Pathogenesis of Emery-Dreifuss Muscular Dystrophy

描述(申请人提供)：Emery-Dreifuss肌营养不良症(EDMD)以区域性肌肉收缩、缓慢进行性肌肉萎缩和伴有房室传导阻滞的心肌病为特征。难以区分的EDMD以常染色体显性和X连锁的方式遗传。Emerin是核膜内膜的一种完整蛋白质，它的突变会导致X连锁EDMD。常染色体显性遗传性EDMD是由编码核膜中间丝蛋白lamins A和C的LMNA基因突变引起的，目前尚不清楚核膜蛋白突变是如何导致肌肉营养不良的。我们假设，这些染色质相关蛋白的突变导致了负责肌肉细胞分化或生存的基因表达的变化。我们的目标是通过在转基因细胞、患者细胞以及组织和动物模型中进行的一系列研究来检验这一假设。 在第一个特定目标中，我们将使用荧光显微镜和光漂白方法来研究来自常染色体显性遗传性EDMD患者的Lamin A和C突变如何影响内核膜上Emerin的迁移率。我们将确定突变的Lamins A和C是否导致Emerin从内核膜“逃逸”到连续的内质网中。由于X连锁EDMD的患者内核膜中没有Emerin，这一发现将证明X连锁和常染色体显性形式之间的联系。在第二个目标中，我们将使用微阵列来比较常染色体显性EDMD和X连锁EDMD和Dunnigan型部分脂营养不良患者细胞中的基因表达，Dunnigan型部分脂营养不良是由lamin A和C的不同区域突变引起的疾病，这将确定导致EDMD的Emerin和lamin突变是否会改变相同基因的表达。我们还将使用微阵列来确定发展为肌营养不良症的lamin A/C“基因敲除”小鼠肌肉中的基因表达谱，并将结果与已知的Duchenne肌营养不良症基因表达的病理变化进行比较。这一结果将在患有EDMD的人体组织中得到证实。在目标3中，我们将建立表达人层粘连蛋白A突变体的转基因小鼠，并确定它们是否出现EDMD的病理异常和类似的基因表达变化。 这项工作将有助于确定核膜异常是如何导致肌肉营养不良的。

DESCRIPTION (provided by applicant): Emery-Dreifuss muscular dystrophy (EDMD) is characterized by region muscle contractures, slow progressive muscle wasting and cardiomyopathy with atrioventricular conduction block. Indistinguishable forms of EDMD are inherited in autosomal dominant and X-linked manners. Mutations in emerin, an integral protein of the nuclear envelope inner membrane, cause X-linked EDMD. Autosomal dominant EDMD is caused by mutations in the LMNA gene, which encodes the nuclear envelope intermediate filament proteins lamins A and C. It is not known how mutations in nuclear envelope proteins cause muscular dystrophy. We hypothesize that mutations in these chromatin-associated proteins cause changes in the expression of genes responsible for muscle cell differentiation or survival. Our goal is to test this hypothesis using a combination of studies in transfected cells, patients' cells and tissues and animals models. In the first specific aim, we will use fluorescence microscopy and photobleaching methods to investigate how lamin A and C mutants from patients with autosomal dominant EDMD influence the mobility of emerin in the inner nuclear membrane. We will determine if mutant lamins A and C cause emerin to "escape" from the inner nuclear membrane into the continuous endoplasmic reticulum. As patients with X-linked EDMD do not have emerin in the inner nuclear membrane, this finding would demonstrate a connection between the X-linked and autosomal dominant forms of the disease. In the second aim, we will use microarrays to compare gene expression in cells from patients with autosomal dominant EDMD to X-linked EDMD and Dunnigan-type partial lipodystrophy, a disease caused by mutations in different regions of lamins A and C. This will establish if emerin and lamin mutations responsible for EDMD alter expression of the same genes. We will also use microarrays to determine gene expression profiles in muscles from lamin A/C "knockout" mice that develop muscular dystrophy and compare the results to what is known about pathologic alterations in gene expression in Duchenne muscular dystrophy. The results will be confirmed in tissues from human subjects with EDMD. In Aim 3, we will generate transgenic mice expressing human lamin A mutants and determine if they develop pathological abnormalities of EDMD and similar gene expression changes. This work will help establish how abnormalities in the nuclear envelope cause muscular dystrophy.