Nuclear Movement LINC Complex and Emery-Dreifuss Muscular Dystrophy

 描述（由申请人提供）：Emery-Dreifuss肌营养不良症（EDMD）是由编码核膜蛋白的基因突变引起的。常染色体EDMD由编码A型核纤层蛋白的LMNA突变引起，X连锁EDMD由编码Emerin的EMD突变引起。编码nesprins和SUN的基因突变也与EDMD表型相关。Nesprins和SUN包含跨越核膜的核骨架和细胞骨架（LINC）复合物的接头。LINC复合物将与SUN结合的核纤层连接到细胞骨架组分，包括与nesprins结合的肌动蛋白。Emerin还与核纤层蛋白和nesprins结合并修饰LINC复合体功能。与EDMD有关的核膜蛋白的表达或一级结构的改变阻止了迁移细胞中细胞核的正确运动和定位。同时，MAP激酶ERK 1/2激活信号传导，其本身阻断核运动。这使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，这对于适当的骨骼肌结构和肌源性祖细胞的定向迁移是必不可少的。我们建议通过检查核运动，ERK 1/2活性，核定位在骨骼肌，肌肉祖细胞迁移和EDMD发病机制在三个特定的目标之间的联系来测试这一假设。目标1将涉及一系列旨在揭示过度激活的ERK 1/2如何阻止核运动的细胞生物学实验，包括对以前未表征的假设制动的研究。在目标2中，我们将确定细胞核运动如何影响ERK 1/2激活，通过解剖其与ERK 1/2活性在激酶的生理激活过程中的关系，然后测试是否移动细胞核是必要的和足够的调节ERK 1/2信号。在目标3中，我们将首先确定是否EDMD相关蛋白的改变，阻止核运动干扰成肌细胞融合和分化在体外。然后，我们将使用EDMD小鼠模型，研究A型核纤层蛋白和emerin在再生骨骼肌中对核运动的作用，并确定这些蛋白质的改变是否会阻止肌源性祖细胞迁移到受伤的肌肉中。我们还将确定降低EDMD骨骼肌中升高的ERK 1/2活性是否对这些过程产生影响。总的来说，拟议的研究将为EDMD的细胞病理学提供新的见解，EDMD是一种知之甚少的肌营养不良症，同时揭示有关核运动的新信息，这是一个对基础细胞生物学具有广泛意义的过程。

 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.