Radiation-induced epigenetic DNA methylation modification of radiation-response pathways
ABSTRACT: Treatment of tumors with ionizing radiation for cancer therapy induces biological responses that include changes in cell cycle, activation of DNA repair mechanisms, and induction of apoptosis or senescence programs. What is not known is whether ionizing radiation induces an epigenetic DNA methylation response or whether epigenetic changes occur in genes in pathways classically associated with the radiation response. We exposed breast cancer cells to 0, 2, or 6 Gy and determined global DNA methylation at 1, 2, 4, 8, 24, 48, and 72 hours post-irradiation. We found that radiation treatment resulted in a DNA methylation response and that cell cycle, DNA repair, and apoptosis pathways were enriched in genes are were differentially-methylated. DNA methylation profiling of ionizing radiation treated cells using the Infinium HumanMethylation450 BeadChip.
Project description:In this study, we have analyzed DNA methylation characteristics of human mesenchymal stem and progenitor cells (MSPCs) form different tissue sources including bone marrow (BM), white adipose tissue (WAT ), umbilical cord (UC) as well as dermal fibroblasts by using the HumanMethylation450K array. Cells able to form bone through endochondral ossification and attract bone marrow in an innovative in vivo model were compared to cells lacking these capacities. Interestingly only BM-derived MSPCs were capable of bone formation and marrow attraction. These features correlated with unique epigenetic characteristics potentially enabling BM-derived cells to undergo endochondral ossification. 12 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Pluripotent stem cells evade replicative senescence, whereas other primary cells lose their proliferation and differentiation potential after a limited number of cell divisions – and this is accompanied by specific senescence-associated DNA methylation (SA-DNAm) changes. Here, we investigate SA-DNAm changes in mesenchymal stromal cells (MSC) upon long-term culture, irradiation-induced senescence, immortalization and reprogramming into induced pluripotent stem cells (iPSC) using high density HumanMethylation450 BeadChips. SA-DNAm changes are highly reproducible and occur particularly in intergenic and non-promoter regions of developmental genes. We demonstrate that ionizing irradiation, although associated with a very similar senescence phenotype, does not affect SA-DNAm. Furthermore, overexpression of the catalytic subunit of the human telomerase (TERT) or conditional immortalization with a doxycycline-inducible system (TERT and SV40 TAg) result in telomere extension but do not influence SA-DNAm. In contrast, we demonstrate that reprogramming into iPSC prevented SA-DNAm changes. Our results indicate that replicative senescence is associated with an epigenetically controlled process which stalls cells in a particular differentiated state, whereas irradiation-induced senescence and immortalization are not causally related to this process. Absence of SA-DNAm in pluripotent cells may play a central role for their escape from cellular senescence. Samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Matrix elasticity influences differentiation of mesenchymal stem cells (MSCs) but it is unclear if these effects are only transient - while the cells reside on the substrate - or if they reflect persistent lineage commitment. In this study, MSCs were continuously culture-expanded in parallel either on polydimethylsiloxane (PDMS) gels of different elasticity or on tissue culture plastic (TCP) to compare impact on replicative senescence, in vitro differentiation, gene expression, and DNA methylation (DNAm) profiles. The maximal number of cumulative population doublings was not affected by matrix elasticity. Differentiation towards adipogenic and osteogenic lineage was increased on soft and rigid biomaterials, respectively - but this propensity was no more evident if cells were transferred to TCP. Global gene expression profiles and DNAm profiles revealed relatively few differences in MSCs cultured on soft or rigid matrices. Furthermore, only moderate DNAm changes were observed upon culture on very soft hydrogels of human platelet lysate (hPL-gel). Our results support the notion that matrix elasticity influences cellular differentiation while the cells are organized on the substrate, but it does not have major impact on cell-intrinsic lineage determination, replicative senescence or DNAm patterns. 20 samples were hybridized to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Hematopoietic stem and progenitor cells (HPCs) can be maintained in vitro, but the vast majority of their progeny loses “stemness” during culture. In this study, we have analyzed DNA methylation (DNAm) profiles of freshly isolated CD34+ cells and upon expansion on either tissue culture plastic (TCP) or mesenchymal stromal cells (MSCs). DNAm profiles of expanded CD34+ versus CD34- subsets reflected hematopoietic differentiation, whereas culture on TCP or MSCs had little impact. Notably, all cultured HPCs - even those which remained CD34 positive - acquired significant DNA-hypermethylation, particularly in up-stream promoter regions, shore-regions of CpG islands, and binding sides for PU.1 and RUNX1. Our results point to a coordinated epigenetic process which needs to be controlled to enhance self-renewal of HPCs in vitro. 12 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:In order to elucidate the role of DNA methylation in the DME gene regulation, global DNA methylation and mRNA expression profiles of human tissues and cell lines were examinde by HumanMethylation450 Bead Chip and SurePrint G3 Human Gene Expression 8×60K v2. We demonstrated DNA methylation landscape of the DME genes in human tissues. Although a fraction of DME genes can be regulated by their DNA methylation, the variable DNA methylation status probably affects drug metabolism and response. Bisulphite converted DNA from the 4 samples were hybridized to the Illumina HumanMethylation450 BeadChip (Sample L and SI were examined twice).
Project description:Reprogramming of somatic cells into induced pluripotent stem cells (iPSC) is an epigenetic phenomenon. It has been suggested that iPSC retain some tissue-specific memory whereas little is known about inter-individual epigenetic variation of iPSC clones. In this study we have reprogrammed mesenchymal stromal cells (MSC) from human bone marrow by retrovirus-mediated overexpression of OCT-3/4, SOX2, c-MYC, and KLF4. Global DNA-methylation profiles of the initial MSC, MSC-derived iPSC (iP-MSC) and embryonic stem cells (ESC) were then compared using a high density DNA-methylation array covering more than 450,000 CpG sites. Overall, DNA-methylation patterns of iP-MSC and ESC were similar whereas some CpG sites revealed highly significant differences, which were not related to parental MSC. Furthermore, hypermethylation in iP-MSC versus ESC was particularly enriched in developmental genes as well as shore regions next to CpG islands indicating that these differences are not due to tissue-specific memory or random de novo methylation. Subsequently, we searched for CpG sites with donor-specific variation in MSC preparations. These “epigenetic fingerprints” were highly enriched in non-promoter regions and outside of CpG islands – and they were maintained upon reprogramming into iP-MSC. In conclusion, DNA methylation profiles of iP-MSC clones from the same donor were closely related despite heterogeneity of MSC. On the other hand, iP-MSC maintain donor-derived epigenetic differences. In the absence of isogenic controls for disease modeling applications, it would therefore be more appropriate to compare iPSC from different donors rather than a high number of different clones from the same patient. 16 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Standardization of mesenchymal stromal cells (MSCs) remains a major obstacle in regenerative medicine. Starting material and culture expansion affect cell preparations and render comparison between studies difficult. In contrast, induced pluripotent stem cells (iPSCs) assimilate towards a ground-state and may therefore give rise to more standardized cell preparations. We reprogrammed bone marrow MSCs into iPSCs which were subsequently re-differentiated towards MSCs. These iPS-MSCs revealed similar morphology, immunophenotype, in vitro differentiation potential, and gene expression profiles as primary MSCs. DNA methylation (DNAm) profiles of iPSCs maintained some donor-specific characteristics, whereas tissue-specific, senescence-associated, and age-related DNAm patterns were erased during reprogramming. iPS-MSCs reacquired senescence-associated DNAm during culture expansion but they remained rejuvenated with regard to age-related DNAm. Overall, iPS-MSCs and MSCs are similar in function but differ in their epigenetic makeup. 12 samples were hybridized to the Illumina Infinium 450k Human Methylation Beadchip
Project description:In order to elucidate the role of DNA methylation in the DME gene regulation, global DNA methylation and mRNA expression profiles of human tissues and cell lines were examinde by HumanMethylation450 Bead Chip and SurePrint G3 Human Gene Expression 8×60K v2. We demonstrated DNA methylation landscape of the DME genes in human tissues. Although a fraction of DME genes can be regulated by their DNA methylation, the variable DNA methylation status probably affects drug metabolism and response. Bisulphite converted DNA from the 7 samples were hybridized to the Illumina HumanMethylation450 BeadChip.
Project description:Genome-wide DNA methylation profiles of SGI-110-treated ovarian cancer xenografts were obtained using next generation Illumina Infinium 450k assay which includes over 450,000 GpG sites. DNA from 6 samples were hybridized to the Illumina's Infinium HumanMethylation 450 BeadChip
Project description:Background: Low birth weight is associated with an increased adult metabolic disease risk. It is widely discussed that poor intrauterine conditions could induce long-lasting epigenetic modifications, leading to systemic changes in regulation of metabolic genes. In a unique cohort of 17 monozygotic (MZ) monochorionic female twins very discordant for birth weight (relative differences ranging from 21.3-35.7%), we examined if adverse prenatal growth conditions experienced by the smaller co-twins lead to systemic long-lasting DNA methylation changes. Genome-wide DNA methylation profiles were acquired from saliva DNA using the Infinium HumanMethylation450 BeadChip, targeting ~2% of all CpGs in the genome. Results: Overall, co-twins showed very similar genome-wide DNA methylation profiles. Since observed differences were almost exclusively caused by variable cellular composition, an original marker-based adjustment strategy was developed to eliminate such variation at affected CpGs. Among adjusted and unchanged CpGs 3153 were differentially methylated between the heavy and light co-twins at nominal significance (p<0.01), of which 45 showed absolute mean β-value differences >0.05 (max=0.08). Deep bisulfite sequencing of eight such loci revealed that differences remained in the range of technical variation, arguing against a reproducible biological effect. Analysis of methylation in repetitive elements using methylation-dependent primer extension assays also indicated no significant intra-pair differences. Conclusions: Severe intrauterine growth differences observed within these MZ twins are not associated with long-lasting DNA methylation differences in cells composing saliva, detectable with up-to-date technologies. Additionally, our results indicate that uneven cell type composition can lead to spurious results and should be addressed in epigenomic studies. DNA methylation profiles of saliva from 17 Adult Female MZ MC Twins discordant for birth weight.