DNA Methylation Profiles Associated with Aberrant Gene Expressions in Endometriosis

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 561-585-Ovarian & Uterine Function II
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-581
Masao Izawa*1, Fuminori Taniguchi2, Naoki Terakawa3 and Tasuku Harada1
1Tottori Univ/Fac of Med, Yonago, Japan, 2Tottori Univ Sch of Med, Yonago, Japan, 3Tottori Univ/Fac of Med, Tottori, Japan
Background:Endometriosis is an estrogen-dependent and inflammatory disease characterized by the presence of endometrium-like tissues primarily on the pelvic peritoneum and ovaries. A marked up-regulation of aromatase gene associated with aberrant DNA demethylation leads to a high estrogen environment in endometriotic tissues (1, 2). Although DNA methylation provides a layer of epigenetic controls that has important implications for diseases, it is unknown whether global alterations in DNA methylation patterns occur in endometriosis and to what extent they are involved in its pathogenesis and pathophysiology.

Objective:Using a genome-wide (GW) profiling of DNA methylation, we challenged an extraction of methylation-dependent gene expression in endometriotic cells.

 Patients: The chocolate cyst lining in ovaries of patients with endometriosis was the source of endometriotic tissue. As control, endometrial tissues were obtained from uteri of cycling premenopausal women who had uterine leiomyoma. These patients had received no hormonal treatment before surgery. We obtained the informed consent from all patients.

Methods:Stromal cells and their cellular DNAs were prepared from 4 endometrial and 4 endometriotic tissues. DNA methylation profiles were assayed using Illumina Infinium HumanMethylation450 BeadChip Array and GeneSpring GX 11.5.  Gene expression was evaluated using qRT-PCR and Western blots.

Results:  1) The 1,811 GpG sites, which were differentially methylated more than 10-fold, were extracted from 485,512 CpGs. Among them, the 954 CpGs (52.7%) were hypermethylated, while the 857 CpGs (47.3%) were hypomethylated in endometriotic cells. 2) When the rate of methylation was restricted to more than 25%, the hypermethylated and hypomethylated CpGs were 657 and 317, respectively. 3) Among them, the promoter proximal CpGs within 1,500bp from transcription start sites were 59 (45 genes) and 47 (35 genes), respectively. 4) GO analysis demonstrated that one third of the hypomethylated CpGs at promoter regions was classified into the regulation of transcription. 5) These hypermethylated and hypomethylated CpGs were observed not only in CpG islands, but also in CpG shores, CpG shelves and open seas. 6) Genes showing the rate of methylation over 90 % in endometrial and endometriotic cells were extracted and their expressions were evaluated.

Conclusion: The overall methylation profile in endometriotic cells was highly similar to that in endometrial cells, supporting the retrograde menstruation theory by Sampson for the pathogenesis of endometriosis. Although the aberrant methylation of CpG was not always in CpG islands within promoter regions, a positive or negative correlation between DNA methylation and gene expression was observed in some genes. These observations show a facet of epigenetic disorder in endometriosis (3).

1) Izawa M, Harada T. et al. (2008) Fertil Steril 89, 1390-6 2) Izawa M, Taniguchi F. et al. (2011) Fertil Steril 95, 33-9 3) Izawa M, Taniguchi F, Harada T. et al. Front Biosci (in press)

Nothing to Disclose: MI, FT, NT, TH

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