卵子发育过程中组蛋白的动态变化

表观遗传修饰是指不改变DNA序列的可逆性修饰,包括DNA甲基化、RNA干涉、基因组印迹和组蛋白密码等多方面,在生物体生长发育过程中对基因表达和调控有重要作用。在卵子发育过程中,卵母细胞经历了一系列的表观遗传动态修饰,这一表观遗传成熟过程对于卵子的减数分裂及发育能力至关重要。其中组蛋白的转录后修饰及不同组蛋白的替换对异染色质的形成及卵母细胞基因组重塑过程起关键作用。现对卵子发育过程中组蛋白甲基化、乙酰化、磷酸化等共价修饰及不同组蛋白替换的研究现状做一总结。     

卵子发育过程中组蛋白的动态变化

表观遗传修饰是指不改变DNA序列的可逆性修饰,包括DNA甲基化、RNA干涉、基因组印迹和组蛋白密码等多方面,在生物体生长发育过程中对基因表达和调控有重要作用.在卵子发育过程中,卵母细胞经历了一系列的表观遗传动态修饰.这一表观遗传成熟过程对于卵子的减数分裂及发育能力至关重要.其中组蛋白的转录后修饰及不同组蛋白的替换对异染色质的形成及卵母细胞基凼组重塑过程起关键作用.现对卵子发育过程中组蛋白甲基化、乙酰化、磷酸化等共价修饰及不同组蛋白替换的研究现状做一总结.     

哺乳动物生殖细胞的发生和发育与表观遗传学的相关性

生殖细胞中的表观遗传信息是由DNA和染色质修饰决定的,这些修饰在生殖细胞的发育过程中是动态变化的。表观遗传修饰因子及其调控蛋白,包括DNA甲基转移酶、组蛋白修饰酶、B淋巴细胞成熟诱导蛋白1(BLIMP1)、钙调蛋白依赖性蛋白激酶4(Camk4)等,在生殖细胞的发生和发育过程中对其细胞基因组的重编程、下游靶基因的激活和抑制以及生殖细胞特异性事件,如生殖细胞的发育、减数分裂的调控、染色体配对以及基因组的完整性等都有重要的作用。结合近年来对哺乳动物生殖细胞发生和发育与表观遗传学相关性的研究进展予以综述。     

DNA甲基化及其影响因素

在人类基因组中,DNA甲基化是一种重要的表遗传修饰,它与多种疾病发生密切相关。DNA甲基化在基因转录过程中起着重要的作用,与组蛋白修饰、染色质构型重塑共同参与转录调控。目前研究发现,基因组中DNA甲基化的水平与DNA甲基转移酶(DNMT)、组蛋白甲基化、饮食与环境、RNA干扰和病毒感染等多种因素有关。     

常见组蛋白修饰调控滋养层细胞谱系分化的研究进展

胎盘是决定妊娠建立及维持胎儿正常生长发育的重要器官, 其介导了母胎间的复杂对话。滋养层细胞是执行胎盘功能的一类重要细胞类型, 在胎盘发育过程中, 滋养层干细胞可分化为多种滋养层细胞亚型, 从而维持胎盘的结构和功能。组蛋白修饰可通过调控染色质的结构及基因转录参与滋养层细胞谱系的建立和维持。本文系统性总结了重要组蛋白甲基化及乙酰化修饰调控滋养层干细胞分化及胎盘发育的复杂作用及机制。     

哺乳动物体细胞核移植后核重编程研究进展

通过体细胞核移植技术获得重构胚胎,在卵母细胞内多种重编程因子的作用下,供体细胞核抹去分化状态,恢复全能性,这就是核重新编程的过程。在这个过程中供体核必须被正确激活与胚胎发育密切相关的基因,同时抑制与分化有关的基因。到目前为止,通过这项技术已获得多种哺乳动物的克隆后代,但克隆成功率低且存活个体大多表型异常。核重编程的不准确性可能是克隆后代存在高死亡率和发育异常的主要原因之一。综述了重编程中DNA甲基化、组蛋白乙酰化、X染色体失活以及基因印迹等的近期研究。     

哺乳动物体细胞核移植后核重编程研究进展

通过体细胞核移植技术获得重构胚胎,在卵母细胞内多种重编程因子的作用下,供体细胞核抹去分化状态,恢复全能性,这就是核重新编程的过程.在这个过程中供体核必须被正确激活与胚胎发育密切相关的基因,同时抑制与分化有关的基因.到目前为止,通过这项技术已获得多种哺乳动物的克隆后代,但克隆成功率低且存活个体大多表型异常.核重编程的不准确性可能是克隆后代存在高死亡率和发育异常的主要原因之一.综述了重编程中DNA甲基化、组蛋白乙酰化、X染色体失活以及基因印迹等的近期研究.     

人胚肺成纤维细胞衰老过程中胰岛素样生长因子2表观遗传活化作用

目的观察体外培养人胚肺成纤维细胞复制性衰老过程中及过氧化氢诱导早衰持续阶段胰岛素样生长因子2(IGF2)表观遗传学修饰。方法荧光定量PCR检测IGF2的mRNA表达,甲基化特异PCR检测其启动子区甲基化改变,染色质免疫沉淀结合定量PCR检测组蛋白修饰,包括组蛋白H3、H4乙酰化,H3(Lys4)及H4(Lys20)甲基化修饰。结果细胞复制性衰老过程中,中年细胞组及复制性衰老细胞组IGF2的mRNA表达升高,早衰持续组升高显著;细胞衰老过程中,仅复制性衰老细胞组在启动子区-658～-456bp具有一定的甲基化水平;复制性衰老细胞组的组蛋白修饰在启动子区-856～-634bp以H4乙酰化,H3甲基化修饰为主;+9～+145bp的修饰,复制性衰老细胞组受组蛋白H3及H4甲基化联合修饰,早衰持续组以H3甲基化修饰为主。结论细胞衰老过程中,IGF2启动子区组蛋白修饰联合调控其mRNA表达,复制性衰老与早衰的调控机制存在差异。     

运动参与儿童早期发育表观遗传调控的认识进展

在儿童早期发育过程中,表观遗传的动态编程一方面与婴幼儿时期的膳食平衡密切相关,同时也与儿童的身体运动紧密相连,它们共同影响了表观遗传修饰的上游代谢平衡,因此更完整地体现了儿童发育过程中遗传与体内环境的交互作用。为此,本文介绍了运动对机体表观遗传修饰的影响以及对下游功能基因的调控作用,重点强调了运动参与DNA甲基化、染色体组蛋白修饰和miRNA调控三个不同层面的表观遗传作用机制的文献进展。本文的介绍对儿童早期发育中的运动需求,尤其是儿童早期发育阶段的亲子运动提供了更为系统的表观遗传学依据。     

DNA甲基化与microRNA相互作用的研究进展

表观遗传修饰是一种遗传外的调控机制,包括DNA甲基化(DNA methylation)、基因组印迹(genomic imprinting)、染色体修饰(chromosome modification)、组蛋白修饰(histone modification )及microRNA(miRNA)调控状态(microRNA regulation)等方式.DNA甲基化和miRNA作为重要的表观遗传学调控机制,在不同水平调控基因表达,不仅参与机体正常生长发育的调节,而且影响肿瘤发生、发展和转移的过程.     

Reprogramming mediated radio-resistance of 3D-grown cancer cells

In vitro 3D growth of tumors is a new cell culture model that more closely mimics the features of the in vivo environment and is being used increasingly in the field of biological and medical research. It has been demonstrated that cancer cells cultured in 3D matrices are more radio-resistant compared with cells in monolayers. However, the mechanisms causing this difference remain unclear. Here we show that cancer cells cultured in a 3D microenvironment demonstrated an increase in cells with stem cell properties. This was confirmed by the finding that cells in 3D cultures upregulated the gene and protein expression of the stem cell reprogramming factors such as OCT4, SOX2, NANOG, LIN28 and miR-302a, compared with cells in monolayers. Moreover, the expression of β-catenin, a regulating molecule of reprogramming factors, also increased in 3D-grown cancer cells. These findings suggest that cancer cells were reprogrammed to become stem cell–like cancer cells in a 3D growth culture microenvironment. Since cancer stem cell–like cells demonstrate an increased radio-resistance and chemo-resistance, our results offer a new perspective as to why. Our findings shed new light on understanding the features of the 3D growth cell model and its application in basic research into clinical radiotherapy and medicine.     

Reprogramming cattle somatic cells by isolated nuclear injection

The development of a somatic cell nuclear transfer procedure for the production of blastocyst stage cattle embryos is described. Bovine fetal fibroblasts were used for fusion experiments with surgically enucleated oocytes (cytoplasts) following the establishment of optimal parameters for electrofusion from isofusion contours. Fusion rates were increased by decreasing size of the cytoplasts used but cleavage was decreased by decreasing size of the cytoplast used (quarter, half and whole cytoplasts). The use of double cytoplasts did not improve cleavage, and development to blastocysts could not be achieved. In a comparison of electrofusion of fibroblasts with cytoplasts in the subzonal perivitelline space with intracytoplasmic injection of nuclei and parthenogenetically activated oocytes, 2%, 14% and 24% developed to blastocysts respectively. In the group injected with isolated nuclei, the passage number (4 to 9) had no apparent influence on developmental competence to blastocysts. The embryos produced by nuclear injection of somatic cell nuclei showed the normal pattern of cell surface appearance of TEC-3 and TEC-4 stage-specific epitopes during development, as seen in fertilized oocytes. We conclude that the nuclear injection of somatic cell nuclei is a relatively efficient way to clone bovine embryos.     

Transgenerational Inheritance of Increased Fat Depot Size,Stem Cell Reprogramming,and Hepatic Steatosis Elicited by Prenatal Exposure to the Obesogen Tributyltin in Mice

Background: We have previously shown that exposure to tributyltin (TBT) modulates critical steps of adipogenesis through RXR/PPARγ and that prenatal TBT exposure predisposes multipotent mesenchymal stem cells (MSCs) to become adipocytes by epigenetic imprinting into the memory of the MSC compartment.Objective: We tested whether the effects of prenatal TBT exposure were heritable in F2 and F3 generations.Methods: We exposed C57BL/6J female mice (F0) to DMSO vehicle, the pharmaceutical obesogen rosiglitazone (ROSI), or TBT (5.42, 54.2, or 542 nM) throughout pregnancy via the drinking water. F1 offspring were bred to yield F2, and F2 mice were bred to produce F3. F1 animals were exposed in utero and F2 mice were potentially exposed as germ cells in the F1, but F3 animals were never exposed to the chemicals. We analyzed the effects of these exposures on fat depot weights, adipocyte number, adipocyte size, MSC programming, hepatic lipid accumulation, and hepatic gene expression in all three generations.Discussion: Prenatal TBT exposure increased most white adipose tissue (WAT) depot weights, adipocyte size, and adipocyte number, and reprogrammed MSCs toward the adipocyte lineage at the expense of bone in all three generations. Prenatal TBT exposure led to hepatic lipid accumulation and up-regulated hepatic expression of genes involved in lipid storage/transport, lipogenesis, and lipolysis in all three subsequent generations.Conclusions: Prenatal TBT exposure produced transgenerational effects on fat depots and induced a phenotype resembling nonalcoholic fatty liver disease through at least the F3 generation. These results show that early-life obesogen exposure can have lasting effects.     

Salmonellas in pigs and animal feeding stuffs in England and Wales and in Denmark

A comparison has been made between the incidence of salmonellas in pigs and feeding stuffs in England and Wales and in Denmark. In Denmark there is veterinary legislation requiring the sterilization of imported and home produced feed ingredients of animal origin. There is no such legislation in England and Wales. In Denmark 0·3% of resterilized imported meat and bone meal was contaminated with salmonellas. This compared with 23% of meat and bone meal in England and Wales and 20-27% of other ingredients of animal origin. In England and Wales salmonellas were isolated from 7% of caecal samples and 6% of lymph node samples, while in Denmark they were isolated from 3% of caecal samples and 4% of lymph node samples. In England and Wales 25 serotypes were found in both pigs and feeds and these included nearly all the most prevalent human pathogens. In Denmark four of the six serotypes in pigs had been found in resterilized feed. One notable difference between the two studies was the very wide range of serotypes found in pigs in England and Wales and the narrow range in Denmark. A second was that Salmonella typhimurium formed 15% of all Salmonella strains isolated from pigs in England and Wales, and 60% of those in Denmark.     

Lunasin is prevalent in barley and is bioavailable and bioactive in in vivo and in vitro studies

Lunasin, a unique 43-amino acid peptide found in a number of seeds, has been shown to be chemopreventive in mammalian cells and in a skin cancer mouse model. To elucidate the role of cereals in cancer prevention, we report here the prevalence, bioavailability, and bioactivity of lunasin from barley. Lunasin is present in all cultivars of barley analyzed. The liver and kidney of rats fed with lunasin-enriched barley (LEB) show the presence of lunasin in Western blot. Lunasin extracted from the kidney and liver inhibits the activities of HATs (histone acetyl transferases), yGCN5 by 20% and 18% at 100 nM, and PCAF activity by 25% and 24% at 100 nM, confirming that the peptide is intact and bioactive. Purified barley lunasin localizes in the nuclei of NIH 3T3 cells. Barley lunasin added to NIH 3T3 cells in the presence of the chemical carcinogen MCA activates the expression of tumor suppressors p21 and p15 by 45% and 47%, decreases cyclin D1 by 98%, and inhibits Rb hyperphosphorylation by 45% compared with the MCA treatment alone. We conclude that lunasin is prevalent in barley, bioavailable, and bioactive and that consumption of barley could play an important role of cancer prevention in barley-consuming populations.     

Prevalence and Trends in Overweight in Mexican-American Adults and Children

Overweight and obesity have been increasing in many countries. Our objective is to describe the trends in overweight and obesity occurring in the Mexican-American population in the United States. Data on measured height and weight for Mexican Americans come from the following surveys: the Hispanic Health and Nutrition Examination Survey (HHANES, 1982–84), the Third National Health and Nutrition Examination Survey (NHANES III, 1988–94), and NHANES 1999–2002. In 1999–2002, 73% of Mexican-American adults were overweight and 33% were obese. Obesity increased between NHANES III and NHANES 1999–2002, from 24% to 27% for men and from 35% to 38% for women. Increases were also seen for children and adolescents. The Mexican-American population in the United States, both children and adults, is showing trends in overweight and obesity over time that are similar to those seen in other segments of the U.S. population and indeed in many countries     

Lead and cadmium in soil and Isopoda woodlice in Croatia

The aim of the study was to determine lead and cadmium concentrations in Isopoda woodlice and soil and to estimate their relation in the environment and the possibility of the use of isopods as biological indicators of pollution. Samples of isopods and soil were collected at two locations in Northern Croatia and analyzed for lead and cadmium. One location was in the forest, and another in the meadow near the road. Isopods were dry- ashed and soil was extracted with nitric acid. Elements were analyzed by atomic absorption spectrometry. Results revealed that the two locations were significantly different in lead and cadmium in extracted soil and isopods. Lead concentration in extracted soil was 34.6 mg/kg dry weight in the forest and 43.3 mg/kg dry weight in the meadow near the road. Respective cadmium values were 0.147 and 0.180 mg/kg. Lead concentrations in isopods were 2.40 and 4.22 mg/kg dry weights, and cadmium 0.757 and 0.411 mg/kg dry weight, respectively. Correlation of lead or cadmium between isopods and soil irrespective of location gave significant and linear relations for both elements.     

环孢素A及其在产科和生殖领域应用的研究

环孢素A(Cyclosporin A,CsA)是一种大环内酯类免疫抑制剂,广泛应用于器官移植后排斥反应和自身免疫性疾病的防治.近年对CsA在产科和生殖领域的应用展开了一系列研究,CsA不仅能从多方面诱导母胎免疫耐受,还能促进滋养细胞增殖、抑制凋亡,增强其运动、迁移和侵袭能力,从而对妊娠起到双重调节作用,有望成为原因不明...