Role of Placental Transport In Fetal Growth

描述(由申请者提供)：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是胎盘滋养外胚层/滋养层细胞中表达的一种特殊的促进性葡萄糖转运蛋白，与GLUT-1一起协调介导经胎盘向胎盘的葡萄糖转运。正常发育(D)导致胎盘GLUT 3表达和浓度在妊娠晚期增加，与胎儿最大生长相关，而母亲营养限制(MNR)或特异性生长因子缺乏(EGF)导致胎儿生长受限时胎盘GLUT 3浓度下降。我们观察到GLUT 3在转录上受顺式元件的调控，这些顺式元件与大鼠滋养层细胞中去磷酸化的Sp1/SP3结合(HRP.1)。为了寻求这些新颖的体外观察的体内扩展，我们创建了Glut 3-荧光素酶转基因小鼠和MNR的小鼠模型。为了进一步研究滋养外胚层/胎盘GLUT 3的功能意义，我们创造了一只GLUT 3缺失的小鼠，该杂合子表现出与细胞凋亡/坏死相关的胎儿生长受限。为了明确胎盘GLUT 3在D和MNR中的作用，本研究的目的是验证胎盘GLUT 3的表达对胎儿发育和MNR的葡萄糖供应至关重要的假说，而GLUT 3的缺失容易导致异常滋养细胞，从而导致胎儿细胞的增殖、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的目标：1)为了确定D和MNR调节胎盘GLUT 3表达的机制(S)，我们计划使用GLUT 3-荧光素酶转基因小鼠，并研究D和MNR对GLUT 3转录调控的影响；2)为了探讨降低GLUT 3浓度对正常胎盘和胎儿D的影响，以及在MNR中，我们将使用GLUT 3缺失杂合子小鼠(50%)，并确定对胎盘和胎儿表型和功能的影响；3)研究GLUT 3对正常胎盘和胎儿D以及在MNR中的功能作用。我们将检测植入前的纯合子空GLUT 3胚胎，并使用Tet-Off系统抑制重组小鼠品系中GLUT 3的表达，并检测其对胎盘和胎儿表型的影响。我们建议的研究将确定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.