NEW IRON TRAFFICKING PATHWAY IN EPITHELIAL INDUCTION

我们对发育中的器官如何获得铁知之甚少，但这个话题在人类怀孕过程中非常重要。事实上，器官发生可以在没有转铁蛋白/转铁蛋白受体的情况下启动，并且在许多谱系中，转铁蛋白传递铁是特定阶段的。然而，几乎没有任何蛋白质可以替代或补充 转铁蛋白。这些研究具有普遍的重要性，因为铁的获得是生长所必需的，而且它具有局部重要性，因为铁通过转录和翻译效应调节特定的基因亚群。 我的实验室致力于寻找肾脏诱导的机制，这是一个从间充质细胞产生肾单位的过程。我们以前发现了一组刺激这种转化的细胞因子，现在我们发现了一种新的肾单位诱导剂NGAL，它是Lipocalin超家族的成员。这些蛋白质并不为人所熟知，而且具有一定的功能 数据有限，但它们被认为是运输低分子化合物，它们通过内吞作用将化合物输送到细胞。我们认为NGAL可以转运铁，其诱导活性来源于铁-NGAL。NGAL不是转铁蛋白的替代品-它们运输到不同的细胞器，并且它们针对发育中的间充质中的不同区域。在体外，NGAL和转铁蛋白都是诱导所必需的，它们以连续的方式起作用。 为了评估NGAL流量，我们将分离NGAL受体。受体应该描述肾脏外围的一个细胞域，它可能包括上皮祖细胞和间质，它将描述一个独特的亚细胞途径。为了评估NGAL在各种上皮性疾病中如此高表达的原因，鉴定也很重要。然后我们将确定调节基因表达的铁池，并确定它是如何 在体内使用一种新的遗传探针，随着发育的不同而变化。通过检查候选基因和微阵列来测试对这一铁池的反应；它似乎包括已知的控制肾脏发育的基因。最后，我们将首先测试在间充质转化的特定阶段需要铁输送的假设。 确定NGAL在体外的诱导活性是否需要铁，然后检查体内转铁蛋白何时何地是必需的。后者需要在体内抢救胚胎。这些研究表明，铁在形态发生中是一个关键的调节因子，并确定了其在间充质细胞向上皮细胞转化过程中的阶段特异性功能。

We know very little about how developing organs obtain iron, but this topic is of great importance in human gestation. Indeed, organogenesis can initiate in the absence of transferrin/transferrin receptor, and in many lineages, iron delivery by transferrin is stage specific. However, there are few, if any proteins that can substitute for, or complement transferrin. These studies are of general importance because acquisition of iron is required for growth, and it is of local importance, because iron regulates specific subsets of genes by transcriptional and translational effects. My lab is dedicated to finding mechanisms of kidney induction, a process that generates nephrons from mesenchymal cells. We previously identified a set of cytokines that stimulate this conversion and now we have identified a new nephron inducer called Ngal, a member of the lipocalin superfamily. These proteins are not well known, and functional data are limited, but they are thought to transport low molecular weight compounds, which they deliver to cells by endocytosis. We propose that Ngal can transport iron, and that its inductive activity results from iron-Ngal. Ngal was not a substitute for transferrin-they traffic to different organelles and they target different domains in the developing mesenchyme. In vitro, Ngal and transferrin were both required for induction, acting in a sequential fashion. To evaluate Ngal traffic, we will isolate the Ngal receptor. The receptor should describe a domain of cells in the periphery of the kidney that is likely to include epithelial progenitors and stroma and it will describe a unique subcellular pathway. The identification is also important in order to evaluate why Ngal is so highly expressed in a variety, of epithelial diseases. Then we will identify the pool of iron that regulates gene expression and determine how it varies with development by using a novel genetic probe in vivo. The response to this pool of iron is tested by examining candidate genes and microarrays; it appears to include genes that are known to control kidney development. Lastly, we will test the hypothesis that iron delivery is required at particular stages of mesenchymal conversion by first determining whether Ngal requires iron for its inductive activity in vitro, and then examining when and where transferrin is essential in vivo. The later requires rescue of the embryos in vivo. These studies implicate iron as a critical regulator in morphogenesis, and define its stage specific functions during the conversion of mesenchyme to epithelia.