Cytosolic DNA is the Link Between Genomic Instability and Cardiovascular Aging

由编码核的LMNA基因突变引起的椎板病中的早衰综合征 包膜蛋白层蛋白A/C(LMNA)是基因组不稳定的典型例子，这是 “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。椎板病和“正常”衰老的发病机制有几个共同的机制。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”的典型特征。在“正常”衰老过程中，LMNA的表达减少。一套类似的 在“正常”衰老和椎板病变中可观察到核缺陷。LMNA还调节几个表观遗传学 衰老调节因子，包括sirtuins和组蛋白脱乙酰酶。此外，LMNA对于基因组来说是必不可少的 双链DNA断裂(DSB)的不稳定性、诱导和修复以及机械完整性 核膜。这些机制也是“正常”衰老的核心机制。 我们已经证明，胞浆DNA(Cydna)敏感蛋白cGAS/STING1被诱导，并且它们的 下游效应器TBK1、IRF3和NFKB被激活，衰老相关的分泌 表型(SASP)在人类心脏和小鼠椎板病变模型中表达。我们还有 鉴定和定义了人心肌细胞(CMS)中的LMNA相关结构域(LAD)，并显示了 LAD在椎板病中发生移位，并调节CpG甲基化和基因表达。此外，我们有 与野生型(WT)不育系相比，LMNA缺陷型CMS的nDNA中存在711个DSB(Q&lt；0.05) 末端测序(END-SEQ)。DSB显示出对蛋白质编码基因的优势，这是一致的 LMNA在界定TADS和TOP2B加工边界方面的作用。此外，我们还拥有 研究表明，编码cGAS的Mb21l1基因的缺失可以减弱心脏病小鼠的表型。 椎板病症。因此，我们的逻辑是，研究椎板病中的过早衰老将为 与“正常”衰老相同的机制。LMNA突变的大效应规模将提供 一个更好的解决办法，以辨别错乱的标志老化，而不是“正常”的老化，其中许多 决定因素，每个都有一个小的影响大小，随机地相互作用，以诱导衰老。因此，我们建议确定 并对CMS、心脏成纤维细胞(CFs)和血管内皮细胞(ECs)的全基因组DSB进行了表征 椎板病和老年WT小鼠受End-Seq影响，前者因参与多种细胞类型参与 后者用于评估椎板病的研究结果是否延伸到“正常”衰老。同样， 我们建议通过以下方法识别和表征椎板病中CMS、CFS和ECs中Cydna的来源 CGAS芯片-序列此外，我们建议确定STING1基因阻断对所选择的 椎板病的衰老和心脏表型的特征。这些发现有望为人们提供关于 椎板病椎管过早老化的分子基础，可能是“正常”衰老的标志。

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.