Mechanism by Which FOXO1 Regulates Somatotrope Differentiation and/or Function

描述（由申请人提供）：脑垂体调节许多器官的发育和功能，以控制生长、应激反应、生育和体内平衡。先天性垂体激素缺乏症很常见，大约每4000名活产婴儿中就有一名。激素缺乏症可表现为单一激素缺乏或垂体激素缺乏综合症（CPHD）。十几个基因的突变已被确定为CPHD的原因，但一半病例的病因仍然未知。拟议研究的长期目标是确定突变时导致垂体激素不足的基因，并确定这些基因的作用机制。为了扩大垂体激素不足的分子诊断，我们集中在一个家族的转录因子称为叉头因子。叉头因子对不同的发育过程是必不可少的，编码这些因子的基因突变是导致许多人类发育障碍的原因。我们以前的研究已经确定叉头转录因子Foxo1作为垂体激素不足的候选基因。FOXO 1在e18.5时的生长激素细胞和成年男性和女性中表达。垂体中缺乏Foxo1的小鼠含有生长激素的细胞数量急剧减少，这表明Foxo1是正常生长激素（GH）产生所必需的。由于GH在生长、健康代谢和心脏功能中的关键作用，因此研究FOXO 1调节GH产生的机制非常重要。我们推测FOXO 1通过调节生长激素基因或控制生长激素产生的上游调节因子的表达来调节生长激素的产生。我们的假设将通过以下目的进行检验：1）确定FOXO 1调节GH产生的机制。这一目标将采用荧光素酶报告基因测定和染色质免疫沉淀测定，以确定哪些基因直接受FOXO 1调控。2)确定生长激素生产何时需要Foxo1。这一目标将分析生长激素的生产在小鼠胚胎发育的早期阶段，有Foxo1基因切除垂体。我们在叉头转录因子功能和垂体发育方面的专业知识使我们处于一个独特的位置来解决这个基本问题。这些研究所产生的知识将进一步探索垂体激素缺乏症候选基因的作用机制，并增加我们对垂体器官发生的认识。

DESCRIPTION (provided by applicant): The pituitary gland regulates development and function of many organs to control growth, response to stress, fertility and homeostasis. Congenital pituitary hormone deficiencies are common, occurring in approximately one out of every 4000 live births. Hormone deficiency can exist as loss of a single hormone or combined pituitary hormone deficiency (CPHD). Mutations in a dozen genes have been identified as causes of CPHD, but the etiology of half of cases remains unknown. The long-term goal of the proposed studies is to identify the genes that, when mutated, cause pituitary hormone insufficiency and determine the mechanism of action of those genes. To expand the molecular diagnoses for pituitary hormone insufficiency, we have focused on a family of transcription factors referred to as forkhead factors. Forkhead factors are essential for diverse developmental processes and mutations in the genes encoding these factors are responsible for a number of human developmental disorders. Our previous studies have identified the forkhead transcription factor, Foxo1, as a candidate gene for pituitary hormone insufficiency. FOXO1 is expressed in somatotrope cells at e18.5 and in adult males and females. Mice lacking Foxo1 in the pituitary have a drastically reduced number of growth hormone-containing cells, suggesting that Foxo1 is required for normal growth hormone (GH) production. It is important to investigate the mechanisms of FOXO1 regulation of GH production because of the critical role of GH in growth, healthy metabolism, and heart function. We hypothesize that FOXO1 regulates GH production beginning early in development by regulating expression of the growth hormone gene or upstream regulators that control GH production. Our hypothesis will be tested by the following aims: 1) Determine the mechanism by which FOXO1 regulates GH production. This aim will employ luciferase reporter assays and chromatin immunoprecipitation assays to determine which genes are directly regulated by FOXO1. 2) Determine when Foxo1 is required for GH production. This aim will analyze GH production at early stages of development in mouse embryos that have the Foxo1 gene excised from the pituitary. Our expertise in both forkhead transcription factor function and pituitary development places us in a unique situation to address this fundamental question. The knowledge generated by these studies will further this field by exploring the mechanism of action of a candidate gene for pituitary hormone deficiency and by adding to our knowledge of pituitary organogenesis.