CELL-SPECIFIC EXPRESSION IN THE PITUITARY GLAND

描述(申请人提供)：脑下垂体包含五种不同类型的细胞，它们专门分泌荷尔蒙。了解细胞规范的机制很重要，因为许多身体功能都依赖于它。基因工程小鼠已经证明了几种转录因子和信号分子的作用，并且与人类垂体疾病的对应关系非常突出。我们证明了同源结构域转录因子PITX2在垂体原基的发育和谱系特异性转录因子基因的激活中具有剂量依赖性的作用。在人类中，PITX2突变是Rieger综合征和孤立性生长激素缺乏的原因之一。我们建议通过细胞特异性缺失来测试PITX2在维持特殊的垂体细胞分化功能中的作用。PITX2的下游靶基因GATA2的作用将使用GATA2的条件零等位基因进行测试。FOXL2是一种叉状转录因子，是发育中的垂体腺分化细胞的最早标志物之一，它能激活促性腺激素释放激素受体的转录。FOXL2单倍体不足的人类会出现眼睛缺陷和卵巢早衰。我们认为，FoxI2在发育过程中调节承诺的前垂体细胞的生长，在成熟促性腺激素的功能中发挥作用，并在垂体肿瘤的易感性方面发挥作用。我们将通过表征FOXL2的表达，将其置于已知转录因子的遗传层次中，并分析小鼠可诱导的功能等位基因丧失的后果来探索这些想法。如果我们在激素基因转录的终末分化和激活之前有标记来识别特化细胞，我们对垂体细胞特性的理解将会进步。为了产生这样的标记，我们建议使用转基因技术来比较垂体细胞类型的转录本，以标记用于纯化和基因阵列分析的细胞。生物信息学将识别每种分化细胞类型特有的转录本，并进行实验验证。在建议的授予周期中，我们将使用成熟的方法确定三种垂体转录因子的作用，并启动一种新的方法来研究细胞规格。我们期望这些研究将为了解人类垂体激素缺乏性疾病的病因和垂体腺瘤的特征提供有价值的见解。

DESCRIPTION (provided by applicant): The pituitary gland contains five different cell types that are specialized in hormone production. Understanding the mechanism of cell specification is important because many body functions depend on it. Genetically engineered mice have proven the roles of several transcription factors and signaling molecules, and the correspondence with human pituitary disease is outstanding. We proved that the homeodomain transcription factor PITX2 has a dosage dependent role in development of the pituitary primordium and in activation of lineage specific transcription factor genes. In humans, PITX2 mutations are a cause of Rieger syndrome and isolated growth hormone deficiency. We propose to test the role of PITX2 in maintenance of differentiated functions of specialized pituitary cells by cell specific deletion in mice. The role of GATA2, a downstream target of PITX2, will be tested using a conditional null allele of Gata2. FOXL2 is a forkhead transcription factor that is one of the earliest markers of differentiated cells in the developing pituitary gland, and it activates gonadotropin releasing hormone receptor transcription. Humans haploinsufficient for FOXL2 have eye defects and premature ovarian failure. We propose that FoxI2 has roles in regulating the growth of committed anterior pituitary cells during development, in the function of mature gonadotropes, and in susceptibility to pituitary tumors. We will explore these ideas by characterizing Foxl2 expression, placing it in the genetic hierarchy of known transcription factors, and analyzing the consequences of an inducible loss of function allele in mice. Our understanding of pituitary cell specification would be advanced if we had markers to identify specialized cells prior to terminal differentiation and activation of hormone gene transcription. To generate such markers we propose to compare the transcriptomes of pituitary cell types using transgenic technology to mark cells for purification and gene array analysis. Transcripts unique to each differentiated cell type will be identified by bioinformatics and verified experimentally. During the proposed grant cycle we will have defined the roles of three pituitary transcription factors using well-established methods and initiated a new approach to studying cell specification. We expect that these studies will provide valuable insight for understanding the etiology of human pituitary hormone deficiency diseases and characterization of pituitary adenomas.