CELL-SPECIFIC EXPRESSION IN THE PITUITARY GLAND

描述（由申请人提供）：脑垂体包含五种不同类型的细胞，专门用于激素的产生。了解细胞分化的机制是很重要的，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，与人类垂体疾病的对应关系是突出的。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作用。在人类中，PITX2突变是Rieger综合征和孤立生长激素缺乏症的一个原因。我们打算在小鼠中通过细胞特异性缺失来测试PITX2在维持特化垂体细胞分化功能中的作用。PITX2的下游靶标GATA2的作用将使用GATA2的条件空等位基因进行测试。FOXL2是叉头转录因子，是发育中的垂体最早分化细胞的标记物之一，激活促性腺激素释放激素受体转录。单倍体缺乏FOXL2的人有眼睛缺陷和卵巢早衰。我们认为FoxI2在调节垂体前叶细胞发育过程中的生长、成熟促性腺激素的功能以及对垂体肿瘤的易感性中发挥作用。我们将通过表征Foxl2表达，将其置于已知转录因子的遗传层次中，并分析小鼠诱导功能等位基因丧失的后果来探索这些想法。如果我们有标记物在最终分化和激素基因转录激活之前识别特化细胞，我们对垂体细胞规范的理解将会提高。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组，以标记细胞进行纯化和基因阵列分析。每种分化细胞类型的转录本将通过生物信息学鉴定并通过实验验证。在拟议的拨款周期内，我们将使用完善的方法定义三种垂体转录因子的作用，并启动研究细胞规范的新方法。我们期望这些研究将为了解人类垂体激素缺乏症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.