151
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Selective binding of anti-DNA antibodies to native dsDNA fragments of differing sequence. Immunol Lett 2012; 143:85-91. [PMID: 22285306 DOI: 10.1016/j.imlet.2012.01.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 01/11/2012] [Indexed: 12/17/2022]
Abstract
Systemic autoimmune diseases are characterized by the development of autoantibodies directed against a limited subset of nuclear antigens, including DNA. DNA-specific B cells take up mammalian DNA through their B cell receptor, and this DNA is subsequently transported to an endosomal compartment where it can potentially engage TLR9. We have previously shown that ssDNA-specific B cells preferentially bind to particular DNA sequences, and antibody specificity for short synthetic oligodeoxynucleotides (ODNs). Since CpG-rich DNA, the ligand for TLR9 is found in low abundance in mammalian DNA, we sought to determine whether antibodies derived from DNA-reactive B cells showed binding preference for CpG-rich native dsDNA, and thereby select immunostimulatory DNA for delivery to TLR9. We examined a panel of anti-DNA antibodies for binding to CpG-rich and CpG-poor DNA fragments. We show that a number of anti-DNA antibodies do show preference for binding to certain native dsDNA fragments of differing sequence, but this does not correlate directly with the presence of CpG dinucleotides. An antibody with preference for binding to a fragment containing optimal CpG motifs was able to promote B cell proliferation to this fragment at 10-fold lower antibody concentrations than an antibody that did not selectively bind to this fragment, indicating that antibody binding preference can influence autoreactive B cell responses.
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152
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Ali I, Mohamoud HSA. An identification and prediction methods for feature-subsets of CpG islands methylation based on human peripheral blood leukocytes of chromosome 21q. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:3233-6. [PMID: 22255028 DOI: 10.1109/iembs.2011.6090879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The pace of technology has allowed classification of feature-subset of methylated and unmethylated of CpG islands of DNA sequence properties. As methylation of CpG islands is involved in various biological phenomena and function of the DNA methylation is correlated to various human diseases such as cancer, analysis of the CpG islands has become important and useful in characterizing and modelling biological phenomena and understanding mechanism of such diseases. However, analysis of the data associated with the CpG islands is a quite new and challenging subject in bioinformatics, systems biology and epigenetics. In this paper, the problems associated with prediction of methylated and unmethylated CpG islands on human chromosome 21q are addressed. In order to carry out the prediction, a data set of 132 samples of the CpG islands from human peripheral blood leukocytes of chromosomes 21q and 4 different feature sub-sets totalling 44 attributes that characterise the methylated and unmethylated groups is extracted for each sample. Due to the nature of this unbalanced data set, in order to avoid disadvantages of traditional leave-one-out (LOO) and m-fold cross validation methods, the LOO method is modified by incorporating the m-fold cross validation approach. In addition, K-nearest neighbour classifier is then adapted for the prediction. The results gained through 440 different comprehensive analyses shows that the methylated CpG islands can be distinguished from the unmethylated CpG islands by a predictive accuracy of between 75% and 80%. More importantly, the modified LOO identifies more clearly and reliably when the feature sub-sets are combined. Another interesting observation is that the modified-LOO-based analysis reveals that the CpGI-specific feature-set achieve the highest predictive accuracy when combined with the other feature sets, which is not the case in the traditional LOO. This also further supports the robustness of the modified-LOO cross validation approach as CpGI-specific feature-set is one of the most important and effective attributes shown in other studies.
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Affiliation(s)
- Isse Ali
- Bio-Health Informatics Research Group within the Centre for Computational Intelligence, De Montfort University, Leicester LE1 9BH, The United Kingdom.
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153
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Sorianello E, Soriano FX, Fernández-Pascual S, Sancho A, Naon D, Vila-Caballer M, González-Navarro H, Portugal J, Andrés V, Palacín M, Zorzano A. The promoter activity of human Mfn2 depends on Sp1 in vascular smooth muscle cells. Cardiovasc Res 2012; 94:38-47. [PMID: 22253285 DOI: 10.1093/cvr/cvs006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Mitofusin-2 (Mfn2) expression is dysregulated in vascular proliferative disorders and its overexpression attenuates the proliferation of vascular smooth muscle cells (VSMCs) and neointimal lesion development after balloon angioplasty. We sought to gain insight into the mechanisms that control Mfn2 expression in VSMCs. METHODS AND RESULTS We cloned and characterized 2 kb of the 5'-flanking region of the human Mfn2 gene. Its TATA-less promoter contains a CpG island. In keeping with this, 5'-rapid amplification of cDNA ends revealed six transcriptional start sites (TSSs), of which TSS2 and TSS5 were the most frequently used. The strong CpG island was found to be non-methylated under conditions characterized by large differences in Mfn2 gene expression. The proximal Mfn2 promoter contains six putative Sp1 motifs. Sp1 binds to the Mfn2 promoter and its overexpression activates the Mfn2 promoter in VSMCs. Chemical inhibition of Sp1 reduced Mfn2 expression, and Sp1 silencing reduced transcriptional activity of the Mfn2 promoter. In keeping with this view, Sp1 and Mfn2 mRNA levels were down-regulated in the aorta early after an atherogenic diet in apolipoprotein E-knockout mice or in VSMCs cultured in the presence of low serum. CONCLUSION Sp1 is a key factor in maintaining basal Mfn2 transcription in VSMCs. Given the anti-proliferative actions of Mfn2, Sp1-induced Mfn2 transcription may represent a mechanism for prevention of VSMC proliferation and neointimal lesion and development.
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Affiliation(s)
- Eleonora Sorianello
- Institute of Research in Biomedicine, Parc Científic de Barcelona, Barcelona, Spain
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154
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Zhang Z, Liu J, Kaur M, Krantz ID. Characterization of DNA methylation and its association with other biological systems in lymphoblastoid cell lines. Genomics 2012; 99:209-19. [PMID: 22269447 DOI: 10.1016/j.ygeno.2012.01.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 01/04/2012] [Accepted: 01/05/2012] [Indexed: 12/17/2022]
Abstract
Lymphoblastoid cell line (LCL) is a common tool to study genetic disorders. However, it has not been fully characterized to what degree LCLs preserve the in vivo status of non-genetic biological systems, such as DNA methylation and gene transcription. We previously reported that DNA methylation in LCLs is highly variable in a data set of ~27,000 CpG dinucleotide sites around transcription start site (TSS) and 63 human subjects including healthy controls and probands of genetic disorders. Disease-causing mutations are linked to differential methylation at some CpG sites, but account for a small proportion of the total variance. In this study, we repeated the experiments to ensure that the high variance is not due to technical error and scrutinized the characteristics of DNA methylation and its association with other biological systems. Using sequence information and ChIP-seq data, we conclude that local CpG density and histone modifications not only correlate to baseline methylation level, but also affect the direction of methylation change in LCLs. Integrative analysis of gene transcription and DNA methylation data of the same subjects shows that medium or high methylation around TSS blocks the transcription while low methylation is a necessary, but not sufficient condition of downstream gene transcription. We utilized epigenetic information around TSS to predict active gene transcription via logistic regression models. The multivariate model using DNA methylation, eight histone modifications, and two regulatory protein complexes (CTCF and cohesin) as predictors has better performance (accuracy=95.1%) than any univariate models of single predictors. Linear regression analysis further shows that the transcriptional levels predicted by epigenetic markers have significant correlation to microarray measurements (p=2.2e-10). This study provides new insights into the epigenetic systems of LCLs and suggests that more specifically designed experiments are needed to improve our understanding on this topic.
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Affiliation(s)
- Zhe Zhang
- Center for Biomedical Informatics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
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155
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Abstract
Epigenetic silencing of genes is now recognized to be an important mechanism for inactivation of tumor suppressor genes in carcinogenesis. Because the role of genetic alterations in colorectal carcinogenesis has been well studied, colorectal cancer also offers an excellent model for elucidation of epigenetic mechanisms involved in carcinogenesis. DNA methylation and histone modification are involved in a complex network to maintain gene silencing and cause carcinogenesis. DNA methylation of cancer-related gene promoters generally begins early in the process of tumorigenesis, affecting various types of colorectal cancer to differing degrees. These advances in the understanding of the biology of tumorigenesis can be expected to provide distinct biomarkers that will aid future diagnosis, risk assessment, and treatment methods for patients with colorectal cancer.
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156
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Rivero S, Ruiz-García A, Díaz-Guerra MJM, Laborda J, García-Ramírez JJ. Characterization of a proximal Sp1 response element in the mouse Dlk2 gene promoter. BMC Mol Biol 2011; 12:52. [PMID: 22185379 PMCID: PMC3296630 DOI: 10.1186/1471-2199-12-52] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 12/20/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND DLK2 is an EGF-like membrane protein, closely related to DLK1, which is involved in adipogenesis. Both proteins interact with the NOTCH1 receptor and are able to modulate its activation. The expression of the gene Dlk2 is coordinated with that of Dlk1 in several tissues and cell lines. Unlike Dlk1, the mouse Dlk2 gene and its locus at chromosome 17 are not fully characterized. RESULTS The goal of this work was the characterization of Dlk2 mRNA, as well as the analysis of the mechanisms that control its basal transcription. First, we analyzed the Dlk2 transcripts expressed by several mouse cells lines and tissues, and mapped the transcription start site by 5' Rapid Amplification of cDNA Ends. In silico analysis revealed that Dlk2 possesses a TATA-less promoter containing minimal promoter elements associated with a CpG island, and sequences for Inr and DPE elements. Besides, it possesses six GC-boxes, considered as consensus sites for the transcription factor Sp1. Indeed, we report that Sp1 directly binds to the Dlk2 promoter, activates its transcription, and regulates its level of expression. CONCLUSIONS Our results provide the first characterization of Dlk2 transcripts, map the location of the Dlk2 core promoter, and show the role of Sp1 as a key regulator of Dlk2 transcription, providing new insights into the molecular mechanisms that contribute to the expression of the Dlk2 gene.
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Affiliation(s)
- Samuel Rivero
- Facultad de Medicina/Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Calle Almansa 14, 02006 Albacete, Spain
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157
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Mertes F, Elsharawy A, Sauer S, van Helvoort JMLM, van der Zaag PJ, Franke A, Nilsson M, Lehrach H, Brookes AJ. Targeted enrichment of genomic DNA regions for next-generation sequencing. Brief Funct Genomics 2011; 10:374-86. [PMID: 22121152 PMCID: PMC3245553 DOI: 10.1093/bfgp/elr033] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In this review, we discuss the latest targeted enrichment methods and aspects of their utilization along with second-generation sequencing for complex genome analysis. In doing so, we provide an overview of issues involved in detecting genetic variation, for which targeted enrichment has become a powerful tool. We explain how targeted enrichment for next-generation sequencing has made great progress in terms of methodology, ease of use and applicability, but emphasize the remaining challenges such as the lack of even coverage across targeted regions. Costs are also considered versus the alternative of whole-genome sequencing which is becoming ever more affordable. We conclude that targeted enrichment is likely to be the most economical option for many years to come in a range of settings.
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Affiliation(s)
- Florian Mertes
- Max Planck Institute for Molecular Genetics, Berlin, Germany.
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158
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Galván SC, Martínez-Salazar M, Galván VM, Méndez R, Díaz-Contreras GT, Alvarado-Hermida M, Alcántara-Silva R, García-Carrancá A. Analysis of CpG methylation sites and CGI among human papillomavirus DNA genomes. BMC Genomics 2011; 12:580. [PMID: 22118413 PMCID: PMC3293833 DOI: 10.1186/1471-2164-12-580] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 11/25/2011] [Indexed: 11/20/2022] Open
Abstract
Background The Human Papillomavirus (HPV) genome is divided into early and late coding sequences, including 8 open reading frames (ORFs) and a regulatory region (LCR). Viral gene expression may be regulated through epigenetic mechanisms, including cytosine methylation at CpG dinucleotides. We have analyzed the distribution of CpG sites and CpG islands/clusters (CGI) among 92 different HPV genomes grouped in function of their preferential tropism: cutaneous or mucosal. We calculated the proportion of CpG sites (PCS) for each ORF and calculated the expected CpG values for each viral type. Results CpGs are underrepresented in viral genomes. We found a positive correlation between CpG observed and expected values, with mucosal high-risk (HR) virus types showing the smallest O/E ratios. The ranges of the PCS were similar for most genomic regions except E4, where the majority of CpGs are found within islands/clusters. At least one CGI belongs to each E2/E4 region. We found positive correlations between PCS for each viral ORF when compared with the others, except for the LCR against four ORFs and E6 against three other ORFs. The distribution of CpG islands/clusters among HPV groups is heterogeneous and mucosal HR-HPV types exhibit both lower number and shorter island sizes compared to cutaneous and mucosal Low-risk (LR) HPVs (all of them significantly different). Conclusions There is a difference between viral and cellular CpG underrepresentation. There are significant correlations between complete genome PCS and a lack of correlations between several genomic region pairs, especially those involving LCR and E6. L2 and L1 ORF behavior is opposite to that of oncogenes E6 and E7. The first pair possesses relatively low numbers of CpG sites clustered in CGIs while the oncogenes possess a relatively high number of CpG sites not associated to CGIs. In all HPVs, E2/E4 is the only region with at least one CGI and shows a higher content of CpG sites in every HPV type with an identified E4. The mucosal HR-HPVs show either the shortest CGI size, followed by the mucosal LR-HPVs and lastly by the cutaneous viral subgroup, and a trend to the lowest CGI number, followed by the cutaneous viral subgroup and lastly by the mucosal LR-HPVs.
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Affiliation(s)
- Silvia C Galván
- Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México.
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159
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An interspecies analysis reveals a key role for unmethylated CpG dinucleotides in vertebrate Polycomb complex recruitment. EMBO J 2011; 31:317-29. [PMID: 22056776 DOI: 10.1038/emboj.2011.399] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 10/13/2011] [Indexed: 01/19/2023] Open
Abstract
The role of DNA sequence in determining chromatin state is incompletely understood. We have previously demonstrated that large chromosomal segments from human cells recapitulate their native chromatin state in mouse cells, but the relative contribution of local sequences versus their genomic context remains unknown. In this study, we compare orthologous chromosomal regions for which the human locus establishes prominent sites of Polycomb complex recruitment in pluripotent stem cells, whereas the corresponding mouse locus does not. Using recombination-mediated cassette exchange at the mouse locus, we establish the primacy of local sequences in the encoding of chromatin state. We show that the signal for chromatin bivalency is redundantly encoded across a bivalent domain and that this reflects competition between Polycomb complex recruitment and transcriptional activation. Furthermore, our results suggest that a high density of unmethylated CpG dinucleotides is sufficient for vertebrate Polycomb recruitment. This model is supported by analysis of DNA methyltransferase-deficient embryonic stem cells.
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160
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Phuong NTT, Kim SK, Lim SC, Kim HS, Kim TH, Lee KY, Ahn SG, Yoon JH, Kang KW. Role of PTEN promoter methylation in tamoxifen-resistant breast cancer cells. Breast Cancer Res Treat 2011; 130:73-83. [PMID: 21170675 DOI: 10.1007/s10549-010-1304-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 12/08/2010] [Indexed: 02/07/2023]
Abstract
Tamoxifen (TAM) resistance is a serious clinical problem in the treatment of breast cancer. Here, we found that S-adenosylmethionine (SAM) and DNA methyltransferase1 (DNMT1) expression are up-regulated in TAM-resistant breast cancer (TAMR-MCF-7) cells. We further focused on whether increased SAM with DNMT1 overexpression in TAMR-MCF-7 cells lead to aberrant methylation of the PTEN gene promoter and its therapeutic potential. Methylation-specific PCR analyses revealed that two sites within the PTEN promoters were methylated in TAMR-MCF-7 cells, which resulted in down-regulation of PTEN expression and increase in Akt phosphorylation. Both the loss of PTEN expression and the increased Akt phosphorylation in TAMR-MCF-7 cells were completely reversed by 5-aza-2'-deoxycytidine (5-Aza), a DNMT inhibitor. 5-Aza inhibited the basal cell proliferation rate of TAMR-MCF-7 cells and intraperitoneal injection of 5-Aza significantly suppressed TAMR-MCF-7 tumor growth in a xenograft study. Immunohistochemistry showed that PTEN expression in TAM-resistant human breast cancer tissues was lower than in TAM-responsive cases. These results suggest that methylation of the PTEN promoter related to both SAM increase and DNMT1 activation contributes to persistent Akt activation and are potential therapeutic targets for reversing TAM resistance in breast cancer.
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Affiliation(s)
- Nguyen Thi Thuy Phuong
- BK21 Project Team, College of Pharmacy, Chosun University, Gwangju, 501-759, South Korea
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161
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Xin Y, O'Donnell AH, Ge Y, Chanrion B, Milekic M, Rosoklija G, Stankov A, Arango V, Dwork AJ, Gingrich JA, Haghighi FG. Role of CpG context and content in evolutionary signatures of brain DNA methylation. Epigenetics 2011; 6:1308-18. [PMID: 22048252 DOI: 10.4161/epi.6.11.17876] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
DNA methylation is essential in brain function and behavior; therefore, understanding the role of DNA methylation in brain-based disorders begins with the study of DNA methylation profiles in normal brain. Determining the patterns and scale of methylation conservation and alteration in an evolutionary context enables the design of focused but effective methylation studies of disease states. We applied an enzymatic-based approach, Methylation Mapping Analysis by Paired-end Sequencing (Methyl-MAPS), which utilizes second-generation sequencing technology to provide an unbiased representation of genome-wide DNA methylation profiles of human and mouse brains. In this large-scale study, we assayed CpG methylation in cerebral cortex of neurologically and psychiatrically normal human postmortem specimens, as well as mouse forebrain specimens. Cross-species human-mouse DNA methylation conservation analysis shows that DNA methylation is not correlated with sequence conservation. Instead, greater DNA methylation conservation is correlated with increasing CpG density. In addition to CpG density, these data show that genomic context is a critical factor in DNA methylation conservation and alteration signatures throughout mammalian brain evolution. We identify key genomic features that can be targeted for identification of epigenetic loci that may be developmentally and evolutionarily conserved and wherein aberrations in DNA methylation patterns can confer risk for disease.
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Affiliation(s)
- Yurong Xin
- Department of Psychiatry, Columbia University and The New York State Psychiatric Institute, New York, NY, USA
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162
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Varga F, Karlic H, Thaler R, Klaushofer K. Functional aspects of cytidine-guanosine dinucleotides and their locations in genes. Biomol Concepts 2011; 2:391-405. [DOI: 10.1515/bmc.2011.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 07/12/2011] [Indexed: 12/31/2022] Open
Abstract
AbstractOriginally, the finding of a particular distribution of cytidine-guanosine dinucleotides (CpGs) in genomic DNA was considered to be an interesting structural feature of eukaryotic genome organization. Despite a global depletion of CpGs, genes are frequently associated with CpG clusters called CpG islands (CGIs). CGIs are prevalently unmethylated but often found methylated in pathologic situations. On the other hand, CpGs outside of CGIs are generally methylated and are found mainly in the heterochromatic fraction of the genome. Hypomethylation of those CpGs is associated with genomic instability in malignancy. Additionally, CpG-rich and CpG-poor regions, as well as CpG-shores, are defined. Usually, the methylation status inversely correlates with gene expression. Methylation of CpGs, as well as demethylation and generation of hydroxmethyl-cytosines, is strictly regulated during development and differentiation. This review deals with the relevance of the organizational features of CpGs and their relation to each other.
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Affiliation(s)
- Franz Varga
- 1Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
| | - Heidrun Karlic
- 2Ludwig Boltzmann Institute for Leukemia Research and Hematology, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria and Ludwig Boltzmann Cluster Oncology, Vienna, Austria
| | - Roman Thaler
- 1Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
| | - Klaus Klaushofer
- 1Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
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163
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Retrotransposon-induced heterochromatin spreading in the mouse revealed by insertional polymorphisms. PLoS Genet 2011; 7:e1002301. [PMID: 21980304 PMCID: PMC3183085 DOI: 10.1371/journal.pgen.1002301] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 08/04/2011] [Indexed: 12/13/2022] Open
Abstract
The "arms race" relationship between transposable elements (TEs) and their host has promoted a series of epigenetic silencing mechanisms directed against TEs. Retrotransposons, a class of TEs, are often located in repressed regions and are thought to induce heterochromatin formation and spreading. However, direct evidence for TE-induced local heterochromatin in mammals is surprisingly scarce. To examine this phenomenon, we chose two mouse embryonic stem (ES) cell lines that possess insertionally polymorphic retrotransposons (IAP, ETn/MusD, and LINE elements) at specific loci in one cell line but not the other. Employing ChIP-seq data for these cell lines, we show that IAP elements robustly induce H3K9me3 and H4K20me3 marks in flanking genomic DNA. In contrast, such heterochromatin is not induced by LINE copies and only by a minority of polymorphic ETn/MusD copies. DNA methylation is independent of the presence of IAP copies, since it is present in flanking regions of both full and empty sites. Finally, such spreading into genes appears to be rare, since the transcriptional start sites of very few genes are less than one Kb from an IAP. However, the B3galtl gene is subject to transcriptional silencing via IAP-induced heterochromatin. Hence, although rare, IAP-induced local heterochromatin spreading into nearby genes may influence expression and, in turn, host fitness.
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164
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Abstract
A variety of immune mechanisms, both humoral and cellular, are involved in the onset and amplification of the inflammatory response in lupus nephritis (LN). Accumulating evidence substantiates the view that innate immunity pathways may also amplify inflammatory reactions within the kidneys. Toll-like receptors (TLRs) are essential modulators of the innate immune response thanks to their ability to rocognize conserved molecular patterns that are microbe specific and other danger signals. Their recognition of endogenous molecules released from injured cells may also contribute to renal inflammation. Studies conducted in vivo and in vitro provide experimental evidence for the functional role of TLRs in LN. Intriguingly, these data suggest that pharmacological TLR signal suppression could be a useful approach to the treatment of systemic lupus erythematosus.
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165
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Hong SM, Park JY, Hruban RH, Goggins M. Molecular signatures of pancreatic cancer. Arch Pathol Lab Med 2011. [PMID: 21631264 DOI: 10.1043/2010-0566-ra.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
CONTEXT The introduction of genome- and epigenome-wide screening techniques has dramatically improved our understanding of the molecular mechanisms underlying the development of pancreatic cancer. There are now 3 recognized histologic precursors of pancreatic cancer: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions is associated with specific molecular alterations. OBJECTIVE To understand the molecular characteristics of pancreatic ductal adenocarcinoma and its precursor lesions. DATA SOURCES PubMed (US National Library of Medicine). CONCLUSIONS In this review, we briefly summarize recent research findings on the genetics and epigenetics of pancreatic cancer. In addition, we characterize these molecular alterations in the context of the histologic subtypes of pancreatic cancer.
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Affiliation(s)
- Seung-Mo Hong
- Department of Pathology, The Sol Goldman Pancreatic Cancer Research Center, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
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166
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Wang W, Wei Z, Lam TW, Wang J. Next generation sequencing has lower sequence coverage and poorer SNP-detection capability in the regulatory regions. Sci Rep 2011; 1:55. [PMID: 22355574 PMCID: PMC3216542 DOI: 10.1038/srep00055] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 07/25/2011] [Indexed: 01/30/2023] Open
Abstract
The rapid development of next generation sequencing (NGS) technology provides a new chance to extend the scale and resolution of genomic research. How to efficiently map millions of short reads to the reference genome and how to make accurate SNP calls are two major challenges in taking full advantage of NGS. In this article, we reviewed the current software tools for mapping and SNP calling, and evaluated their performance on samples from The Cancer Genome Atlas (TCGA) project. We found that BWA and Bowtie are better than the other alignment tools in comprehensive performance for Illumina platform, while NovoalignCS showed the best overall performance for SOLiD. Furthermore, we showed that next-generation sequencing platform has significantly lower coverage and poorer SNP-calling performance in the CpG islands, promoter and 5'-UTR regions of the genome. NGS experiments targeting for these regions should have higher sequencing depth than the normal genomic region.
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Affiliation(s)
- Weixin Wang
- Department of Biochemistry, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
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167
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Lim SP, Neilsen P, Kumar R, Abell A, Callen DF. The Application of Delivery Systems for DNA Methyltransferase Inhibitors. BioDrugs 2011; 25:227-42. [DOI: 10.2165/11592770-000000000-00000] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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168
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Samuels ME. Saturation of the human phenome. Curr Genomics 2011; 11:482-99. [PMID: 21532833 PMCID: PMC3048311 DOI: 10.2174/138920210793175886] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Revised: 06/22/2010] [Accepted: 06/22/2010] [Indexed: 12/26/2022] Open
Abstract
The phenome is the complete set of phenotypes resulting from genetic variation in populations of an organism. Saturation of a phenome implies the identification and phenotypic description of mutations in all genes in an organism, potentially constrained to those encoding proteins. The human genome is believed to contain 20-25,000 protein coding genes, but only a small fraction of these have documented mutant phenotypes, thus the human phenome is far from complete. In model organisms, genetic saturation entails the identification of multiple mutant alleles of a gene or locus, allowing a consistent description of mutational phenotypes for that gene. Saturation of several model organisms has been attempted, usually by targeting annotated coding genes with insertional transposons (Drosophila melanogaster, Mus musculus) or by sequence directed deletion (Saccharomyces cerevisiae) or using libraries of antisense oligonucleotide probes injected directly into animals (Caenorhabditis elegans, Danio rerio). This paper reviews the general state of the human phenome, and discusses theoretical and practical considerations toward a saturation analysis in humans. Throughout, emphasis is placed on high penetrance genetic variation, of the kind typically asociated with monogenic versus complex traits.
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Affiliation(s)
- Mark E Samuels
- Centre de Recherche de Ste-Justine, 3175, Côte Ste-Catherine, Montréal QC H3T 1C5, Canada
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169
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Increased frequency of CpG island methylator phenotype and CDH1 methylation in a gastric cancer high-risk region of china. Transl Oncol 2011; 1:28-35. [PMID: 18607505 DOI: 10.1593/tlo.07103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 07/02/2007] [Accepted: 07/23/2007] [Indexed: 12/13/2022] Open
Abstract
This study aimed to profile the methylation statuses of CDH1/E-cadherin and five CpG island methylator phenotype (CIMP)-associated genes (p16, hMLH1, MINT1, MINT2, and MINT31) in gastric specimens of 47 Dalian long-term residents with and 31 without gastric cancers (GCs). CIMP patterns were classified as CIMP-H with over three methylated genes, CIMP-L with one to two methylated genes, and CIMP-N without methylation. Of 47 GC cases, 24 (51.1%) were CIMP-H, 18 (38.3%) were CIMP-L, and 5 (10.6%) were CIMP-N, whereas 5 of 21 (23.8%) premalignant lesions were CIMP-H and 15 (71.4%) were CIMP-L. CIMP-L was found in 75% (12/16) of GC-adjacent mucosa and in 38.7% (12/31) of mucosa from GC-free patients. CDH1 methylation occurred in 48.9% (23/47) of cancer, in 23.8% (5/21) of premalignant, and in 25% (4/16) of noncancerous tissues and was correlated with patients' age (P = .01), lymph node metastasis, and CIMP severity (P = .000-.028). Our results demonstrated that the frequencies of CIMP-H in Dalian GCs, CIMP-L, and p16 methylation in GC-adjacent tissues and in GC-free mucosa were much higher than those reported previously, indicating the elevated methylation pressure in this GC high-risk region. The close correlation between CDH1 methylation and CIMP severity suggests the necessity of their combination in GC prevention and earlier diagnosis.
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170
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Zhu C, Yu ZB, Chen XH, Ji CB, Qian LM, Han SP. DNA hypermethylation of the NOX5 gene in fetal ventricular septal defect. Exp Ther Med 2011; 2:1011-1015. [PMID: 22977613 DOI: 10.3892/etm.2011.294] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 06/22/2011] [Indexed: 11/06/2022] Open
Abstract
Ventricular septal defect (VSD) is the most comon form of congenital heart disease (CHD). DNA hypermethylation analysis may provide an insight into the molecular features and pathogenesis of this heart disease. Although aberrant DNA hypermethylation is implicated in the pathophysiology of this heart disease, only a limited number of genes are known to be epigenetically altered in VSD. We previously identified regulation of the NOX5 gene by hypermethylation in VSD fetuses by promoter methylation microarrays. This study was designed to detect the expression of NOX5 mRNA in VSD and normal fetuses. We also verified the results of promoter methylation microarrays by methylation-specific PCR. DNA extraction and nested methylation-specific PCR were performed on myocardial tissue samples from 21 VSD and 15 normal fetuses. The primers specific for methylated vs. unmethylated DNA were designed and amplified by nested PCR. The products were visualized on agarose gel. Hypermethylation of the NOX5 promoter was more frequent in VSD fetuses (66.67%) than in normal fetuses (20%). There was a significant concordance between NOX5 methylation and a decrease in its mRNA expression. Taken together, our results demonstrate that hypermethylation of the NOX5 gene may be involved in the pathogenesis of VSD.
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Affiliation(s)
- Chun Zhu
- Department of Pediatrics, Nanjing Maternal and Child Health Hospital of Nanjing Medical University, Nanjing 210004
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171
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Radhakrishnan R, Kabekkodu S, Satyamoorthy K. DNA hypermethylation as an epigenetic mark for oral cancer diagnosis. J Oral Pathol Med 2011; 40:665-76. [PMID: 21649736 DOI: 10.1111/j.1600-0714.2011.01055.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Oral cancer is the largest group of cancers which fall into the head and neck category. While genetic alterations in oral cancer have long been documented, the effect of epigenetic changes is more recent. The recent explosion in science of how chromatin organization modulates the gene expression has highlighted the epigenetic mechanism of oral cancer pathogenesis. DNA methylation, which is an important epigenetic marker, is perhaps the best characterized chemical modification of mammalian DNA and provides a stable, heritable, and critical component of epigenetic regulation. This review attempts to decipher the epigenetic aspects of oral cancer by evaluating the DNA methylation status through its various stages from normal to potentially malignant to malignant states. In doing so, we emphasize DNA methylation as a novel biomarker in oral cancer research, thus opening newer avenues in oral cancer research.
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Affiliation(s)
- Raghu Radhakrishnan
- Department of Oral Pathology, Manipal College of Dental Sciences, Manipal University, Manipal, Karnataka, India.
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172
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Abstract
CONTEXT The introduction of genome- and epigenome-wide screening techniques has dramatically improved our understanding of the molecular mechanisms underlying the development of pancreatic cancer. There are now 3 recognized histologic precursors of pancreatic cancer: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions is associated with specific molecular alterations. OBJECTIVE To understand the molecular characteristics of pancreatic ductal adenocarcinoma and its precursor lesions. DATA SOURCES PubMed (US National Library of Medicine). CONCLUSIONS In this review, we briefly summarize recent research findings on the genetics and epigenetics of pancreatic cancer. In addition, we characterize these molecular alterations in the context of the histologic subtypes of pancreatic cancer.
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Affiliation(s)
- Seung-Mo Hong
- Department of Pathology, The Sol Goldman Pancreatic Cancer Research Center, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
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173
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Expanded methyl-sensitive cut counting reveals hypomethylation as an epigenetic state that highlights functional sequences of the genome. Proc Natl Acad Sci U S A 2011; 108:9715-20. [PMID: 21602498 DOI: 10.1073/pnas.1105713108] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Methyl-sensitive cut counting (MSCC) with the HpaII methylation-sensitive restriction enzyme is a cost-effective method to pinpoint unmethylated CpGs at single base-pair resolution. However, it has the drawback of addressing only CpGs in the context of the CCGG site, leaving out the remainder of the possible 16 XCGX tetranucleotides in which CpGs are found. We expanded MSCC to include three additional enzymes to address a total of 5 of the 16 XCGX combinations. This allowed us to survey methylation at about one-third of all a mammalian genome's CpGs. Applied to mouse liver DNA, we correctly confirmed data reported with other methods showing hypomethylation to be concentrated at promoters and in CpG islands (CGIs), with gene bodies and intergenic regions being mostly methylated. Grouping unmethylated CpGs, characterized by high MSCC scores (7% false discovery rate), we found a large number of unmethylated regions not qualifying as CGIs located in intergenic and intronic regions, which are highly enriched in functional DNA sequences (open regulatory annotation database) as well as in noncoding yet highly conserved mammalian sequences thought to be important but with as yet unknown function. About 50% of MSCC-defined unmethylated regions do not overlap algorithm-defined CGIs and offer a novel search space in which new functionalities of DNA may be found in health and disease.
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174
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Liang P, Song F, Ghosh S, Morien E, Qin M, Mahmood S, Fujiwara K, Igarashi J, Nagase H, Held WA. Genome-wide survey reveals dynamic widespread tissue-specific changes in DNA methylation during development. BMC Genomics 2011; 12:231. [PMID: 21569359 PMCID: PMC3118215 DOI: 10.1186/1471-2164-12-231] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Accepted: 05/11/2011] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Changes in DNA methylation in the mammalian genome during development are frequent events and play major roles regulating gene expression and other developmental processes. It is necessary to identify these events so that we may understand how these changes affect normal development and how aberrant changes may impact disease. RESULTS In this study Methylated DNA ImmunoPrecipitation (MeDIP) was used in conjunction with a NimbleGen promoter plus CpG island (CpGi) array to identify Tissue and Developmental Stage specific Differentially Methylated DNA Regions (T-DMRs and DS-DMRs) on a genome-wide basis. Four tissues (brain, heart, liver, and testis) from C57BL/6J mice were analyzed at three developmental stages (15 day embryo, E15; new born, NB; 12 week adult, AD). Almost 5,000 adult T-DMRs and 10,000 DS-DMRs were identified. Surprisingly, almost all DS-DMRs were tissue specific (i.e. methylated in at least one tissue and unmethylated in one or more tissues). In addition our results indicate that many DS-DMRs are methylated at early development stages (E15 and NB) but are unmethylated in adult. There is a very strong bias for testis specific methylation in non-CpGi promoter regions (94%). Although the majority of T-DMRs and DS-DMRs tended to be in non-CpGi promoter regions, a relatively large number were also located in CpGi in promoter, intragenic and intergenic regions (>15% of the 15,979 CpGi on the array). CONCLUSIONS Our data suggests the vast majority of unique sequence DNA methylation has tissue specificity, that demethylation has a prominent role in tissue differentiation, and that DNA methylation has regulatory roles in alternative promoter selection and in non-promoter regions. Overall, our studies indicate changes in DNA methylation during development are a dynamic, widespread, and tissue-specific process involving both DNA methylation and demethylation.
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Affiliation(s)
- Ping Liang
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada.
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175
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Díaz de León-Guerrero S, Pedraza-Alva G, Pérez-Martínez L. In sickness and in health: the role of methyl-CpG binding protein 2 in the central nervous system. Eur J Neurosci 2011; 33:1563-74. [PMID: 21453447 PMCID: PMC3110863 DOI: 10.1111/j.1460-9568.2011.07658.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The array of specialized neuronal and glial cell types that characterize the adult central nervous system originates from neuroepithelial proliferating precursor cells. The transition from proliferating neuroepithelial precursor cells to neuronal lineages is accompanied by rapid global changes in gene expression in coordination with epigenetic modifications at the level of the chromatin structure. A number of genetic studies have begun to reveal how epigenetic deregulation results in neurodevelopmental disorders such as mental retardation, autism, Rubinstein-Taybi syndrome and Rett syndrome. In this review we focus on the role of the methyl-CpG binding protein 2 (MeCP2) during development of the central nervous system and its involvement in Rett syndrome. First, we present recent findings that indicate a previously unconsidered role of glial cells in the development of Rett syndrome. Next, we discuss evidence of how MeCP2 deficiency or loss of function results in aberrant gene expression leading to Rett syndrome. We also discuss MeCP2's function as a repressor and activator of gene expression and the role of its different target genes, including microRNAs, during neuronal development. Finally, we address different signaling pathways that regulate MeCP2 expression at both the post-transcriptional and post-translational level, and discuss how mutations in MeCP2 may result in lack of responsiveness to environmental signals.
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Affiliation(s)
- Sol Díaz de León-Guerrero
- Laboratorio de Neuroinmunobiología, Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A.P. 510-3, Cuernavaca, Morelos 62271, México.
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176
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Ali I, Seker H. A comparative study for characterisation and prediction of tissue-specific DNA methylation of CpG islands in chromosomes 6, 20 and 22. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:1832-5. [PMID: 21096144 DOI: 10.1109/iembs.2010.5626437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Advanced technology has enabled identification of tissue-specific methylated CpG islands of different human tissues. As methylation of CpG islands is involved in various biological phenomena and function of the DNA methylation is linked to various human diseases such as cancer, analysis of the CpG islands has become important and useful in characterising and modelling biological phenomena and understanding mechanism of such diseases. However, analysis of the data associated with the CpG islands is a quite new and challenging subject in bioinformatics, systems biology and epigenetics.
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Affiliation(s)
- Isse Ali
- Bio-Health Informatics Research Group within the Centre for Computational Intelligence, Faculty of Technology, De Montfort University, Leicester, LE1 9BH, United Kingdom.
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177
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Chou JL, Chen LY, Lai HC, Chan MWY. TGF-β: friend or foe? The role of TGF-β/SMAD signaling in epigenetic silencing of ovarian cancer and its implication in epigenetic therapy. Expert Opin Ther Targets 2011; 14:1213-23. [PMID: 20925461 DOI: 10.1517/14728222.2010.525353] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
IMPORTANCE OF THE FIELD The TGF-β signaling pathway plays an important role in regulating numerous cellular processes including growth inhibition of ovarian surface epithelial (OSE) cells. However, epithelial ovarian cancer is refractory to the inhibitory functions of TGF-β, and yet TGF-β induces metastasis or epithelial-mesenchymal transition (EMT) in advanced ovarian cancer. How TGF-β plays a certain role in one cell but a different role in its malignant counterpart is not fully understood. AREAS COVERED IN THIS REVIEW The role of TGF-β/SMAD signaling both in normal OSE cells and ovarian cancer as well as how dysregulation of this signaling pathway leads to epigenetic silencing of its downstream targets in ovarian neoplasias are reviewed. The therapeutic implication of this signaling pathway in epigenetic therapy of ovarian cancer are also discussed. WHAT THE READER WILL GAIN The reader will gain insight on how dysregulation of TGF-β signaling alters promoter methylation and histone modifications of TGF-β downstream targets in ovarian cancer. TAKE HOME MESSAGE Disruption of TGF-β/SMAD signaling leads to epigenetic silencing of its target genes transiently through histone modifications but permanently by promoter hypermethylation. Targeting the TGF-β signaling pathway may be a novel therapeutic strategy in ovarian cancer.
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Affiliation(s)
- Jian-Liang Chou
- National Chung Cheng University, Department of Life Science, Min-Hsiung, Chia-Yi, Taiwan, ROC
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178
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Abstract
CpG islands mark CpG-enriched regions in otherwise CpG-depleted vertebrate genomes. While the regulatory importance of CpG islands is widely accepted, it is little appreciated that CpG islands vary greatly in lengths. For example, CpG islands in the human genome vary ∼30-fold in their lengths. Here we report findings suggesting that the lengths of CpG islands have functional consequences. Specifically, we show that promoters associated with long CpG islands (long-CGI promoters) are distinct from other promoters. First, long-CGI promoters are uniquely associated with genes with an intermediate level of gene expression breadths. Notably, intermediate expression breadths require the most complex mode of gene regulation, from the standpoint of information content. Second, long-CGI promoters encode more RNA polymerase II (Polr2a) binding sites than other promoters. Third, the actual binding patterns of Polr2a occur in a more tissue-specific manner in long-CGI promoters compared to other CGI promoters. Moreover, long-CGI promoters contain the largest numbers of experimentally characterized transcription start sites compared to other promoters, and the types of transcription start sites in them are biased toward tissue-specific patterns of gene expression. Finally, long-CGI promoters are preferentially associated with genes involved in development and regulation. Together, these findings indicate that functionally relevant variations of CpG islands exist. By investigating consequences of certain CpG island traits, we can gain additional insights into the mechanism and evolution of regulatory complexity of gene expression.
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179
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Beisel C, Paro R. Silencing chromatin: comparing modes and mechanisms. Nat Rev Genet 2011; 12:123-35. [PMID: 21221116 DOI: 10.1038/nrg2932] [Citation(s) in RCA: 270] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent transcriptome analyses show that substantial proportions of eukaryotic genomes can be copied into RNAs, many of which do not encode protein sequences. However, cells have developed mechanisms to control and counteract the high transcriptional activity of RNA polymerases in order to achieve cell-specific gene activity or to prevent the expression of deleterious sequences. Here we compare how two silencing modes - the Polycomb system and heterochromatin - are targeted, established and maintained at different chromosomal locations and how DNA-binding proteins and non-coding RNAs connect these epigenetically stable and heritable structures to the sequence information of the DNA.
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Affiliation(s)
- Christian Beisel
- Department of Biosystems Science and Engineering, ETH Zürich, Switzerland
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180
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Li M, Chen SS. The tendency to recreate ancestral CG dinucleotides in the human genome. BMC Evol Biol 2011; 11:3. [PMID: 21208429 PMCID: PMC3025853 DOI: 10.1186/1471-2148-11-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 01/05/2011] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The CG dinucleotides are known to be deficient in the human genome, due to a high mutation rate from 5-methylated CG to TG and its complementary pair CA. Meanwhile, many cellular functions rely on these CG dinucleotides, such as gene expression controlled by cytosine methylation status. Thus, CG dinucleotides that provide essential functional substrates should be retained in genomes. How these two conflicting processes regarding the fate of CG dinucleotides - i.e., high mutation rate destroying CG dinucleotides, vs. functional processes that require their preservation remains an unsolved question. RESULTS By analyzing the mutation and frequency spectrum of newly derived alleles in the human genome, a tendency towards generating more CGs was observed, which was mainly contributed by an excess number of mutations from CA/TG to CG. Simultaneously, we found a fixation preference for CGs derived from TG/CA rather than CGs generated by other dinucleotides. These tendencies were observed both in intergenic and genic regions. An analysis of Integrated Extended Haplotype Homozygosity provided no evidence of selection for newly derived CGs. CONCLUSIONS Ancestral CG dinucleotides that were subsequently lost by mutation tend to be recreated in the human genome, as indicated by a biased mutation and fixation pattern favoring new CGs that derived from TG/CA.
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Affiliation(s)
- Mingkun Li
- CAS-MPG Partner Institute of Computational Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, 200000 Shanghai, PR China.
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181
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Lemaire M, Deleu S, De Bruyne E, Van Valckenborgh E, Menu E, Vanderkerken K. The microenvironment and molecular biology of the multiple myeloma tumor. Adv Cancer Res 2011; 110:19-42. [PMID: 21704227 DOI: 10.1016/b978-0-12-386469-7.00002-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Multiple myeloma (MM) is a deadly plasma cell cancer that resides in the bone marrow (BM). Numerous studies have demonstrated the involvement of the BM microenvironment supporting tumor growth, angiogenesis, bone disease and drug resistance. Reciprocal interactions between the different components of the BM microenvironment and the MM cells are necessary to regulate migration, differentiation, proliferation and survival of the malignant plasma cells. In this review we focus on the interactions and molecular mechanisms by which the BM microenvironment exert these effects. Better understanding of these interactions and the study of the epigenetic changes that tumor cells undergo are necessary in order to improve current treatments and for the discovery of new therapies that may eventually lead to a potential cure.
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182
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Wu SF, Zhang H, Hammoud SS, Potok M, Nix DA, Jones DA, Cairns BR. DNA methylation profiling in zebrafish. Methods Cell Biol 2011; 104:327-39. [PMID: 21924171 DOI: 10.1016/b978-0-12-374814-0.00018-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
DNA methylation on cytosine in vertebrates such as zebrafish serves to silence gene expression by interfering with the binding of certain transcription factors and through the recruitment of repressive chromatin machinery. Cytosine DNA methylation is chemically stable and heritable through the germline - but also reversible through many modes, making it a useful and dynamic epigenetic modification. Virtually all of the enzymes and factors involved in the deposition, binding, and removal of cytosine methylation are conserved in zebrafish, and therefore the organism an excellent model for understanding the use of DNA methylation in the control of gene regulation and other processes. Here, we discuss the main approaches to quantifying DNA methylation levels genome-wide in zebrafish: one is an established method for revealing regional methylation (methylated DNA immunoprecipitation (MeDIP)), and the other is an emerging method that reveals DNA methylation at base-pair resolution (shotgun bisulphite sequencing). We also introduce some of the analytical methods that are useful for identifying regions of hypo- or hyper-methylation, and ways to identify differentially methylated regions.
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Affiliation(s)
- Shan-Fu Wu
- Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
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183
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Kakumani R, Ahmad MO, Devabhaktuni V. Identification of CpG islands in DNA sequences using matched filters. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2011:6029-6032. [PMID: 22255714 DOI: 10.1109/iembs.2011.6091490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
CpG islands (CGIs), rich in CG dinucleotides, are usually located in the promoter regions of genes in DNA sequences and are used as gene markers. Identification of CGIs plays an important role in the analysis of DNA sequences. In this paper, we propose a new digital signal processing (DSP) based approach using matched filters for the identification of CGIs. We also formulate a new/reliable CGI identification characteristic replacing the several existing probability transition tables for CGIs and non-CGIs. The peaks in matched filter output, obtained by correlating the CGI characteristic with the DNA sequence to be analyzed, accurately and reliably identify CGIs. This approach is tested on a number of DNA sequences and is proved to be capable of identifying CpG islands efficiently and reliably.
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Affiliation(s)
- Rajasekhar Kakumani
- Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd, WestMontreal, Quebec H3G1M8, Canada
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184
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Chávez L, Kauder S, Verdin E. In vivo, in vitro, and in silico analysis of methylation of the HIV-1 provirus. Methods 2011; 53:47-53. [PMID: 20670606 PMCID: PMC3566233 DOI: 10.1016/j.ymeth.2010.05.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 04/21/2010] [Accepted: 05/26/2010] [Indexed: 11/28/2022] Open
Abstract
HIV-1 latency is a barrier to overcome in the effort to fully eradicate the virus from infected individuals using highly active anti-retroviral therapy (HAART). Therefore, the study of the mechanisms underlying the establishment and maintenance of HIV-1 latency are vital to achieving a cure. Transcriptional repression of the viral promoter is the major cause of HIV-1 latency. DNA methylation of genomic regions known as CpG islands (CpGIs) is a well-established transcriptional regulatory mechanism, and the HIV-1 provirus contains several conserved CpGIs including two that are located within the viral promoter region. The study of these CpGIs in both in vitro and in vivo models of HIV-1 latency using the technique of bisulfite-mediated methylcytosine mapping has led to their identification as factors that contribute to the maintenance of HIV-1 latency. Here, we discuss the identification of CpGIs within the HIV-1 provirus and the study of their differential methylation patterns in several HIV-1 latency models using bisulfite-mediated methylcytosine mapping.
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Affiliation(s)
- Leonard Chávez
- Gladstone Institute of Virology & Immunology, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
- Department of Medicine, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
| | - Steven Kauder
- Gladstone Institute of Virology & Immunology, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
- Department of Medicine, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
| | - Eric Verdin
- Gladstone Institute of Virology & Immunology, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
- Department of Medicine, University of California, San Francisco, 1650 Owens Street, San Francisco, CA, USA, 94158-2261
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185
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Khare T, Pal M, Petronis A. Understanding bipolar disorder: the epigenetic perspective. Curr Top Behav Neurosci 2011; 5:31-49. [PMID: 25236548 DOI: 10.1007/7854_2010_64] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Bipolar disease (BPD) is a complex major psychiatric disorder that affects between 1% and 2% of the population and exhibits ?85% heritability. This has made BPD an appealing target for genetic studies yet, despite numerous attempts, the genetic basis of this disease remains elusive. Recently, it has come to light that epigenetic factors may also influence the development of BPD. These factors act via stable but reversible modifications of DNA and chromatin structure. In this chapter, we revisit the epidemiological, clinical, and molecular findings in BPD and reanalyze them from the perspective of inherited and acquired epigenetic misregulation. Epigenetic research has great potential to enhance our understanding of the molecular basis of BPD.
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Affiliation(s)
- Tarang Khare
- The Krembil Family Epigenetics Laboratory, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada,
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186
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Abstract
AbstractNumerous epigenetic modifications have been identified and correlated with transcriptionally active euchromatin or repressed heterochromatin and many enzymes responsible for the addition and removal of these marks have been characterized. However, less is known regarding how these enzymes are regulated and targeted to appropriate genomic locations. Mammalian CXXC finger protein 1 is an epigenetic regulator that was originally identified as a protein that binds specifically to any DNA sequence containing an unmethylated CpG dinucleotide. Mouse embryos lacking CXXC finger protein 1 die prior to gastrulation, and embryonic stem cells lacking CXXC finger protein 1 are viable but are unable to achieve cellular differentiation and lineage commitment. CXXC finger protein 1 is a regulator of both cytosine and histone methylation. It physically interacts with DNA methyltransferase 1 and facilitates maintenance cytosine methylation. Rescue studies reveal that CXXC finger protein 1 contains redundant functional domains that are sufficient to support cellular differentiation and proper levels of cytosine methylation. CXXC finger protein 1 is also a component of the Setd1 histone H3-Lys4 methyltransferase complexes and functions to target these enzymes to unmethylated CpG islands. Depletion of CXXC finger protein 1 leads to loss of histone H3-Lys4 tri-methylation at CpG islands and inappropriate drifting of this euchromatin mark into areas of hetero-chromatin. Thus, one function of CXXC finger protein 1 is to serve as an effector protein that interprets cytosine methylation patterns and facilitates crosstalk with histone-modifying enzymes.
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Affiliation(s)
- David G. Skalnik
- 1Wells Center for Pediatric Research, Section of Pediatric Hematology/Oncology, Departments of Pediatrics and Biochemistry and Molecular Biology, Indiana University School of Medicine, 1044 W. Walnut St., Indianapolis, IN 46202, USA
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187
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Association between hMLH1 hypermethylation and JC virus (JCV) infection in human colorectal cancer (CRC). Clin Epigenetics 2010; 2:1-5. [PMID: 22704265 PMCID: PMC3365371 DOI: 10.1007/s13148-010-0013-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 11/11/2010] [Indexed: 12/31/2022] Open
Abstract
Incorporation of viral DNA may interfere with the normal sequence of human DNA bases on the genetic level or cause secondary epigenetic changes such as gene promoter methylation or histone acetylation. Colorectal cancer (CRC) is the second leading cause of cancer mortality in the USA. Chromosomal instability (CIN) was established as the key mechanism in cancer development. Later, it was found that CRC results not only from the progressive accumulation of genetic alterations but also from epigenetic changes. JC virus (JCV) is a candidate etiologic factor in sporadic CRC. It may act by stabilizing β-catenin, facilitating its entrance to the cell nucleus, initialing proliferation and cancer development. Diploid CRC cell lines transfected with JCV-containing plasmids developed CIN. This result provides direct experimental evidence for the ability of JCV T-Ag to induce CIN in the genome of colonic epithelial cells. The association of CRC hMLH1 methylation and tumor positivity for JCV was recently documented. JC virus T-Ag DNA sequences were found in 77% of CRCs and are associated with promoter methylation of multiple genes. hMLH1 was methylated in 25 out of 80 CRC patients positive for T-Ag (31%) in comparison with only one out of 11 T-Ag negative cases (9%). Thus, JCV can mediate both CIN and aberrant methylation in CRC. Like other viruses, chronic infection with JCV may induce CRC by different mechanisms which should be further investigated. Thus, gene promoter methylation induced by JCV may be an important process in CRC and the polyp-carcinoma sequence.
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188
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Bai G, Liu Y, Zhang H, Su D, Tao D, Yang Y, Ma Y, Zhang S. Promoter demethylation mediates the expression of ZNF645, a novel cancer/testis gene. BMB Rep 2010; 43:400-6. [PMID: 20587329 DOI: 10.5483/bmbrep.2010.43.6.400] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cancer/testis (CT) antigens exhibit highly tissue-restricted expression and are considered promising targets for cancer vaccines. Here we identified a novel CT gene ZNF645 which restrictively expresses in normal human testes and lung cancer patients (68.3%). To investigate the promoter methylation status of ZNF645, we carried out bisulfite genomic sequencing and found that the CpG island in its promoter was heavily methylated in normal lung tissues without the expression of ZNF645, whereas there was high demethylation in normal human testes and lung carcinoma tissues with its expression. Also ZNF645 could be remarkably activated in A549 and HEK293T cells treated by DNA demethylation agent 5'-aza-2'-deoxycytidine. And the dual luciferase assay revealed that the promoter activity of the ZNF645 was inhibited by methylation of the CpG island region. Therefore, we proposed that ZNF645 is a CT gene and activated in human testis and lung cancers by demethylation of its promoter region.
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Affiliation(s)
- Gang Bai
- Division of Human Morbid Genomics, State Key Lab of Biotherapy, P R China
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189
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Epigenetics and chemical safety assessment. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2010; 705:83-95. [DOI: 10.1016/j.mrrev.2010.04.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 03/29/2010] [Accepted: 04/08/2010] [Indexed: 01/01/2023]
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190
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Illingworth RS, Gruenewald-Schneider U, Webb S, Kerr ARW, James KD, Turner DJ, Smith C, Harrison DJ, Andrews R, Bird AP. Orphan CpG islands identify numerous conserved promoters in the mammalian genome. PLoS Genet 2010; 6:e1001134. [PMID: 20885785 PMCID: PMC2944787 DOI: 10.1371/journal.pgen.1001134] [Citation(s) in RCA: 377] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 08/23/2010] [Indexed: 01/23/2023] Open
Abstract
CpG islands (CGIs) are vertebrate genomic landmarks that encompass the promoters of most genes and often lack DNA methylation. Querying their apparent importance, the number of CGIs is reported to vary widely in different species and many do not co-localise with annotated promoters. We set out to quantify the number of CGIs in mouse and human genomes using CXXC Affinity Purification plus deep sequencing (CAP-seq). We also asked whether CGIs not associated with annotated transcripts share properties with those at known promoters. We found that, contrary to previous estimates, CGI abundance in humans and mice is very similar and many are at conserved locations relative to genes. In each species CpG density correlates positively with the degree of H3K4 trimethylation, supporting the hypothesis that these two properties are mechanistically interdependent. Approximately half of mammalian CGIs (>10,000) are “orphans” that are not associated with annotated promoters. Many orphan CGIs show evidence of transcriptional initiation and dynamic expression during development. Unlike CGIs at known promoters, orphan CGIs are frequently subject to DNA methylation during development, and this is accompanied by loss of their active promoter features. In colorectal tumors, however, orphan CGIs are not preferentially methylated, suggesting that cancer does not recapitulate a developmental program. Human and mouse genomes have similar numbers of CGIs, over half of which are remote from known promoters. Orphan CGIs nevertheless have the characteristics of functional promoters, though they are much more likely than promoter CGIs to become methylated during development and hence lose these properties. The data indicate that orphan CGIs correspond to previously undetected promoters whose transcriptional activity may play a functional role during development. In the decade since the sequence of the human genome was announced, efforts have been made to annotate all genes with their regulatory sequences. CpG islands are short regions containing the sequence CG at high density that map to regions controlling the expression of most human genes (known as promoters). Using a biochemical method, we have identified and mapped all CpG islands in the human and mouse genomes and find that over half are remote from known gene promoters—so-called “orphans.” Mice, which were thought to possess far fewer CpG islands than humans, turn out to have a very similar number. Surprisingly, orphan CpG islands in both species often mark hitherto unknown promoters. The activity of these novel promoters is particularly dynamic during normal development, as they are often silenced by DNA methylation. In colorectal cancers, however, aberrant DNA methylation affects all CpG islands equally.
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Affiliation(s)
- Robert S. Illingworth
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Shaun Webb
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alastair R. W. Kerr
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Keith D. James
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Daniel J. Turner
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Colin Smith
- Neuropathology Unit, Division of Pathology, University of Edinburgh, Edinburgh, United Kingdom
| | - David J. Harrison
- Division of Pathology, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
| | - Robert Andrews
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Adrian P. Bird
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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191
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Baumann M, Pontiller J, Ernst W. Structure and basal transcription complex of RNA polymerase II core promoters in the mammalian genome: an overview. Mol Biotechnol 2010; 45:241-7. [PMID: 20300884 DOI: 10.1007/s12033-010-9265-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mammalian core promoter is a sophisticated and crucial component for the regulation of transcription mediated by the RNA polymerase II. It is generally defined as the minimal region of contiguous DNA sequence that is sufficient to accurately initiate a basal level of gene expression. The core promoter represents the ultimate target for nucleation of a functional pre-initiation complex composed of the RNA polymerase II and associated general transcription factors. Among the more than 40 distinct proteins assembling the basal transcription complex, TFIID plays a central role in recognizing and binding specific core promoter elements to support creating an environment that facilitates transcription initiation. Several common DNA motifs, like the TATA box, initiator region, or the downstream promoter element, are found in a subset of core promoters present in various combinations. Another class of promoters that is usually absent of a TATA box is constituted by the so-called CpG islands, which are associated with the majority of protein-coding genes within the mammalian genome.
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Affiliation(s)
- Martina Baumann
- Department of Biotechnology, Austrian Center of Biopharmaceutical Technology, University of Natural Resources and Applied Life Sciences, Vienna, Austria.
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192
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Hutter B, Paulsen M, Helms V. Identifying CpG islands by different computational techniques. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2010; 13:153-64. [PMID: 19196100 DOI: 10.1089/omi.2008.0046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
CpG islands (CGIs) are generally regarded as important epigenetic regulatory elements due to their association with promoter regions. However, identification of functional CGIs is hampered by repetitive elements and species-specific particularities. Here, we compared the performance of different CGI detection programs on genomic sequences of human and mouse genes. Although mouse CGIs are shorter and G+C poorer than their human counterparts, the different tools tested in our study reliably identify CGIs in promoter regions in both species. Our study confirms that substantially fewer murine than human CGIs coincide with repetitive elements and indicates that such CGIs are subject to accelerated cytosine deamination. In addition, CpG depletion appears to anticorrelate with the epigenetic features of functional regulatory CGIs. Taking into account different deamination rates in unmethylated CGIs versus those in methylated CGIs might support the detection of functional CGIs in other species for which there is little epigenetic information available.
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Affiliation(s)
- Barbara Hutter
- Lehrstuhl für Computational Biology, Universität des Saarlandes, Saarbrücken, Germany
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193
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CpG island clusters and pro-epigenetic selection for CpGs in protein-coding exons of HOX and other transcription factors. Proc Natl Acad Sci U S A 2010; 107:15485-90. [PMID: 20716685 DOI: 10.1073/pnas.1010506107] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
CpG dinucleotides contribute to epigenetic mechanisms by being the only site for DNA methylation in mammalian somatic cells. They are also mutation hotspots and approximately 5-fold depleted genome-wide. We report here a study focused on CpG sites in the coding regions of Hox and other transcription factor genes, comparing methylated genomes of Homo sapiens, Mus musculus, and Danio rerio with nonmethylated genomes of Drosophila melanogaster and Caenorhabditis elegans. We analyzed 4-fold degenerate, synonymous codons with the potential for CpG. That is, we studied "silent" changes that do not affect protein products but could damage epigenetic marking. We find that DNA-binding transcription factors and other developmentally relevant genes show, only in methylated genomes, a bimodal distribution of CpG usage. Several genetic code-based tests indicate, again for methylated genomes only, that the frequency of silent CpGs in Hox genes is much greater than expectation. Also informative are NCG-GNN and NCC-GNN codon doublets, for which an unusually high rate of G to C and C to G transversions was observed at the third (silent) position of the first codon. Together these results are interpreted as evidence for strong "pro-epigenetic" selection acting to preserve CpG sites in coding regions of many genes controlling development. We also report that DNA-binding transcription factors and developmentally important genes are dramatically overrepresented in or near clusters of three or more CpG islands, suggesting a possible relationship between evolutionary preservation of CpG dinucleotides in both coding regions and CpG islands.
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194
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Huang THM, Esteller M. Chromatin remodeling in mammary gland differentiation and breast tumorigenesis. Cold Spring Harb Perspect Biol 2010; 2:a004515. [PMID: 20610549 DOI: 10.1101/cshperspect.a004515] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
DNA methylation and histone modifications have essential roles in remodeling chromatin structure of genes necessary for multi-lineage differentiation of mammary stem/progenitor cells. The role of this well-defined epigenetic programming is to heritably maintain transcriptional plasticity of these loci over multiple cell divisions in the differentiated progeny. Epigenetic events can be deregulated in progenitor cells chronically exposed to xenoestrogen or inflammatory microenvironment. In addition, epigenetically mediated silencing of genes associated with tumor suppression can take place, resulting in clonal proliferation of undifferentiated or semidifferentiated cells. Alternatively, microRNAs that negatively regulate the expression of their protein-coding targets may become epigenetically repressed, leading to oncogenic expression of these genes. Here we further discuss interactions between DNA methylation and histone modifications that have significant contributions to the differentiation of mammary stem/progenitor cells and to tumor initiation and progression.
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Affiliation(s)
- Tim H-M Huang
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, Ohio 43220, USA.
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195
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Epigenetics in autoimmune disorders: Highlights of the 10th Sjögren's Syndrome Symposium. Autoimmun Rev 2010; 9:627-30. [DOI: 10.1016/j.autrev.2010.05.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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196
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Asadollahi R, Hyde CA, Zhong XY. Epigenetics of ovarian cancer: From the lab to the clinic. Gynecol Oncol 2010; 118:81-7. [DOI: 10.1016/j.ygyno.2010.03.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 03/08/2010] [Accepted: 03/10/2010] [Indexed: 01/22/2023]
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197
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Li Y, Tollefsbol T. Impact on DNA Methylation in Cancer Prevention and Therapy by Bioactive Dietary Components. Curr Med Chem 2010; 17:2141-51. [DOI: 10.2174/092986710791299966] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2010] [Accepted: 04/23/2010] [Indexed: 12/12/2022]
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198
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Comparative analysis of CpG islands in four fish genomes. Comp Funct Genomics 2010:565631. [PMID: 18483567 PMCID: PMC2375969 DOI: 10.1155/2008/565631] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 04/01/2008] [Indexed: 11/17/2022] Open
Abstract
There has been much interest in CpG islands (CGIs), clusters of CpG dinucleotides in GC-rich regions, because they are considered gene markers and involved in gene regulation. To date, there has been no genome-wide analysis of CGIs in the fish genome. We first evaluated the performance of three popular CGI identification algorithms in four fish genomes (tetraodon, stickleback, medaka, and zebrafish). Our results suggest that Takai and Jones' (2002) algorithm is most suitable for comparative analysis of CGIs in the fish genome. Then, we performed a systematic analysis of CGIs in the four fish genomes using Takai and Jones' algorithm, compared to other vertebrate genomes. We found that both the number of CGIs and the CGI density vary greatly among these genomes. Remarkably, each fish genome presents a distinct distribution of CGI density with some genomic factors (e.g., chromosome size and chromosome GC content). These findings are helpful for understanding evolution of fish genomes and the features of fish CGIs.
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199
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Fluorescent conjugated polymer-based FRET technique for detection of DNA methylation of cancer cells. Nat Protoc 2010; 5:1255-64. [PMID: 20595954 DOI: 10.1038/nprot.2010.79] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This protocol describes a homogeneous, convenient and sensitive DNA methylation detection method, using an optically amplifying cationic conjugated polymer (CCP, poly((1,4-phenylene)-2,7-[9,9-bis(6'-N,N,N-trimethyl ammonium)-hexyl fluorene] dibromide)). Genomic DNA from cancer cells is pretreated with a methylation-sensitive restriction endonuclease, followed by PCR amplification in the presence of fluorescein-labeled dNTP and Taq polymerase. The PCR only occurs for methylated DNA. DNA methylation of the gene sequence of interest is detected as a result of the fluorescence resonance energy transfer (FRET) between CCP and fluorescein that is incorporated into DNA. The methylated statuses of the p16, HPP1 and GALR2 promoters of five cancer cell lines (HT29, HepG2, A498, HL60 and M17) were assayed to provide an association study between the cancers and susceptibility genes, which shows great potential for early cancer diagnosis. This protocol simplifies previously available procedures by avoiding the need for primer labeling, isolation or purification steps, and sophisticated instruments. The assay takes about 20 h to obtain the methylated statuses of cancer cells.
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200
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Fant M, Farina A, Nagaraja R, Schlessinger D. PLAC1 (Placenta-specific 1): a novel, X-linked gene with roles in reproductive and cancer biology. Prenat Diagn 2010; 30:497-502. [PMID: 20509147 PMCID: PMC4627609 DOI: 10.1002/pd.2506] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Placenta-specific 1 (PLAC1) is a recently described X-linked gene with expression restricted primarily to cells derived from trophoblast lineage during embryonic development. PLAC1 localizes to a region of the X chromosome thought to be important in placental development although its role in this process has not been defined. This review summarizes our current understanding of its expression, regulation, and function. PLAC1 is expressed throughout human pregnancy by the differentiated trophoblast and localizes to membranous structures in the syncytiotrophoblast, including the microvillous plasma membrane surface. Recent studies have demonstrated that PLAC1 is also expressed by a wide variety of human cancers. Studies of the PLAC1 promoter regions indicate that its expression in both normal placenta and cancer cells is driven by specific interactions involving a combination of transcription factors. Although functional insight into PLAC1 in the normal trophoblast is lacking, preliminary studies suggest that cancer-derived PLAC1 has the potential to promote tumor growth and function. In addition, it also appears to elicit a specific immunologic response that may influence survival in some cancer patients, suggesting that it may provide a therapeutic target for the treatment of some cancers. We also discuss a potential role for PLAC1 as a biomarker predictive of specific pregnancy complications, such as preeclampsia.
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Affiliation(s)
- Michael Fant
- Department of Pediatrics, University of South Florida College of Medicine, Tampa, FL 33606-350, USA.
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