17（17 alpha hydroxylase/17，2 lyase，17 α羟化酶/17，2裂解酶）基因是类固醇激素合成的关键分支点，与PCOS的发病有关，可能参与神经系统和生殖系统的早期发育。 它在人肾上腺中的表达是合成17羟基C21类固醇（例如皮质醇）以及在性腺和脑中合成C19性类固醇所必需的。 在神经系统中，P450 c17的表达也导致DHEA的合成，DHEA是一种有效的神经调节剂。 我们一直使用啮齿动物作为我们的模型系统研究该基因的转录调控，并确定了顺式作用的DNA元件和几个新的反式作用的核因子。 这些转录因子之一，SET，已经从急性未分化白血病患者的染色体易位中鉴定出来，但其作为转录因子的作用尚不清楚。 我们现在将确定SET行动的机制，通过确定其DNA结合，反式激活，和潜在的二聚化结构域，并确定可能与SET相互作用，参与其反式激活功能的辅因子。 由于SET在发育中的性腺和神经系统中大量表达并调节P450 c17的表达，我们将确定这些辅因子是否是组织特异性表达的，和/或它们是否修饰SET的其他已知功能。 我们定位大鼠P450 c17基因中的顺式活性元件的研究已经确定了一个被我们称为StF-IT-2的因子结合的区域，该因子以一种新的方式与孤儿核受体SF-1相互作用，以调节P450 c17转录。我们将表征这种相互作用，并纯化、表征和克隆StF-IT-2的cDNA。 这些研究的成功完成将使我们更好地了解性腺和神经系统如何启动类固醇生成，一类新的转录因子的作用机制，SF-1调节基因表达的新机制，并将确定另一种可能参与P450 c17表达的独特方面的转录因子。

The long term objective of this project is a thorough understanding of how steroid hormone synthesis is regulated in a developmental and tissue-specific fashion, and how dysregulation may result in reproductive disorders such as polycystic ovarian syndrome (PCOS). The genes for steroidogenic enzymes are transcriptionally regulated at several levels: developmentally, tissue specifically, and hormonally. This regulation shares common features but also differs among the various genes for the steroidogenic enzymes and among various mammals. We will focus on the gene encoding P450c17 (17alpha hydroxylase/17,2 lyase) as it is the key branch point in steroidogenesis, it has been implicated in the etiology of PCOS, and it may be involved in early development of nervous and reproductive systems. Its expression in the human adrenal is required for the synthesis of 17 hydroxy C21 steroids (e.g. cortisol) and for synthesis of C19 sex steroids in the gonads and brain. In the nervous system, expression of P450c17 also results in DHEA synthesis, a potent neuromodulators. We have been using the rodent as our model system for studying the transcriptional regulation of this gene, and have identified cis-acting DNA elements and several novel trans-acting nuclear factors. One of these transcription factors, SET, had been identified from a chromosomal translocation in a patient with acute undifferentiated leukemia, but its role as a transcription factor way unknown. We shall now determine the mechanism of SET action by identifying its DNA binding, transactivation, and potential dimerization domains, and identifying co-factors that may interact with SET to participate in its transactivating functions. AS SET is abundantly expressed and regulates P450c17 expression in the developing gonad and nervous system, we will determine if these co-factors are tissue- specifically expressed, and/or if they modify other known functions of SET. Our studies localizing cis-active elements in the rat P450c17 gene have identified a region bound by a factor that we call StF-IT-2, that interacts with the orphan nuclear receptor SF-1 in a novel way, to regulate P450c17 transcription. We will characterize that interaction, and purify, characterize and clone the cDNA for StF-IT-2. Successful completion of these studies will give us a better understanding of how the gonadal and nervous systems initiate steroidogenesis, the mechanism of action of a new class of transcription factor, novel mechanisms by which SF-1 regulates gene expression, and will identify another transcription factor that may participate in a unique aspect of P450c17 expression.