Department of Anesthesiology, University of California, Los Angeles, Los Angeles, California;
Am J Physiol Heart Circ Physiol. 2013 Dec 1;305(11):H1624-38. doi: 10.1152/ajpheart.00529.2013. Epub 2013 Sep 27.
Myocyte hypertrophy antecedent to heart failure involves changes in global gene expression, although the preceding mechanisms to coordinate DNA accessibility on a genomic scale are unknown. Chromatin-associated proteins alter chromatin structure by changing their association with DNA, thereby altering the gene expression profile. Little is known about the global changes in chromatin subproteomes that accompany heart failure, and the mechanisms by which these proteins alter chromatin structure. The present study tests the fundamental hypothesis that cardiac growth and plasticity in the setting of disease recapitulates conserved developmental chromatin remodeling events. We used quantitative proteomics to identify chromatin-associated proteins extracted via detergent and to quantify changes in their abundance during disease. Our study identified 321 proteins in this subproteome, demonstrating it to have modest conservation (37%) with that revealed using strong acid. Of these proteins, 176 exhibited altered expression during cardiac hypertrophy and failure; we conducted extensive functional characterization of one of these proteins, Nucleolin. Morpholino-based knockdown of nucleolin nearly abolished protein expression but surprisingly had little impact on gross morphological development. However, hearts of fish lacking Nucleolin displayed severe developmental impairment, abnormal chamber patterning and functional deficits, ostensibly due to defects in cardiac looping and myocyte differentiation. The mechanisms underlying these defects involve perturbed bone morphogenetic protein 4 expression, decreased rRNA transcription, and a shift to more heterochromatic chromatin. This study reports the quantitative analysis of a new chromatin subproteome in the normal and diseased mouse heart. Validation studies in the complementary model system of zebrafish examine the role of Nucleolin to orchestrate genomic reprogramming events shared between development and disease.
心肌细胞肥大是心力衰竭发生的前体，涉及到整体基因表达的改变，尽管在基因组水平上协调 DNA 可及性的先前机制尚不清楚。染色质相关蛋白通过改变与 DNA 的结合来改变染色质结构，从而改变基因表达谱。关于伴随心力衰竭的染色质亚蛋白组的整体变化以及这些蛋白质改变染色质结构的机制，人们知之甚少。本研究检验了一个基本假设，即在疾病背景下，心脏的生长和可塑性再现了保守的发育性染色质重塑事件。我们使用定量蛋白质组学技术鉴定了通过去污剂提取的染色质相关蛋白，并定量了它们在疾病过程中丰度的变化。我们的研究在这个亚蛋白组中鉴定了 321 种蛋白质，表明其与使用强酸时揭示的蛋白质组具有适度的保守性（37%）。在这些蛋白质中，有 176 种在心肌肥大和衰竭期间表达发生改变；我们对其中一种蛋白质 Nucleolin 进行了广泛的功能表征。Nucleolin 的基于 morpholino 的敲低几乎完全消除了蛋白质表达，但令人惊讶的是，对大体形态发育几乎没有影响。然而，缺乏 Nucleolin 的鱼的心脏显示出严重的发育障碍、异常的腔室模式和功能缺陷，表面上是由于心脏环化和心肌细胞分化缺陷。这些缺陷的机制涉及骨形态发生蛋白 4 表达的扰动、rRNA 转录的减少以及更异染色质染色质的转变。本研究报告了正常和患病小鼠心脏中新的染色质亚蛋白组的定量分析。在斑马鱼互补模型系统中的验证研究检验了 Nucleolin 协调发育和疾病之间共享的基因组重编程事件的作用。
