Cytosolic DNA is the Link Between Genomic Instability and Cardiovascular Aging

核纤层蛋白病中LMNA基因突变引起的早衰综合征， 包膜蛋白核纤层蛋白A/C（LMNA）是基因组不稳定性的原型实例，这是基因组不稳定性的标志。 “正常”衰老。心血管受累是主要的表型和死亡的主要原因， 发病率层粘连蛋白病的发病机制和“正常”衰老有几个共同的机制。LMNA 调节线粒体功能、端粒长度、营养感应、干细胞再生和自噬， 是“正常衰老”的典型标志LMNA表达在“正常”衰老中减少。类似的一组 在“正常”衰老和核纤层蛋白病中观察到核缺陷。LMNA还调节几种表观遗传 衰老的调节剂，包括sirtuins和组蛋白脱乙酰酶。此外，LMNA对于基因组学是必不可少的。 不稳定性和双链DNA断裂（DSB）的诱导和修复以及机械完整性 的核膜。这些机制也是“正常”衰老的核心机制。 我们已经证明，细胞溶质DNA（CyDNA）传感蛋白CGAS/STING 1是诱导的，它们的表达水平也是诱导的。 下游效应物TBK 1、IRF 3和NF κ B被激活，衰老相关的分泌性 表型（SASP）在人心脏和核纤层蛋白病小鼠模型中表达。我们也有 鉴定和定义了人心肌细胞（CM）中的LMNA相关结构域（LAD），并显示 LAD在核纤层蛋白病中发生移位并调节CpG甲基化和基因表达。而且我们 与野生型（WT）CM相比，在LMNA缺陷型CM的nDNA中鉴定了711个DSB（q<0.05）， 末端测序（END-Seq）。DSB对蛋白质编码基因表现出优势，这与 LMNA在定义TADs和TOP 2B处理的边界中的作用。此外，我们有 显示编码CGAS Mb 21 l1基因的缺失减弱了心脏病小鼠模型中的表型 核纤层蛋白病因此，我们的逻辑是，研究核纤层蛋白病中的过早衰老将提供以下方面的见解： 与“正常”衰老共有的机制。LMNA突变的大效应量将提供 一个更好的解决方案，在辨别老年人的精神错乱的标志比“正常”老化，其中许多 决定因素，每一个都有一个小的效应量，随机相互作用，诱导衰老。因此，我们建议确定 并描述了在心肌细胞、心脏成纤维细胞（CF）和内皮细胞（EC）中的全基因组DSB， 核纤层蛋白病和老年野生型小鼠通过END-Seq，前者因为涉及多种细胞类型， 核纤层蛋白病和后者，以评估核纤层蛋白病中的发现对“正常”衰老的延伸。同样地， 我们建议通过以下方法鉴定和表征层粘连蛋白病中CM、CF和EC中CyDNA的来源： CGAS ChIP-Seq.此外，我们建议确定STING 1基因阻断对选择的 核纤层蛋白病中的衰老和心脏表型的标志。这些发现有望为以下方面提供见解： 核纤层蛋白病中过早CV老化的分子基础，可能是“正常”老化的标志。

Premature aging syndromes in laminopathies caused by mutations in the LMNA gene, encoding nuclear envelope protein lamin A/C (LMNA), are the prototypic examples of genomic instability, which is a hallmark of “normal” aging. Cardiovascular involvement is the cardinal phenotype and the major cause of mortality and morbidity. The pathogenesis of laminopathies and “normal” aging share several common mechanisms. LMNA regulates mitochondrial function, telomere length, nutrient sensing, stem cell regeneration, and autophagy, which are the classic hallmarks of “normal aging”. LMNA expression is reduced in “normal” aging. A similar set of nuclear defects are observed in “normal” aging and laminopathies. LMNA also regulates several epigenetic regulators of aging, including sirtuins and histone deacetylases. Furthermore, LMNA is essential for genomic instability and induction and repair of the double-stranded DNA breaks (DSBs) as well as the mechanical integrity of the nuclear membrane. These mechanisms are also the core mechanisms of “normal” aging. We have shown that the cytosolic DNA (CyDNA)-sensing proteins CGAS/STING1 are induced and their downstream effectors TBK1, IRF3, and NFKB are activated, and the senescence-associated secretory phenotype (SASP) is expressed in the human hearts and mouse models of laminopathies. We also have identified and defined the LMNA-associated domains (LADs) in human cardiac myocytes (CMs) and have shown that LADs are shifted in laminopathies and regulate CpG methylation and gene expression. Moreover, we have identified 711 DSBs (q<0.05) in the nDNA in the LMNA-deficient as compared to the wild-type (WT) CMs by END-Sequencing (END-Seq). DSBs show a preponderance toward the protein-coding genes, which is consistent with the role of the LMNA in defining the boundaries of TADs and TOP2B processing. Furthermore, we have shown that deletion of the Mb21l1 gene, encoding CGAS, attenuates the phenotype in a mouse model of cardiac laminopathies. Therefore, we logic that studying premature aging in laminopathies would provide insights into the mechanisms that are shared with “normal” aging. The large effect sizes of the LMNA mutations would provide a better resolution in discerning the deranged hallmarks of aging than the “normal” aging, whereby numerous determinants, each with a small effect size, interact stochastically to induce aging. Thus, we propose to identify and characterize the genome-wide DSBs in CMs, cardiac fibroblasts (CFs), and endothelial cells (ECs) in laminopathies and the old WT mice by END-Seq, the former because of the involvement of multiple cell types in laminopathies and the latter to assess the extension of the findings in laminopathies to “normal” aging. Likewise, we propose to identify and characterize the sources of the CyDNA in CMs, CFs, and ECs in laminopathies by CGAS ChIP-Seq. Moreover, we propose to determine the effects of genetic blockade of the STING1 on selected hallmarks of aging and cardiac phenotype in laminopathies. The findings are expected to provide insights into the molecular basis of premature CV aging in laminopathies and likely the hallmarks of “normal” aging.