Cell type-specific function of LMNA during myocardial stress in the development of cardiomyopathy

项目摘要 编码层蛋白A/C的LMNA基因突变导致多种人类疾病，称为 椎板病症。最常见的椎板病是扩张型心肌病(这里称为LMNA 心肌病)。尽管最近在了解Lamin A/C的不同细胞功能方面取得了进展，但 致病机制是由特定类型心肌细胞中的LMNA突变触发的，以及它们是如何 在组织水平上整合产生心脏表型在很大程度上是未知的。普遍的观点是， LMNA突变导致无数的细胞缺陷，这些缺陷都与疾病有关，但这一广泛的断言 从未经过严格的测试。我们的初步数据表明，层蛋白A/C在心脏成纤维细胞中起着关键作用 (CF)在纤维化和LMNA心肌病的发病和/或致病性中的作用如果 心肌细胞(CM)中层粘连蛋白A/C功能选择性受损。成人型CMS体内特异性LmNA缺失 导致迅速发病的纤维化和严重的心脏功能障碍。相反，在CFS中Lmna缺失显示为无 即刻心脏病理。令人惊讶的是，相对于CM-缺失，在CMS中伴随着LmNA的缺失 CFS的纤维化程度和病理重塑程度较轻。这些结果提示CFS中层蛋白A/C 在纤维化/心脏重塑的发展中起关键作用，这些病理特征是基础 CM应激反应的疾病进展和严重程度。在分子水平上，我们认为 纤维化所致的基质僵硬与内质网应激标志物及其成员MED25的CM表达有关 被认为是内质网应激反应的调节因子的介体复合体。综上所述，我们的结果表明 Lamin A/C耗竭的CFS对心肌病发展的抑制作用及其与CFS之间的相互作用 CMS是LMNA心肌病进展速度和严重程度的重要决定因素。 根据我们的初步数据，我们假设LMNA的发病机制与层蛋白A/C有关 心肌病以相反的方式取决于细胞类型；层蛋白A/C促进CF介导的心肌纤维化 对心肌应激的反应同时保护CMS免受内质网应激和细胞损伤。测试我们的 假设，Aim1将决定CF功能的层蛋白A/C调节是否是比率和严重程度的基础 疾病的进展。我们将阐明LmNA缺失损害CF功能的可能机制 在紧张的心肌中。在AIM2中，我们将确定纤维化的机械成分是如何起作用的 LMNA突变引起的CM损伤。在不同的矩阵刚度下，我们将描述其机理 LMNA突变引起的潜在CM损伤并与内质网应激有关。这些目标 将不仅有助于更好地了解层蛋白A/C在CFS、CMS中的功能及其在疾病中的串扰 发病机制，但也可能使开发新的治疗LMNA心肌病，并可能 其他形式的心肌病，其中纤维化是其发病机制的组成部分。

Project Summary Mutations in the LMNA gene encoding lamin A/C cause a diverse group of human diseases termed laminopathies. The most prevalent laminopathy is dilated cardiomyopathy (herein referred to as LMNA cardiomyopathy). Despite recent progress in understanding the diverse cellular function of lamin A/C, what pathogenic mechanisms are triggered by LMNA mutations in specific cell types of the myocardium and how they are integrated at the tissue level to produce a cardiac phenotype is largely unknown. The prevailing view is that LMNA mutations cause a myriad of cellular defects that all contribute to the disease but this broad assertion has never been rigorously tested. Our preliminary data suggest that lamin A/C play a crucial role in cardiac fibroblasts (CF) function in fibrosis and the onset and/or the pathogenicity of LMNA cardiomyopathy is more severe if the lamin A/C function is selectively impaired in cardiomyocytes (CM). In vivo Lmna deletion specifically in adult CMs caused rapid onset of fibrosis and severe cardiac dysfunction. In contrast, Lmna deletion in CFs displayed no immediate cardiac pathology. Surprisingly, relative to CM-deletion alone, concomitant deletion of Lmna in CMs and CFs resulted in lesser fibrosis and pathological remodeling. These results suggest that lamin A/C in CFs play a crucial role in the development of fibrosis/cardiac remodeling and that these pathological features underlie the disease progression and severity in response to CM stress. At the molecular level, we implicate increased matrix stiffness from fibrosis contribute to CM expression of ER stress markers and MED25, which is a member of the Mediator complex identified as a regulator of ER stress responses. Taken together, our results suggest lamin A/C-depleted CFs mediate a brake on cardiomyopathy development and interactions between CFs and CMs are important determinants of the rate of progression and the severity of LMNA cardiomyopathy. Based on our preliminary data, we hypothesize that lamin A/C contribute to the pathogenesis of LMNA cardiomyopathy in an opposing manner depending on the cell type; lamin A/C promote CF-mediated fibrosis in response to myocardial stress while in parallel protect CMs from ER stress and cell damage. To test our hypothesis, Aim1 will determine whether lamin A/C regulation of CF function underlies the rate and the severity of disease progression. We will elucidate the putative mechanisms by which Lmna deletion impairs CF function in the stressed myocardium. In Aim2, we will determine how the mechanical component of fibrosis contributes to CM damage caused by LMNA mutations. Under varying matrix stiffness, we will delineate the mechanism underlying CM damage caused by LMNA mutations and contextualize the involvement of ER stress. These aims will not only lead to a better understanding of lamin A/C function in CFs, CMs, and their crosstalk in disease pathogenesis but may also enable the development of new therapies for LMNA cardiomyopathy and perhaps other forms of cardiomyopathies in which fibrosis is integral to their pathogenesis.