Table of Contents

Volume 1, Issue 4

  October/November/December 2006

  Pages 155 - 189

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 Issue Catalogue (MARC XML)

RESEARCH PAPERS

Open Access Article

In Vivo Methylation Patterns of the Leptin Promoter in Human and Mouse

Reinhard Stöger
Pages 155 - 162
http://dx.doi.org/10.4161/epi.1.4.3400
Abstract | PDF

Leptin is a fat hormone regulating energy homeostasis. Here, it is reported that the promoter and CpG island of the autosomal gene Leptin (LEP) is a tissue-specific differentially methylated region (T-DMR) and subject to dynamic methylation in human and mouse in vivo. Highly variable densities of cytosine methylation were detected by hairpin-bisulfite PCR among cells in human adipose tissue and peripheral blood leukocytes. Intermediate and low levels of methylation characterize the majority of human LEP epialleles. Low-density epialleles are often methylated at a specific CG site within the binding element of the C/EBP-alpha transcription factor. In the human LEP promoter, the methylation frequency at that site is 1.8-fold as great as the average frequency for all other CG sites analyzed. The Lep promoter has a significantly higher methylation density in mouse somatic tissues than in the human LEP promoter. Though the LEP CpG island is generally unmethylated in both human and mouse sperm, depletion of CG sites within the mouse promoter indicates occasional presence of methylated Lep epialleles in the germline. These findings suggest that LEP promoter methylation is normally imposed during postzygotic development, and that this epigenetic mark may play a role in modulating expression of an important metabolic gene.

Open Access Article

Epigenetic Regulation of Manganese Superoxide Dismutase Expression in Human Breast Cancer Cells

Michael Hitchler, Kornwipa Wikainapakul, Lei Yu, Kristy Powers, Watcharee Attatippaholkun and Frederick Domann
Pages 163 - 171
http://dx.doi.org/10.4161/epi.1.4.3401
Abstract | PDF

Malignant breast cancer cells often exhibit lower expression and activity of manganese superoxide dismutase (MnSOD) than their normal cell counterparts; however, the mechanism(s) responsible for this change remains unclear. We examined whether SOD2, the gene encoding MnSOD, was epigenetically repressed in breast cancer cell lines by DNA methylation and histone acetylation. RT-PCR analysis of SOD2 mRNA showed the non-tumorigenic breast epithelial cell line MCF-10A to have two to three fold higher expression levels than either UACC-893 or MDA-MB-435 breast carcinoma cells. Analysis of a region in the SOD2 promoter by sodium bisulfite genomic sequencing demonstrated significantly higher levels of CpG methylation in both human breast carcinoma cell lines assessed than in MCF-10A cells. CREB binding in vitro to a cognate site derived from this region was repressed by DNA methylation, and CREB binding to the 5’ regulatory region of the SOD2 gene in vivo as determined by ChIP was significantly lower in breast carcinoma cells than in MCF-10A. Increased cytosine methylation was also accompanied by a significant decrease in the level of acetylated histones in the same region of the SOD2 promoter. Finally, a causal link between cytosine methylation and transcriptional repression was established by increasing MnSOD mRNA, protein and activity in breast carcinoma cells using the DNA methyltransferase inhibitor 5-aza-2’-deoxycytidine. These findings indicate that epigenetic silencing of SOD2 constitutes one mechanism leading to the decreased expression of MnSOD observed in many breast cancers.

Open Access Article

Reduced MeCP2 Expression is Frequent in Autism Frontal Cortex and Correlates with Aberrant MECP2 Promoter Methylation

Raman Nagarajan, Amber Hogart, Ynnez Gwye, Michelle R Martin and Janine M. LaSalle
Pages 172 - 182
http://dx.doi.org/10.4161/epi.1.4.3514
Abstract | PDF

Mutations in MECP2, encoding methyl CpG binding protein 2 (MeCP2), cause most cases of Rett syndrome (RTT), an X-linked neurodevelopmental disorder. Both RTT and autism are “pervasive developmental disorders” and share a loss of social, cognitive and language skills and a gain in repetitive stereotyped behavior, following apparently normal perinatal development. Although MECP2 coding mutations are a rare cause of autism, MeCP2 expression defects were previously found in autism brain. To further study the role of MeCP2 in autism spectrum disorders (ASDs), we determined the frequency of MeCP2 expression defects in brain samples from autism and other ASDs. We also tested the hypotheses that MECP2 promoter mutations or aberrant promoter methylation correlate with reduced expression in cases of idiopathic autism. MeCP2 immunofluorescence in autism and other neurodevelopmental disorders was quantified by laser scanning cytometry and compared with control postmortem cerebral cortex samples on a large tissue microarray. A significant reduction in MeCP2 expression compared to age-matched controls was found in 11/14 autism (79%), 9/9 RTT (100%), 4/4 Angelman syndrome (100%), 3/4 Prader-Willi syndrome (75%), 3/5 Down syndrome (60%), and 2/2 attention deficit hyperactivity disorder (100%) frontal cortex samples. One autism female was heterozygous for a rare MECP2 promoter variant that correlated with reduced MeCP2 expression. A more frequent occurrence was significantly increased MECP2 promoter methylation in autism male frontal cortex compared to controls. Furthermore, percent promoter methylation of MECP2 significantly correlated with reduced MeCP2 protein expression. These results suggest that both genetic and epigenetic defects lead to reduced MeCP2 expression and may be important in the complex etiology of autism.

Open Access Article

CD44 and PTGS2 Methylation are Independent Prognostic Markers for Biochemical Recurrence Among Prostate Cancer Patients with Clinically Localized Disease

Karen Woodson, Keith J O’Reilly, David E Ward, Jack Walter, Jeffery Hanson, Elyse L Walk and Joseph A Tangrea
Pages 183 - 186
http://dx.doi.org/10.4161/epi.1.4.3530
Abstract | PDF

Up to 30% of men with clinically localized disease who receive radical prostatectomy develop a biochemical recurrence. Gene methylation in tumor tissue may distinguish men with aggressive cancer. This study evaluated methylation of GSTP1, RARβ2, CD44 and PTGS2 with biochemical recurrence among 60 patients who underwent radical prostatectomy using logistic regression and Kaplan Meier time to event analysis. Methylation of GSTP1 and RARβ2 was not associated with recurrence, however, CD44 and PTGS2 methylation were significant predictors. In multivariate models adjusting for Gleason grade, methylation profile of CD44 and PTGS2 combined was an independent predictor of biochemical recurrence (associated with 9-fold increased risk). In addition, Kaplan Meier analysis showed CD44 and PTGS2 methylation was associated with shorter time to recurrence. CD44 and PTGS2 methylation may predict biochemical recurrence in prostate cancer patients undergoing radical prostatectomy and if validated in larger studies, may identify patients with aggressive cancer.




MEETING REPORT

Open Access Article

DMMC Workshop: Unravelling Chromatin and the Role of Epigenetics in Disease

Steven G Gray
Pages 187 - 189
http://dx.doi.org/10.4161/epi.1.4.3399
Abstract | PDF

No abstract available at this time.