Nucleocytoplasmic Interactions and Dynamics in Emery-Dreifuss Muscular Dystrophy

描述（由申请人提供）： Emery-Dreifuss肌营养不良症（EDMD）由两个基因突变引起。常染色体显性EDMD和罕见的常染色体隐性病例由LMNA突变引起。LMNA编码A型核纤层蛋白，其是与内核膜相关的中间丝蛋白。X连锁EDMD是由EMD突变引起的，EMD编码核膜内膜的一种整合蛋白，称为emerin。EDMD中常见的现象是核结构缺陷;然而，关于这些结构缺陷如何与异常功能相关知之甚少。新出现的证据表明，细胞核内部通过一种称为LING复合物的相互作用蛋白质复合物与细胞骨架相连。这些蛋白质包括核纤层蛋白、SUN（其是内核膜的跨膜蛋白）和nesprins（其中一些是定位于外核膜的跨膜蛋白）。巢蛋白反过来可以与细胞骨架成分如肌动蛋白相互作用。我们推测，A型核纤层蛋白和emerin编码基因的突变导致LINC复合物的破坏，从而导致异常的核细胞骨架连接和相关的核定位和迁移缺陷。使用一个模型系统的成纤维细胞进行极化，我们已经获得了初步的数据表明，核纤层蛋白A突变体的表达发现在EDMD导致核运动缺陷。在本项目的目标1中，我们将仔细检查表达A型核纤层蛋白的细胞的核迁移和中心体定位，A型核纤层蛋白具有导致EDMD和相关肌肉疾病的氨基酸取代，缺乏A型核纤层蛋白的细胞和表达A型核纤层蛋白的细胞具有导致不同疾病的氨基酸取代。在目标2中，我们将使用荧光光漂白技术来确定A型核纤层蛋白突变对LINC复合物蛋白质动力学的影响。在目的3中，为了将常染色体EDMD的致病过程与X连锁EDMD联系起来，我们将研究Emerin对核运动和LINC复合物蛋白动力学的影响。由于核定位和核迁移在肌纤维组织和分化中至关重要，这些研究将确定核质相互作用的缺陷是否会导致常染色体和X连锁EDMD发病机制的功能异常。

DESCRIPTION (provided by applicant): Emery-Dreifuss muscular dystrophy (EDMD) results from mutations in two genes. Autosomal dominant EDMD, and infrequent autosomal recessive cases, result from mutations in LMNA. LMNA encodes A-type nuclear lamins, which are intermediate filament proteins associated with the inner nuclear membrane. Xlinked EDMD results from mutations in EMD, which encodes an integral protein of the nuclear envelope inner membrane called emerin. A commonly observed phenomenon in EDMD is defects in nuclear structure; however, little is known about how these structural defects relate to abnormal function. An emerging body of evidence demonstrates that the inside of the nucleus is connected to the cytoskeleton by a complex of interacting proteins termed the LING complex. These proteins include lamins, SUNs, which are transmembrane proteins of the inner nuclear membrane, and nesprins, some of which are transmembrane proteins localized to the outer nuclear membrane. Nesprins in turn can interact with cytoskeletal components such as actin. We hypothesize that mutations in the genes encoding A-type lamins and emerin cause a disruption of the LINC complex, which leads to abnormal nucleocytoskeletal connections and related defects in nuclear positioning and migration. Using a model system of fibroblasts undergoing polarization, we have obtained preliminary data showing that expression of lamin A mutants found in EDMD lead to nuclear movement defects. In Aim 1 of this project, we will carefully examine nuclear migration and centrosome positioning in cells expressing A-type lamins with amino acid substitutions that cause EDMD and related muscle disorders, cells lacking A-type lamins and cells expressing A-type lamins with amino acid substitutions that cause different diseases. In Aim 2, we will use fluorescence photobleaching techniques to determine the effects of mutations in A-type lamins on the dynamics of proteins of the LINC complex. In Aim 3, to link the pathogenic processes in autosomal EDMD to X-linked EDMD, we will examine the effects of emerin on nuclear movement and LINC complex protein dynamics. As nuclear positioning and nuclear migration are of critical importance in muscle fiber organization and differentiation, these studies will establish if defects in nucleocytoplasmic interactions lead to functional anomalies that can underlie the pathogenesis of autosomal and X-linked EDMD.