Nuclear Movement LINC Complex and Emery-Dreifuss Muscular Dystrophy

 描述(申请人提供)：Emery-Dreifuss肌营养不良症(EDMD)是由核膜蛋白编码基因突变引起的。常染色体EDMD是由编码A-型层蛋白的LMNA突变和编码Emerin的EMD突变导致的X连锁EDMD。Nesprint和SUN编码基因的突变也与EDMD表型有关。Nesprs和Suns组成了跨越核膜的核骨架和细胞骨架(LINC)复合体的连接物。LINC复合体将与太阳细胞结合的核层连接到包括肌动蛋白在内的细胞骨架成分，肌动蛋白与尼斯普林斯结合。Emerin还与lamins和nerprint关联，并修改LINC复杂函数。EDMD所涉及的核膜蛋白的表达或一级结构的改变阻碍了细胞核在迁移细胞中的正确移动和定位。同时，MAP激酶ERK1/2也激活了信号，而ERK1/2本身就阻止了核的移动。这导致我们假设，所有的核膜“EDMD蛋白”都有助于控制核定位的共同细胞途径，这对正确的骨骼肌结构和肌源性祖细胞的定向迁移是必不可少的。我们建议在三个特定的目标下，通过检测细胞核运动、ERK1/2活性、骨骼肌核定位、肌祖细胞迁移和EDMD发病机制之间的联系来检验这一假设。目标1将涉及一系列细胞生物学实验，旨在揭示过度激活的ERK1/2如何阻止核移动，包括研究以前未确定的假设刹车。在目标2中，我们将通过解剖其与ERK1/2在生理激活过程中的活性的关系来确定核移动如何影响ERK1/2的激活，然后测试移动核是否必要且足以调节ERK1/2信号。在目标3中，我们将首先确定阻止核运动的EDMD相关蛋白改变是否会在体外干扰成肌细胞的融合和分化。然后，我们将使用EDMD的小鼠模型来研究A-型层粘连蛋白和Emerin在再生骨骼肌中的核运动中的作用，并确定这些蛋白的变化是否阻止成肌祖细胞向受损肌肉的迁移。我们还将确定降低ERK1/2活性是否对这些过程有影响。EDMD患者骨骼肌中ERK1/2活性升高。总体而言，拟议的研究将为EDMD(一种鲜为人知的肌肉营养不良)的细胞病理学提供新的见解，同时发现有关核运动的新信息，这一过程对基础细胞生物学具有广泛意义。

 DESCRIPTION (provided by applicant): Emery-Dreifuss muscular dystrophy (EDMD) is caused by mutations in genes encoding proteins of the nuclear envelope. Autosomal EDMD results from mutations in LMNA, which encodes A-type lamins, and X-linked EDMD from mutations in EMD, which encodes emerin. Mutations in genes encoding nesprins and SUNs are also associated with the EDMD phenotype. Nesprins and SUNs comprise the linker of the nucleoskeleton and cytoskeleton (LINC) complex that spans the nuclear membranes. The LINC complex connects the nuclear lamina, which binds to SUNs, to cytoskeletal components including actin, which bind to nesprins. Emerin also associates with lamins and nesprins and modifies LINC complex function. Alterations in expression or primary structure of the nuclear envelope proteins implicated in EDMD prevent the proper movement and positioning of nuclei in migrating cells. In parallel, there is an activation in signaling by the MAP kinase ERK1/2, which itself blocks nuclear movement. This has lead us to hypothesize that all of the nuclear envelope "EDMD proteins" contribute to a common cellular pathway that controls nuclear positioning, which is essential for proper skeletal muscle structure and directed migration of myogenic progenitors. We propose to test this hypothesis by examining links between nuclear movement, ERK1/2 activity, nuclear positioning in skeletal muscle, muscle progenitor cell migration and EDMD pathogenesis in three specific aims. Aim 1 will involve a series of cell biological experiments designed to uncover how hyperactivated ERK1/2 prevents nuclear movement, including investigation of a previously uncharacterized hypothetical brake. In Aim 2, we will determine how nuclear movement affects ERK1/2 activation by dissecting its relationship to ERK1/2 activity during physiological activation of the kinase and then testing if moving the nucleus is necessary and sufficient to regulate ERK1/2 signaling. In Aim 3, we will first determine if EDMD-associated protein alterations that block nuclear movement interfere with myoblast fusion and differentiation in vitro. We will then use mouse models of EDMD to investigate the role A-type lamins and emerin on nuclear movement in regenerating skeletal muscle and to determine if alterations in these proteins block migration of myogenic progenitors into injured muscle. We will also determine if reducing ERK1/2 activity, which is elevated in skeletal muscle in EDMD, has effects on these processes. Overall, the proposed research will provide novel insights into the cellular pathology of EDMD, a poorly understood muscular dystrophy, and simultaneously uncover new information about nuclear movement, a process of broad significance to basic cell biology.