Claudins: Critical Regulators of Epithelial Barriers and Morphogenesis

我们的目标是了解简单的上皮细胞层是如何转变为复杂的3D形状的。为此，我们正在研究鸡胚胎中神经管的形成。在这个过程中，一片扁平的上皮细胞转化为一个封闭的管，上面覆盖着一层表面外胚层。我们的数据揭示了紧密连接蛋白的Claudin家族的新功能，该家族在调节细胞间离子和小分子的运动方面起着至关重要的作用。具体地说，我们发现(I)Cldn8是细胞形状变化所必需的，允许神经外胚层弯曲形成神经管的底部；(Ii)非神经外胚层需要Cldn3关闭神经管的顶部并将其与表面外胚层分离；以及(Iii)这些claudins需要将调节细胞形状变化的蛋白质定位到紧密连接的细胞质表面。我们的发现，即Claudins位于调节肌动蛋白-细胞骨架和细胞形状变化的分子的上游，这是新的发现。*我们假设Claudins以一种上下文相关的方式与蛋白质复合体以独特的方式相互作用，以调节对上皮形态发生至关重要的细胞形状变化。为了验证这一假设，我们需要了解claudin的表达是如何调节的，以确保正确的家族成员在特定组织中适当表达。我们将确定在非神经性外胚层中启动Cldn3和在神经性外胚层中启动Cldn8的信号通路(目标1)。我们还将描述由个别Claudin家族成员独特调控的蛋白质相互作用网络，并确定这些相互作用如何转化为上皮形态发生(目标2和3)。*Claudins因其在疾病状态下的表达模式改变而受到极大关注，但对其在胚胎发育过程中的正常生物学功能知之甚少。我们正在结合经典胚胎学和最先进的分子方法来定义Claudin在形态发生中的功能。我的研究项目产生的数据将促进我们对Claudins在胚胎发生过程中的动态调节及其功能的理解，并使我们能够开发出可用于理解整个胚胎背景下的上皮形态发生的范例。重要的是，该计划将为本科生和研究生提供独特的培训机会，并促进国内外的合作。

Our goal is to understand how simple epithelial cell layers are transformed into complex 3D shapes. To do this, we are studying neural tube formation in the chick embryo. During this process, a flat sheet of epithelial cells is transformed into a closed tube with an overlying layer of surface ectoderm. Our data revealed new functions the claudin family of tight junction proteins that have an essential role in regulating the movement of ions and small molecules between cells. Specifically, we showed that (i) Cldn8 is required for cell shape changes that allow the neural ectoderm to bend to form the base of the neural tube, (ii) Cldn3 is required in the non-neural ectoderm to close the top of the neural tube and separate it from the surface ectoderm, and (iii) these claudins are required to localize proteins that regulate cell shape changes to the cytoplasmic face of tight junctions. Our findings, that claudins are upstream of molecules that regulate the actin-cytoskeleton and cell-shape changes, are novel.****** We hypothesize that claudins uniquely interact with protein complexes in a context-dependent manner to regulate cell-shape changes that are essential for epithelial morphogenesis. To test this hypothesis, we need to understand how claudin expression is regulated to ensure that the correct family members are appropriately expressed in particular tissues. We will identify the signaling pathways that turn on Cldn3 in non-neural ectoderm and Cldn8 in neural ectoderm (Aim 1). We will also characterize the network of protein interactions that are uniquely regulated by individual claudin family members and determine how these interactions are translated into epithelial morphogenesis (Aims 2 & 3). ****** Claudins have received significant attention based on their altered expression patterns during disease states, yet relatively little is known regarding their normal biological function during embryonic development. We are combining classical embryology with state-of-the-art molecular approaches to define claudin function in morphogenesis. The data generated by my research program will advance our understanding of the dynamic regulation of claudins and their function during embryogenesis and allow us to develop paradigms that can be used to understand epithelial morphogenesis in the context of the whole embryo. Importantly, this program will provide unique training opportunities for undergraduate and graduate students and foster collaborations both locally and abroad.*****