The Forkhead Transcription Factor, FOXO1, and its Role in Pituitary Gland Develop

描述（由申请人提供）：先天性激素缺乏症很常见，大约每4000个活产婴儿中就有一个。垂体激素缺乏症包括单一激素（孤立激素缺乏症）或几种激素（联合垂体激素缺乏症）的丧失。垂体前叶激素的缺乏不会影响胎儿的生存能力，但对于出生后的生存、性腺分化和胎儿甲状腺的成熟是必需的。转录因子PITX1、PITX2、HESX1、LHX3、LHX4、TPIT、PROP1和PIT1的损伤导致小鼠和人类垂体激素联合缺乏症。然而，这些转录因子的突变只占人类先天性激素缺乏症的一小部分。为了确定导致人类先天性激素缺乏的其他因素，我们正在研究叉头转录因子fox01，它对几个器官的正常发育很重要。Foxo1敲除小鼠模型在胚胎日(e)10.5时由于血管缺陷导致胚胎死亡。我们的目的是研究fox01在先天性垂体激素缺乏症中的作用。我们假设，消除垂体中的fox01将导致垂体增生和组织紊乱，从而导致激素产生的损失和/或激素产生细胞类型的错误规范。这一假设是基于以下观察。首先，我们的初步结果表明，fox01在e14.5开始的非分裂垂体细胞细胞核中存在，当这些细胞开始分化时。其次，fox01抑制胰腺2细胞、成肌细胞、脂肪细胞和内皮细胞的增殖并调节其分化和迁移。为了验证这一假设，我们提出了三个具体目标：确定发育过程中垂体细胞fox01的特异性。我们将对标记5种垂体细胞类型的激素进行免疫组化，并结合小鼠胚胎组织中FOXO1的免疫组化。具体目标2。探讨垂体发育和功能对Foxo1的需求。我们将分析垂体中Foxo1表达消除的小鼠胚胎的垂体（Foxo1窝/-）。我们将评估垂体形态学，分析垂体前叶激素的产生，并测量细胞增殖和凋亡。具体目标3。将fox01置于脑垂体发育控制的遗传层次中。我们将对Foxo1窝/-小鼠胚胎进行免疫组化，寻找正常垂体发育所需的基因。这些研究产生的知识将通过确定先天性垂体激素缺乏症的候选基因以及增加我们对叉头因子突变如何导致出生缺陷的了解，进一步推动这一领域的发展。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解决这一问题的独特境地。

DESCRIPTION (provided by applicant): Congenital hormone deficiencies are common, occurring in approximately one in 4,000 live births. Pituitary hormone deficiency can consist of loss of a single hormone (isolated hormone deficiency) or several hormones (combined pituitary hormone deficiency). Absence of anterior pituitary hormones does not interfere with fetal viability, but are required for survival after birth, gonadal differentiation, and maturation of the fetal thyroid. Lesions in the transcription factors PITX1, PITX2, HESX1, LHX3, LHX4, TPIT, PROP1 and PIT1 lead to combined pituitary hormone deficiency in mice and humans. However mutations in these transcription factors account for only a fraction of congenital hormone deficiencies in humans. To identify additional factors that contribute to human congenital hormone deficiencies, we are investigating the forkhead transcription factor, FOXO1, which is important for the normal development of several organs. Mouse knockout models for Foxo1 result in embryonic lethality at embryonic day (e)10.5 due to vascular defects. Our objective is to investigate the contributions of FOXO1 to congenital pituitary hormone deficiency. We hypothesize that eliminating FOXO1 in the pituitary will cause hyperplasia and misorganization of the pituitary gland resulting in loss of hormone production and/or mis-specification of hormone-producing cell types. This hypothesis is based on the following observations. First, our preliminary results show that FOXO1 is present in nuclei of non-dividing pituitary cells starting at e14.5 when these cells are beginning to differentiate. Secondly, FOXO1 inhibits proliferation and regulates differentiation and migration of pancreatic 2-cells, myoblasts, adipocytes, and endothelial cells. To test this hypothesis we propose three specific aims: Specific Aim 1. Determine the pituitary cell specificity for FOXO1 during development. We will perform immunohistochemistry for the hormones that mark the five pituitary cell types in combination with immunohistochemistry for FOXO1 on mouse embryonic tissue at e18.5. Specific Aim 2. Investigate the requirement for Foxo1 in pituitary gland development and function. We will analyze pituitary glands from mouse embryos that have had Foxo1 expression eliminated in the pituitary gland (Foxo1 pit/-). We will assess pituitary morphology, analyze anterior pituitary hormone production, and measure cell proliferation and apoptosis. Specific Aim 3. Place Foxo1 in the genetic hierarchy of pituitary gland developmental control. We will perform immunohistochemistry on Foxo1 pit/- mouse embryos for genes that are required during normal pituitary development. The knowledge generated by these studies will further this field by identifying a candidate gene for congenital pituitary hormone deficiency and by adding to our knowledge of how forkhead factor mutations cause birth defects. Our expertise in both forkhead transcription factor function and pituitary development places us in a unique situation to address this problem. PUBLIC HEALTH RELEVANCE: Pituitary hormones are essential for survival after birth and for the normal development of gonads and thyroid gland. The forkhead transcription factor, FOXO1, is essential for the normal development and function of muscle, blood vessels, and pancreas. The pattern of FOXO1 localization in the pituitary gland during development suggests a role for inhibiting cell division and regulating cell differentiation. Our objective is to determine the requirement of FOXO1 for normal pituitary development by analyzing the pituitary phenotype in mice that lack FOXO1 in the pituitary gland.