Role of Placental Transport In Fetal Growth

描述（由申请人提供）：本提案的总体目标是了解调节胎儿生长的胎盘营养机制。GLUT 3是一种特异性的葡萄糖转运蛋白，在胎盘的滋养外胚层/滋养层中表达，并与GLUT 1沿着协同介导葡萄糖经胎盘转运至孕体。正常发育（D）导致妊娠晚期胎盘GLUT 3表达和浓度增加，与最大胎儿生长相关，而母体营养限制（MNR）或特定生长因子缺乏（EGF）导致胎盘GLUT 3浓度下降，胎儿生长受限。我们已经观察到，GLUT 3是转录调控的顺式元件，结合脱磷酸化的Sp1/Sp3在大鼠滋养层细胞（HRP.1）。为了追求这些新的体外观察的体内扩展，我们已经创建了GLUT 3-荧光素酶转基因小鼠和MNR小鼠模型。为了进一步研究滋养外胚层/胎盘GLUT 3的功能意义，我们创建了GLUT 3缺失小鼠，杂合子显示与细胞凋亡/坏死相关的胎儿生长受限。为了定义胎盘GLUT 3在D期间和对MNR的反应中的作用，本提案的近期目标是测试以下假设：胎盘GLUT 3表达对于通过发育和MNR的胎儿葡萄糖供应至关重要，并且GLUT 3的缺乏容易导致异常滋养层，从而导致胎儿细胞增殖、分化、凋亡和/或坏死。为了验证这一假设，我们提出了三个具体目标：1]为了确定D和MNR调节胎盘GLUT 3表达的机制，我们计划使用GLUT 3-荧光素酶转基因小鼠系并研究D和MNR对GLUT 3转录调节的影响，2]为了研究降低的GLUT 3浓度对正常胎盘和胎儿D和MNR的影响，我们将使用GLUT 3无效杂合小鼠系（50%），并确定对胎盘和胎儿表型和功能的影响，以及[3]为了研究GLUT 3对正常胎盘和胎儿D以及在MNR中的功能作用，我们将检查纯合无效GLUT 3植入前胚胎，用Tet-Off系统抑制重组小鼠GLUT 3的表达，并检测其对胎盘和胎儿表型的影响。我们提出的研究将确定GLUT 3在正常和异常胎儿生长中的生物学作用。

DESCRIPTION (provided by applicant): The overall aim of this proposal is to understand the placental nutrient mechanisms that regulate fetal growth. GLUT 3, a specific facilitative glucose transporter is expressed in the trophoectoderm/trophoblasts of the placenta and along with GLUT 1 coordinately mediates trans-placental glucose transport to the conceptus. Normal development (D) causes an increase in placental GLUT 3 expression and concentrations in late gestation associated with maximal fetal growth, while maternal nutrient restriction (MNR) or specific growth factor deficiency (EGF) leads to a decline in placental GLUT 3 concentrations with fetal growth restriction. We have observed that GLUT 3 is transcriptionally regulated by cis elements that bind dephosphorylated Sp1/Sp3 in rat trophoblast cells (HRP.1). To pursue an in-vivo extension of these novel in-vitro observations, we have created a GLUT 3-luciferase transgenic mouse and a mouse model of MNR. Further to investigate the functional significance of trophoectoderm/placental GLUT 3 we created a GLUT 3 null mouse, the heterozygote demonstrates fetal growth restriction which is associated with cellular apoptosis/necrosis. To define the role of placental GLUT 3 during D and in response to MNR, the proximate goal of this proposal is to test the hypothesis that placental GLUT 3 expression is critical for fetal glucose supply through development and MNR, and the absence of GLUT 3 predisposes towards aberrant trophoblast and thereby fetal cellular proliferation, differentiation, apoptosis, and/or necrosis. To test this hypothesis, we propose three specific aims: 1] To determine the mechanism(s) by which D and MNR regulates placental GLUT 3 expression, we plan to employ the GLUT 3-luciferase transgenic mouse lines and investigate the effect of D and MNR on transcriptional regulation of GLUT 3, 2] To explore the effect of decreased GLUT 3 concentrations on normal placental and fetal D and in MNR, we will employ the GLUT 3 null heterozygous mouse line (50%), and determine the effect on placental and fetal phenotype and function, and 3] To investigate the functional role of GLUT 3 on normal placental and fetal D and in MNR, we will examine homozygous null GLUT 3 pre-implantation embryos, and employ the Tet-Off system to repress GLUT 3 expression in a recombinant mouse strain, and examine the effect on placental and fetal phenotype. Our proposed studies will define the biological role of GLUT 3 in normal and aberrant fetal growth.