Cytoskeletal force generation on the nucleus

描述(由申请人提供)：细胞爬行是伤口愈合、组织维持、分化、发育(形态发生)和癌症转移等生理过程的核心。爬行细胞在执行突出、粘连和收回后缘的正常任务时如何定位其细胞核，目前还知之甚少。我们提出了两个特定的目标：目标1：解释爬行成纤维细胞如何通过在核表面产生机械力来定位核的中心位置。目的2：解释细胞核和F-肌动蛋白细胞骨架之间的机械连接如何介导成纤维细胞爬行的定向持续。这一建议是创新的，原因如下：1)大多数关于核运动的体外研究都是在损伤细胞单层边缘的运动背景下进行的，重点是初始极化事件(核被推离前沿)。相反，这项研究将确定一个孤立的爬行细胞如何在细胞爬行的方向上平移其细胞核。2)我们从这个新的概念观点出发，认为核定位是向前和向后相互竞争的力量平衡的结果，这些力量可以是推动的，也可以是拉动的。3)我们建议使用工程和生物分子工具的组合来扰乱这种核力平衡，并推导出驱动核定位的主要细胞骨架力的方向和相对大小。这项工作的医学意义在于，核-细胞骨骼力量异常转移被认为与许多疾病有关，包括Emery-Dreifuss肌营养不良症、扩张型心肌病、Hutchinson-Gilford早衰症和Dunnigan型家族性部分脂营养不良症。虽然这些疾病背后的分子机制尚不清楚，但已经假设这些疾病可能(部分)是由于从细胞骨架到细胞核的力异常传递所致。我们在这项提议中的方法依赖于与这些疾病相关的核-细胞骨架连接物的突变，并检查力量平衡的变化。因此，这项工作既具有科学意义，也具有医学意义。

DESCRIPTION (provided by applicant): Cell crawling is central to physiological processes like wound healing, maintenance of tissue, differentiation, development (morphogenesis) and cancer metastasis. How a crawling cell positions its nucleus as it executes its normal tasks of protrusion, adhesion, and retraction of the trailing edge is poorly understood. We propose two specific aims: Aim 1: Explain how the nucleus is positioned centrally through generation of mechanical forces on the nuclear surface in crawling fibroblasts. Aim 2: Explain how the mechanical linkages between the nucleus and the F-actin cytoskeleton mediate directional persistence of fibroblast crawling. This proposal is innovative for the following reasons: 1) The majority of in vitro studies on nuclear motion have been performed in the context of motility at the edge of a wounded cell monolayer with an emphasis on initial polarization events (where the nucleus is pushed away from the leading edge). In contrast, this study will determine how an isolated crawling cell translates its nucleus in the direction of cell crawling. 2) We work from th novel conceptual view that nuclear positioning is a result of a balance of competing forward and rearward forces which can be pushing or pulling. 3) We propose to use a combination of engineering and biomolecular tools to perturb this nuclear force balance and deduce the direction and relative magnitude of the dominant cytoskeletal forces driving nuclear positioning. The medical significance of this work is due to the fact that abnormal nuclear-cytoskeletal force transfer is thought to be involved in a number of diseases including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy, Hutchinson-Gilford progeria syndrome and Dunnigan-type familial partial lipodystrophy. Although the molecular mechanism underlying these diseases remains unclear, it has been hypothesized that these diseases may result (in part) due to abnormal force transmission from the cytoskeleton to the nucleus. Our approach in this proposal relies on mutating nuclear- cytoskeletal linkers that are associated with these diseases and examining alterations in the force balance. This work therefore has both scientific and medical significance.