Mechanical signaling through the nuclear membrane in lung alveolar health

项目总结 作为正常功能的一部分，哺乳动物的呼吸系统会经历周期性的机械压力。肺 已经进化到能够灵活地适应这种菌株，这种菌株涉及到肺泡有节奏的充气和收缩 高效的气体交换。包括肺泡1型(AT1)和肺泡型(AT1)在内的多种细胞系组成了肺泡龛 肺泡2型(AT2)上皮细胞以及各种独特的间充质细胞和内皮细胞类型。AT1细胞 是通过内皮毛细血管丛进行有效的气体交换所必需的，同时AT2细胞产生 肺表面活性物质，并作为兼性祖细胞分化为AT1细胞。虽然大多数研究都是关于 机械转导集中在间充质系的反应，上皮细胞的能力，在 尤其是肺泡内的那些，在面对这种情况时，应对并保持其身份和功能 连续性和节律性生物力学应变尚未得到很好的定义。利用多重遗传和生物物理 方法，我们提供了新的初步数据，证明细胞骨架-细胞外基质的丢失 AT1细胞通过遗传、机械和化学扰动相互作用，导致其快速重新编程 转化为体内的AT2细胞。单细胞RNA-seq(scRNA-seq)分析表明，这些重新编程的AT2细胞 与正常的AT2细胞非常相似。AT1细胞命运的丧失伴随着板层的坐标变化- 相关的染色质结构域(LAD)组织，导致AT1或AT2特定基因座的隔离或释放 位于LAD的核外围。这种现象与肺泡的变化呈负相关。 上皮细胞的命运。重要的是，我们开发了一种新的单边机械卸载模型 来自肺部呼吸运动的周期性紧张，并表明这导致了对 AT1转化为AT2细胞。与这些新的初步数据一致，我们的实验室最近证明 YAP/Taz存在于AT1细胞的胞核中，但不存在于AT2细胞的胞核中，它们是维持AT1细胞命运所必需的 在老鼠的整个生命周期中。YAP/Taz的丢失导致AT1细胞快速重新编程为AT2细胞 没有受伤。由于YAP/Taz可以在细胞内作为细胞质机械转导和转运 在肌动蛋白调控的细胞伸展和拉伸过程中，我们的初步数据和已发表的数据相结合表明 这种机械转导在AT1细胞中发挥着特殊的作用，以维持肺内平衡状态下的肺泡功能。 因此，我们发表的和初步的数据提出了一个具有挑衅性的假设，即肺已经进化成特定的 在面对来自正常的机械应变时维持细胞命运的表观遗传和转录机制 呼吸和这些途径在对伤害和疾病的反应中被改变。这项建议把 两个在肺发育、表观遗传控制研究方面拥有丰富经验的互补实验室 关于细胞命运，以及再生和疾病的内在含义，我们的目标是解决尚未回答的关键问题 肺发育和再生中细胞命运调控的问题。

PROJECT SUMMARY The mammalian respiratory system undergoes cyclical mechanical strain as part of its normal function. Lungs have evolved to be flexible to adapt to this strain, which involves rhythmic inflation and deflation of the alveoli for efficient gas exchange. Multiple cell lineages comprise the alveolar niche including alveolar type 1 (AT1) and alveolar type 2 (AT2) epithelial cells as well as various unique mesenchymal and endothelial cell types. AT1 cells are required for efficient gas exchange across the endothelial capillary plexus while AT2 cells generate pulmonary surfactant and act as facultative progenitors that differentiate into AT1 cells. While most studies on mechanotransduction have focused on the response of mesenchymal lineages, the ability of epithelial cells, in particular those within the lung alveoli, to respond to and maintain their identity and function in the face of this continuous and rhythmic biomechanical strain has not been well defined. Using multiple genetic and biophysical approaches, we present new preliminary data demonstrating that loss of cytoskeletal-extracellular matrix interactions via genetic, mechanical and chemical perturbations in AT1cells, leads to their rapid reprogramming into AT2 cells in vivo. Single cell RNA-seq (scRNA-seq) analysis shows that these reprogrammed AT2 cells are very similar to normal AT2 cells. Loss of AT1 cell fate is accompanied by coordinate changes in lamina- associated chromatin domain (LAD) organization, causing sequestration or release of AT1 or AT2 specific loci located in LAD sat the nuclear periphery. This phenomenon inversely correlates to the changes in alveolar epithelial cell fate. Importantly, we have developed a novel model of unilateral mechanical unloading of the cyclical strain from breathing movements in the lungs and show that this causes a profound reprogramming of AT1 into AT2 cells. In agreement with these new Preliminary Data, our laboratories recently demonstrated that Yap/Taz are found in the nucleus of AT1, but not AT2cells, and are essential for maintaining AT1 cell fate throughout the lifespan of mice. Loss of Yap/Taz results in a rapid reprogramming of AT1 cells into AT2 cells in the absence of injury. Since Yap/Taz can function as cytoplasmic mechanotransducers in cells and translocate to the nucleus upon actin-regulated cell stretch and strain, our combined preliminary and published data suggest that mechanotransduction plays a specific role in AT1cells to maintain alveolar function in the homeostatic lung. Thus, our published and preliminary data raise a provocative hypothesis that the lung has evolved specific epigenetic and transcriptional mechanisms to maintain cellular fate in the face of mechanical strain from normal respiration and these pathways are altered in the response to injury and disease. This proposal brings together two complementary laboratories with extensive experience in the study of lung development, epigenetic control of cell fate, and the inherent implications for regeneration and disease and we aim to address key unanswered questions in cell fate regulation in lung development and regeneration.