肿瘤细胞中的表遗传编码紊乱

不改变基因的DNA编码，通过改变DNA双链与组蛋白间紧密度来决定基因是否转录表达，这称为表遗传编码机制。表遗传编码的生理作用是通过组蛋白修饰和DNA甲基化，调控细胞在适当的时间、空间位置表达适当的基因，从而控制细胞的增殖状况和分化方向。在细胞发育过程中，细胞内DNA甲基化水平增龄性增高，基因转录活性逐渐降低，使细胞从幼稚增殖进入成熟分化。肿瘤细胞中出现表遗传编码紊乱，致细胞增殖失控，不能进入分化成熟阶段。基因启动子出现甲基化重排，阻碍转录因子与启动子结合，导致基因转录丧失正常调控，合成成熟功能蛋白受阻。利用表遗传机制（如RNA干涉）可成为肿瘤治疗的新方法。     

microRNA在肿瘤表观遗传学中的研究进展

microRNA(miRNA)是一类长约22nt的非编码小RNA,转录后水平调节基因的表达,在个体发育、细胞的增殖、凋亡、分化中发挥重要的作用。近年来研究发现,miRNA的表达异常与肿瘤的发生关系密切。新近研究发现,属于广义表观遗传范畴的miRNA,其自身的表达不仅受到DNA甲基化等表观遗传的调控,而且两者可能存在相互作用,参与肿瘤的发生、发展。microRNA在肿瘤表观遗传学的研究将为肿瘤的诊断、治疗和预防开辟了新的思路和方向。     

表观遗传修饰改变与线粒体疾病

线粒体功能失调是导致线粒体疾病的主要原因,因此了解线粒体功能的调节机制非常重要。近期的研究表明,表观遗传修饰的对象不仅包括细胞核DNA还包括线粒体DNA,表观遗传修饰的变化对线粒体功能的调节机制有重要影响。文章主要概括了线粒体DNA甲基化、细胞核基因组的DNA甲基化和微RNA ( microRNA, miRNA)调控等表观遗传修饰与线粒体疾病发生的关联研究进展。     

乳腺癌发生模型MCF10 抑癌基因NOEY2启动子区甲基化及mRNA表达

DNA甲基化是常见的表观遗传学变化。越来越多的证据表明,抑癌基因启动子区CpG岛甲基化可使其转录沉默,从而解除其抑癌作用,导致肿瘤的发生和发展。NOEY2是近年来发现的抑癌基因,表达于正常乳腺导管上皮细胞和卵巢生发上皮细胞,但在乳腺癌和卵巢癌细胞中表达显著减少或不表达。在本实验中检测乳腺癌发生模型MCF10中不同阶段的细胞系NOEY2基因启动子区CpG岛Ⅰ甲基化状态,并与mRNA表达水平进行比较,以研究乳腺癌的发生机制和早期诊断。     

结合消减杂交筛选肝癌细胞系中差异甲基化位点

为探索有效分离两样品间差异甲基化片段的方法,以DNMT1(DNA methyltransferase 1,DNMT1)表达抑制前后的肝癌细胞系7721-sMT1和7721-pMT1为研究对象,结合消减杂交和磁珠分离的方法,在两细胞系全基因组DNA范围内进行扫描差异性甲基化片段;将这些片段进行生物信息学分析,发现所获38条差异甲基化片段分布于不同的染色体上,但集中于重复序列、基因的启动子区,此特点符合DNA甲基化位点分布规律.实验结果证明消减杂交结合磁珠分离的方法,能筛选出两样品间的差异甲基化片段,该方法的建立为筛选肿瘤细胞中特异性差异甲基化片段作为肿瘤诊断的标志物提供了可能性.     

心肌肥大表观遗传调控的研究进展

心肌肥大是各种严重心血管疾病的独立危险因素.表观遗传学涉及的机制,如DNA甲基化、组蛋白修饰、RNA甲基化等参与心肌肥大的发生发展.因此,了解表观遗传对心肌肥大的作用有助于为心肌肥大的预防和早期治疗提供有效方案和科学依据.     

长链非编码RNA在表观遗传学中的研究进展

表观遗传学是基于遗传学基础之上发展起来的生物学分支,研究发现人类很多疾病与表观遗传调控相关,其主要机制包括:染色质重塑、组蛋白修饰,基因组印记及非编码RNA(ncRNA)调控.而长链非编码RNA(lncRNA)是非编码RNA中的一类,不仅可以通过与靶基因直接结合调控靶基因的转录,还能募集调控因子,参与基因的沉默,在表观遗传调控中起着重要作用.     

表观遗传调控在阻塞性睡眠呼吸暂停综合征中的作用研究进展

慢性间歇性低氧在阻塞性睡眠呼吸暂停综合征(OSA)的各种不良反应的发生机制中发挥重要作用.表观遗传过程通过影响慢性间歇性低氧条件下的适应潜能和表型变异,参与OSA及并发症的发生和发展.所以,了解表观遗传调控对OSA的作用有助于为OSA的临床表型和靶向治疗提供新的思路.     

CpG岛甲基化检测技术比较

Cp G岛过甲基化所致基因去表达是主要的表遗传学 (epigenetics)改变之一 ,是一种在突变、缺失、异位等序列变异之外的非序列性变化。这种表遗传异常不仅与复制延迟、染色体压缩、转录抑制密切相关 ,而且与疾病的易感性、发生发展、预后和转归均有密切关系。很多肿瘤发生都涉及到基因组甲基化的改变 ,包括抑癌基因的高甲基化和原癌基因的去甲基化。因此 ,检测甲基化的相关技术也随着甲基化研究的深入而不断推陈出新。简便高效快捷检测方法的出现极大地提高了工作效率 ,关键性 Cp G位点概念的建立增加了实验结果的实用性     

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.     

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Breast Cancer Metastasis Suppressor 1 (BRMS1) suppresses metastasis of human breast cancer, ovarian cancer and melanoma in athymic mice. Studies have also shown that BRMS1 is significantly downregulated in some breast tumors, especially in metastatic disease. However, the mechanisms which regulate BRMS1 expression are currently unknown. Upon examination of the BRMS1 promoter region by methylation specific PCR (MSP) analysis, we discovered a CpG island (−3477 to −2214), which was found to be hypermethylated across breast cancer cell lines. A panel of 20 patient samples analyzed showed that 45% of the primary tumors and 60% of the matched lymph node metastases, displayed hypermethylation of BRMS1 promoter. Furthermore, we found a direct correlation between the methylation status of the BRMS1 promoter in the DNA isolated from tissues, with the loss of BRMS1 expression assessed by immunohistochemistry. There are several studies investigating the mechanism by which BRMS1 suppresses metastasis; however thus far there is no study that reports the cause(s) of loss of BRMS1 expression in aggressive breast cancer. Here we report for the first time that BRMS1 is a novel target of epigenetic silencing; and aberrant methylation in the BRMS1 promoter may serve as a cause of loss of its expression. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

肿瘤化疗药物中的表遗传药理学研究

表遗传事件与肿瘤的发生、发展密不可分。近年来,对肿瘤化疗药物的研究已不再局限于原有单独使用经典的化疗药物,而发展到从表遗传药理(epigenetic pharmacology)角度进行单独或联合用药的深入研究。现就与表遗传药理相关的甲基化抑制剂、去乙酰化酶抑制剂、两者联合使用及其与经典化疗药物联合应用的研究进展进行综述。     

Epigenetics and Epigenetic Alterations in Pancreatic Cancer

Pancreatic cancer remains a major therapeutic challenge. In 2008, there will be approximately 37,680 new cases and 34,290 deaths attributable to pancreatic cancer in the United States (U.S.), making it the fourth leading cause of cancer-related death. Recent comprehensive pancreatic cancer genome project found that pancreatic adenocarcinomas harbored 63 intragenic mutations or amplifications/homozygous deletions and these alterations clustered in 12 signaling pathways. In addition to widespread genetic alterations, it is now apparent that epigenetic mechanisms are also central to the evolution and progression of human cancers. Since epigenetic silencing processes are mitotically heritable, they can drive neoplastic progression and undergo the same selective pressure as genetic alterations. This review will describe recent developments in cancer epigenetics and their importance in our understanding of pancreatic adenocarcinomas.     

Epigenetic characteristics in inflammatory candidate genes in aggressive periodontitis

BackgroundPeriodontitis is a chronic inflammatory disease triggered by the host immune response. Epigenetic modifications also affect the immune response. We assessed CpG methylation in 22 inflammatory candidate genes (ATF2, CCL25, CXCL14, CXCL3, CXCL5, CXCL6, FADD, GATA3, IL10RA, IL12A, IL12B, IL13, IL13RA1, IL15, IL17C, IL17RA, IL4R, IL6R, IL6ST, IL7, INHA, and TYK2) with respect to the occurrence of aggressive periodontitis (AgP).Patients and methodsIn this study 15 AgP patients (53.3% males, 41.4 ± 10.5 years) and 10 controls (40.0% males, 36.9 ± 17.5 years) were included. The methylation patterns of gingival biopsies were quantified using EpiTect® Methyl Signature PCR Array Human Inflammatory Response.ResultsIn gingival biopsies taken from patients with AgP, CpG methylation of CCL25 (1.73% vs. 2.59%, p = 0.015) and IL17C (6.89% vs. 19.27%, p = 0.002) was significantly reduced as compared with periodontally healthy tissues.DiscussionWe showed for the first time a differential methylation pattern for CCL25 and IL17C in periodontitis. CCL25 plays an important role in T-cell development, whereas IL17C regulates innate epithelial immune responses. The decrease in CpG methylation is presumably accompanied by an increase in gene expression. This could lead to a greater availability of CCL25 and interleukin 17C and support periodontal loss of attachment.     

先天性小耳畸形EYA1基因筛查及其启动子区域甲基化研究

目的EYA1基因编码的蛋白质对鳃弓和耳部的正常发育至关重要,本研究选择EYA1基因作为候选基因对先天性小耳畸形患者进行突变检测,并对其启动子区域CpG岛甲基化状态进行研究。方法研究对象选择先天性小耳畸形患者100例,其中包括13个家系（先证者和家系其他患病成员共31人）,散发患者69人。通过PCR和直接测序对EYA1基因进行突变检测。并应用基质辅助激光解吸附电离飞行时间质谱分析技术检测了病例组和正常对照的EYA1基因启动子区域CpG岛甲基化情况。结果检测到4种EYA1核苷酸改变,分别为258G〉A（Q86Q）、813A〉G（T271T）、1278C〉T（G426G）和1755T〉C（H585H）。先天性小耳畸形患者EYA1基因的CpG_Unit3和CpG_Unit5甲基化程度分别为0.09258±0.033846和0.0922±0.02379,与正常对照相比明显降低,其差异具有统计学意义。结论本实验未能在先天性小耳畸形伴耳前凹、耳前赘患者中检测到EYA1基因的突变,考虑EYA1基因突变可能不是中国人群先天小耳畸形的主要致病原因。先天性小耳畸形存在EYA1基因低甲基化情况,可能与该病的发生发展相关。     

The CpG island in intron 22 of the factor VIII gene is predominantly methylated on the X chromosome of human males

The inactivation of one of the two X chromosomes in females is a random process associated with methylation principally in CpG islands. The methylation status of a CpG island in intron 22 of the human factor VIII (FVIII) gene was investigated using a novel practical approach. Genomic DNA from men and women was digested with various methylation-sensitive (MS) restriction enzymes, the recognition sequences of which occurred at least once in the FVIII CpG island. Long distance-polymerase chain reaction (LD-PCR) was then used to amplify the island. Successful amplification indicated that the island was methylated and the absence of a PCR product indicated that at least one restriction site was unmethylated. To analyze the relative methylation status of the extragenic and intragenic copies of the island, we used Southern blot with MS restriction enzymes. The MS LD-PCR patterns obtained from male and female DNA samples indicated that at least some copies of the intragenic CG island were fully methylated at all sites investigated. Additionally, the island showed consistent differences among individuals. Southern blot studies using female DNA showed partial resistance to MS digestion for the intragenic and extragenic CpG island homologs. Our observations indicate that this CpG island is predominantly methylated on the X chromosome of males and suggest that its methylation pattern does not correlate with X inactivation of females. This prevents the use of this island coupled with DNA polymorphisms for investigation of X-chromosome inactivation. Received: December 4, 2001 / Accepted: February 12, 2002     

焦磷酸测序技术及其在DNA甲基化研究中的应用

焦磷酸测序技术（pyrosequencing）是近年来刚兴起的一种新型的酶联级联测序技术。该技术是一种高效的DNA分析技术,具有分析结果快速准确、灵敏度高、自动化的优势。DNA甲基化是表遗传学的一个重要组成部分,焦磷酸测序技术对于准确高效地进行甲基化研究提供了很好的技术平台。此文主要就焦磷酸测序技术的原理及该技术在DNA甲基化研究中的应用进行综述。     

FMR1基因启动子区CpG岛甲基化与智力低下的相关性研究

目的探讨智力低下基因1启动子区CpG岛甲基化与智力低下的相关性。方法应用甲基化PCR方法对79例智力低下儿童及79例正常儿童的外周血中FMRI基因启动子区CpG岛甲基化状态及（CGG）n进行检测。结果2例智力低下儿童的FMRI启动子区CpG岛发生甲基化,正常儿童基因CpG岛无甲基化;两组（CGG）n重复数分别为33—48、27—43,两者之间比较（P〉0．05）无统计学意义。结论FMRl基因启动子区CpG岛甲基化可能引起智力低下。     

Pattern of expression of genes linked to epigenetic silencing in human breast cancer

Epigenetic mechanisms such as DNA methylation are now recognized to play an important role in neoplasia. The aim of this study is to relate the pattern of expression of multiple cancer genes known to undergo epigenetic inactivation by promoter hypermethylation in breast cancer with histologic and outcome data. We used immunohistochemistry to study expression of the tumor suppressor gene p16, estrogen receptor (ER) alpha, ERbeta, progesterone receptor (PR), and the DNA repair gene MGMT (O6 -methylguanine-DNA methyltransferase) in a panel of 200 breast cancers. Methylation-specific polymerase chain reaction was used to confirm MGMT promoter methylation. Loss of expression of MGMT, ERalpha, ERbeta, PR, and p16 was observed in 19%, 24%, 13%, 40%, and 50% of cases, respectively. A significant correlation was seen between grade III tumor and loss of expression of ERalpha, ERbeta, PR (all P < .0001), and MGMT (P = .04), whereas loss of expression of p16 was associated with grades I and II tumors (P < .001). Cases that expressed 3 or less of the 5 proteins studied had significantly reduced survival (P = .0016). Methylation-specific polymerase chain reaction in a subset of 20 cancers showed DNA methylation associated with the loss of MGMT expression (P < .001). In conclusion, there is silencing of several key genes in breast cancer affecting molecular pathways involved in cell immortalization, DNA repair, and hormonal regulation, and this correlates significantly with risk of cancer-specific death. This expression profile could be linked to epigenetic events, and if so, these pathways have potential as targets for therapeutic strategies based on reversal of epigenetic silencing.