Epithelial apical membrane polarization, morphogenesis, and regulation of gene expression

上皮是排列在我们身体和内表面的细胞片，如肠道和肾脏，以及眼睛的前面和后面。答：我们所有的器官都需要上皮细胞才能正常运作，在大多数器官中，它们是主要的功能细胞类型。例如，在肠道中，它们支持营养物质从肠腔消化和运输到潜在的血液中。在其他组织中，上皮细胞具有重要的支持功能。一个例子是眼睛后面的视网膜色素上皮，它为感光细胞--感光细胞--提供重要的支持功能。如果没有健康的视网膜色素上皮，光感受器就会停止运作并死亡。我们感兴趣的是决定这些上皮细胞如何形成并在整个生命中保持的过程，以及这些过程的放松如何导致组织退化和不同类型的疾病。这些知识对于与衰老相关的疾病非常重要，在这些疾病中，正常组织的功能往往会因为上皮细胞的缺陷而下降。为了能够形成细胞膜并正常发挥作用，上皮细胞需要相互黏附，它们需要通过形成具有不同组成和功能角色的不同细胞表面域来极化。典型的上皮细胞有一个与其下面的组织相互作用的基底域，一个与其相邻区域粘连的侧向域，以形成片状结构，以及一个面向上皮外部的顶端域。顶端和侧端区域被称为紧密连接的大型蛋白质复合体隔开。紧密连接通过使细胞彼此粘连，并作为调节中心引导细胞增殖、行为、极化和组织形成，从而支持屏障的形成。上皮细胞极化缺陷出现在许多严重的疾病中，这些疾病可以由衰老、环境因素或感染遗传或诱导。在这里，我们关注的是我们最近发现的一种调节细胞极化和细胞形状的机制。我们已经在培养的细胞中发现了这种机制，但它在组织中也是必不可少的，因为它在视网膜色素上皮中的破坏会导致功能障碍和视网膜退化。该途径的主要作用之一是对细胞骨架的调节，细胞骨架是一种由细丝和产生机械力的马达蛋白形成的动态结构。我们的初步研究提出了一种模型，在该模型中，激活顶端区域的机制会诱导信号级联，导致整个细胞的机械力重塑，促进细胞极化和形状变化，以及调节与细胞增殖和功能有关的基因的表达。我们的第一个目标是确定这一机制如何调节上皮细胞的机械力，并使用操纵相反力的方法来检验这一假说。我们的第二个目标是确定该机制在细胞培养模型和小鼠视网膜色素上皮中调节细胞增殖和基因表达的潜在分子机制。我们期待我们的结果建立新的原则，管理上皮如何形成，以及对潜在生物机制的放松如何导致组织功能障碍和疾病。预期的知识将支持开发新的方法来修复感染和癌症等急性疾病以及影响眼睛和其他器官的慢性和与年龄相关的疾病中出现故障的组织。

Epithelia are sheets of cells that line our bodies and internal surfaces such as the intestine and the kidney, as well as the front and back of the eye. A. All our organs require epithelial cells for normal functioning and, in most of them, they are the main functional cell type. For example, in the intestine they support digestion and transport of nutrients from the intestinal lumen to the underlying blood stream. In other tissues, epithelia have crucial support functions. An example is the retinal pigment epithelium at the back of the eye, which provides vital support functions for photoreceptors, the cells that sense light. Without a healthy retinal pigment epithelium, photoreceptors stop to function and die. We are interested in the processes that determine how such epithelia form and are maintained throughout life, and how deregulation of such processes leads to tissue degeneration and different types of diseases. Such knowledge is important for diseases associated with aging, in which normal tissue often function often declines due to defects in epithelia. To be able to form cell sheets and to function correctly, epithelial cells need to adhere to each other, and they need to polarize by forming distinct cell surface domains that have different compositions and functional roles. A typical epithelial cell has a basal domain with which it interacts with the underlying tissue, a lateral domain with which it adheres to its neighbours enabling sheet formation, and an apical domain that faces the outside of an epithelium. The apical and lateral domains are separated by a large protein complex called tight junctions. Tight junctions support barrier formation by making cells adhere to each other and by functioning as regulatory centres that guide cell proliferation, behaviour, polarization, and tissue formation. Defects in epithelial cell polarization occur in many serious diseases that can be inherited or induced by aging, environmental factors, or infections. Here, we are focusing on a mechanism that we have recently discovered to regulate cells polarization and cell shape. We have discovered this mechanism in cells in culture, but it is also essential in tissues as its disruption in the retinal pigment epithelium leads to malfunction and retinal degeneration. One of the main effects of the pathway is on the regulation of the cytoskeleton, a dynamic structure formed by filaments and motor proteins that generate mechanical forces. Our pilot studies suggest a model in which activation of the mechanism at the apical domain induces a signalling cascade that leads to remodelling of mechanical forces across the cell, promoting cell polarisation and shape changes, as well as regulating expression of genes that are involved in cell proliferation and function. Our first aim is to determine how this mechanism regulates mechanical forces across epithelial cells and to test the hypothesis using approaches to manipulate opposing forces. Our second aim is to determine the underlying molecular mechanisms by which this mechanism regulates cell proliferation and gene expression in cell culture models as well as the retinal pigment epithelium in mice. We expect our results to establish new principles that govern how epithelia form and how deregulation of the underlying biological mechanisms leads to tissue malfunction and disease. The expected knowledge will support the development of new approaches to repair malfunctioning tissues in acute diseases such as infections and cancer, as well as chronic and age-related diseases that affect the eye and other organs.