Project description:Glycine 34 to tryptophan (G34W) substitutions in H3.3 arise in ~90% of giant cell tumour of bone (GCT). Here, we show H3.3G34W is necessary for tumour formation. Profiling the epigenome, transcriptome and secreted proteome of patient samples and tumour-derived cells CRISPR/Cas9-edited for H3.3G34W shows that H3.3K36me3 loss on mutant H3.3 induces a shift of the repressive H3K27me3 mark from intergenic to genic regions, beyond areas of H3.3 deposition. This promotes the redistribution of antagonistic chromatin marks and aberrant downregulation of contractile myofibroblast-associated genes altering cell fate in mesenchymal progenitors. Single-cell transcriptomics reveals that H3.3G34W stromal cells recapitulate a neoplastic trajectory from an SPP1+ osteoblast progenitor-like population towards an ACTA2+ myofibroblast population, which secretes extracellular matrix ligands predicted to recruit and activate osteoclasts. Our findings suggest that H3.3G34W leads to GCT by sustaining a transformed state in osteoblast-like progenitors which promotes neoplastic growth, pathological recruitment of giant osteoclasts, and bone destruction.
Project description:Background:; Osteoblast differentiation requires the coordinated stepwise expression of multiple genes. Histone deacetylase inhibitors (HDIs) accelerate the osteoblast differentiation process by blocking the activity of histone deacetylases (HDACs), which alter gene expression by modifying chromatin structure. We previously demonstrated that HDIs and HDAC3 shRNAs accelerate matrix mineralization and the expression of osteoblast maturation genes (e.g. alkaline phosphatase, osteocalcin). Identifying other genes that are differentially regulated by HDIs might identify new pathways that contribute to osteoblast differentiation. Results:; To identify other osteoblast genes that are altered early by HDIs, we incubated MC3T3-E1 preosteoblasts with HDIs (trichostatin A, MS-275, or valproic acid) for 18 hours in osteogenic conditions. The promotion of osteoblast differentiation by HDIs in this experiment was confirmed by osteogenic assays. Gene expression profiles relative to vehicle-treated cells were assessed by microarray analysis with Affymetrix GeneChip 430 2.0 arrays. The regulation of several genes by HDIs in MC3T3-E1 cells and primary osteoblasts was verified by quantitative real-time PCR. Nine genes were differentially regulated by at least two-fold after exposure to each of the three HDIs and six were verified by PCR in osteoblasts. Four of the verified genes (solute carrier family 9 isoform 3 regulator 1 (Slc9a3r1), sorbitol dehydrogenase 1, a kinase anchor protein, and glutathione S-transferase alpha 4) were induced. Two genes (proteasome subunit, beta type 10 and adaptor-related protein complex AP-4 sigma 1) were suppressed. We also identified eight growth factors and growth factor receptor genes that are significantly altered by each of the HDIs, including Frizzled related proteins 1 and 4, which modulate the Wnt signaling pathway. Conclusions: This study identifies osteoblast genes that are regulated early by HDIs and indicates pathways that might promote osteoblast maturation following HDI exposure. One gene whose upregulation following HDI treatment is consistent with this notion is Slc9a3r1. Also known as NHERF1, Slc9a3r1 is required for optimal bone density. Similarly, the regulation of Wnt receptor genes indicates that this crucial pathway in osteoblast development is also affected by HDIs. These data support the hypothesis that HDIs regulate the expression of genes that promote osteoblast differentiation and maturation. Experiment Overall Design: To identify other osteoblast genes that are altered early by HDIs, we incubated MC3T3-E1 preosteoblasts with HDIs (trichostatin A, MS-275, or valproic acid) or the vehicle control (DMSO) for 18 hours in osteogenic conditions. Gene expression profiles relative to vehicle-treated cells were assessed in triplicate (in some cases quadruplicate) samples by microarray analysis with Affymetrix GeneChip 430 2.0 arrays.
Project description:Many plants, including Arabidopsis thaliana, respond to elevated ambient temperatures by altering their growth through a process known as thermomorphogenesis. This response involves the depletion of the repressive histone variant H2A.Z from the gene bodies of PIF4-regulated auxin-related genes, enabling their transcriptional activation. Interestingly, this activation also requires the histone deacetylase HDA9, raising the question of how histone deacetylation, typically associated with transcriptional repression, can instead promote gene activation. Here, we identify FVE as a co-regulator that partners with HDA9 to activate PIF4 target genes at elevated temperatures. PIF4 directly interacts with and recruits the FVE-HDA9 complex to its target genes to remove acetylation from histone H4 and H2A.Z. We show that H2A.Z acetylation is required for recruiting the SWR1 complex, which deposits H2A.Z. Consequently, FVE-HDA9-mediated deacetylation reduces SWR1 complex binding and limits H2A.Z deposition. Moreover, we demonstrate that in addition to limiting H2A.Z deposition, H2A.Z depletion also results from H2A.Z eviction mediated by the INO80 complex. Together, these findings uncover a dual mechanism contributing to H2A.Z depletion: INO80-mediated active eviction and histone deacetylation-mediated inhibition of H2A.Z deposition, which underlies PIF4 target gene activation and explain the paradoxical role of histone deacetylation in transcriptional activation.
Project description:Chemical inhibition of histone demethyase LSD1 and histone methyltransferase DOT1L promotes maturation of neurons derived from pluripotent stem cells. We profiled the genome distribution of histone marks targeted by these enzymes in immature hPSC-derived cortical neurons.
Project description:Glycine 34 to tryptophan (G34W) substitutions in H3.3 arise in ~90% of giant cell tumour of bone (GCT). Here, we show H3.3G34W is necessary for tumour formation. Profiling the epigenome, transcriptome and secreted proteome of patient samples and tumour-derived cells CRISPR/Cas9-edited for H3.3G34W shows that H3.3K36me3 loss on mutant H3.3 induces a shift of the repressive H3K27me3 mark from intergenic to genic regions, beyond areas of H3.3 deposition. This promotes the redistribution of antagonistic chromatin marks and aberrant downregulation of contractile myofibroblast-associated genes altering cell fate in mesenchymal progenitors. Single-cell transcriptomics reveals that H3.3G34W stromal cells recapitulate a neoplastic trajectory from an SPP1+ osteoblast progenitor-like population towards an ACTA2+ myofibroblast population, which secretes extracellular matrix ligands predicted to recruit and activate osteoclasts. Our findings suggest that H3.3G34W leads to GCT by sustaining a transformed state in osteoblast-like progenitors which promotes neoplastic growth, pathological recruitment of giant osteoclasts, and bone destruction.
Project description:Glycine 34 to tryptophan (G34W) substitutions in H3.3 arise in ~90% of giant cell tumour of bone (GCT). Here, we show H3.3G34W is necessary for tumour formation. Profiling the epigenome, transcriptome and secreted proteome of patient samples and tumour-derived cells CRISPR/Cas9-edited for H3.3G34W shows that H3.3K36me3 loss on mutant H3.3 induces a shift of the repressive H3K27me3 mark from intergenic to genic regions, beyond areas of H3.3 deposition. This promotes the redistribution of antagonistic chromatin marks and aberrant downregulation of contractile myofibroblast-associated genes altering cell fate in mesenchymal progenitors. Single-cell transcriptomics reveals that H3.3G34W stromal cells recapitulate a neoplastic trajectory from an SPP1+ osteoblast progenitor-like population towards an ACTA2+ myofibroblast population, which secretes extracellular matrix ligands predicted to recruit and activate osteoclasts. Our findings suggest that H3.3G34W leads to GCT by sustaining a transformed state in osteoblast-like progenitors which promotes neoplastic growth, pathological recruitment of giant osteoclasts, and bone destruction.