The Function of the Mia3 Gene in Murine Placentation

描述（由申请人提供）：胎盘是哺乳动物胚胎发生的重要器官，在母体和胎儿之间提供有效的营养、气体和废物交换，并为胎儿创造一个免疫优越的环境，分泌维持母体妊娠状态的激素。胎盘的结构是复杂的，包括子宫内的侵袭和锚定区以及血管交换区，滋养细胞是其主要的结构和功能成分。滋养细胞侵入胎盘并形成胎盘的能力对胎盘的成功发育至关重要；胎盘功能障碍与许多妊娠疾病有关，包括自然流产、宫内生长受限和先兆子痫，所有这些疾病通常与胎盘脉管系统受损有关。滋养细胞起源于胚泡的上皮性滋养外胚层细胞，并逐渐分化为具有特殊功能的各种亚型。一些调节滋养细胞特化的因素已经开始被确定，但胎盘分化和形态发生的细胞和分子机制在很大程度上是未知的。我们在小鼠中发现了一个参与胎盘形态发生的新基因，黑色素瘤抑制活性3 (melanoma inhibitory activity 3, Mia3)，该基因编码一种参与膜运输和高尔基组织（TANGO1）的蛋白。该基因在胚胎干细胞中产生的基因诱捕突变，被命名为Xst199，导致纯合突变胚胎在妊娠10.5天死亡，胎盘形态发生严重缺陷。这种缺陷似乎至少早在E8.5就开始了，因为纯合子突变体的绒毛膜和外胎盘锥体比杂合子和野生型凋落物发育得更差。在培养的人类细胞中，TANGO1的功能是促进COPII包被的分泌囊泡装载特定的货物蛋白，因此我假设小鼠胚胎中TANGO1的Xst199突变干扰了滋养细胞分化所需的特异性蛋白质的分泌，导致胎盘功能障碍。在这个前期研究中，我建议进一步表征这个突变的表型和Tango1在滋养细胞中的正常功能，并确定这个新途径对滋养细胞分化调节的重要性。

DESCRIPTION (provided by applicant): The placenta is a critical organ of mammalian embryogenesis, providing efficient nutrient, gas and waste exchange between the mother and fetus, as well as creating an immunologically privileged environment for the fetus and secreting hormones that maintain the pregnant state of the mother. The structure of the placenta is complex, consisting of regions of invasion and anchorage within the uterus as well as a region of vascular exchange, all of which have trophoblast cells as their primary structural and functional elements. The ability of the trophoblast cells to invade and form the placenta properly is crucial for successful development; placental dysfunction is associated with many disorders of pregnancy, including spontaneous abortions, intrauterine growth restriction, and preeclampsia, all of which are commonly associated with compromised placental vasculature. Trophoblast cells arise from the epithelial trophectoderm cells of the blastocyst and progressively differentiate into a variety of subtypes with specialized functions. Some of the factors regulating trophoblast specialization have begun to be identified, but the cellular and molecular mechanisms underlying differentiation and morphogenesis of the placenta are largely unknown. We have identified a novel gene involved in placental morphogenesis in the mouse, melanoma inhibitory activity 3 (Mia3), which encodes a protein involved in membrane transport and Golgi organization (TANGO1). A gene-trap mutation of this gene generated in ES cells, designated Xst199, leads to death of homozygous mutant embryos at day 10.5 of gestation, with severe defects in placental morphogenesis. The defect appears to originate at least as early as E8.5, as the chorion and ectoplacental cone are less well developed in the homozygous mutants than in heterozygous and wild type litter mates. TANGO1 in cultured human cells functions to facilitate loading of COPII coated secretory vesicles with specific cargo proteins, thus I hypothesize that the Xst199 mutation of Tango1 in mouse embryos interferes with secretion of proteins specifically required for trophoblast differentiation, leading to placental dysfunction. In this pilot study I propose to further characterize the phenotype of this mutation and the normal function of Tango1 in trophoblast cells, and determine the importance of this novel pathway to the regulation of trophoblast cell differentiation. PUBLIC HEALTH RELEVANCE: Many of the diseases of pregnancy such as preeclampsia, spontaneous abortion, and intrauterine growth retardation are due to defects in the formation of the placenta, and can lead to significant morbidity and mortality to both fetus and mother. To understand their causes, we need to better understand the mechanisms governing the formation and function of the placenta. The Xst199 mutation of the Mia3 gene has uncovered a novel pathway that is critical for the proper formation of the placenta, and thus further work is important to fully understand how this gene is functioning, and how it affects placentation.