Regulation of claudin expression in chick embryos

所有脊椎动物在外部都是两侧对称的，但在内部，它们的内脏器官在体内的位置有大量的不对称。我们感兴趣的是理解一组“胚胎指令”，这些指令指导单个器官具体定位于胚胎的左侧或右侧。有趣的是，这种模式在进化上是保守的。目前，我们正在研究这些机制，负责这一过程的初始步骤，并将双边对称的胚胎转化为具有明显的左右不对称的胚胎。我们正在研究的分子之一是Claudin-1，这是一种紧密连接蛋白，有助于调节分子在细胞层之间的运动，并保持分子在细胞表面的适当分布。我们已经证明，在胚胎发生过程中，Claudin-1的不适当表达改变了胚胎的正常不对称发育。因此，我们推测Claudin-1的动态表达模式必须暂时和空间调节正常胚胎发生。我们的数据表明，Claudin-1基因的表达在转录水平上受到调控。我们设计了一系列的实验来确定在鸡的胚胎发育过程中Claudin-1的表达是如何被调节的。我们将确定在胚胎发生的关键时刻打开和关闭Claudin-1表达所需的DNA序列。然后，我们将确定与这些DNA序列结合以调节Claudin-1启动子的转录活性的蛋白质。这些蛋白在体内调节Claudin-1表达中的功能将被检查，反过来，我们将询问这些因子在发育中总体上还有什么其他功能，特别是在左右不对称的模式中。我们的研究将确定调节Claudin-1基因表达的因素。我们还将确定这些因素是否调节对左右轴发育很重要的其他基因的表达，以及它们在鸡胚胎发育过程中是否有额外的影响。

All vertebrates are bilaterally symmetrical on the outside but internally they have a large number of asymmetries with respect to how the internal organs are positioned within the body.  We are interested in understanding the set of "embryonic instructions" that direct the individual organs to become specifically localized to the left or right sides of the embryo. Interestingly, this pattern has been evolutionarily conserved.  Currently, we are investigating those mechanisms that are responsible for the initial steps of this process and convert a bilaterally symmetrical embryo into an embryo with distinct left and right asymmetries.  One of the molecules that we are studying is Claudin-1, a tight junction protein that helps to regulate the movement of molecules between cell layers and to maintain the proper distribution of molecules on the cell surface.  We have shown that the inappropriate expression of Claudin-1 during embryogenesis alters the normal asymmetric development of the embryo.  Therefore, we hypothesize that the dynamic expression pattern of Claudin-1 must be temporarily and spatially regulated for normal embryogenesis.         Our data suggests that Claudin-1 gene expression is regulated at the level of transcription.  We have designed a series of experiments to define how Claudin-1 expression is regulated during embryonic development in the chick.  We will identify the DNA sequences that are required to turn Claudin-1 expression "on" and "off" at critical points during embryogenesis.  We will then identify the proteins that bind to these DNA sequences to regulate the transcriptional activity of the Claudin-1 promoter.  The function of these proteins in regulating Claudin-1 expression in vivo will be examined and, in turn, we will ask what other functions these factors have overall in development and, specifically, in patterning left-right asymmetries.  Our studies will identify the factors that regulate Claudin-1 gene expression.  We will also determine if these factors regulate the expression of other genes that are important for the development of the left-right axis and if they have additional effects during development of the chick embryo.