PLZF targets developmental enhancers for activation during osteogenic differentiation of human mesenchymal stem cells (4C-seq)
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ABSTRACT: The PLZF transcription factor is essential for osteogenic differentiation of hMSCs, however, its regulation and molecular function during this process is not fully understood. Here we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naïve hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.
Project description:The PLZF transcription factor is essential for osteogenic differentiation of hMSCs, however, its regulation and molecular function during this process is not fully understood. Here we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naïve hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.
Project description:The PLZF transcription factor is essential for osteogenic differentiation of hMSCs, however, its regulation and molecular function during this process is not fully understood. Here we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naïve hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.
Project description:During fundamental proteotranscriptomic analysis of human valve interstitial cells (VICs) osteogenic differentiation, we revealed ZBTB16 (PLZF) as one of the most upregulated proteins. Thus, to investigate its physiological role in VICs osteogenic differentiation we performed its overexpression by lentiviral transduction with subsequent proteomics analysis. Despite obvious PLZF overexpression and its reinforcing effect on osteogenic differentiation, we revealed surprisingly small amount of differentially expressed proteins that assumed to be the targets of PLZF.
Project description:Cell-fate determination of human mesenchymal stem/stromal cells (hMSCs) is precisely regulated by lineage-specific transcription factors and epigenetic enzymes. We found that CTR9, a key scaffold subunit of Polymerase Associated Factor Complex (PAFc), selectively regulates hMSC differentiation to osteoblasts and chondrocytes, but not to adipocytes. An in vivo ectopic osteogenesis assay confirmed the essentiality of CTR9 in hMSC-derived bone formation. CTR9 counteracts the activity of EZH2, the epigenetic enzyme that deposits H3K27me3, in hMSCs. Accordingly, CTR9 knockdown (1) hMSCs gain H3K27me3 mark, and the osteogenic differentiation defects of CTR9 KD hMSCs can be partially rescued by treatment with EZH2 inhibitors. Transcriptome analyses identified Bone Morphology Protein-2 (BMP-2) as a downstream effector of CTR9. BMP-2 secretion, membrane anchorage, as well as the BMP-SMAD pathway were impaired in CTR9 KD MSCs, and the effects were rescued by BMP-2 supplementation. This study uncovers an epigenetic mechanism engaging CTR9-H3K27me3-BMP-2 axis to regulate osteochondral lineage differentiation of hMSCs. To investigate the function of CTR9 in the gene regulation of early osteogenic committment , we established human MSCs in which CTR9 gene has been knocked down by two individual shRNAs (shControl vs shCTR9#3/#5).
Project description:Human adult mesenchymal stromal cells (hMSC) have the potential to differentiate into chondrogenic, adipogenic or osteogenic lineages, providing a potential source for tissue regeneration. An important issue for efficient bone regeneration is to identify factors that can be targeted to promote the osteogenic potential of hMSCs. Using transcriptomic analysis, we found that integrin alpha5 (ITGA5) expression is upregulated during dexamethasone-induced hMSCs osteoblast differentiation. Gain-of-function studies showed that ITGA5 promotes the expression of osteoblast phenotypic markers as well as in vitro osteogenesis in hMSCs. Downregulation of endogenous ITGA5 using shRNA blunted osteoblast marker expression and osteogenic differentiation. Pharmacological and molecular analyses showed that the enhanced hMSCs osteoblast differentiation induced by ITGA5 was mediated by activation of FAK/ERK1/2-MAPKs and PI3K signaling pathways. Remarkably, activation of ITGA5 using a specific antibody that primes the integrin or a peptide that specifically activates ITGA5 was sufficient to enhance ERK1/2-MAPKs and PI3K signaling and to promote osteoblast differentiation and osteogenic capacity of hMSCs. We also demonstrate that hMSCs engineered to over-express ITGA5 exhibited a marked increase in their osteogenic potential in vivo. These findings not only reveal that ITGA5 is required for osteoblast differentiation of adult human MSCs but also provide a novel targeted strategy using ITGA5 agonists to promote the osteogenic capacity of hMSCs, which may be used for tissue regeneration in bone disorders where the recruitment or capacity of MSCs is compromised. Experiment Overall Design: Gene expression profiles were generated from bone marrow MSC before and 1, 3 and 7 days after stimulation with 10E-7M dexamethasone to study the early molecular processes of osteogenic differentiation. 3 replicates per timepoint.
Project description:Human adult mesenchymal stromal cells (hMSC) have the potential to differentiate into chondrogenic, adipogenic or osteogenic lineages, providing a potential source for tissue regeneration. An important issue for efficient bone regeneration is to identify factors that can be targeted to promote the osteogenic potential of hMSCs. Using transcriptomic analysis, we found that integrin alpha5 (ITGA5) expression is upregulated during dexamethasone-induced hMSCs osteoblast differentiation. Gain-of-function studies showed that ITGA5 promotes the expression of osteoblast phenotypic markers as well as in vitro osteogenesis in hMSCs. Downregulation of endogenous ITGA5 using shRNA blunted osteoblast marker expression and osteogenic differentiation. Pharmacological and molecular analyses showed that the enhanced hMSCs osteoblast differentiation induced by ITGA5 was mediated by activation of FAK/ERK1/2-MAPKs and PI3K signaling pathways. Remarkably, activation of ITGA5 using a specific antibody that primes the integrin or a peptide that specifically activates ITGA5 was sufficient to enhance ERK1/2-MAPKs and PI3K signaling and to promote osteoblast differentiation and osteogenic capacity of hMSCs. We also demonstrate that hMSCs engineered to over-express ITGA5 exhibited a marked increase in their osteogenic potential in vivo. These findings not only reveal that ITGA5 is required for osteoblast differentiation of adult human MSCs but also provide a novel targeted strategy using ITGA5 agonists to promote the osteogenic capacity of hMSCs, which may be used for tissue regeneration in bone disorders where the recruitment or capacity of MSCs is compromised. Keywords: Time course of osteogenic differentiation processes
Project description:hMSCs (Lonza) were differentiated towards adipocytes with three cycles of adipocyte differentiation induction and maintenance. hMSCs were differentiated towards osteocytes with osteogenic differentiation medium for 3 days and for 7 days. ArrayCGH experiments were performed before differentiation induction, after 2 and 3 cycles of adipogenic differentiation induction and after 3 days and 7 days of osteogenic differentiation induction.
Project description:Gene Expression analysis of a differentiation timeseries of human Mesenchymal Stem Cells (hMSCs) in the presence of adipogenic/osteogenic factors. hMSCs differentiate into fat cells when treated with dexamethasone (10^-6 M), insulin (10 ug/ml), rosiglitazone (10^-7 M) and IBMX (250 uM). TGFbeta (5 ng/ml) inhibits this process and redirects these cells to differentiate into bone cells. Introduction: Patients suffering from osteoporosis show an increased number of adipocytes in their bone marrow, concomitant with a reduction in the pool of human mesenchymal stem cells (hMSCs) that are able to differentiate into osteoblasts, thus leading to suppressed osteogenesis. Methods: In order be able to interfere with this process, we have investigated in vitro culture conditions whereby adipogenic differentiation of hMSCs is impaired and osteogenic differentiation is promoted. By means of gene expression microarray analysis, we have investigated genes which are potential targets for prevention of fat cell differentiation. Results: Our data show that BMP2 promotes both adipogenic and osteogenic differentiation of hMSCs, while TGFβ inhibits differentiation into both lineages. However, when cells are cultured under adipogenic differentiation conditions, which contains cAMP-enhancing agents such as IBMX of PGE2, TGFβ promotes osteogenic differentiation, while at the same time inhibiting adipogenic differentiation. Gene expression and immunoblot analysis indicated that cAMP-induced suppression of HDAC5 levels plays an important role in the inhibitory effect of TGFβ on osteogenic differentiation. By means of gene expression microarray analysis, we have investigated genes which are downregulated by TGFβ under adipogenic differentiation conditions and may therefore be potential targets for prevention of fat cell differentiation. We thus identified 9 genes for which FDA-approved drugs are available. Our results show that drugs directed against the nuclear hormone receptor PPARG, the metalloproteinase ADAMTS5 and the aldo-keto reductase AKR1B10 inhibit adipogenic differentiation in a dose-dependent manner, although in contrast to TGFβ they do not appear to promote osteogenic differentiation. Conclusions: The approach chosen in this study has resulted in the identification of new targets for inhibition of fat cell differentiation, which may not only be relevant for prevention of osteoporosis, but also of obesity. hMSCs were induced to differentiate in the presence dexamethasone, insulin and rosiglitazone, to which was added either 50 ng/ml BMP2; BMP2 + TGFbeta; BMP2 + IBMX; BMP2 + TGFbeta + IBMX.
Project description:• Polycomb (PcG) regulation is crucial for development across eukaryotes, but how PcG targets are specified is still incompletely understood. The slow timescale of cold-induced Polycomb Repressive Complex 2 silencing during vernalization at Arabidopsis thaliana FLOWERING LOCUS C (FLC) provides an excellent system to elucidate the sequence of events. Association of the DNA binding protein VAL1 to an FLC intronic RY motif within the PcG nucleation region is an important step. VAL1 is associated in vivo with APOPTOSIS AND SPLICING ASSOCIATED PROTEIN (ASAP) complex and Polycomb Repressive Complex 1 (PRC1). Here, we show that ASAP and PRC1 functions are necessary for co-transcriptional repression and chromatin regulation during FLC silencing. ASAP mutants affect FLC transcription in warm conditions, but the rate of FLC silencing in the cold is unaffected. PRC1-mediated H2Aub accumulation increases at the nucleation region upon exposure to cold, but unlike the PRC2-delivered H3K27me3 does not spread across the locus. H2Aub is thus involved in the transition to epigenetic silencing at FLC facilitating H3K27me3 accumulation, which in turn is necessary for long-term epigenetic memory. Overall, our work highlights the importance of the DNA sequence-specific binding protein VAL1 as an assembly platform coordinating the co-transcriptional repression and chromatin regulation necessary for the epigenetic silencing of FLC.
Project description:Osteogenic differentiation of human mesenchymal stromal cells (hMSCs) may potentially be used in cell-based bone tissue-engineering applications to enhance the bone-forming potential of these cells. Osteogenic differentiation and adipogenic differentiation are thought to be mutually exclusive, and although several signaling pathways and cues that induce osteogenic or adipogenic differentiation, respectively, have been identified, there is no general consensus on how to optimally differentiate hMSCs into the osteogenic lineage. Some pathways have also been reported to be involved in both adipogenic and osteogenic differentiation, as for example, the protein kinase A (PKA) pathway, and the aim of this study was to investigate the role of cAMP/PKA signaling in differentiation of hMSCs in more detail. We show that activation of this pathway with dibutyryl-cAMP results in enhanced alkaline phosphatase expression, whereas another cAMP analog induces adipogenesis in long-term mineralization cultures. Adipogenic differentiation, induced by 8-bromo-cAMP, was accompanied by stronger PKA activity and higher expression of cAMP-responsive genes, suggesting that stronger activation correlates with adipogenic differentiation. In addition, a whole-genome expression analysis showed an increase in expression of adipogenic genes in 8-br-cAMP-treated cells. Furthermore, by means of quantitative polymerase chain reaction, we show differences in peroxisome proliferator-activated receptor-gamma activation, either alone or in combination with dexamethasone, thus demonstrating differential effects of the PKA pathway, most likely depending on its mode of activation.