Nuclear envelope protein LEMD2 in heart

项目摘要 编码核膜（NE）成分的基因突变会引起一系列疾病， 通常表现为心肌病的核性心肌病。NE将核质与 细胞质，由核膜和内膜组成。核层（NL）是一个广泛的 核纤层蛋白聚合物和相关蛋白质的网络，嵌入内核膜（INM）。 在功能上，NL和INM蛋白不仅为细胞核提供机械稳定性，而且还充当细胞核的机械稳定性。 核周围染色质的锚定点，在染色质组织中起关键作用， 通过与表观遗传机制成分的相互作用和调节来调节基因表达。的 LAP 2-Emerin-MAN 1-domain（LEM-D）蛋白家族在细胞凋亡与细胞凋亡之间的关联中起重要作用。 NL和染色质。LEMD 2（LEM domain containing protein 2）是位于INM中的跨膜蛋白， 参与核完整性和核周束缚以及异染色质的转录沉默。 最近，已经报道了LEMD 2中亮氨酸13到精氨酸（L13 R）的单个氨基酸取代， 会导致常染色体隐性遗传的人类心肌病然而，尽管其临床相关性，很少有人知道， LEMD 2在心肌细胞（CM）中的特定作用，以及L13 R突变导致心肌细胞（CM） 心肌病为了解决这一知识缺口，我们已经产生了三种小鼠模型：组成型CM- 特异性Lemd 2敲除（cKO）、诱导型CM特异性Lemd 2敲除（icKO）和LEMD 2 L13 R敲入 小鼠我们还将利用LEMD 2 L13 R的人诱导多能干细胞（iPSC）衍生的CM模型， 突变以解决LEMD 2中L13 R突变对人CM的影响。初步研究显示， 胚胎或成人CM中LEMD 2的缺失是有害的，LEMD 2 L13 R突变影响CM患者的心脏功能。 小鼠模型，表明LEMD 2在维持正常CM结构和功能中起关键作用， 发育和成年的心脏。因此，我们假设LEMD 2介导的NE完整性的维持和/或 异染色质束缚和沉默的调节对于CM的结构和功能是必不可少的，LEMD 2 L13 R突变损害LEMD 2功能的特定方面，导致心肌病。因此，我们 具体目标是：1。通过分析LEMD 2在发育和成年心肌中的作用， 用于心脏形态发生、结构的组成型（cKO）和诱导型（icKO）Lemd 2 CM特异性敲除小鼠 和功能，以及心肌病的进展;以及2.为了阐明 通过详细分析LEMD 2 L13 R基因敲入导致LEMD 2 L13 R突变的心肌病 小鼠和人诱导多能干细胞（iPSC）衍生的LEMD 2 L13 R突变CM。

PROJECT SUMMARY Mutations in genes encoding nuclear envelope (NE) components cause an array of diseases referred to as nuclear envelopathies that often manifest as cardiomyopathies. The NE separates the nucleoplasm from cytoplasm and is composed of outer and inner nuclear membranes. The nuclear lamina (NL) is an extensive network of lamin polymers and associated proteins that are embedded in the inner nuclear membrane (INM). Functionally, NL and INM proteins not only provide mechanical stability to the nucleus but also serve as the anchoring point for chromatin at the nuclear periphery, playing a critical role in chromatin organization and regulation of gene expression via interaction with and modulation of epigenetic machinery components. The LAP2-Emerin-MAN1-domain (LEM-D) family of proteins play an important role in the association between the NL and chromatin. LEMD2 (LEM domain-containing protein 2), is a transmembrane protein located in the INM, involved in nuclear integrity and perinuclear tethering and transcriptional silencing of heterochromatin. Recently, it has been reported that a single amino acid substitution of leucine 13 to arginine (L13R) in LEMD2 leads to autosomal recessive human cardiomyopathy. However, despite its clinical relevance, little is known as to the specific role of LEMD2 in cardiomyocytes (CMs), and mechanisms by which the L13R mutation leads to cardiomyopathy. To address this gap in knowledge, we have generated three mouse models: constitutive CM- specific Lemd2 knockout (cKO), inducible CM-specific Lemd2 knockout (icKO), and LEMD2 L13R knock-in mice. We will also utilize a human induced pluripotent stem cell (iPSC)-derived CM model of the LEMD2 L13R mutation to address the impact of L13R mutation in LEMD2 on human CMs. Preliminary studies revealed that loss of LEMD2 in embryonic or adult CMs is detrimental, and LEMD2 L13R mutation affects cardiac function in a murine model, indicating that LEMD2 plays a critical role in maintaining normal CM structure and function in developing and adult hearts. Thus, we hypothesize that LEMD2-mediated maintenance of NE integrity and/or regulation of heterochromatin tethering and silencing is essential for CM structure and function, and LEMD2 L13R mutation impairs specific aspects of LEMD2 function leading to cardiomyopathy. Accordingly, Our Specific Aims are: 1. To determine the role of LEMD2 in the developing and adult myocardium by analyzing constitutive (cKO) and inducible (icKO) Lemd2 CM-specific knockout mice for heart morphogenesis, structure and function, and the progression of cardiomyopathy; and 2. To elucidate molecular mechanisms underlying cardiomyopathy consequent to the L13R mutation in LEMD2 by detailed analyses of LEMD2 L13R knock-in mice and human induced pluripotent stem cell (iPSC)-derived LEMD2 L13R mutant CMs.