TY - JOUR A1 - Hansmann, Tamara A1 - Pliushch, Galyna A1 - Leubner, Monika A1 - Kroll, Patricia A1 - Endt, Daniela A1 - Gehrig, Andrea A1 - Preisler-Adams, Sabine A1 - Wieacker, Peter A1 - Haaf, Thomas T1 - Constitutive promoter methylation of BRCA1 and RAD51C in patients with familial ovarian cancer and early-onset sporadic breast cancer JF - Human Molecular Genetics N2 - Genetic defects in breast cancer (BC) susceptibility genes, most importantly BRCA1 and BRCA2, account for ∼40% of hereditary BC and ovarian cancer (OC). Little is known about the contribution of constitutive (soma-wide) epimutations to the remaining cases. We developed bisulfite pyrosequencing assays to screen >600 affected BRCA1/BRCA2 mutation-negative patients from the German Consortium for Hereditary Breast and Ovarian Cancer for constitutive hypermethylation of ATM, BRCA1, BRCA2, RAD51C, PTEN and TP53 in blood cells. In a second step, patients with ≥6% promoter methylation were analyzed by bisulfite plasmid sequencing to demonstrate the presence of hypermethylated alleles (epimutations), indicative of epigenetic gene silencing. Altogether we identified nine (1.4%) patients with constitutive BRCA1 and three (0.5%) with RAD51C hypermethylation. Epimutations were found in both sporadic cases, in particular in 2 (5.5%) of 37 patients with early-onset BC, and familial cases, in particular 4 (10%) of 39 patients with OC. Hypermethylation was always confined to one of the two parental alleles in a subset (12–40%) of the analyzed cells. Because epimutations occurred in cell types from different embryonal layers, they most likely originated in single cells during early somatic development. We propose that analogous to germline genetic mutations constitutive epimutations may serve as the first hit of tumor development. Because the role of constitutive epimutations in cancer development is likely to be largely underestimated, future strategies for effective testing of susceptibility to BC and OC should include an epimutation screen. KW - promoter methylation Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125673 VL - 21 IS - 21 ER - TY - JOUR A1 - Schneider, Eberhard A1 - Pliushch, Galyna A1 - El Hajj, Nady A1 - Galetzka, Danuta A1 - Puhl, Alexander A1 - Schorsch, Martin A1 - Frauenknecht, Katrin A1 - Riepert, Thomas A1 - Tresch, Achim A1 - Mueller, Annette M. A1 - Coerdt, Wiltrud A1 - Zechner, Ulrich A1 - Haaf, Thomas T1 - Spatial, temporal and interindividual epigenetic variation of functionally important DNA methylation patterns N2 - DNA methylation is an epigenetic modification that plays an important role in gene regulation. It can be influenced by stochastic events, environmental factors and developmental programs. However, little is known about the natural variation of genespecific methylation patterns. In this study, we performed quantitative methylation analyses of six differentially methylated imprinted genes (H19, MEG3, LIT1, NESP55, PEG3 and SNRPN), one hypermethylated pluripotency gene (OCT4) and one hypomethylated tumor suppressor gene (APC) in chorionic villus, fetal and adult cortex, and adult blood samples. Both average methylation level and range of methylation variation depended on the gene locus, tissue type and/or developmental stage. We found considerable variability of functionally important methylation patterns among unrelated healthy individuals and a trend toward more similar methylation levels in monozygotic twins than in dizygotic twins. Imprinted genes showed relatively little methylation changes associated with aging in individuals who are >25 years. The relative differences in methylation among neighboring CpGs in the generally hypomethylated APC promoter may not only reflect stochastic fluctuations but also depend on the tissue type. Our results are consistent with the view that most methylation variation may arise after fertilization, leading to epigenetic mosaicism. KW - Medizin Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-68371 ER -