Project description:Background: Human bone marrow mesenchymal stem cells (MSCs) expanded in vitro exhibit not only a tendency to lose their proliferative potential, homing ability and telomere length but also genetic or epigenetic modifications such as DNA methylation and the noncoding RNA-mediated mechanism. This results in the senescence of MSCs. We compared differential methylation patterns of genes and miRNAs between early-passage and late-passage cells and estimated the relationship between senescence and DNA methylation patterns. Genomic DNA of MSCs cultured at passage 5 (P5) and passage 15 (P15) was enriched using methylated DNA immunoprecipitation assays, and DNA methylation changes due to long-term culture of MSCs were analyzed using Human 2.1M Deluxe Promoter Arrays (NimbleGen). Results: When we analyzed the methylation differences between P5 and P15 more than twice, 3,338 genes showed more than two-fold higher methylation at P5 than P15, whereas 4,670 genes showed more than two-fold higher methylation at P15 than P5. When we examined hypermethylated genes (methylation peak ≥ 2) at P5 or P15, 2,739 genes, including those related to fructose and mannose metabolism and calcium signaling pathways, and 2,587 genes, including those related to DNA replication, cell cycle and the PPAR signaling pathway, were hypermethylated at P5 and P15, respectively. There was common hypermethylation of 1,205 genes at both P5 and P15. In addition, genes that were hypermethylated at P5 (CPEB1, GMPPA, CDKN1A, TBX2, SMAD9 and MCM2) showed lower mRNA expression than did those hypermethylated at P15, whereas genes that were hypermethylated at P15 (MAML2, FEN1 and CDK4) showed lower mRNA expression than did those that were hypermethylated at P5, demonstrating that hypermethylation at DNA promoter regions inhibited gene expression and that hypomethylation increased gene expression. In the case of hypermethylation on miRNA, 27 miRNAs were hypermethylated at P5, whereas 44 miRNAs were hypermethylated at P15. Conclusion: These results show that hypermethylation increases at genes related to DNA replication, cell cycle and adipogenic differentiation due to long-term culture, which may in part affect MSC senescence.

Project description:The realization of human embryonic stem cells (hESC) as a model for human developmental hematopoiesis and potential cell replacement strategies relies on an improved understanding of the extrinsic and intrinsic factors regulating hematopoietic-specific hESC differentiation. Mesenchymal stem cells (hMSCs) are multipotent cells of mesodermal origin that form part of hematopoietic stem cell niches and have an important role in the regulation of hematopoiesis through production of secreted factors and/or cell-to-cell interactions. We have previously shown that hESCs may be successfully maintained feeder-free using hMSC-conditioned media (MSC-CM). Here, we hypothesized that hESCs maintained in MSC-CM may be more prone to differentiation towards hematopoietic lineage than hESCs grown in standard human foreskin fibroblast (HFF)-conditioned media (HFF-CM). We report that specification into hemogenic progenitors and subsequent hematopoietic differentiation and clonogenic progenitor capacity is robustly enhanced in hESC lines maintained in MSC-CM. Interestingly, co-culture of hESCs on hMSCs fully abrogates hematopoietic specification of hESCs suggesting that the improved hematopoietic differentiation is mediated by MSC-secreted factors rather than by MSC-hESC physical interactions. To investigate the molecular mechanism involved in this process, we analyzed global (LINE-1) methylation and genome-wide promoter DNA methylation. Human ESCs grown in MSC-CM showed a decrease of 20% in global DNA methylation and a promoter DNA methylation signature consisting in 45 genes commonly hypomethylated and 102 genes frequently hypermethylated. Our data indicate that maintenance of hESCs in MSC-CM robustly augments hematopoietic specification and that the process seems mediated by MSC-secreted factors conferring a DNA methylation signature to undifferentiated hESCs which may influence further predisposition towards hematopoietic specification. Total DNA isolated by standard procedures from human embryonic stem cells (hESC) cultured in different conditioned media

Project description:Myelodysplastic Syndrome (MDS) is a heterogenous group of clonal hematopoietic disorders characterized by ineffective hematopoiesis, cytopenias and dysplasia. The gene encoding Ten-ele¬ven translocation 2 (TET2), a dioxygenase enzyme that catalyzes the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine, is a recurrently mutated tumor suppressor gene in MDS and other myeloid malignancies. Previously, we reported a stable zebrafish line with a loss-of-function mutation in the tet2 gene. The tet2m/m mutant zebrafish developed a pre-MDS state with kidney marrow dysplasia but normal circulating blood counts by 11 months of age and accompanying anemia signifying the onset of MDS by 24 months of age. In the current study, we collected progenitor cells from the kidney marrows of the adult tet2m/m and tet2wt/wt fish at 4 and 15 months of age and performed enhanced reduced representation of bisulphite sequencing (ERRBS) and bulk RNA-seq to measure changes in DNA methylation and gene expression of HSPCs. A global increase in DNA methylation of gene promoter regions and CpG islands was observed in tet2m/m HSPCs at 4 months of age when compared to the wildtype. Further, hypermethylated genes were significantly enriched for targets of SUZ12 and MTF2 - involved in polycomb repressive complex 2 (PRC2). However, between 4 and 15 months of age, however, we observed a paradoxical global decrease in DNA methylation in tet2m/m HSPCs. Gene expression analysis identified upregulation of genes associated mTORC1 signaling and interferon gamma and alpha response in tet2m/m HSPCs at 4 months of age when compared to the wildtype. Downregulated genes in HSPCs of tet2 mutant fish at 4 months of age were enriched for cell cycle regulation, heme metabolism, and IL2/STAT5 signaling, possibly related to increased self-renewal and clonal advantage in HSPCs with tet2 loss of function. Finally, there was an overall inverse correlation between overall increased promoter methylation and gene expression.

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CRISPR/dCas9 DNA methylation editing is heritable during human hematopoiesis and shapes immune progeny [RNA-seq]

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