胚胎干细胞向心肌细胞分化过程中的表观遗传调控

干细胞向心肌细胞分化是一个复杂、动态的过程.在这个过程中,相关基因的激活和关闭都受到严格的调控,并随着分化的不同阶段呈现规则有序的表达规律.表观遗传在调节基因激活和关闭过程中起着非常重要的作用,其中DNA的甲基化、组蛋白的表观遗传修饰、长链非编码RNA以及microRNA是胚胎干细胞向心肌细胞分化过程中表观遗传调控的关键作用方式.因此,对心肌细胞分化过程中表观遗传调控的探索将有助于了解心脏发育的生理过程以及相关心脏疾病的发病机制.     

表观遗传分子机制及其在肿瘤发生中的作用

表观遗传指不改变DNA序列的基因表达改变,是多细胞真核生物的重要生物学现象.在个体发生过程中,干细胞一旦分化为某种分化细胞,该分化细胞的特征就会维持.肿瘤发生中基因组相同的细胞一旦成为肿瘤细胞,就会维持肿瘤的特征,一旦成为非肿瘤细胞多数也会维持非肿瘤特性.表观遗传关系到细胞分化、分化状态维持、肿瘤发生、衰老等过程.DNA甲基化、组蛋白乙酰化、小RNA与表观遗传的分子机制有关.DNA的CpG甲基化影响基因表达,甲基化状态可以传递给子链DNA,小RNA通过改变DNA甲基化参与表观遗传;组蛋白乙酰化改变染色质构象影响基因表达.基因组的广泛低甲基化和抑癌基因高甲基化在肿瘤细胞中普遍存在,改变表观遗传的药物已试用于肿瘤治疗.     

基因组医学、染色体组和人类疾病基因(4)

表观遗传信息、表现遗传调控和疾病 组织功能的分化需要一些特定基因表达,DNA甲基化对特定类型细胞的表达谱设定和维持起关键作用.这种表观遗传信息(Epigenetic information)和基因表达的联系,属于表观遗传调控(Epigenetie Contr01)的范畴,说明了表观遗传调控在决定基因活性中的作用.染色体修饰与siRNA有关.DNA甲基化作用和相关修饰作用会导致致病基因表达的变化,而表观遗传变化(EpigeneticChangec)常成为儿童疾病和癌症的重要原因,异常DNA甲基化与大部分癌症有一定关系.基因表达图谱的筛选有助于揭示表观遗传的缺陷,并为诊断和治疗药物的研究提供有关信息.     

基于表观遗传学的肿瘤化学预防

DNA甲基化是表观遗传学的重要部分,同组蛋白修饰相互作用,通过改变染色质结构,调控基因表达.在哺乳类细胞或人体细胞中,DNA甲基化与细胞的增殖、衰老、癌变等生命现象有着重大关系.以DNA甲基化作为切入点,总结近年来关于饮食化合物对表观遗传学调控的新进展,并阐述抑制DNA甲基化或组蛋白去乙酰化的作用来发挥其对肿瘤的化学预防作用.     

肥大心肌钠钙交换体的调控机制

心肌肥大是心脏对几乎所有引起心脏病变因素的一种适应性反应,虽然心肌肥大是心脏维持正常心输出量的一种有效代偿机制,但是持续的心肌肥大会导致失代偿而发生扩张性心肌病、心衰和猝死.是心血管病患者死亡的重要原因之一.     

Akta和FoxO1在超负荷性心肌肥大时大鼠心肌的表达

目的 通过检测Akt和FoxO1基因在大鼠超负荷性心肌肥大过程中的表达,探讨心肌肥大时的细胞周期调控机制.方法 采用升主动脉缩窄的方法制作大鼠超负荷心肌肥大动物模型,通过三维彩色超声技术评价心肌肥大程度,采用RT-PCR技术检测心肌组织Akt和FoxO1的mRNA表达,用Western blots方法检测Akt磷酸化水平.结果 与假手术组相比,模型组的左室后壁厚度(LVPW)、室间隔厚度(IVS)增加(P<0.01),左室舒张末内径(LVDD)减小(P<0.01).模型组心肌组织中FoxO1的mRNA表达下调(P<0.01).Akt的基因表达没有明显变化但蛋白的磷酸化水平显著增加(P<0.01).结论 大鼠超负荷性心肌肥大时Akt激活,同时FoxO1的表达下调.     

DNA去甲基化与肿瘤治疗的研究进展

近年来大量的研究结果显示,肿瘤的发生不但存在遗传学上的改变,而且存在表观遗传学的改变[1].遗传学改变是指基于基因序列改变而导致基因表达水平的变化,如基因突变、杂合性缺失、微卫星不稳定性等.表观遗传学是非基因序列改变所导致的基因水平的变化,如组蛋白修饰、染色质重塑、DNA甲基化等染色质结构上的变异.其中DNA甲基化异常已成为DNA突变、缺失以外导致抑癌基因失活的第三大机制,主要表现为肿瘤细胞中普遍性低甲基化和CpG岛区域性高甲基化.研究提示肿瘤抑癌基因启动子区域性高甲基化是肿瘤抑癌基因失活的重要途径,而抑癌基因的去甲基化已成为近年来研究和开发抗癌药物的新靶点.     

肿瘤低氧微环境对DNA及组蛋白甲基化的影响

肿瘤细胞的表观遗传修饰受低氧条件的影响,DNA甲基化和组蛋白甲基化是表观遗传调控肿瘤的两种方式。低氧对DNA甲基化的影响可能通过DNA甲基化供体水平的变化、DNA甲基转移酶的活性的改变以及DNA去甲基化过程来实现。组蛋白去甲基化酶在组蛋白甲基化过程中发挥了重要作用,低氧微环境下组蛋白去甲基化酶表达的改变是影响组蛋白甲基化过程的重要原因。深入研究低氧对表观遗传调控肿瘤的影响的分子机制,为临床治疗肿瘤提供帮助。     

短链酰基辅酶A脱氢酶在大鼠生理性和病理性心肌肥大中的作用

 目的：研究短链酰基辅酶A脱氢酶(short-chain acyl-CoA dehydrogenase, SCAD)在大鼠生理性和病理性心肌肥大中的变化,探讨其与心肌肥大之间的关系。方法：以自发性高血压大鼠作为病理性心肌肥大模型,游泳运动训练性大鼠作为生理性心肌肥大模型。检测大鼠的血压、左室重量指数、血清和心肌游离脂肪酸含量、SCAD mRNA、蛋白表达及其酶活性的变化,采用超声心动图观察心脏的结构及功能。结果：与对照组比较,运动组大鼠出现了明显的离心性肥大,心肌收缩功能增强;而高血压组大鼠呈现出明显的向心性肥大,心肌收缩功能减退。与对照组比较,运动组和高血压组大鼠的左室重量指数均明显增高,但两组间比较无显著差异,二者发生了相同程度的心肌肥大。与对照组比较,运动组大鼠左心室SCAD mRNA和蛋白表达均明显上调,酶活性增高,血清和心肌游离脂肪酸含量明显减少;而自发性高血压大鼠左心室SCAD mRNA和蛋白表达均明显下调,酶活性下降,血清和心肌游离脂肪酸含量明显增多。结论：SCAD在生理性和病理性心肌肥大中呈现出不一致的变化趋势,可能作为区别2种不同心肌肥大的分子标志物以及病理性心肌肥大的潜在治疗靶点。     

表观遗传学对骨髓间充质干细胞调控作用的研究进展

表观遗传学对骨髓间充质干细胞的调控作用已经成为医学领域的研究热点。本文主要综述了DNA甲基化、组蛋白乙酰化、小干扰RNA(siRNA)诱导基因沉默以及微小RNA(miRNA)四个方面对骨髓间充质干细胞调控作用的进展。结果表明,表观遗传学对骨髓间充质干细胞的调控作用在骨修复、神经修复和心肌修复等方面的应用具有重要的意义。     

Cardiotrophin-1 and the role of gp130-dependent signaling pathways in cardiac growth and development

 The reactivation of an embryonic pattern of gene expression is a central feature common to virtually all forms of cardiac hypertrophy. Unraveling the regulatory mechanisms, growth factors and cytokines controlling gene expression and cell fate during cardiac development may therefore have implications for our understanding of cardiac hypertrophy in the adult. Along this line, a cDNA expression library was established from an embryonic stem cell-based in vitro model of cardiogenesis, and screened for clones that would induce an increase in cell size in cultured cardiomyocytes. This experimental strategy resulted in the isolation of a novel cytokine, cardiotrophin-1 (CT-1), that activates several features of cardiomyocyte hypertrophy in vitro, including sarcomeric organization and embryonic gene expression. CT-1 displays structural similarities to the interleukin (IL)-6 related cytokines. Furthermore, receptor binding studies and functional studies reveal that CT-1 shares the signal transducing receptor components gp130 and LIFR with the previously identified members of the IL-6 cytokine family. CT-1 rapidly activates gp130 and LIFR tyrosine phosphorylation in cultured cardiac myocytes. The growth promoting effects of CT-1 therefore indicate that signaling pathways emanating from gp130 and LIFR are coupled to cardiomyocyte hypertrophy. In support of this notion, the simultaneous overexpression of IL-6 and the IL-6 receptor in transgenic mice has been shown to result in a constitutive tyrosine phosphorylation of gp130 in the myocardium and cardiac hypertrophy. The striking phenotype of gp130 null-mutant mice, generated by homologous recombination, implies gp130 in cardiac development as well: mutant mice exhibit severe ventricular hypoplasia, suggesting a role for gp130-dependent signaling pathways in the expansion of the compact layer of the ventricular myocardium. CT-1 is expressed at high levels in the myocardium during the course of cardiogenesis, and promotes the proliferation and survival of embryonic cardiomyocytes. CT-1 may therefore represent a candidate cytokine to activate gp130 during cardiac development. In summary, cytokines signaling through gp130 are emerging as potent regulators of embryonic heart development and adult cardiac hypertrophy. Received: 1 January 1997 / Accepted: 14 March 1997     

小鼠心肌肥厚枢纽基因的筛选与鉴定

目的 通过生物信息学分析结合生物学实验,筛选和鉴定与心肌肥厚密切相关的枢纽基因。 方法 从基因表达数据库(GEO)下载小鼠心肌肥厚相关芯片数据,利用GEO2R在线工具筛选差异表达基因;利用DAVID 6.7、String 11.0和Cytoscape 3.7.0软件对差异基因进行分析;昆明小鼠随机分为生理盐水组（n=6）和血管紧张素Ⅱ（Ang Ⅱ）组（n=6）,建立心肌肥厚模型,通过Real-time PCR方法检测枢纽基因在Ang Ⅱ诱导的昆明小鼠心肌肥厚模型中的表达。 结果 筛选出共有差异表达基因202个,枢纽基因12个;Real-time PCR结果显示核心蛋白聚糖（Dcn）、HADHA和热休克蛋白(HSP)90αA1在AngⅡ组中表达明显下调。 结论 筛选出的枢纽基因可以通过细胞外基质和转化生长因子β(TGF-β)影响昆明小鼠心肌肥厚的发生发展。     

Cardiac hypertrophy: a risk factor for QT-prolongation and cardiac sudden death

Cardiac hypertrophy was viewed as a compensatory response to hemodynamic stress. However, cumulative evidence obtained from studies using more advanced technologies in human patients and animal models suggests that cardiac hypertrophy is a maladaptive process of the heart in response to intrinsic and extrinsic stimuli. Although hypertrophy can normalize wall tension, it is a risk factor for QT-prolongation and cardiac sudden death. Studies using molecular biology techniques such as transgenic and knockout mice have revealed many important molecules that are involved in the development of heart hypertrophy and have demonstrated signaling pathways leading to the pathogenesis. With the same approach, the consequence of heart hypertrophy has been examined. The significance of hypertrophy in the development of overt heart failure has been demonstrated and several critical molecular pathways involved in the process were revealed. A comprehensive understanding of the threats of heart hypertrophy to patients has helped to develop novel treatment strategies. The recognition of hypertrophy as a major risk factor for QT-prolongation and cardiac sudden death is an important advance in cardiac medicine. Cellular and molecular mechanisms of this risk aspect are currently under extensively exploring. These studies would lead to more comprehensive approaches to prevention of potential life threatening arrhythmia and cardiac sudden death. The adaptation of new approaches such as functional genomics and proteomics will further advance our knowledge of heart hypertrophy.     

Cardiac hypertrophy: mechanisms and therapeutic opportunities

Cardiac hypertrophy and heart failure are major causes of morbidity and mortality in Western societies. Many factors have been implicated in cardiac remodeling, including alterations in gene expression in myocytes, cardiomyocytes apoptosis, cytokines and growth factors that influence cardiac dynamics, and deficits in energy metabolism as well as alterations in cardiac extracellular matrix composition. Many therapeutic means have been shown to prevent or reverse cardiac hypertrophy. New concepts for characterizing the pathophysiology of cardiac hypertrophy have been drawn from various aspects, including medical therapy and gene therapy, or use of stem cells for tissue regeneration. In this review, we focus on various types of cardiac hypertrophy, defining the causes of hypertrophy, describing available animal models of hypertrophy, discussing the mechanisms for development of hypertrophy and its transition to heart failure, and presenting the potential use of novel promising therapeutic strategies derived from new advances in basic scientific research.     

Catecholamine-induced cardiac hypertrophy: significance of proto-oncogene expression

The effect of β- and α-adrenergic stimulation on cardiovascular function and development of cardiac hypertrophy was studied in rats by measuring the heart weight/body weight and cardiac RNA/DNA ratios. β-Receptor stimulation with isoproterenol over 3 days induced an increase in the biosynthesis of cardiac adenine nucleotides, myocardial protein synthesis, and the heart weight/body weight ratio. The isoproterenol-induced metabolic effects were prevented by simultaneous β-adrenergic blockade with propranolol. α-Adrenergic stimulation with norfenephrine for 3 days induced an increase in heart rate, total peripheral resistance, the myocardial RNA/DNA, and left ventricular weight/body weight ratio. The calcium antagonist verapamil prevented the hemodynamic changes but did not influence the development of cardiac hypertrophy. The α-adrenergic blocker prazosin reversed the norfenephrine-induced functional changes and prevented cardiac hypertrophy. Norepinephrine was infused into isolated perfused working rat hearts to elucidate some molecular biological changes that precede the development of cardiac hypertrophy. It increased transiently and sequentially the mRNA of c-fos and c-myc. This enhancement occurred at about the same time as that induced by elevation of pre- and afterload but was more pronounced. These findings were compared with those obtained in other studies assessing the effects of catecholamines on proto-oncogene expression. Combination of norepinephrine with pre- and afterload elevation induced the c-fos mRNA signal to appear earlier, to be more pronounced, and to persist for a longer period of time. Similar results were obtained in regard to the c-myc mRNA. These findings indicate that the combination of two hypertrophy-inducing stimuli which may cause a higher degree of cardiac hypertrophy in vivo induce an earlier, more pronounced, and longer lasting expression of the proto-oncogenes c-fos and c-myc.     

Mitochondrial adaptations during myocardial hypertrophy induced by abdominal aortic constriction

IntroductionMyocardial hypertrophy is an adaptive response of the heart to work overload. Pathological cardiac hypertrophy is usually associated with the ultimate development of cardiac dysfunction and heart failure. The mitochondria have an important function in the development of cardiac hypertrophy. However, mitochondrial adaptations to hypertrophic stimulus remain ambiguous.MethodsA rat model of myocardial hypertrophy was established using abdominal aortic constriction. The expression of mitochondrial complexes was evaluated through electrophoresis using blue native and blue native/sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme activity of mitochondrial complexes was detected through in-gel activity.ResultsMitochondrial function and biogenesis decreased in hypertrophied myocardium. The content and activity of mitochondrial Complex V dimers and Complex I significantly decreased during hypertrophy, as well as those of the α, β, B, and D chains of the Complex V dimers. However, the content and activity of mitochondrial Complex V oligomers and Complexes II, III, and IV did not change.ConclusionsThe decreased content and activity of Complex V dimers and Complex I caused the decline in mitochondrial function and biogenesis during cardiac hypertrophy.     

丝裂原活化蛋白激酶信号途径在心肌肥厚中的作用进展

Myocardial hypertrophy is an independent risk factor for cardiac events. Mitogen-activated protein kinases(MAPK), including extracellular signal-regulated kinases, C-jun N-terminal kinases and P38-MAPK, are the common intracellular pathway of transducing hypertrophic signs. All three MAPK subfamilies play an important role in development of myocardial hypertrophy.