Studies on the Methylation Status of CpG Sequences Located in Promoters of Selected Tumour Suppressor Genes in Breast Cancer Cells

In the tested samples of sporadic breast cancer (100 cases), hypermethylation of CpG sequences located in ERα promoter was observed in 62 cases. It correlated with: (i) deficiency of ERα protein in 45%, (ii) hypermethylation of BRCA1 promoter in 95%, and (iii) nonmethylated E-cadherin promoter in 90%. Fifty-eight percent of the patients with nonmethylated E-cadherin promoter (56 cases) did not show metastasis to lymphatic nodes. The analysis of the methylation level of the promoter of ERα, BRCA1, and E-cadherin, frequently connected with their activity, shows that it can be an important parameter in the diagnosis and therapeutic strategies in sporadic breast cancer.     

Persistence of Epstein-Barr Virus in Self-Reactive Memory B Cells

Epstein-Barr virus infection has been epidemiologically associated with the development of multiple autoimmune diseases, particularly systemic lupus erythematosus and multiple sclerosis. Currently, there is no known mechanism that can account for these associations. The germinal-center (GC) model of EBV infection and persistence proposes that EBV gains access to the memory B cell compartment via GC reactions by driving infected cells to differentiate using the virus-encoded LMP1 and LMP2a proteins, which act as functional homologues of CD40 and the B cell receptor, respectively. The ability of LMP2a, when expressed in mice, to allow escape of autoreactive B cells suggests that it could perform a similar role in infected GC B cells, permitting the survival of potentially pathogenic autoreactive B cells. To test this hypothesis, we cloned and expressed antibodies from EBV⁺ and EBV⁻ memory B cells present during acute infection and profiled their self- and polyreactivity. We find that EBV does persist within self- and polyreactive B cells but find no evidence that it favors the survival of pathogenic autoreactive B cells. On the contrary, EBV⁺ memory B cells express lower levels of self-reactive and especially polyreactive antibodies than their uninfected counterparts do. Our work suggests that EBV has only a modest effect on the GC process, which allows it to access and persist within a subtly unique niche of the memory compartment characterized by relatively low levels of self- and polyreactivity. We suggest that this might reflect an active process where EBV and its human host have coevolved so as to minimize the virus''s potential to contribute to autoimmune disease.     

活性型粒酶B基因的异位表达导致多核巨细胞产生

粒酶B（granzyme B, GrB）是一种重要的丝氨酸蛋白酶参与细胞毒性T淋巴细胞(CTL)和自然杀伤细胞(NK)介导的细胞杀伤过程.为研究粒酶B在肿瘤细胞中异位表达后能否诱导细胞死亡,将构建的活性型粒酶B（GrBa）基因及其酶活性中心突变型（mGrBa）基因的真核表达载体,以脂质体法瞬时转染HeLa细胞,通过绿色荧光蛋白(GFP)共表达、间接免疫荧光、细胞计数、MTT等方法,观察到GrBa蛋白的异位表达引起多核巨细胞形态异常,并且表达细胞的生长受到抑制.Percoll分离多核巨细胞后,观察到其生长状态较差,是导致生长抑制的直接原因.细胞骨架破坏和具有多极纺锤体的异常有丝分裂,推测是多核巨细胞不断产生的根源.上述结果为GrBa应用于肿瘤基因治疗提供了一定依据.     

The Absence of M1 Leads to Increased Establishment of Murine Gammaherpesvirus 68 Latency in IgD-Negative B Cells

The secreted M1 protein of murine gammaherpesvirus 68 (MHV68) promotes effector Vβ4⁺ CD8⁺ T cell expansion to impact virus control and immune-mediated pathologies in C57BL/6 mice, but not BALB/c mice. We report a striking increase in the number of genome-positive, IgD⁻ B cells during chronic infection of both mouse strains. This suggests a novel role for M1 in influencing long-term maintenance in a major latency reservoir irrespective of the degree of Vβ4⁺ CD8⁺ T cell expansion.     

Divergent Requirements for the MAPKERK Signal Transduction Pathway during Initial Virus Infection of Quiescent Primary B Cells and Disruption of Epstein-Barr Virus Latency by Phorbol Esters

Quiescent primary B lymphocytes and Epstein-Barr virus (EBV)-immortalized lymphoblastoid cell lines express components of the extracellular response kinase arm of the mitogen-activated protein kinase (MAPK(ERK)) signal transduction pathway and transmit signals through the pathway when exposed to appropriate stimuli. Although the MAPK(ERK) pathway is activated following infection with EBV, MAPK/ERK kinase (MEK1) activity is not required to drive the proliferation of infected cells. However, MEK1 contributes to EBV latency control.     

NTRK3 Is a Potential Tumor Suppressor Gene Commonly Inactivated by Epigenetic Mechanisms in Colorectal Cancer

NTRK3 is a member of the neurotrophin receptor family and regulates cell survival. It appears to be a dependence receptor, and thus has the potential to act as an oncogene or as a tumor suppressor gene. NTRK3 is a receptor for NT-3 and when bound to NT-3 it induces cell survival, but when NT-3 free, it induces apoptosis. We identified aberrantly methylated NTRK3 in colorectal cancers through a genome-wide screen for hypermethylated genes. This discovery led us to assess whether NTRK3 could be a tumor suppressor gene in the colon. NTRK3 is methylated in 60% of colon adenomas and 67% of colon adenocarcinomas. NTRK3 methylation suppresses NTRK3 expression. Reconstitution of NTRK3 induces apoptosis in colorectal cancers, if NT-3 is absent. Furthermore, the loss of NTRK3 expression associates with neoplastic transformation in vitro and in vivo. We also found that a naturally occurring mutant NTRK3 found in human colorectal cancer inhibits the tumor suppressor activity of NTRK3. In summary, our findings suggest NTRK3 is a conditional tumor suppressor gene that is commonly inactivated in colorectal cancer by both epigenetic and genetic mechanisms whose function in the pathogenesis of colorectal cancer depends on the expression status of its ligand, NT-3.     

Dopamine Signaling Leads to Loss of Polycomb Repression and Aberrant Gene Activation in Experimental Parkinsonism

Polycomb group (PcG) proteins bind to and repress genes in embryonic stem cells through lineage commitment to the terminal differentiated state. PcG repressed genes are commonly characterized by the presence of the epigenetic histone mark H3K27me3, catalyzed by the Polycomb repressive complex 2. Here, we present in vivo evidence for a previously unrecognized plasticity of PcG-repressed genes in terminally differentiated brain neurons of parkisonian mice. We show that acute administration of the dopamine precursor, L-DOPA, induces a remarkable increase in H3K27me3S28 phosphorylation. The induction of the H3K27me3S28p histone mark specifically occurs in medium spiny neurons expressing dopamine D1 receptors and is dependent on Msk1 kinase activity and DARPP-32-mediated inhibition of protein phosphatase-1. Chromatin immunoprecipitation (ChIP) experiments showed that increased H3K27me3S28p was accompanied by reduced PcG binding to regulatory regions of genes. An analysis of the genome wide distribution of L-DOPA-induced H3K27me3S28 phosphorylation by ChIP sequencing (ChIP-seq) in combination with expression analysis by RNA-sequencing (RNA-seq) showed that the induction of H3K27me3S28p correlated with increased expression of a subset of PcG repressed genes. We found that induction of H3K27me3S28p persisted during chronic L-DOPA administration to parkisonian mice and correlated with aberrant gene expression. We propose that dopaminergic transmission can activate PcG repressed genes in the adult brain and thereby contribute to long-term maladaptive responses including the motor complications, or dyskinesia, caused by prolonged administration of L-DOPA in Parkinson''s disease.     

Tumor Suppressor WWOX Contributes to the Elimination of Tumorigenic Cells in Drosophila melanogaster

WWOX is a >1Mb gene spanning FRA16D Common Chromosomal Fragile Site, a region of DNA instability in cancer. Consequently, altered WWOX levels have been observed in a wide variety of cancers. In vitro studies have identified a large number and variety of potential roles for WWOX. Although its normal role in vivo and functional contribution to cancer have not been fully defined, WWOX does have an integral role in metabolism and can suppress tumor growth. Using Drosophila melanogaster as an in vivo model system, we find that WWOX is a modulator of TNFα/Egr-mediated cell death. We found that altered levels of WWOX can modify phenotypes generated by low level ectopic expression of TNFα/Egr and this corresponds to altered levels of Caspase 3 activity. These results demonstrate an in vivo role for WWOX in promoting cell death. This form of cell death is accompanied by an increase in levels of reactive oxygen species, the regulation of which we have previously shown can also be modified by altered WWOX activity. We now hypothesise that, through regulation of reactive oxygen species, WWOX constitutes a link between alterations in cellular metabolism observed in cancer cells and their ability to evade normal cell death pathways. We have further shown that WWOX activity is required for the efficient removal of tumorigenic cells from a developing epithelial tissue. Together these results provide a molecular basis for the tumor suppressor functions of WWOX and the better prognosis observed in cancer patients with higher levels of WWOX activity. Understanding the conserved cellular pathways to which WWOX contributes provides novel possibilities for the development of therapeutic approaches to restore WWOX function in cancer.     

Different Patterns of Epstein-Barr Virus Latency in Endemic Burkitt Lymphoma (BL) Lead to Distinct Variants within the BL-Associated Gene Expression Signature

Epstein-Barr virus (EBV) is present in all cases of endemic Burkitt lymphoma (BL) but in few European/North American sporadic BLs. Gene expression arrays of sporadic tumors have defined a consensus BL profile within which tumors are classifiable as “molecular BL” (mBL). Where endemic BLs fall relative to this profile remains unclear, since they not only carry EBV but also display one of two different forms of virus latency. Here, we use early-passage BL cell lines from different tumors, and BL subclones from a single tumor, to compare EBV-negative cells with EBV-positive cells displaying either classical latency I EBV infection (where EBNA1 is the only EBV antigen expressed from the wild-type EBV genome) or Wp-restricted latency (where an EBNA2 gene-deleted virus genome broadens antigen expression to include the EBNA3A, -3B, and -3C proteins and BHRF1). Expression arrays show that both types of endemic BL fall within the mBL classification. However, while EBV-negative and latency I BLs show overlapping profiles, Wp-restricted BLs form a distinct subgroup, characterized by a detectable downregulation of the germinal center (GC)-associated marker Bcl6 and upregulation of genes marking early plasmacytoid differentiation, notably IRF4 and BLIMP1. Importantly, these same changes can be induced in EBV-negative or latency I BL cells by infection with an EBNA2-knockout virus. Thus, we infer that the distinct gene profile of Wp-restricted BLs does not reflect differences in the identity of the tumor progenitor cell per se but differences imposed on a common progenitor by broadened EBV gene expression.     

Host Cell Detection of Noncoding Stuffer DNA Contained in Helper-Dependent Adenovirus Vectors Leads to Epigenetic Repression of Transgene Expression

Helper-dependent adenovirus (hdAd) vectors have shown great promise as therapeutic gene delivery vehicles in gene therapy applications. However, the level and duration of gene expression from hdAd can differ considerably depending on the nature of the noncoding stuffer DNA contained within the vector. For example, an hdAd containing 22 kb of prokaryotic DNA (hdAd-prok) expresses its transgene 60-fold less efficiently than a similar vector containing eukaryotic DNA (hdAd-euk). Here we have determined the mechanistic basis of this phenomenon. Although neither vector was subjected to CpG methylation and both genomes associated with cellular histones to similar degrees, hdAd-prok chromatin was actively deacetylated. Insertion of an insulator element between the transgene and the bacterial DNA derepressed hdAd-prok, suggesting that foreign DNA nucleates repressive chromatin structures that spread to the transgene. We found that Sp100B/Sp100HMG and Daxx play a role in repressing transgene expression from hdAd and act independently of PML bodies. Thus, we have identified nuclear factors involved in recognizing foreign DNA and have determined the mechanism by which associated genes are repressed.Efficient delivery and expression of foreign genes are of great importance in medicine and basic science. In many gene therapy applications, expression of the therapeutic gene would be required for the lifetime of the patient, yet many vector systems display only transient expression, lasting as little as a few days or weeks. Helper-dependent adenovirus (hdAd) vectors can enhance the duration of expression of a therapeutic gene; studies of mice and nonhuman primates have yielded several years of gene expression after a single administration (28). Indeed, several studies have described lifelong expression of a gene and persistent phenotypic correction in mouse models of human disease (18, 26, 42).Most hdAds contain noncoding “stuffer” DNA to maintain the size of the vector within appropriate limits for efficient DNA packaging; vectors constructed below ∼27 kb undergo DNA rearrangement in order to increase the size of the genome to 27 to 38 kb (31, 38). Interestingly, the nature of the stuffer DNA included in the hdAd has a significant effect on the function of the vector. An hdAd vector containing 22 kb of eukaryotic DNA (hdAd-euk) expressed a transgene to a higher level and for a longer duration than a vector containing 22 kb of prokaryotic DNA (hdAd-prok), both in vitro and in vivo (29). The genomes of the two vectors persisted at similar levels within the livers of transduced mice, suggesting that incorporation of prokaryote-derived stuffer DNA into an hdAd leads to the shutoff of associated transgenes. As a result of these observations, most current hdAd vectors are constructed using stuffer DNA derived from eukaryotic sources (27).Silencing of transgenes associated with prokaryotic DNA is not unique to hdAd. Removal of the bacterial origin of replication and antibiotic resistance gene from herpes simplex virus (HSV) amplicons resulted in a 20-fold improvement in gene expression in normal human fibroblasts in vitro, and more-persistent reporter gene expression in nude mice, compared to amplicons retaining the bacterial elements (39). Similarly, removal of bacterial sequences from plasmids results in significantly improved transgene expression in vitro and in vivo (2, 3, 34). For both plasmid and HSV amplicons, the mechanisms by which the bacterial sequences impair transgene expression are not fully understood. However, the bacterial sequences appear to nucleate the formation of a repressive chromatin structure(s) that spreads to the transgene (4, 39).In this study, we experimentally address the mechanism behind the repressive effects of prokaryotic DNA on gene expression in hdAd vectors. We found that prokaryotic DNA inhibits eukaryotic gene expression in cis, via induction of histone deacetylation, which is independent of DNA methylation. Furthermore, our data indicate that Sp100 and Daxx are involved in repressing the expression of genes associated with prokaryotic DNA.     

Trpm4 Gene Invalidation Leads to Cardiac Hypertrophy and Electrophysiological Alterations

Rationale

TRPM4 is a non-selective Ca²⁺-activated cation channel expressed in the heart, particularly in the atria or conduction tissue. Mutations in the Trpm4 gene were recently associated with several human conduction disorders such as Brugada syndrome. TRPM4 channel has also been implicated at the ventricular level, in inotropism or in arrhythmia genesis due to stresses such as ß-adrenergic stimulation, ischemia-reperfusion, and hypoxia re-oxygenation. However, the physiological role of the TRPM4 channel in the healthy heart remains unclear.

Objectives

We aimed to investigate the role of the TRPM4 channel on whole cardiac function with a Trpm4 gene knock-out mouse (Trpm4 ^-/-) model.

Methods and Results

Morpho-functional analysis revealed left ventricular (LV) eccentric hypertrophy in Trpm4 ^-/- mice, with an increase in both wall thickness and chamber size in the adult mouse (aged 32 weeks) when compared to Trpm4^+/+ littermate controls. Immunofluorescence on frozen heart cryosections and qPCR analysis showed no fibrosis or cellular hypertrophy. Instead, cardiomyocytes in Trpm4^-/- mice were smaller than Trpm4^+/+with a higher density. Immunofluorescent labeling for phospho-histone H3, a mitosis marker, showed that the number of mitotic myocytes was increased 3-fold in the Trpm4^-/-neonatal stage, suggesting hyperplasia. Adult Trpm4 ^-/- mice presented multilevel conduction blocks, as attested by PR and QRS lengthening in surface ECGs and confirmed by intracardiac exploration. Trpm4^-/-mice also exhibited Luciani-Wenckebach atrioventricular blocks, which were reduced following atropine infusion, suggesting paroxysmal parasympathetic overdrive. In addition, Trpm4 ^-/- mice exhibited shorter action potentials in atrial cells. This shortening was unrelated to modifications of the voltage-gated Ca²⁺ or K⁺ currents involved in the repolarizing phase.

Conclusions

TRPM4 has pleiotropic roles in the heart, including the regulation of conduction and cellular electrical activity which impact heart development.     

用PCR技术检测活检组织和鼻咽上皮细胞内EB病毒基因

选用Epstin-Barr病毒(EBV)基因组内部重复序列1(IR1)片断作为多聚酶链反应(Polymerase Chain Reaction,PCR)扩增引物,用于检测了31例不同病例活检组织和4例新鲜鼻咽组织经体外培养6周以上的新生上皮细胞内EBV基因,其中检出EBVDNA:高分化鼻咽癌5/5,低分化鼻咽癌4/4,何杰金氏病5/5,非何杰金氏病0/2,头颈其他肿瘤1/6,鼻咽慢性炎症0/5,正常鼻咽组织0/4;新生上皮细胞DNA抽提物;低分化鼻咽癌2/2,炎症0/1,正常人胚鼻咽上皮0/1;携带EBV基因组细胞系(Raji,B_(95-8)各1)2/2,致淋巴细胞转化之B_(95-8)病毒为10~(-4),PCR检测10~(-4)～10~(-6)均阳性,10~(-7)未检出。结果表明EBV与鼻咽癌与何杰金氏病有关,常规石蜡包埋切片仅8μm×0.1mm~2,贮存时间至三年仍可用于PCR检测EBV DNA,证实PCR是一种快速、灵敏和特异测捡EBV基因组的方法,可作为肿瘤和疚病病毒病因回顾性调直研究的有力手段。