251
|
Impact of aging on the biology of breast cancer. Crit Rev Oncol Hematol 2007; 66:65-74. [PMID: 17949989 DOI: 10.1016/j.critrevonc.2007.09.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 08/31/2007] [Accepted: 09/05/2007] [Indexed: 12/30/2022] Open
Abstract
Breast cancer is a heterogeneous malignancy; its age-specific incidence profile rises exponentially until menopause and increases more slowly thereafter, reflecting the superimposition of early-onset and late-onset breast cancer rates. While early-onset breast cancers largely represent inherited or early life transforming effects on immature mammary epithelium, late-onset breast cancers likely follow extended exposures to promoting stimuli of susceptible epithelium that has failed to age normally. Among stimuli thought to promote late-onset breast tumorigenesis are the altered extracellular matrix and secreted products of senescent fibroblasts; however, the extent to which these senescent influences exist within the aging breast remains unknown. Clinical observations and biomarker studies indicate that late-onset breast cancers grow more slowly and are biologically less aggressive than early-onset breast cancers, even when controlled for hormone receptor (e.g. estrogen receptor, ER) and growth factor receptor (e.g. HER2) expression, supporting the conclusion that the biology of breast cancer is age-dependent.
Collapse
|
252
|
Pilsner JR, Liu X, Ahsan H, Ilievski V, Slavkovich V, Levy D, Factor-Litvak P, Graziano JH, Gamble MV. Genomic methylation of peripheral blood leukocyte DNA: influences of arsenic and folate in Bangladeshi adults. Am J Clin Nutr 2007; 86:1179-86. [PMID: 17921400 DOI: 10.1093/ajcn/86.4.1179] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Studies in cell culture and animal models indicate that arsenic exposure induces modifications in DNA methylation, including genome-wide DNA hypomethylation. It is not known whether arsenic exposure influences genomic DNA methylation in human populations chronically exposed to arsenic-contaminated drinking water. OBJECTIVE The objective of this study was to determine whether arsenic is associated with genomic hypomethylation of peripheral blood leukocyte (PBL) DNA in Bangladeshi adults who are chronically exposed to arsenic. We also investigated whether arsenic-induced alterations in DNA methylation may be influenced by folate nutritional status. DESIGN PBL DNA methylation and concentrations of plasma folate, plasma arsenic, and urinary arsenic were assessed in 294 adults in Araihazar, Bangladesh. Genomic PBL DNA methylation was measured by using a [(3)H]-methyl incorporation assay. RESULTS Urinary arsenic, plasma arsenic, and plasma folate were positively associated with the methylation of PBL DNA (P = 0.009, 0.03, and 0.03, respectively). Stratification of participants by folate nutritional status [<9 nmol/L (n = 190) or >or=9 nmol/L (n = 104)] showed that the associations between arsenic exposure and methylation of PBL DNA were restricted to persons with folate concentrations >or= 9 nmol/L. CONCLUSIONS Contrary to our a priori hypothesis, arsenic exposure was positively associated with genomic PBL DNA methylation in a dose-dependent manner. This effect is modified by folate, which suggests that arsenic-induced increases in DNA methylation cannot occur in the absence of adequate folate. The underlying mechanisms and physiologic implications of increased genomic DNA methylation are unclear, and they warrant further study.
Collapse
Affiliation(s)
- J Richard Pilsner
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 60 Haven Avenue, B1, New York, NY 10032, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
253
|
Environment, diet and CpG island methylation: epigenetic signals in gastrointestinal neoplasia. Food Chem Toxicol 2007; 46:1346-59. [PMID: 17976883 DOI: 10.1016/j.fct.2007.09.101] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 09/14/2007] [Accepted: 09/19/2007] [Indexed: 12/26/2022]
Abstract
The epithelial surfaces of the mammalian alimentary tract are characterised by very high rates of cell proliferation and DNA synthesis, and in humans they are highly susceptible to cancer. The role of somatic mutations as drivers of carcinogenesis in the alimentary tract is well established, but the importance of gene silencing by epigenetic mechanisms is increasingly recognised. Methylation of CpG islands is an important component of the epigenetic code that regulates gene expression during development and normal cellular differentiation, and a number of genes are well known to become abnormally methylated during the development of tumours of the oesophagus, stomach and colorectum. Aberrant patterns of DNA methylation develop as a result of pathological processes such as chronic inflammation, and in response to various dietary factors, including imbalances in the supply of methyl donors, particularly folates, and exposure to DNA methyltransferase inhibitors, which include polyphenols and possibly isothiocyanates from plant foods. However the importance of these environmental interactions in human health and disease remains to be established. Recent moves to modify the exposure of human populations to folate, by mandatory supplementation of cereal foods, emphasise the importance of understanding the susceptibility of the human epigenome to dietary and other environmental effects.
Collapse
|
254
|
Chevanne M, Calia C, Zampieri M, Cecchinelli B, Caldini R, Monti D, Bucci L, Franceschi C, Caiafa P. Oxidative DNA damage repair and parp 1 and parp 2 expression in Epstein-Barr virus-immortalized B lymphocyte cells from young subjects, old subjects, and centenarians. Rejuvenation Res 2007; 10:191-204. [PMID: 17518695 DOI: 10.1089/rej.2006.0514] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Oxidative DNA damage has been implicated in the aging process and in some of its features such as telomere shortening and replicative senescence. Poly(ADP-ribosyl)ation is involved in many molecular and cellular processes, including DNA damage detection and repair, chromatin modification, transcription, and cell death pathways. We decided to examine the behavior of poly(ADP-ribosyl)ation in centenarians, i.e., those subjects who represent the best example of longevity having reached a very advanced age avoiding the main age-associated diseases. In this study we investigated the relationship between DNA repair capacity and poly(ADP-ribose) polymerase activity in Epstein-Barr virus-immortalized B lymphocyte cell lines from subjects of three different groups of age, including centenarians. Our data show that cells from centenarians have characteristics typical of cells from young people both in their capability of priming the mechanism of repair after H(2)O(2) sublethal oxidative damage and in poly(ADP-ribosyl)ation capacity, while in cells from old subjects these phenomena are delayed or decreased. Moreover, cells from old subjects show a constitutive expression level of both parp 1 and parp 2 genes reduced by a half, together with a reduced presence of modified PARP 1 and other poly(ADP-ribosyl)ated chromatin proteins in comparison to cells from young subjects and centenarians. Our data support the hypothesis that this epigenetic modification is an important regulator of the aging process in humans and it appears to be rather preserved in healthy centenarians, the best example of successful aging.
Collapse
Affiliation(s)
- Marta Chevanne
- Department of Experimental Pathology and Oncology, University of Florence, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
255
|
Edwards TM, Myers JP. Environmental exposures and gene regulation in disease etiology. ENVIRONMENTAL HEALTH PERSPECTIVES 2007; 115:1264-70. [PMID: 17805414 PMCID: PMC1964917 DOI: 10.1289/ehp.9951] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2006] [Accepted: 05/21/2007] [Indexed: 05/17/2023]
Abstract
OBJECTIVE Health or disease is shaped for all individuals by interactions between their genes and environment. Exactly how the environment changes gene expression and how this can lead to disease are being explored in a fruitful new approach to environmental health research, representative studies of which are reviewed here. DATA SOURCES We searched Web of Science and references of relevant publications to understand the diversity of gene regulatory mechanisms affected by environmental exposures with disease implications. DATA SYNTHESIS Pharmaceuticals, pesticides, air pollutants, industrial chemicals, heavy metals, hormones, nutrition, and behavior can change gene expression through a broad array of gene regulatory mechanisms. Mechanisms include regulation of gene translocation, histone modifications, DNA methylation, DNA repair, transcription, RNA stability, alternative RNA splicing, protein degradation, gene copy number, and transposon activation. Furthermore, chemically induced changes in gene regulation are associated with serious and complex human diseases, including cancer, diabetes and obesity, infertility, respiratory diseases, allergies, and neurodegenerative disorders such as Parkinson and Alzheimer diseases. One of the best-studied areas of gene regulation is epigenetics, especially DNA methylation. Our examples of environmentally induced changes in DNA methylation are presented in the context of early development, when methylation patterns are initially laid down. This approach highlights the potential role for altered DNA methylation in fetal origins of adult disease and inheritance of acquired genetic change. CONCLUSIONS The reviewed studies indicate that genetic predisposition for disease is best predicted in the context of environmental exposures. Second, the genetic mechanisms investigated in these studies offer new avenues for risk assessment research. Finally, we are likely to witness dramatic improvements in human health, and reductions in medical costs, if environmental pollution is decreased.
Collapse
Affiliation(s)
- Thea M Edwards
- Department of Zoology, University of Florida, Gainesville, Florida 32611, USA.
| | | |
Collapse
|
256
|
Richardson B. Primer: epigenetics of autoimmunity. ACTA ACUST UNITED AC 2007; 3:521-7. [PMID: 17762851 DOI: 10.1038/ncprheum0573] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Accepted: 06/04/2007] [Indexed: 01/03/2023]
Abstract
Interactions between environmental and genetic factors are proposed to explain why autoimmunity afflicts certain individuals and not others. Genes and genetic loci predisposing to autoimmunity are being identified, but theories as to how the environment contributes to autoimmunity still rely largely on examples such as drug-induced systemic lupus erythematosus (SLE) and epidemiologic evidence of occupational exposure, without clear mechanistic explanations or identification of specific environmental agents. Eukaryotic gene expression requires not only transcription factor activation but also regional modification of chromatin structure into a transcriptionally permissive configuration through epigenetic mechanisms, including DNA methylation and histone modifications. The realization that epigenetic mechanisms can alter gene expression and, therefore, cellular function has led to new insights into how environmental agents might contribute to the development of diseases in genetically predisposed individuals. The observation that some SLE-inducing drugs, such as procainamide and hydralazine, affect T cell DNA methylation and thereby cellular function, and that identical changes in T cell DNA methylation and cellular function are found in patients with SLE, implicates epigenetic mechanisms in the pathogenesis of human SLE, and perhaps other autoimmune diseases. In this Review we discuss how epigenetic mechanisms affect gene expression, how environmental agents can affect epigenetic mechanisms, and how epigenetic changes in gene expression can contribute to autoimmunity. Similar mechanisms might also contribute to the pathogenesis of other poorly understood human diseases.
Collapse
Affiliation(s)
- Bruce Richardson
- University of Michigan and Ann Arbor Veterans Affairs Hospital, Ann Arbor, MI, USA.
| |
Collapse
|
257
|
Thakur MK, Kumar RC. 17Beta-estradiol modulates age-dependent binding of 40 kDa nuclear protein to androgen receptor promoter in mouse cerebral cortex. Biogerontology 2007; 8:575-82. [PMID: 17619166 DOI: 10.1007/s10522-007-9102-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 05/15/2007] [Indexed: 11/24/2022]
Abstract
Androgen influences the function of central and peripheral nervous system and plays a crucial role in maintaining reproductive behaviors and neuroendocrine regulation. Such action is mediated by interaction of androgen receptor (AR) promoter with nuclear proteins, which are involved in transcriptional regulation of androgen responsive genes. We have analyzed the binding of AR core promoter to nuclear proteins from the cerebral cortex of adult and old mice of both sexes by electrophoretic mobility shift assay (EMSA) and characterized the bound protein by Southwestern blotting. EMSA showed that the binding of nuclear proteins declined in the cerebral cortex of intact old mice as compared to adult. Following gonadectomy, the binding was reduced in old male and adult female but increased in old female. In contrast, estradiol supplementation increased the binding in old male and adult female but decreased in old female. Southwestern blotting analysis revealed that a 40 kDa nuclear protein bound to the promoter and the binding pattern was similar to that observed in EMSA. Further characterization of this protein may help to explore the intricate mechanism that underlies the transcriptional regulation of androgen responsive genes during aging.
Collapse
Affiliation(s)
- Mahendra K Thakur
- Biochemistry & Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, India.
| | | |
Collapse
|
258
|
Keyes MK, Jang H, Mason JB, Liu Z, Crott JW, Smith DE, Friso S, Choi SW. Older age and dietary folate are determinants of genomic and p16-specific DNA methylation in mouse colon. J Nutr 2007; 137:1713-7. [PMID: 17585020 DOI: 10.1093/jn/137.7.1713] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Older age and inadequate folate intake are strongly implicated as important risk factors for colon cancer and each is associated with altered DNA methylation. This study was designed to determine the effects of aging and dietary folate on select features of DNA methylation in the colon that are relevant to carcinogenesis. Old (18 mo; n = 34) and young (4 mo; n = 32) male C57BL/6 mice were randomly divided into 3 groups and fed diets containing 0, 4.5, or 18 mumol folate/kg (deplete, replete, and supplemented groups, respectively) for 20 wk. Genomic DNA methylation and p16 promoter methylation in the colonic mucosa were analyzed by liquid chromatography/electrospray ionization/MS and methylation-specific PCR, respectively. p16 gene expression was determined by real-time RT-PCR. Old mice had significantly lower genomic DNA methylation compared with young mice at each level of dietary folate (4.5 +/- 0.2, 4.8 +/- 0.1, and 4.9 +/- 0.1 vs. 6.0 +/- 0.1, 5.3 +/- 0.2, and 5.9 +/- 0.2%, in folate-deplete, -replete, and -supplemented groups, respectively, P < 0.05) and markedly higher p16 promoter methylation (61.0 +/- 2.7, 69.7 +/- 6.9, and 87.1 +/- 13.4 vs. 10.8 +/- 3.6, 8.4 +/- 1.8, and 4.9 +/- 1.7%, respectively, P < 0.05). In old mice, genomic and p16 promoter DNA methylation each increased in a manner that was directly related to dietary folate (P(trend) = 0.009). Age-related enhancement of p16 expression occurred in folate-replete (P = 0.001) and folate-supplemented groups (P = 0.041), but not in the folate-deplete group. In conclusion, aging decreases genomic DNA methylation and increases promoter methylation and expression of p16 in mouse colons. This effect is dependent on the level of dietary folate.
Collapse
Affiliation(s)
- Mary K Keyes
- Vitamins and Carcinogenesis Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02478, USA
| | | | | | | | | | | | | | | |
Collapse
|
259
|
Kim TM, Chung YJ, Rhyu MG, Jung MH. Germline methylation patterns inferred from local nucleotide frequency of repetitive sequences in the human genome. Mamm Genome 2007; 18:277-85. [PMID: 17514347 DOI: 10.1007/s00335-007-9016-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Accepted: 03/12/2007] [Indexed: 12/31/2022]
Abstract
Given the genomic abundance and susceptibility to DNA methylation, interspersed repetitive sequences in the human genome can be exploited as valuable resources in genome-wide methylation studies. To learn about the relationships between DNA methylation and repeat sequences, we performed a global measurement of CpG dinucleotide frequencies for interspersed repetitive sequences and inferred germline methylation patterns in the human genome. Although extensive CpG depletion was observed for most repeat sequences, those in the proximity to CpG islands have been relatively removed from germline methylation being the potential source of germline activation. We also investigated the CpG depletion patterns of Alu pairs to see whether they might play an active role in germline methylation. Two kinds of Alu pairs, direct or inverted pairs classified according to the orientation, showed contrast CpG depletion patterns with respect to separating distance of Alus, i.e., as two Alu elements are more closely spaced in a pair, a higher extent of CpG depletion was observed in inverted orientation and vice versa for directly repetitive Alu pairs. This suggests that specific organization of repetitive sequences, such as inverted Alu pairs, might play a role in triggering DNA methylation consistent with a homology-dependent methylation hypothesis.
Collapse
Affiliation(s)
- Tae-Min Kim
- Division of Metabolic Disease, Center for Biomedical Science, National Institute of Health, Nokbun-dong 5, Eunpyung-gu, Seoul 122-701, Korea
| | | | | | | |
Collapse
|
260
|
Abstract
Monozygotic twins share the same genotype because they are derived from the same zygote. However, monozygotic twin siblings frequently present many phenotypic differences, such as their susceptibility to disease and a wide range of anthropomorphic features. Recent studies suggest that phenotypic discordance between monozygotic twins is at least to some extent due to epigenetic factors that change over the lifetime of a multicellular organism. It has been proposed that epigenetic drift during development can be stochastic or determined by environmental factors. In reality, a combination of the two causes prevails in most cases. Acute environmental factors are directly associated with epigenetic-dependent disease phenotypes, as demonstrated by the increased CpG-island promoter hypermethylation of tumor suppressor genes in the normal oral mucosa of smokers. Since monozygotic twins are genetically identical they are considered ideal experimental models for studying the role of environmental factors as determinants of complex diseases and phenotypes.
Collapse
|
261
|
Celewicz L, Mayer M, Shetlar MD. The Photochemistry of Thymidylyl-(3′-5′)-5-methyl-2′-deoxycytidine in Aqueous Solution¶. Photochem Photobiol 2007. [DOI: 10.1111/j.1751-1097.2005.tb00201.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
262
|
Park IY, Sohn BH, Yu E, Suh DJ, Chung YH, Lee JH, Surzycki SJ, Lee YI. Aberrant epigenetic modifications in hepatocarcinogenesis induced by hepatitis B virus X protein. Gastroenterology 2007; 132:1476-94. [PMID: 17408664 DOI: 10.1053/j.gastro.2007.01.034] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 12/14/2006] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS The involvement of the hepatitis B virus X (HBx) protein in epigenetic modifications during hepatocarcinogenesis has not been previously characterized. The aim of the present study was to identify the involvement of HBx in regional hypermethylation and global hypomethylation during the formation of hepatocellular carcinoma (HCC). METHODS Liver cell lines were transiently or stably transfected with an HBx-expressing vector. DNA methyltransferase (DNMT) promoter activity changes were examined by luciferase assay and chromatin immunoprecipitation. The methylation status of insulin-like growth factor binding protein-3 was examined by methyl-specific polymerase chain reaction and bisulfite sequencing. Global DNA methylation levels were examined using 5-methylcytosine dot blot and methylation-sensitive Southern blot analysis. HBx-mediated DNA methylation abnormalities were confirmed in patient HCC samples using methyl-specific polymerase chain reaction and 5-methylcytosine dot blot analysis. RESULTS HBx expression increased total DNMT activities by up-regulation of DNMT1, DNMT3A1, and DNMT3A2 and selectively promoted regional hypermethylation of specific tumor suppressor genes. HBx specifically repressed insulin-like growth factor-3 expression through de novo methylation via DNMT3A1 and DNMT3A2 and by inhibiting SP1 binding via recruiting methyl CpG binding protein 2 to the newly methylated SP1 binding element. HBx also induced global hypomethylation of satellite 2 repeat sequences by down-regulating DNMT3B. The prevalence of these specific methylation abnormalities by HBx was significantly correlated with HBx expression in HBV-infected HCC patients. CONCLUSIONS Targeted deregulation of DNMTs by HBx promotes both specific regional hypermethylation and global hypomethylation. These epigenetic modulations by HBx may suggest a mechanism for epigenetic tumorigenesis during HBV-mediated hepatocarcinogenesis.
Collapse
Affiliation(s)
- In Young Park
- Liver Cell Signal Transduction Laboratory, Molecular Cancer Research Center, KRIBB, Daejeon, Korea
| | | | | | | | | | | | | | | |
Collapse
|
263
|
Brena RM, Morrison C, Liyanarachchi S, Jarjoura D, Davuluri RV, Otterson GA, Reisman D, Glaros S, Rush LJ, Plass C. Aberrant DNA methylation of OLIG1, a novel prognostic factor in non-small cell lung cancer. PLoS Med 2007; 4:e108. [PMID: 17388669 PMCID: PMC1831740 DOI: 10.1371/journal.pmed.0040108] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Accepted: 01/31/2007] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Lung cancer is the leading cause of cancer-related death worldwide. Currently, tumor, node, metastasis (TNM) staging provides the most accurate prognostic parameter for patients with non-small cell lung cancer (NSCLC). However, the overall survival of patients with resectable tumors varies significantly, indicating the need for additional prognostic factors to better predict the outcome of the disease, particularly within a given TNM subset. METHODS AND FINDINGS In this study, we investigated whether adenocarcinomas and squamous cell carcinomas could be differentiated based on their global aberrant DNA methylation patterns. We performed restriction landmark genomic scanning on 40 patient samples and identified 47 DNA methylation targets that together could distinguish the two lung cancer subgroups. The protein expression of one of those targets, oligodendrocyte transcription factor 1 (OLIG1), significantly correlated with survival in NSCLC patients, as shown by univariate and multivariate analyses. Furthermore, the hazard ratio for patients negative for OLIG1 protein was significantly higher than the one for those patients expressing the protein, even at low levels. CONCLUSIONS Multivariate analyses of our data confirmed that OLIG1 protein expression significantly correlates with overall survival in NSCLC patients, with a relative risk of 0.84 (95% confidence interval 0.77-0.91, p < 0.001) along with T and N stages, as indicated by a Cox proportional hazard model. Taken together, our results suggests that OLIG1 protein expression could be utilized as a novel prognostic factor, which could aid in deciding which NSCLC patients might benefit from more aggressive therapy. This is potentially of great significance, as the addition of postoperative adjuvant chemotherapy in T2N0 NSCLC patients is still controversial.
Collapse
Affiliation(s)
- Romulo M Brena
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Virology, Immunology and Medical Genetics, Division of Human Cancer Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Carl Morrison
- Department of Pathology, The Ohio State University, Columbus, Ohio, United States of America
| | - Sandya Liyanarachchi
- Department of Molecular Virology, Immunology and Medical Genetics, Division of Human Cancer Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - David Jarjoura
- Division of Biostatistics, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio, United States of America
| | - Ramana V Davuluri
- Department of Molecular Virology, Immunology and Medical Genetics, Division of Human Cancer Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Gregory A Otterson
- Department of Internal Medicine, Division of Hematology and Oncology, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio, United States of America
| | - David Reisman
- Department of Internal Medicine, Division of Hematology and Oncology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Selina Glaros
- Department of Internal Medicine, Division of Hematology and Oncology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Laura J Rush
- Department of Veterinary Biosciences and the Comprehensive Cancer Center, The Ohio State University Columbus, Ohio, United States of America
| | - Christoph Plass
- Department of Molecular Virology, Immunology and Medical Genetics, Division of Human Cancer Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * To whom correspondence should be addressed. E-mail:
| |
Collapse
|
264
|
de Magalhães JP, Church GM. Analyses of human-chimpanzee orthologous gene pairs to explore evolutionary hypotheses of aging. Mech Ageing Dev 2007; 128:355-64. [PMID: 17459455 PMCID: PMC2288694 DOI: 10.1016/j.mad.2007.03.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2006] [Revised: 03/01/2007] [Accepted: 03/17/2007] [Indexed: 11/30/2022]
Abstract
Compared to chimpanzees (Pan troglodytes), the onset of aging appears to be delayed in the human species. Herein, we studied human-chimpanzee orthologous gene pairs to investigate the selective forces acting on genes associated with aging in different model systems, which allowed us to explore evolutionary hypotheses of aging. Our results show that aging-associated genes tend to be under purifying selection and stronger-than-average functional constraints. We found little evidence of accelerated evolution in aging-associated genes in the hominid or human lineages, and pathways previously related to aging were largely conserved between humans and chimpanzees. In particular, genes associated with aging in non-mammalian model organisms and cellular systems appear to be under stronger functional constraints than those associated with aging in mammals. One gene that might have undergone rapid evolution in hominids is the Werner syndrome gene. Overall, our findings offer novel insights regarding the evolutionary forces acting on genes associated with aging in model systems. We propose that genes associated with aging in model organisms may be part of conserved pathways related to pleiotropic effects on aging that might not regulate species differences in aging.
Collapse
|
265
|
Affiliation(s)
- John C Mathers
- Human Nutrition Research Centre, School of Clinical Medical Sciences, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK.
| |
Collapse
|
266
|
Abstract
The retinal pigment epithelium (RPE) maintains retinal function as the metabolic gatekeeper between photoreceptors (PRs) and the choriocapillaries. The RPE and Bruch's membrane (BM) suffer cumulative damage over lifetime, which is thought to induce age-related macular degeneration (AMD) in susceptible individuals. Unlike palliative pharmacologic treatments, replacement of the RPE has a curative potential for AMD. This article reviews mechanisms leading to RPE dysfunction in aging and AMD, laboratory studies on RPE transplantation, and surgical techniques used in AMD patients. Future strategies using ex vivo steps prior to transplantation, BM prosthetics, and stem cell applications are discussed. The functional peculiarity of the macular region, epigenetic phenomena leading to an age-related shift in protein expression, along with the accumulation of lipofuscin may affect the metabolism in the central RPE. Thickening of BM with age decreases its hydraulic conductivity. Drusen are deposits of extracellular material and formed in part by activation of the alternative complement pathway in individuals carrying a mutant allele of complement factor H. AMD likely represents an umbrella term for a disease entity with multifactorial etiology and manifestations. Presently, a slow progressing (dry) non-neovascular atrophic form and a rapidly blinding neovascular (wet) form are discerned. No therapy is currently available for the former, while RPE transplantation and promising (albeit non-causal) anti-angiogenic therapies are available for the latter. The potential of RPE transplantation was demonstrated in animal models. Rejection of allogeneic homologous transplants in patients focused further studies on autologous sources. In vitro studies elucidated cell adhesion and wound healing mechanisms on aged human BM. Currently, autologous RPE, harvested from the midperiphery, is being transplanted as a cell suspension or a patch of RPE and choroid in AMD patients. These techniques have been evaluated from several groups. Autologous RPE transplants may have the disadvantage of carrying the same genetic information that may have led to AMD manifestation. An intermittent culturing step would allow for in vitro therapy of the RPE, its rejuvenation and prosthesis of BM to improve the success RPE transplants. Recent advances in stem cell biology when combined with lessons learned from studies of RPE transplantation are intriguing future therapeutic modalities for AMD patients.
Collapse
Affiliation(s)
- Susanne Binder
- Department of Ophthalmology, Rudolf Foundation Clinic, Hospital of the City of Vienna, Vienna, Austria.
| | | | | | | |
Collapse
|
267
|
Roach HI, Aigner T. DNA methylation in osteoarthritic chondrocytes: a new molecular target. Osteoarthritis Cartilage 2007; 15:128-37. [PMID: 16908204 DOI: 10.1016/j.joca.2006.07.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Accepted: 07/09/2006] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To review the current knowledge of the mechanism of DNA methylation, its association with transcriptional silencing, possible mechanisms of hyper- and hypomethylation and how epigenetic changes may relate to the pathogenesis of osteoarthritis (OA). METHODS Journal literature was searched using Pubmed. Since there are very few publications directly on epigenetic phenomena in OA, the search was extended to give an overview of epigenetic mechanisms as they relate to the molecular mechanisms of the disease. RESULTS While the epigenetics of cancer cells have been intensively investigated, little attention has so far been paid as to whether epigenetic changes contribute to the pathology of non-neoplastic diseases such as OA. This review explains the mechanisms of DNA methylation, its role in transcriptional regulation, and possible demethylation mechanisms that may be applicable to OA. Preliminary evidence suggests that changes in DNA methylation, together with cytokines, growth factors and changes in matrix composition, are likely to be important in determining the complex gene expression patterns that are observed in osteoarthritic chondrocytes. CONCLUSION Early evidence points to a role of epigenetics in the pathogenesis of OA. Since epigenetic changes, although heritable at the cellular level, are potentially reversible, epigenetics could be a new molecular target for therapeutic intervention, especially early in the disease.
Collapse
Affiliation(s)
- H I Roach
- Bone and Joint Research Group, Division of Developmental Origins of Health and Disease, University of Southampton, UK.
| | | |
Collapse
|
268
|
Huang Y, Peng K, Su J, Huang Y, Xu Y, Wang S. Different effects of homocysteine and oxidized low density lipoprotein on methylation status in the promoter region of the estrogen receptor alpha gene. Acta Biochim Biophys Sin (Shanghai) 2007; 39:19-26. [PMID: 17213955 DOI: 10.1111/j.1745-7270.2007.00251.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We investigated the effects of homocysteine (Hcy) and oxidized low density lipoprotein (ox-LDL) on DNA methylation in the promoter region of the estrogen receptor alpha (ERalpha) gene, and its potential mechanism in the pathogenesis of atherosclerosis. Cultured smooth muscle cells (SMCs) of humans were treated by Hcy and ox-LDL with different concentrations for different periods of time. The DNA methylation status was assayed by nested methylation-specific polymerase chain reaction, the lipids that accumulated in the SMCs and foam cell formations were examined with Oil red O staining. The proliferation of SMCs was assayed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. The results showed that ox-LDL in moderate concentrations (10-40 mg/L) induced de novo methylation in the promoter region of the ERalpha gene of SMCs. However, high concentrations (50 mg/L) of ox-LDL, resulted in demethylation of ERalpha. The Hcy treatment resulted in de novo methylation in the promoter region of the ERalpha gene with a concentration- and treating time-dependent manner, and a dose-dependent promoting effect on SMC proliferation. These data indicated that the two risk factors for atherosclerosis had the function of inducing de novo methylation in the promoter region of the ERalpha gene of SMCs. However, high concentrations (50 mg/L) of ox-LDL induced demethylation, indicating that different risk factors of atherosclerosis with different potency might cause different aberrant methylation patterns in the promoter region of the ERalpha gene. The atherogenic mechanism of Hcy might involve the hypermethylation of the ERalpha gene, leading to the proliferation of SMCs in atherosclerotic lesions.
Collapse
Affiliation(s)
- Yushan Huang
- Department of Pathophysiology, West China School of Preclinic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu 610041, China
| | | | | | | | | | | |
Collapse
|
269
|
Hu CJ, Chen SD, Yang DI, Lin TN, Chen CM, Huang THM, Hsu CY. Promoter region methylation and reduced expression of thrombospondin-1 after oxygen-glucose deprivation in murine cerebral endothelial cells. J Cereb Blood Flow Metab 2006; 26:1519-26. [PMID: 16570076 DOI: 10.1038/sj.jcbfm.9600304] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Angiogenesis is induced in response to ischemia. Thrombospondin-1 (TSP-1) is a potent angiostatic factor. Silencing of TSP-1 expression may contribute to the postischemic angiogenesis. Upregulation of TSP-1, in contrast, may terminate the postischemic angiogenesis. A possible mechanism that silences TSP-1 expression is the DNA methylation of its promoter region. DNA methylation has been reported following cerebral ischemia. The present study aimed to explore whether methylation of the promoter region of TSP-1 regulates its expression after oxygen-glucose deprivation (OGD) in murine cerebral endothelial cells (CECs) in vitro. Sublethal OGD increased the extent of methylation of the promoter region of TSP-1 with a concurrent decrease in TSP-1 mRNA and protein expression in CECs. After reoxygenation, demethylation of the TSP-1 promoter region led to the restoration of TSP-1 mRNA and protein expression. The extent of methylation of the promoter region of TSP-1 was inversely correlated with the extent of TSP-1 gene expression at mRNA and protein levels after OGD. Oxygen-glucose deprivation-induced reduction in the TSP-1 mRNA level was not accompanied by a change in mRNA stability. These findings raise the possibility that OGD downregulation of TSP-1 expression is at least in part due to methylation of its promoter region.
Collapse
Affiliation(s)
- Chaur-Jong Hu
- Department of Neurology, Taipei Medical University, Taipei, Taiwan
| | | | | | | | | | | | | |
Collapse
|
270
|
Lu Q, Qiu X, Hu N, Wen H, Su Y, Richardson BC. Epigenetics, disease, and therapeutic interventions. Ageing Res Rev 2006; 5:449-67. [PMID: 16965942 DOI: 10.1016/j.arr.2006.07.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 07/20/2006] [Accepted: 07/24/2006] [Indexed: 12/13/2022]
Abstract
Heritable changes in gene expression that do not involve coding sequence modifications are referred to as "epigenetic". Epigenetic mechanisms principally include DNA methylation and a variety of histone modifications, of which the best characterized is acetylation. DNA hypermethylation and histone hypoacetylation are hallmarks of gene silencing, while DNA hypomethylation and acetylated histones promote active transcription. Aberrant DNA methylation and histone acetylation have been linked to a number of age related disorders including cancer, autoimmune disorders and others. Since epigenetic alterations are reversible, modifying epigenetic marks contributing to disease development may provide an approach to designing new therapies. Herein we review the role of epigenetic changes in disease development, and recent advances in the therapeutic modification of epigenetic marks.
Collapse
Affiliation(s)
- Q Lu
- Department of Dermatology and Epigenetic Research Center, Second Xiangya Hospital, Central South University, Hunan 410011, PR China
| | | | | | | | | | | |
Collapse
|
271
|
Wang Y, Zheng W, Luo J, Zhang D, Zuhong L. In situ bisulfite modification of membrane-immobilized DNA for multiple methylation analysis. Anal Biochem 2006; 359:183-8. [PMID: 17069744 DOI: 10.1016/j.ab.2006.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Revised: 08/16/2006] [Accepted: 09/01/2006] [Indexed: 12/31/2022]
Abstract
Increasing interest in DNA methylation has resulted in the recent development of array-based methods. However, these method require complex sample treatment processes, such as bisulfite modification in the liquid state of every sample. Here, we describe a microarray-based technology for interrogating DNA methylation status of multiple DNA samples at the same time, in which the DNA samples are first dotted on membranes and then treated with bisulfite directly. In this assay, plasmid pUC19 DNA is immobilized on nylon membranes and soaked in bisulfite reaction mixtures for 16h to convert unmethylated Cs to Us, and methylated Cs remain unchanged. The probes for detecting the methylation patterns of CpG sites are hybridized with the converted DNA dotted on the membranes, and the signals are revealed by chemiluminescence of DIG-labeled probes. The experiments show that this method can simplify the experimental processes and increase the efficiency of the bisulfite treatment. This new method could be used as a convenient tool for detecting the methylation status of multiple genes for a large number of samples in the future.
Collapse
Affiliation(s)
- Yan Wang
- The State Key Laboratory of Bioelectronics, Department of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | | | | | | | | |
Collapse
|
272
|
Zheng QH, Ma LW, Zhu WG, Zhang ZY, Tong TJ. p21Waf1/Cip1 plays a critical role in modulating senescence through changes of DNA methylation. J Cell Biochem 2006; 98:1230-48. [PMID: 16514663 DOI: 10.1002/jcb.20838] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
It has been reported that genomic DNA methylation decreases gradually during cell culture and an organism's aging. However, less is known about the methylation changes of age-related specific genes in aging. p21(Waf1/Cip1) and p16(INK4a) are cyclin-dependent kinase (Cdk) inhibitors that are critical for the replicative senescence of normal cells. In this study, we show that p21(Waf1/Cip1) and p16(INK4a) have different methylation patterns during the aging process of normal human 2BS and WI-38 fibroblasts. p21(Waf1/Cip1) promoter is gradually methylated up into middle-aged fibroblasts but not with senescent fibroblasts, whereas p16(INK4a) is always unmethylated in the aging process. Correspondently, the protein levels of DNA methyltransferase 1 (DNMT1) and DNMT3a increase from young to middle-aged fibroblasts but decrease in the senescent fibroblasts, while DNMT3b decreases stably from young to senescent fibroblasts. p21(Waf1/Cip1) promoter methylation directly represses its expression and blocks the radiation-induced DNA damage-signaling pathway by p53 in middle-aged fibroblasts. More importantly, demethylation by 5-aza-CdR or DNMT1 RNA interference (RNAi) resulted in an increased p21(Waf1/Cip1) level and premature senescence of middle-aged fibroblasts demonstrated by cell growth arrest and high beta-Galactosidase expression. Our results suggest that p21(Waf1/Cip1) but not p16(INK4a) is involved in the DNA methylation mediated aging process. p21(Waf1/Cip1) promoter methylation may be a critical biological barrier to postpone the aging process.
Collapse
Affiliation(s)
- Quan Hui Zheng
- Peking University Research Center on Aging, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100083, China
| | | | | | | | | |
Collapse
|
273
|
Xu J, Disteche CM. Sex differences in brain expression of X- and Y-linked genes. Brain Res 2006; 1126:50-5. [PMID: 16962077 DOI: 10.1016/j.brainres.2006.08.049] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 08/07/2006] [Accepted: 08/14/2006] [Indexed: 10/24/2022]
Abstract
The X chromosome plays an important role in brain development and function, as evidenced by its disproportionately high content of genes whose mutations cause mental retardation. These X-linked brain genes may play a role in sexual differentiation if they are expressed at a higher level in XX females than in XY males, due to incomplete X inactivation in females. The expression of several X escapee genes is indeed higher in brain tissues from females when compared to males. In mouse, some of the sex differences are only found in adult brains but not in other tissues. Determining the brain expression pattern of these X escapee genes is important for a better understanding of their role in the neurological phenotypes of XO Turner syndrome.
Collapse
Affiliation(s)
- Jun Xu
- Department of Pathology, University of Washington, Seattle, WA 98195, USA.
| | | |
Collapse
|
274
|
Newman JC, Bailey AD, Weiner AM. Cockayne syndrome group B protein (CSB) plays a general role in chromatin maintenance and remodeling. Proc Natl Acad Sci U S A 2006; 103:9613-8. [PMID: 16772382 PMCID: PMC1480455 DOI: 10.1073/pnas.0510909103] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cockayne syndrome (CS) is an inherited neurodevelopmental disorder with progeroid features. Although the genes responsible for CS have been implicated in a variety of DNA repair- and transcription-related pathways, the nature of the molecular defect in CS remains mysterious. Using expression microarrays and a unique method for comparative expression analysis called L2L, we sought to define this defect in cells lacking a functional CS group B (CSB) protein, the SWI/SNF-like ATPase responsible for most cases of CS. Remarkably, many of the genes regulated by CSB are also affected by inhibitors of histone deacetylase and DNA methylation, as well as by defects in poly(ADP-ribose)-polymerase function and RNA polymerase II elongation. Moreover, consistent with these microarray expression data, CSB-null cells are sensitive to inhibitors of histone deacetylase or poly(ADP-ribose)-polymerase. Our data indicate a general role for CSB protein in maintenance and remodeling of chromatin structure and suggest that CS is a disease of transcriptional deregulation caused by misexpression of growth-suppressive, inflammatory, and proapoptotic pathways.
Collapse
Affiliation(s)
- John C. Newman
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195-7350
| | - Arnold D. Bailey
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195-7350
| | | |
Collapse
|
275
|
Budovsky A, Muradian KK, Fraifeld VE. From Disease-Oriented to Aging/Longevity-Oriented Studies. Rejuvenation Res 2006; 9:207-10. [PMID: 16706644 DOI: 10.1089/rej.2006.9.207] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Aging should be considered a major risk factor for life-threatening degenerative pathologies including atherosclerosis, cancer, neurodegeneration, diabetes type II, osteoporosis, and sarcopenia. Although an apparent paradox, it appears that the most effective way to delay or even to avert age-related diseases is to live longer. Common changes in the epigenetic control of gene expression may be one of the central mechanisms behind both aging and age-associated pathologies. If so, epigenetic interventions may serve in a twofold manner: (a) to extend the lifespan and (b) cure age-related degenerative diseases. Currently predominant disease-oriented paradigm should be reconsidered toward aging/longevity oriented.
Collapse
Affiliation(s)
- Arie Budovsky
- Department of Microbiology and Immunology, Center for Multidisciplinary Research in Aging, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | | | | |
Collapse
|
276
|
Yang I, Park IY, Jang SM, Shi LH, Ku HK, Park SR. Rapid quantification of DNA methylation through dNMP analysis following bisulfite-PCR. Nucleic Acids Res 2006; 34:e61. [PMID: 16679448 PMCID: PMC1458279 DOI: 10.1093/nar/gkl257] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We report a novel method for rapid quantification of the degree of DNA methylation of a specific gene. Our method combined bisulfite-mediated PCR and quantification of deoxyribonucleoside monophosphate (dNMP) contents in the PCR product through capillary electrophoresis. A specific bisulfite-PCR product was enzymatically hydrolyzed to dNMP monomers which were quantitatively analyzed through subsequent capillary electrophoresis. PCR following bisulfite treatment converts unmethylated cytosines to thymines while leaving methyl-cytosines unchanged. Then the ratio of cytosine to thymine determined by capillary electrophoresis represents the ratio of methyl-cytosine to cytosine in genomic locus of interest. Pure oligonucleotides with known sequences were processed in parallel as standards for normalization of dNMP peaks in capillary electrophoresis. Sources of quantification uncertainty such as carryovers of dNTPs or primers and incomplete hydrolysis were examined and ruled out. When the method was applied to samples with known methylation levels (by bisulfite-mediated sequencing) as a validation, deviations were within ±5%. After bisulfite-PCR, the analytical procedure can be completed within 1.5 h.
Collapse
Affiliation(s)
| | - In Young Park
- Division of Genomics and Proteomics, Korea Research Institute of Bioscience and BiotechnologyDaejeon 305-333, Korea
| | | | | | | | - Sang-Ryoul Park
- To whom correspondence should be addressed. Tel: +82 42 868 5658; Fax: +82 42 868 5801;
| |
Collapse
|
277
|
Ray D, Wu A, Wilkinson JE, Murphy HS, Lu Q, Kluve-Beckerman B, Liepnieks JJ, Benson M, Yung R, Richardson B. Aging in heterozygous Dnmt1-deficient mice: effects on survival, the DNA methylation genes, and the development of amyloidosis. J Gerontol A Biol Sci Med Sci 2006; 61:115-24. [PMID: 16510855 DOI: 10.1093/gerona/61.2.115] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We previously reported that heterozygous DNA methyltransferase 1-deficient (Dnmt1(+/-)) mice maintain T-cell immune function and DNA methylation levels with aging, whereas controls develop autoimmunity, immune senescence, and DNA hypomethylation. We therefore compared survival, cause of death, and T-cell DNA methylation gene expression during aging in Dnmt1(+/-) mice and controls. No difference in longevity was observed, but greater numbers of Dnmt1(+/-) mice developed jejunal apolipoprotein AII amyloidosis. Both groups showed decreased Dnmt1 expression with aging. However, expression of the de novo methyltransferases Dnmt3a and Dnmt3b increased with aging in stimulated T cells from control mice. MeCP2, a methylcytosine binding protein that participates in maintenance DNA methylation, increased with age in Dnmt1(+/-) mice, suggesting a mechanism for the sustained DNA methylation levels. This model thus provides potential mechanisms for DNA methylation changes of aging, and suggests that changes in DNA methylation may contribute to some forms of amyloidosis that develop with aging.
Collapse
Affiliation(s)
- Donna Ray
- Department of Medicine, University of Michigan, Ann Arbor, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
278
|
Rodenhiser D, Mann M. Epigenetics and human disease: translating basic biology into clinical applications. CMAJ 2006; 174:341-8. [PMID: 16446478 PMCID: PMC1373719 DOI: 10.1503/cmaj.050774] [Citation(s) in RCA: 270] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Epigenetics refers to the study of heritable changes in gene expression that occur without a change in DNA sequence. Research has shown that epigenetic mechanisms provide an "extra" layer of transcriptional control that regulates how genes are expressed. These mechanisms are critical components in the normal development and growth of cells. Epigenetic abnormalities have been found to be causative factors in cancer, genetic disorders and pediatric syndromes as well as contributing factors in autoimmune diseases and aging. In this review, we examine the basic principles of epigenetic mechanisms and their contribution to human health as well as the clinical consequences of epigenetic errors. In addition, we address the use of epigenetic pathways in new approaches to diagnosis and targeted treatments across the clinical spectrum.
Collapse
Affiliation(s)
- David Rodenhiser
- EpiGenWestern Research Group, Children's Health Research Institute, London, Ont.
| | | |
Collapse
|
279
|
Abstract
Genetic, or genomic, instability refers to a series of observed spontaneous genetic changes occurring at an accelerated rate in cell populations derived from the same ancestral precursor. This is far from a new finding, but is one that has increasingly gained more attention in the last decade due to its plausible role(s) in tumorigenesis. The majority of genetic alterations contributing to the malignant transformation are seen in growth regulatory genes, and in genes involved in cell cycle progression and arrest. Genomic instability may present itself through alterations in the length of short repeat stretches of coding and non-coding DNA, resulting in microsatellite instability. Tumors with such profiles are referred to as exhibiting a mutator phenotype, which is largely a consequence of inactivating mutations in DNA damage repair genes. Genomic instability may also, and most commonly, results from gross chromosomal changes, such as translocations or amplifications, which lead to chromosomal instability. Telomere length and telomerase activity, important in maintaining chromosomal structure and in regulating a normal cell's lifespan, have been shown to have a function in both suppressing and facilitating malignant transformation. In addition to such direct sequence and structural changes, gene silencing through the hypermethylation of promoter regions, or increased gene expression through the hypomethylation of such regions, together, form an alternative, epigenetic mechanism leading to instability. Emerging evidence also suggests that dietary and environmental agents can further modulate the contribution of genetic instability to tumorigenesis. Currently, there is still much debate over the distinct classes of genomic instability and their specific roles in the initiation of tumor formation, as well as in the progressive transition to a cancerous state. This review examines the various molecular mechanisms that result in this genomic instability and the potential contribution of the latter to human carcinogenesis.
Collapse
Affiliation(s)
- Stavroula Raptis
- Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, M5G 1X5 Canada.
| | | |
Collapse
|
280
|
Brena RM, Huang THM, Plass C. Quantitative assessment of DNA methylation: potential applications for disease diagnosis, classification, and prognosis in clinical settings. J Mol Med (Berl) 2006; 84:365-77. [PMID: 16416310 DOI: 10.1007/s00109-005-0034-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Accepted: 11/29/2005] [Indexed: 12/31/2022]
Abstract
Deregulation of the epigenome is now recognized as a major mechanism involved in the development and progression of human diseases such as cancer. As opposed to the irreversible nature of genetic events, which introduce changes in the primary DNA sequence, epigenetic modifications are reversible and leave the original DNA sequence intact. There is now evidence that the epigenetic landscape in humans undergoes modifications as the result of normal aging, with older individuals exhibiting higher levels of promoter hypermethylation compared to younger ones. Thus, it has been proposed that the higher incidence of certain disease in older individuals might be, in part, a consequence of an inherent change in the control and regulation of the epigenome. These observations are of remarkable clinical significance since the aberrant epigenetic changes characteristic of disease provide a unique platform for the development of new therapeutic approaches. In this review, we address the significance of DNA methylation changes that result or lead to disease, occur with aging, or may be the result of environmental exposure. We provide a detailed description of quantitative techniques currently available for the detection and analysis of DNA methylation and provide a comprehensive framework that may allow for the incorporation of protocols which include DNA methylation as a tool for disease diagnosis and classification, which could lead to the tailoring of therapeutic approaches designed to individual patient needs.
Collapse
Affiliation(s)
- Romulo Martin Brena
- Division of Human Cancer Genetics, Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | | | | |
Collapse
|
281
|
Genescà A, Martín M, Latre L, Soler D, Pampalona J, Tusell L. Telomere dysfunction: a new player in radiation sensitivity. Bioessays 2006; 28:1172-80. [PMID: 17120191 DOI: 10.1002/bies.20501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Human individuals often exhibit important differences in their sensitivity to ionising radiation. Extensive literature links radiation sensitivity with impaired DNA repair which is due to a lack of correct functioning in many proteins involved in DNA-repair pathways and/or in DNA-damage checkpoint responses. Given that ionising radiation is an important and widespread diagnostic and therapeutic tool, it is important to investigate further those factors and mechanisms that underlie individual radiosensitivity. Recently, evidence is accumulating that telomere function may well be involved in cellular and organism responses to ionising radiation, broadening still further the currently complex and challenging scenario.
Collapse
Affiliation(s)
- Anna Genescà
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Spain.
| | | | | | | | | | | |
Collapse
|
282
|
Park HW, Kang HC, Kim IJ, Jang SG, Kim K, Yoon HJ, Jeong SY, Park JG. Correlation between hypermethylation of theRASSF2A promoter and K-ras/BRAF mutations in microsatellite-stable colorectal cancers. Int J Cancer 2006; 120:7-12. [PMID: 17013898 DOI: 10.1002/ijc.22276] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recently, RASSF2A was identified as a potential tumor suppressor epigenetically inactivated in human cancers. Here, we evaluated the methylation status of RASSF2A in colorectal cancer (CRC) and analyzed its correlation with K-ras/BRAF mutations, microsatellite instability status and other clinicopathological features. Using methylation-specific PCR and bisulfite sequencing, we analyzed the methylation status in primary CRC, adenomas and corresponding normal tissues and then compared it with the presence of K-ras and BRAF mutations. We also examined the expression and methylation status of RASSF2A in CRC cell lines. We found that aberrant methylation of RASSF2A promoter regions is associated with gene silencing in CRC cell lines. In primary CRC, the frequency of RASSF2A methylation was 72.6%, and it was found in 16 of 16 (100%) adenomas. In addition, there was a positive correlation between K-ras/BRAF mutations and RASSF2A methylation in primary CRC. Furthermore, a significant positive correlation between K-ras/BRAF mutations and RASSF2A methylation was also observed in microsatellite-stable (p = 0.033) and distal CRC (p = 0.025). These results show that RASSF2A methylation is a frequent event in colorectal tumorigenesis and positively correlates with K-ras/BRAF mutation in microsatellite-stable or distal CRC.
Collapse
Affiliation(s)
- Hye-Won Park
- Laboratory of Cell Biology, Cancer Research Institute and Cancer Research Center, Seoul National University, Korea
| | | | | | | | | | | | | | | |
Collapse
|
283
|
Mani ST, Thakur MK. In the cerebral cortex of female and male mice, amyloid precursor protein (APP) promoter methylation is higher in females and differentially regulated by sex steroids. Brain Res 2005; 1067:43-7. [PMID: 16360126 DOI: 10.1016/j.brainres.2005.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 09/22/2005] [Accepted: 10/02/2005] [Indexed: 01/20/2023]
Abstract
The over-expression of amyloid precursor protein (APP) gene in certain areas of the brain indicates abnormalities in gene regulation as an important factor for the development of Alzheimer's disease (AD). We have reported recently that APP mRNA expression is lower in female as compared to male and is regulated by sex steroids. As methylation of promoter is crucial for such regulation, we have used isoschizomeric restriction enzymes MspI and HpaII to analyze the pattern of APP promoter methylation in the cerebral cortex of intact, gonadectomized, testosterone- and estradiol-treated adult and old mice of both sexes. Southern blots of DNA digested with HindIII/MspI or HindIII/HpaII from different groups of mice were probed with a 1.27-kb DIG-11-dUTP labeled APP promoter fragment. The results revealed four distinct bands of 315 bp, 596 bp, 911 bp, and 2.6 kb by MspI, a single band of 2.6 kb by HpaII in all groups and an additional 2.9 kb in intact and estradiol treated old male and testosterone-treated adult female mice. The intensity of 2.6-kb band was relatively lower in intact female as compared to male and varied with different treatments in both ages, indicating the modulation of methylation. Thus, these findings showed that APP promoter methylation is higher in female and differentially regulated by sex steroids in the mice cerebral cortex, suggesting a strong correlation between promoter methylation and transcriptional silencing of APP.
Collapse
Affiliation(s)
- S T Mani
- Biochemistry and Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, India
| | | |
Collapse
|
284
|
Jeong KS, Lee S. Estimating the total mouse DNA methylation according to the B1 repetitive elements. Biochem Biophys Res Commun 2005; 335:1211-6. [PMID: 16115613 DOI: 10.1016/j.bbrc.2005.08.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 08/02/2005] [Indexed: 12/31/2022]
Abstract
Measuring the degree of methylation of the B1 element in mouse may represent the global DNA methylation status because about 30,000 copies of the B1 element are randomly dispersed in the total mouse genome. Six CpG dinucleotides are located within each 163 bp size of B1 element, and each CpG dinucleotide was partially methylated. We quantitated the DNA methylation of the B1 repetitive elements by performing PCR for the methylation specific PCR (MSP) and also by the pyrosequencing. Each CpG dinucleotide was methylated at an average of 9% in the mouse genome by the pyrosequencing and MSP. Especially, we checked whether CpG methylation of the B1 element could respond to a treatment of the DNA methylation inhibitor, 5-azacytidine (5-AzaC). Consequently, the calibration graph resulting from measuring the relative CpG methylation percentage of the B1 element is linearly decreased with the increasing amount of 5-AzaC (up to 50 ng/ml concentration) in the NIH3T3 cells with a standard deviation of only 1.73% between three independent assays. Our methods can be applied to the routine analysis of the global DNA methylation changes in mouse in vivo and in vitro in pharmaceuticals and basic epigenetic research with efforts being less labor-intensive.
Collapse
Affiliation(s)
- Kyoung-Sin Jeong
- Functional Genomics Lab, CHA Research Institute, Bundang Campus, College of Medicine, Pochon CHA University, 222 Yatap-Dong, Bundang-Gu, Sungnam-Si, Kyunggi-Do, 463-836, Republic of Korea
| | | |
Collapse
|
285
|
Roach HI, Yamada N, Cheung KSC, Tilley S, Clarke NMP, Oreffo ROC, Kokubun S, Bronner F. Association between the abnormal expression of matrix-degrading enzymes by human osteoarthritic chondrocytes and demethylation of specific CpG sites in the promoter regions. ACTA ACUST UNITED AC 2005; 52:3110-24. [PMID: 16200590 DOI: 10.1002/art.21300] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To investigate whether the abnormal expression of matrix metalloproteinases (MMPs) 3, 9, and 13 and ADAMTS-4 by human osteoarthritic (OA) chondrocytes is associated with epigenetic "unsilencing." METHODS Cartilage was obtained from the femoral heads of 16 patients with OA and 10 control patients with femoral neck fracture. Chondrocytes with abnormal enzyme expression were immunolocalized. DNA was extracted, and the methylation status of the promoter regions of MMPs 3, 9, and 13 and ADAMTS-4 was analyzed with methylation-sensitive restriction enzymes, followed by polymerase chain reaction amplification. RESULTS Very few chondrocytes from control cartilage expressed the degrading enzymes, whereas all clonal chondrocytes from late-stage OA cartilage were immunopositive. The overall percentage of non-methylated sites was increased in OA patients (48.6%) compared with controls (20.1%): 20% versus 4% for MMP-13, 81% versus 47% for MMP-9, 57% versus 30% for MMP-3, and 48% versus 0% for ADAMTS-4. Not all CpG sites were equally susceptible to loss of methylation. Some sites were uniformly methylated, whereas in others, methylation was generally absent. For each enzyme, there was 1 specific CpG site where the demethylation in OA patients was significantly higher than that in controls: at -110 for MMP-13, -36 for MMP-9, -635 for MMP-3, and -753 for ADAMTS-4. CONCLUSION This study provides the first evidence that altered synthesis of cartilage-degrading enzymes by late-stage OA chondrocytes may have resulted from epigenetic changes in the methylation status of CpG sites in the promoter regions of these enzymes. These changes, which are clonally transmitted to daughter cells, may contribute to the development of OA.
Collapse
|
286
|
Kannanayakal TJ, Eberwine J. mRNA methods used in dissecting gene expression of the brain. Ageing Res Rev 2005; 4:513-28. [PMID: 16257586 DOI: 10.1016/j.arr.2005.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022]
Affiliation(s)
- Theresa Joseph Kannanayakal
- Department of Pharmacology, University of Pennsylvania School of Medicine, 37 John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA 19104-6084, USA
| | | |
Collapse
|
287
|
Lindsey JC, Anderton JA, Lusher ME, Clifford SC. Epigenetic events in medulloblastoma development. Neurosurg Focus 2005; 19:E10. [PMID: 16398460 DOI: 10.3171/foc.2005.19.5.11] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Over the last decade, the analysis of genetic defects in primary tumors has been central to the identification of molecular events and biological pathways involved in the pathogenesis of medulloblastoma, the most common malignant brain tumor of childhood. Despite this, understanding of the molecular basis of the majority of cases remains poor. In recent years, the emerging field of epigenetics, which describes heritable alterations in gene expression that occur in the absence of DNA sequence changes, has forced a revision of the understanding of the mechanisms of gene disruption in cancer. Accumulating evidence indicates a significant involvement for epigenetic events in medulloblastoma development. Recent studies have identified a series of candidate tumor suppressor genes (for example, RASSF1A, CASP8, and HIC1) that are each specifically epigenetically inactivated in a large proportion (> 30%) of medulloblastomas by promoter hypermethylation, leading to the silencing of their gene expression. These findings shed new light on medulloblastoma and offer great potential for an improved understanding of its molecular pathology. The authors review the current understanding of epigenetic events in cancer and their contribution to medulloblastoma development. Their nature, origins, and functional role(s) in tumorigenesis are considered, and the authors assess the potential utility of these events as a basis for novel diagnostic and therapeutic approaches.
Collapse
Affiliation(s)
- Janet C Lindsey
- Northern Institute for Cancer Research, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | | | | | | |
Collapse
|
288
|
Xu J. Age-related changes in Usp9x protein expression and DNA methylation in mouse brain. ACTA ACUST UNITED AC 2005; 140:17-24. [PMID: 16023255 DOI: 10.1016/j.molbrainres.2005.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 06/13/2005] [Accepted: 06/15/2005] [Indexed: 01/24/2023]
Abstract
Usp9x, a ubiquitin-specific protease implicated in synaptic development, was found to be more abundant in adult as compared to newborn mouse brain tissue. The Usp9x gene was less methylated in adults than in newborns in both the promoter and the protein coding region. Compared with newborns, the adult mouse brain also had lower levels of Dnmt1, the enzyme responsible for maintaining DNA methylation state. These age-associated changes in DNA methylation and ubiquitin system protein concentrations potentially contribute to developmental changes in brain structure and function.
Collapse
Affiliation(s)
- Jun Xu
- Department of Physiological Science, University of California, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1606, USA.
| |
Collapse
|
289
|
Celewicz L, Mayer M, Shetlar MD. The photochemistry of thymidylyl-(3'-5')-5-methyl-2'-deoxycytidine in aqueous solution. Photochem Photobiol 2005; 81:404-18. [PMID: 15493957 DOI: 10.1562/2004-06-15-ra-201.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The photochemistry of the dinucleoside monophosphate thymidylyl-(3'-5')-5-methyl-2'-deoxycytidine (Tpm5dC) has been studied in aqueous solution using both 254 nm and UV-B radiation. A variety of dinucleotide photoproducts containing 5-methylcytosine (m5C) have been isolated and characterized. These include two cyclobutane dimers (CBD) (the cis-syn [c,s]and trans-syn forms), a (6-4) adduct and its related Dewar isomer, and two isomers of a product in which the m5C moiety was converted into an acrylamidine. Small amounts of thymidylyl-(3'-5')-thymidine (TpT) were also formed, presumably as a secondary photoreaction product. In addition, a photoproduct was characterized in which the m5C moiety was lost, thus generating 3'-thymidylic acid esterified with 2'-deoxyribose at the 5-hydroxyl on the sugar moiety. The c,s CBD of Tpm5dC readily undergoes deamination to form the corresponding CBD of TpT. The kinetics of this deamination process has been studied; the corresponding enthalpy and entropy of activation for the reaction have been evaluated at pH 7.4 as being, respectively, 73.4 kJ/mol and -103.5 J/K mol. Deamination was not observed for the other characterized photoproducts of Tpm5dC.
Collapse
Affiliation(s)
- Lech Celewicz
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, CA 94143-0446, USA
| | | | | |
Collapse
|
290
|
Newman JC, Weiner AM. L2L: a simple tool for discovering the hidden significance in microarray expression data. Genome Biol 2005; 6:R81. [PMID: 16168088 PMCID: PMC1242216 DOI: 10.1186/gb-2005-6-9-r81] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Revised: 06/16/2005] [Accepted: 07/26/2005] [Indexed: 12/11/2022] Open
Abstract
L2L is a database consisting of lists of differentially expressed genes compiled from published mammalian microarray studies, along with an easy-to-use application for mining the database with the user's own microarray data. As illustrated by re-analysis of a recent study of diabetic nephropathy, L2L identifies novel biological patterns in microarray data, providing insights into the underlying nature of biological processes and disease. L2L is available online at the authors' website [http://depts.washington.edu/l2l/].
Collapse
Affiliation(s)
- John C Newman
- Department of Biochemistry, University of Washington, Seattle, WA 98115, USA
| | - Alan M Weiner
- Department of Biochemistry, University of Washington, Seattle, WA 98115, USA
| |
Collapse
|
291
|
Pandolfi S, Bonafè M, Di Tella L, Tiberi L, Salvioli S, Monti D, Sorbi S, Franceschi C. p66shc is highly expressed in fibroblasts from centenarians. Mech Ageing Dev 2005; 126:839-44. [PMID: 15992607 DOI: 10.1016/j.mad.2005.03.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Revised: 03/01/2005] [Accepted: 03/04/2005] [Indexed: 11/21/2022]
Abstract
p66(shc-/-) mice exhibit prolonged lifespan and increased resistance to oxidative and hypoxic stress. To investigate p66(shc) involvement in human longevity, p66(shc) mRNA and protein were evaluated in fibroblasts from young people, elderly and centenarians, exposed to oxidative or hypoxic stress. Unexpectedly, centenarians showed the highest basal levels of p66(shc). Oxidative stress induced p66(shc) in all samples. At variance, hypoxic stress caused p66(shc) reduction only in cells from centenarians. These changes occurred in absence of any modification of p66(shc) promoter methylation pattern. Intriguingly, in cells from centenarians, p66(shc) induction was affected by p53 codon 72 polymorphism. Thus, cells from centenarians present a peculiar regulation of p66(shc), suggesting that its role in mammalian longevity is more complex than previously thought.
Collapse
Affiliation(s)
- S Pandolfi
- Department of Experimental Pathology, University of Bologna, via S. Giacomo 12, 40126 Bologna, Italy
| | | | | | | | | | | | | | | |
Collapse
|
292
|
Ulrey CL, Liu L, Andrews LG, Tollefsbol TO. The impact of metabolism on DNA methylation. Hum Mol Genet 2005; 14 Spec No 1:R139-47. [PMID: 15809266 DOI: 10.1093/hmg/ddi100] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Methylation of genomic cytosines is one of the best characterized epigenetic mechanisms, and investigation of its relationship with other biochemical pathways represents a critical stage in the elucidation of biological information processing. The field also has immense potential for the development of medical treatments for any number of conditions ranging from aging to neurological disorders. The DNA methylation status of genes is responsible for many heritable traits and varies more or less independently of the genetic code. This variation is often a result of cellular environmental factors including metabolism. A key metabolite in this regard is homocysteine. Knowledge of homocysteine metabolism continues to be amassed, yet the part played by aberrant DNA methylation in homocysteine-related pathologies is often, at best, conjectural. In this analysis, we will review recent insights and attempt to speculate meaningfully concerning the dynamics of the methionine cycle in relation to DNA methylation and disease.
Collapse
Affiliation(s)
- Clayton L Ulrey
- Department of Biology, University of Alabama at Birmingham, 35294, USA
| | | | | | | |
Collapse
|
293
|
Bhalla KN. Epigenetic and chromatin modifiers as targeted therapy of hematologic malignancies. J Clin Oncol 2005; 23:3971-93. [PMID: 15897549 DOI: 10.1200/jco.2005.16.600] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Epigenetic regulation of gene expression is mediated through alterations in the DNA methylation status, covalent modifications of core nucleosomal histones, rearrangement of histones, and by RNA interference. It is now abundantly clear that deregulation of epigenetic mechanisms cooperates with genetic alterations in the development and progression of cancer and leukemia. Epigenetic deregulation affects several aspects of tumor cell biology, including cell growth, cell cycle control, differentiation, DNA repair, and cell death. This raises the strong possibility that reversing deregulated epigenetic mechanisms may be an effective treatment strategy for leukemia and cancer. This treatment strategy may either be designed to separately or collectively target the specific perturbations in the epigenetic mechanisms found in human hematologic malignancies. The following review describes our current understanding of the important deregulated epigenetic mechanisms and the preclinical and clinical development of epigenetic and chromatin modifiers in the therapy of these disorders.
Collapse
Affiliation(s)
- Kapil N Bhalla
- Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center and Research Institute University of South Florida, Tampa, FL 33612, USA.
| |
Collapse
|
294
|
Shelnutt KP, Kauwell GPA, Gregory JF, Maneval DR, Quinlivan EP, Theriaque DW, Henderson GN, Bailey LB. Methylenetetrahydrofolate reductase 677C-->T polymorphism affects DNA methylation in response to controlled folate intake in young women. J Nutr Biochem 2005; 15:554-60. [PMID: 15350988 DOI: 10.1016/j.jnutbio.2004.04.003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Revised: 03/24/2004] [Accepted: 04/05/2004] [Indexed: 12/12/2022]
Abstract
DNA methylation is critical for normal genomic structure and function and is dependent on adequate folate status. A polymorphism (677C-->T) in a key folate enzyme, methylenetetrahydrofolate reductase (MTHFR), may impair DNA methylation when folate intake is inadequate and may increase the risk of reproductive abnormalities. The present study was designed to evaluate the effect of the MTHFR 677C-->T polymorphism on changes in global DNA methylation in young women consuming a low folate diet followed by repletion with the current Recommended Dietary Allowance (RDA). Women (age 20-30 years) with the TT (variant; n = 19) or CC (n = 22) genotype for the MTHFR 677C-->T polymorphism participated in a folate depletion-repletion study (7 weeks, 115 microg DFE/day; 7 weeks, 400 microg DFE/day). DNA methylation was measured at baseline, week 7, and week 14 using a [3H]methyl acceptance assay and a novel liquid chromatography tandem mass spectrometry assay of the DNA bases methylcytosine and cytosine. [3H]Methyl group acceptance tended to increase (P = 0.08) during depletion in all subjects, indicative of a decrease in global DNA methylation. During repletion, the raw change and the percent change in the methylcytosine/total cytosine ratio increased (P = 0.03 and P = 0.04, respectively) only in the subjects with the TT genotype. Moderate folate depletion in young women may cause a decrease in overall DNA methylation. The response to folate repletion suggests that following folate depletion women with the MTHFR 677 TT genotype have a greater increase in DNA methylation with folate repletion than women with the CC genotype.
Collapse
Affiliation(s)
- Karla P Shelnutt
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, FL 32611, USA
| | | | | | | | | | | | | | | |
Collapse
|
295
|
Geigl JB, Langer S, Barwisch S, Pfleghaar K, Lederer G, Speicher MR. Analysis of gene expression patterns and chromosomal changes associated with aging. Cancer Res 2005; 64:8550-7. [PMID: 15574761 DOI: 10.1158/0008-5472.can-04-2151] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Age is the largest single risk factor for the development of cancer in mammals. Age-associated chromosomal changes, such as aneuploidy and telomere erosion, may be vitally involved in the initial steps of tumorigenesis. However, changes in gene expression specific for increased aneuploidy with age have not yet been characterized. Here, we address these questions by using a panel of fibroblast cell lines and lymphocyte cultures from young and old age groups. Oligonucleotide microarrays were used to characterize the expression of 14,500 genes. We measured telomere length and analyzed chromosome copy number changes and structural rearrangements by multicolor interphase fluorescence in situ hybridization and 7-fluorochrome multiplex fluorescence in situ hybridization, and we tried to show a relationship between gene expression patterns and chromosomal changes. These analyses revealed a number of genes involved in both the cell cycle and proliferation that are differently expressed in aged cells. More importantly, our data show an association between age-related aneuploidy and the gene expression level of genes involved in centromere and kinetochore function and in the microtubule and spindle assembly apparatus. To verify that some of these genes may also be involved in tumorigenesis, we compared the expression of these genes in chromosomally stable microsatellite instability and chromosomally unstable chromosomal instability colorectal tumor cell lines. Three genes (Notch2, H2AFY2, and CDC5L) showed similar expression differences between microsatellite instability and chromosomal instability cell lines as observed between the young and old cell cultures suggesting that they may play a role in tumorigenesis.
Collapse
Affiliation(s)
- Jochen B Geigl
- Institute of Human Genetics, Technical University, Munich, Germany
| | | | | | | | | | | |
Collapse
|
296
|
Jung KY, Dean D, Jiang J, Gaylor S, Griffith WH, Burghardt RC, Parrish AR. Loss of N-cadherin and alpha-catenin in the proximal tubules of aging male Fischer 344 rats. Mech Ageing Dev 2005; 125:445-53. [PMID: 15178134 DOI: 10.1016/j.mad.2004.04.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Revised: 02/16/2004] [Accepted: 04/06/2004] [Indexed: 11/29/2022]
Abstract
Aging is associated with a loss of renal reserve, and increased sensitivity to either xenobiotic or physiologic insult. Given the critical role of the cadherin/catenin complex in establishing and maintaining the integrity and polarity of tubular epithelial cells, it was hypothesized that aging was associated with alterations in renal cadherin/catenin complexes. Histological assessment of aged (24 months) kidneys harvested from male Fischer 344 rats demonstrates mild degeneration of proximal tubules, multifocal chronic lymphocytic infiltration, moderate development of protein casts inside tubules, and tubular dilatation or degeneration. Western blot analysis revealed that N-cadherin protein expression is not constant over 24 months. N-cadherin expression increased from 4 to 9 months, with peak levels at 9 and 13 months. A decrease in expression was seen at 19 months and an almost complete loss of expression was seen at 24 months. In contrast, the expression of E- and Ksp-cadherin was constant over 24 months. A loss of alpha-catenin at was seen at 19 and 24 months in the absence of changes in beta-, gamma-, and p120-catenin. This pattern of N-cadherin expression (increase followed by decrease) was confirmed by real-time PCR analysis, which demonstrated a similar pattern as the Western blot, suggesting that the loss of N-cadherin protein was due to decreased gene expression. The loss of N-cadherin was specific for the kidney, as no changes in N-cadherin expression in the liver, brain, or testes were seen during aging. The conclusion that loss of N-cadherin expression is a critical component of the renal dysfunction associated with aging is supported by the finding that caloric restriction attenuates the loss of N-cadherin, as well as the finding that a significant loss of N-cadherin is seen in the kidneys of ZDF x SHHF rats, a genetic model of end-stage renal disease. Cadherin and catenin expression was further analyzed by immunofluorescence. A significant loss of staining of both N-cadherin and alpha-catenin was seen in the proximal tubules of rats at 24 months. Interestingly, this corresponded with delocalization of the alpha-1 subunit of the Na+K+-ATPase, i.e. aberrant staining on cell-cell borders and some indication of apical staining in proximal tubules. Taken together, these data suggest that aging is associated with decreased expression of N-cadherin and alpha-catenin and is associated with a loss of cell polarity.
Collapse
Affiliation(s)
- Ki-Yoon Jung
- Department of Medical Pharmacology and Toxicology, College of Medicine, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA
| | | | | | | | | | | | | |
Collapse
|
297
|
Abstract
AbstractInadequate folate intake and aging are each strongly implicated as important risk factors for certain cancers. Since both folate depletion and aging are strongly associated with hyperhomocysteinemia, genomic DNA hypomethylation, and increased uracil misincorporation into DNA, it appears that each of them enhances carcinogenesis by inducing a derangement of one-carbon metabolism that supplies one-carbons to biological methylation reactions and nucleotide synthesis. Recent studies have demonstrated that inadequate dietary folate and aging may interact and synergistically disturb the normal homeostasis of one-carbon metabolism, thereby provoking subsequent biochemical and molecular aberrations, including alterations in critical gene expression related to carcinogenesis. These studies have further indicated that modest folate supplementation may reverse or partially ameliorate those adverse effects induced by folate depletion and aging.
Collapse
Affiliation(s)
- Sang-Woon Choi
- Vitamins and Carcinogenesis Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
| | | |
Collapse
|
298
|
Abstract
Epigenetic mechanisms act to change the accessibility of chromatin to transcriptional regulation locally and globally via modifications of the DNA and by modification or rearrangement of nucleosomes. Epigenetic gene regulation collaborates with genetic alterations in cancer development. This is evident from every aspect of tumor biology including cell growth and differentiation, cell cycle control, DNA repair, angiogenesis, migration, and evasion of host immunosurveillance. In contrast to genetic cancer causes, the possibility of reversing epigenetic codes may provide new targets for therapeutic intervention.
Collapse
Affiliation(s)
- Anders H Lund
- Division of Molecular Genetics, The Netherlands Cancer Institute, 1066CX Amsterdam, The Netherlands.
| | | |
Collapse
|
299
|
Varga AE, Leonardos L, Jackson P, Marreiros A, Cowled PA. Methylation of a CpG island within the uroplakin Ib promoter: a possible mechanism for loss of uroplakin Ib expression in bladder carcinoma. Neoplasia 2004; 6:128-35. [PMID: 15140401 PMCID: PMC1502093 DOI: 10.1593/neo.03337] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Uroplakin Ib is a structural protein on the surface of urothelial cells. Expression of uroplakin Ib mRNA is reduced or absent in many transitional cell carcinomas (TCCs) but molecular mechanisms underlying loss of expression remain to be determined. Analysis of the uroplakin Ib promoter identified a weak CpG island spanning the proximal promoter, exon 1, and the beginning of intron 1. This study examined the hypothesis that methylation of this CpG island regulates uroplakin Ib expression. Uroplakin Ib mRNA levels were determined by reverse transcription polymerase chain reaction and CpG methylation was assessed by bisulfite modification of DNA, PCR, and sequencing. A correlation was demonstrated in 15 TCC lines between uroplakin Ib mRNA expression and lack of CpG methylation. In support of a regulatory role for methylation, incubating uroplakin Ib-negative lines with 5-aza-2'-deoxycytidine reactivated uroplakin Ib mRNA expression. A trend between uroplakin Ib mRNA expression and CpG methylation was also observed in normal urothelium and bladder carcinomas. In particular, loss of uroplakin Ib expression correlated with methylation of a putative Sp1/NFkappaB binding motif. The data are consistent with the hypothesis that methylation of specific sites within the uroplakin Ib promoter may be an important factor in the loss of uroplakin Ib expression in TCCs.
Collapse
Affiliation(s)
- Andrea E Varga
- Department of Surgery, The University of Adelaide, The Queen Elizabeth Hospital, Woodville, South Australia, Australia
| | | | | | | | | |
Collapse
|
300
|
McKay JA, Williams EA, Mathers JC. Folate and DNA methylation during in utero development and aging. Biochem Soc Trans 2004; 32:1006-7. [PMID: 15506948 DOI: 10.1042/bst0321006] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
DNA methylation is one of several epigenetic mechanisms that play a regulatory role in genome programming and imprinting during embryogenesis. Aberrant DNA methylation has been implicated in the pathogenesis of a number of diseases associated with aging, including cancer and cardiovascular and neurological diseases. Evidence is accumulating that dietary factors in utero modulate disease risk in later life. Although folic acid is a key component of DNA methylation, the impact of folic acid availability in utero on DNA methylation patterns and disease risk in adulthood is at present poorly characterized. This review describes the relationship between folic acid and DNA methylation, and the association between DNA methylation during in utero development and aging.
Collapse
Affiliation(s)
- J A McKay
- Human Nutrition Research Centre, School of Clinical Medical Sciences, University of Newcastle upon Tyne, NE1 7RU, UK.
| | | | | |
Collapse
|