Pathogenesis of Emery-Dreifuss Muscular Dystrophy

 描述（由申请人提供）：Emery-Dreifuss肌营养不良症（EDMD）是一种可能由几种不同基因突变引起的综合征，其中大多数基因编码核膜蛋白。典型的临床表现为骨骼肌萎缩无力、关节挛缩和危及生命的心肌病。常染色体EDMD是由LMNA突变引起的，LMNA编码A型核纤层蛋白，一种内衬核内膜的中间丝蛋白。大多数X连锁EDMD病例是由EMD突变引起的，EMD编码一种称为emerin的内核膜整合蛋白。新出现的人类遗传数据表明，编码LAP 1的基因突变也会导致肌营养不良症，LAP 1是另一种与A型核纤层蛋白和emerin相互作用的内核膜整合蛋白。根据我们之前的研究，我们设计了一个关于EDMD发病机制的假设，提出：1）A型核纤层蛋白、emerin和LAP 1在核膜中形成复合物，其在横纹肌维持中起关键作用，2）该复合物调节MAP激酶ERK 1/2，其破坏激活该激酶，3）双特异性磷酸酶DUSP 4连接ERK 1/2的激活。2增强的AKT-mTOR信号传导，其损害自噬并诱导导致心脏和骨骼肌病理的代谢缺陷。使用新的小鼠和细胞模型，我们将测试这一假设。在目标1中，我们将使用具有A型核纤层蛋白、emerin和LAP 1基因缺失的小鼠来测试以确定这些蛋白在体内横纹肌细胞维持中一起起作用。在目标2中，我们将使用生物化学和生物物理方法来表征lamin-emerin-LAP 1复合物，并研究其与ERK 1/2和DUSP 4的相互作用。我们还将确定层粘连蛋白-emerin-LAP 1复合物的破坏是否激活ERK 1/2。在目标3中，我们将通过将层粘连蛋白-emerin-LAP 1复合物改变的小鼠与缺乏DUSP 4的小鼠杂交来测试我们假设的第三部分，并确定这是否会降低AKT-mTOR活性，逆转自噬缺陷，使细胞能量代谢正常化并改善病理学。从公共卫生的角度来看，该项目将提供对编码核膜蛋白的不同基因突变如何导致EDMD和相关肌病的理解，并确定可能改变当前治疗模式的治疗新靶点。

 DESCRIPTION (provided by applicant): Emery-Dreifuss muscular dystrophy (EDMD) is a syndrome that can result from mutations in several different genes, most of which encode proteins of the nuclear envelope. Skeletal muscle wasting and weakness, joint contractions and life-threatening cardiomyopathy are the classical clinical features. Autosomal EDMD results from mutations in LMNA, which encodes A-type lamins, intermediate filament proteins lining the inner nuclear membrane. Most cases of X-linked EDMD result from mutations in EMD, which encodes an integral protein of the inner nuclear membrane called emerin. Emerging human genetic data demonstrate that mutations in the gene encoding LAP1, another integral protein of the inner nuclear membrane that interacts with A-type lamins and emerin, also cause muscular dystrophy. Based on our previous research, we have devised a hypothesis regarding the pathogenesis of EDMD proposing that: 1) A-type lamins, emerin and LAP1 form a complex in the nuclear envelope that plays a critical role in striated muscle maintenance, 2) this complex regulates the MAP kinase ERK1/2 and its disruption activates this kinase and 3) the dual-specific phosphatase DUSP4 links activation of ERK1/2 to enhanced AKT-mTOR signaling, which impairs autophagy and induces metabolic defects that lead to heart and skeletal muscle pathology. Using novel murine and cellular models, we will test this hypothesis. In Aim 1, we will use mice with genetic depletions of A-type lamins, emerin and LAP1 to test to establish that these proteins function together in striated muscle cell maintenance in vivo. In Aim 2, we will use biochemical and biophysical methods to characterize the lamin-emerin-LAP1 complex and examine its interactions with ERK1/2 and DUSP4. We will also determine if disruption of the lamin-emerin-LAP1 complex activates ERK1/2. In Aim 3, we will test the third part of our hypothesis by crossing mice with alterations in the lamin-emerin-LAP1 complex to mice lacking DUSP4 and determining if this reduces AKT-mTOR activity, reverses defects in autophagy, normalizes cellular energy metabolism and ameliorates pathology. From a public health standpoint, this project will provide an understanding of how mutations in different genes encoding nuclear envelope proteins cause EDMD and related myopathies and identify novel targets for therapies that could change current treatment paradigms.