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成复杂的3D形状的。为了做到这一点，我们正在研究鸡胚胎中神经管的形成。在这个过程中，一层上皮细胞被转化成一个封闭的管，上面覆盖着一层表面外胚层。我们的数据揭示了claudin家族的新功能，这些紧密连接蛋白在调节细胞间离子和小分子的运动中起着重要作用。具体来说，我们发现(i) Cldn8是使神经外胚层弯曲形成神经管基部的细胞形状变化所必需的，（ii） Cldn3是非神经外胚层关闭神经管顶部并将其与表面外胚层分离所必需的，（iii）这些Cldn3是调节细胞形状变化的蛋白质定位到紧密连接的细胞质面所必需的。我们的发现是新颖的，即cladin是调节肌动蛋白-细胞骨架和细胞形状变化的分子的上游。******我们假设，cladin以一种环境依赖的方式与蛋白质复合物相互作用，以调节上皮形态发生所必需的细胞形状变化。为了验证这一假设，我们需要了解如何调节claudin的表达，以确保正确的家族成员在特定组织中得到适当的表达。我们将确定在非神经外胚层中开启Cldn3和在神经外胚层中开启Cldn8的信号通路（目的1）。我们还将描述由单个claudin家族成员独特调节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（目的2）claudin在疾病状态下改变的表达模式受到了极大的关注，但对其在胚胎发育过程中的正常生物学功能知之甚少。我们将经典胚胎学与最先进的分子方法相结合，以确定claudin在形态发生中的功能。我的研究项目所产生的数据将促进我们对胚胎发生过程中claudin及其功能的动态调控的理解，并使我们能够开发可用于理解整个胚胎背景下上皮形态发生的范式。重要的是，该项目将为本科生和研究生提供独特的培训机会，并促进本地和国外的合作。*****

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 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.*****