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

项目摘要 编码核纤层蛋白A/C的LMNA基因的突变导致一组不同的人类疾病，称为 核纤层蛋白病最普遍的核纤层蛋白病是扩张型心肌病（本文称为LMNA 心肌病）。尽管最近在理解核纤层蛋白A/C的多种细胞功能方面取得了进展， 致病机制是由心肌特定细胞类型中的LMNA突变触发的， 在组织水平上整合以产生心脏表型在很大程度上是未知的。普遍的看法是， LMNA突变导致无数的细胞缺陷，所有这些都有助于疾病，但这一广泛的断言， 从未经过严格测试。我们的初步数据表明，核纤层蛋白A/C在心脏成纤维细胞中起关键作用 (CF)在纤维化中的作用，如果LMNA心肌病的发病和/或致病性更严重， 核纤层蛋白A/C功能在心肌细胞（CM）中选择性受损。在成年CM中特异性的体内Lmna缺失 导致纤维化和严重的心功能不全相比之下，CFs中Lmna缺失显示没有 即刻心脏病理学检查。令人惊讶的是，相对于单独的CM-缺失，CM中Lmna的伴随缺失 而CF导致较少的纤维化和病理性重塑。这些结果表明，CF中的核纤层蛋白A/C 在纤维化/心脏重塑的发展中起着至关重要的作用，这些病理特征是 对CM应激的反应的疾病进展和严重程度。在分子水平上，我们暗示 纤维化引起的基质硬度有助于CM表达ER应激标志物和MED 25，MED 25是CM的一个成员。 作为ER应激反应的调节剂。综合来看，我们的结果表明 核纤层蛋白A/C缺失CF介导心肌病发展的制动以及CF和 CM是LMNA心肌病进展速度和严重程度的重要决定因素。 基于我们的初步数据，我们假设核纤层蛋白A/C参与了LMNA的发病机制 核纤层蛋白A/C促进CF介导的纤维化， 同时保护CM免受ER应激和细胞损伤。来测试我们 假设，Aim 1将确定核纤层蛋白A/C调节CF功能是否是CF功能的速率和严重程度的基础。 疾病的发展。我们将阐明Lmna缺失损害CF功能的假定机制 在应激心肌中。在Aim 2中，我们将确定纤维化的机械成分如何贡献 由LMNA突变引起的CM损伤。在不同的基质刚度下，我们将描绘出 潜在的CM损害引起的LMNA突变和情境参与ER应激。这些目标 不仅可以更好地理解CF、CM中核纤层蛋白A/C的功能， 发病机制，但也可能使LMNA心肌病的新疗法的发展， 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.