The effects of H3.3K27M mutation on developing mouse brain and cooperation with Trp53 on enhancing tumorigenesis in the genetic model of H3.3K27M [Exome-Seq]
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE120883 | GEO | 2020/10/27
REPOSITORIES: GEO
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Project description:Diffuse intrinsic pontine gliomas (DIPG) are devastating pediatric brain tumors for which there is no effective therapy. A lack of pre-clinical genetic models has affected efforts to develop therapies targeted to DIPG. Over 60% of DIPG patients carry a mutation in the histone H3F3A gene (H3.3K27M) that is often accompanied by a mutation in the TP53 gene. Here we created a genetic model in which H3.3K27M is expressed under the mouse Fabp7 promoter. These mice have disrupted embryonic development and increased susceptibility to development of lymphomas. Crosses to Trp53 knockout mice further accelerated lymphomagenesis and led to brain tumour development. Some but not all tumours acquired additional oncogenic alterations. The brain tumours faithfully recapitulate the expression profiles of DIPG patients, and brain tumours and lymphomas share significant similarities in pathway alterations, pointing to a core H3.3K27M transcriptome. Overall, this mouse model provides key insights into how H3.3K27M mutations regulate DIPG at the cellular and tumour level.
2020-10-27 | GSE120882 | GEO
Project description:Diffuse intrinsic pontine gliomas (DIPG) are a deadly paediatric brain tumours, non-resectable due to brainstem localisation and diffusive growth. Patients with DIPG have a dismal prognosis of 9-12 months of survival with no effective therapy. Over 80% of DIPGs harbour a mutation in histone 3 (H3.3 or H3.1) resulting in a lysine to methionine substitution (H3K27M). H3K27M causes global epigenetic alterations (a loss of H3K27 trimethylation and an increase in H3K27 acetylation) resulting in aberrant gene expression. To date, no therapeutic strategy exists to suppress the levels of oncogenic H3K27M.
We show that pan-HDAC inhibitors (HDACi) lead to the temporary but significant reduction in the H3.33K27M protein (up to 80%) in multiple glioma cell lines expressing the H3.3K27M histone variant, without changes in the H3F3A mRNA expression. The H3.3K27M occupancy at the chromatin is greatly reduced upon HDACi (SB939) treatment, as shown by ChIPseq analysis. H3.3K27M loss is most striking at SB939-upregulated genes suggesting the role in repression of these genes. In addition, genes previously reported as H3K27M-dependent become downregulated in response to SB939 treatment. We discover that the SB939-mediated loss of H3.3K27M is partially blocked by a lysosomal inhibitor, chloroquine. Moreover, the loss of H3.3K27M is facilitated by co-occurrence of H2A.Z, as evidenced by the knock-down of H2A.Z histone isoforms. ChIPseq analysis confirms the occupancy of H3.3K27M and H2A.Z at the same SB939-inducible genes.
Altogether, we provide new insight into disease-specific mechanism of HDAC inhibition and demonstrate pharmacological modulation of the oncogenic H3.3K27M protein levels. These findings open a new possibility to directly target the H3.3K27M oncohistone, which may be exploited in future therapies.
2023-10-05 | MSV000093052 | MassIVE
Project description:Expression of histone H3.3K27M mutant proteins in diffuse intrinsic pontine glioma (DIPG) results in a global reduction of tri-methylation of H3K27 (H3K27me3), and paradoxically, H3K27me3 peaks remain at hundreds of genomic loci, a dichotomous change that lacks mechanistic insights. Here we show that the PRC2 complex is sequestered at poised enhancers, but not at active promoters with high levels of H3.3K27M proteins, thereby contributing to the global reduction of H3K27me3. Moreover, the levels of H3.3K27M proteins are low at the retained H3K27me3 peaks and consequently having minimal effects on the PRC2 activity at these loci. H3K27me3-mediated silencing at specific tumor suppressor genes, including Wilms Tumor 1, promotes proliferation of DIPG cells. These results support a model in which the PRC2 complex is redistributed to poised enhancers in H3.3K27M mutant cells and supports the proliferation of DIPG cells in part through silencing of tumor suppressor gene WT1.
2018-07-02 | GSE94834 | GEO
Project description:Diffuse Intrinsic Pontine Glioma (DIPG) is a universally fatal childhood brain tumour which frequently carries a mutation in genes encoding histone H3. These mutations lead to a lysine-to-methionine (K-to-M) substitution at position 27 (H3K27M) within the histone H3 tail and initiate global shifts in the abundance of Polycomb Repressive Complex 2 (PRC2) mediated H3K27 methylation (me) and P300/CBP mediated acetylation (ac). Acquisition of the H3K27M mutation is the founding genetic event in DIPG tumours, making it likely that these global shifts in H3K27me/ac are instrumental in promoting the early steps toward gliomagenesis. Here, we show that the H3.3K27M oncogene directly disrupts the function of tissue specific gene enhancers and increases Polycomb target gene repression limiting developmental potential of neural stem cells (NSCs). To study the initial functional consequences of H3K27M in glioma, we developed an isogenic human model system. To do this, we modelled the earliest stages of DIPG development by introducing either K27M or wildtype (WT) H3.3 into hindbrain derived NSC cultures. Importantly, this model faithfully recapitulated the global H3K27ac/me dynamics observed in patient samples. Moreover, epitope tagging of the K27M and WT histones allowed us to globally assess the localisation of K27M and WT H3.3. This for the first time facilitated a global analysis of H3.3K27M distribution, as it relates to the WT histone in a biologically relevant context. We found that the presence of the K27M mutation does not alter the localisation of the mutant histone, which is most abundant at enhancer elements with lower levels at gene promoters. Remarkably, the H3.3K27M oncogene limits the developmental potential of NSCs by directly impeding tissue specific enhancer function. Moreover, we found that PRC2 function is primarily altered outside of stably bound Polycomb target sites, with the majority of H3K27me3 lost outside of these regions. Finally, we provide in vivo evidence for sequestration of the PRC2 complex at a subset of Polycomb target promoters. Taken together, these findings provide important new mechanistic insights on the initial steps of DIPG development.
2021-06-01 | GSE154267 | GEO
Project description:Recent studies have identified a Lys 27-to-methionine (K27M) mutation at one allele of H3F3A, one of the two genes encoding histone H3 variant H3.3, in 60% of high-grade pediatric glioma cases. The median survival of this group of patients after diagnosis is ∼1 yr. Here we show that the levels of H3K27 di- and trimethylation (H3K27me2 and H3K27me3) are reduced globally in H3.3K27M patient samples due to the expression of the H3.3K27M mutant allele. Remarkably, we also observed that H3K27me3 and Ezh2 (the catalytic subunit of H3K27 methyltransferase) at chromatin are dramatically increased locally at hundreds of gene loci in H3.3K27M patient cells. Moreover, the gain of H3K27me3 and Ezh2 at gene promoters alters the expression of genes that are associated with various cancer pathways. These results indicate that H3.3K27M mutation reprograms epigenetic landscape and gene expression, which may drive tumorigenesis. We performed chromatin-immunoprecipitation of H3K27me3, H3K4me3, and EZH2 in SF7761 and NSC cell lines. And do RNA-seq in SF7761, SF8828 and NSC cell lines. SF7761 and SF8628 cell lines from patients harboring the histone H3.3 K27M mutation were obtained from Hashizume et al. (2012). NSCs (N7800-100) were purchased from Invitrogen and cultured and maintained in NSC medium (A10509-01, StemPro NSC SFM, Invitrogen).
2014-09-20 | E-GEOD-61586 | biostudies-arrayexpress
Project description:Diffuse intrinsic pontine glioma (DIPG) is a rare and fatal pediatric brain cancer without cure. DIPG has high percentage histone mutation at K27M on histone H3 locus, which is believed to be one of the drivers of the tumorigenesis. Dysregulation of G1/S cell cycle checkpoint is more enriched in the H3.3K27M mutant subgroup. In this study, we reported that palbociclib (PD0332991), a specific and cytostatic inhibitor of CDK4/6, effectively suppresses the growth of DIPG cells in vitro and in vivo. We established patient derived cell lines from treatment-naïve specimens, which all have H3.3K27M mutation. And our DIPG cell lines with H3.3K27M mutation have high CDK4/6 expression. Then, we showed that depletion of CDK4 or CDK6 inhibits DIPG cells growth and blocks G1/S transition. Furthermore, palbociclib effectively repressed all 8 cell lines self-renewal, proliferation and cell cycle progression from G1 to S phase in vitro. Transcriptome analysis showed that palbociclib not only blocks G1/S transition, it also blocks other oncogenic targets such as Myc. Finally, palbociclib activity was assayed in vivo against DIPG orthotropic xenografts to demonstrate the high efficiency of blocking tumor growth. Our findings revealed that palbociclib could be the therapy strategy for DIPG.
2019-06-20 | GSE115976 | GEO
Project description:Diffuse intrinsic pontine gliomas (DIPGs) are highly lethal childhood brain tumors. Their unique genetic makeup, pathological heterogeneity, and brainstem location all present challenges to treatment. Developing mouse models that accurately reflect each of these distinct features will be critical to advance our understanding of DIPG development, progression, and therapeutic resistance. The aim of this study was to generate new mouse models of DIPG, and characterize the role of specific oncogenic combinations in DIPG pathogenesis. We used in utero electroporation (IUE) to transfect neural stem cells in the developing brainstem with PiggyBac DNA transposon plasmids. Combinations of PDGFB or PdgfraD842V, dominant negative Trp53 (DNp53), and H3.3K27M expression induced fully penetrant brainstem gliomas. IUE enabled the targeted transfection of brainstem neural stem cells. PDGFB + DNp53 induced the rapid development of grade-IV gliomas. PdgfraD842V + DNp53 produced slower forming grade-III gliomas. Addition of H3.3K27M only significantly accelerated PdgfraD842V DIPG development. Glioma subgroup molecular signatures were associated with differences in bulk PDGFB and PdgfraD842V tumor composition. H3.3K27M induced both overlapping and unique gene expression changes in PDGFB and PdgfraD842V tumors. Paracrine effects of PDGFB promote disruption of pericyte-endothelial interactions and angiogenesis in PDGFB DIPG mouse models. Brainstem targeted in utero electroporation provides a rapid and flexible system to generate diverse DIPG mouse models. Using IUE to investigate mutation and pathohistological heterogeneity of DIPG will provide a valuable tool for future genetic and preclinical studies.
2019-11-14 | GSE128807 | GEO
Project description:Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive brain tumour that is located in the pons and primarily affects children. Whole-exome sequencing studies have identified recurrent driver mutations in H3F3A and HIST1H3B, leading to the expression of histone H3 in which lysine 27 is substituted with methionine (H3K27M) in nearly 80% of DIPGs. H3K27M inhibits Polycomb Repressive Complex 2 (PRC2) activity by binding to its catalytic subunit EZH2 and although DIPGs with H3K27M mutation show global loss of H3 with trimethylated lysine 27 (H3K27me3), several genomic loci are still H3K27me3 positive. Here, we describe a new mouse DIPG model in which H3K27M potentiates tumourigenesis. Using this model and primary patient-derived DIPG cell lines, we show that H3K27M expressing tumours require PRC2 for proliferation. Furthermore, we demonstrate that small molecule EZH2 inhibitors abolish in vitro and in vivo tumour cell growth through a mechanism involving induction of the tumour suppressor protein p16INK4A. In agreement with this, we show that tumour cells with inactivated p16INK4A function do not respond to EZH2 inhibitors. By analysing genome-wide H3K27me3 enrichment profile in mouse DIPG model, we highlight distinct features of the loci that lose or retain H3K27me3 in H3K27M expressing cells. Taken together these results show that residual PRC2 activity is required for the proliferation of H3K27M positive DIPGs, and we propose a therapeutic strategy for these tumours using EZH2 inhibitors and expression of p16INK4A as a marker for stratifying potential responding tumours.
2017-08-31 | GSE71387 | GEO
Project description:The histone H3 variant, H3.3, is localized at specific regions in the genome, especially promoters and active enhancers, and has been shown to play important roles in development. A lysine to methionine substitution in position 27 (H3.3K27M) is a main cause of Diffuse Intrinsic Pontine Glioma, a lethal type of pediatric cancer. H3.3K27M has a dominant-negative effect by inhibiting the Polycomb Repressor Complex 2 (PRC2) activity. Here, we studied the immediate, genome-wide, consequences of the H3.3K27M mutation independent of PRC2 activity. We developed Doxycycline (Dox)-inducible mouse embryonic stem cells (ESCs) carrying a single copy of WT-H3.3, H3.3K27M and H3.3K27L, all fused to HA. We performed RNA-Seq and ChIP-Seq at different timepoints following Dox in undifferentiated and differentiated ESCs. We find increased binding of H3.3 around transcription start sites in cells expressing both H3.3K27M and H3.3K27L compared with WT, but not in cells treated with PRC2 inhibitors. Differentiated cells carrying either H3.3K27M or H3.3K27L retain expression of ESC-active genes, in expense of expression of genes related to neuronal differentiation. Taken together, our data suggest that a modifiable H3.3K27 is required for proper histone incorporation and cellular maturation, independent of PRC2 activity.
2022-09-01 | GSE195789 | GEO
Project description:Background: The histone variant H3.3 K27M mutation is a defining characteristic of diffuse intrinsic pontine glioma (DIPG)/diffuse midline glioma (DMG). This histone mutation is responsible for major alterations to histone H3 post-translational modification (PTMs) and subsequent aberrant gene expression. However, much less is known about the effect this mutation has on chromatin structure and function, including open versus closed chromatin regions as well as their transcriptomic consequences. Results: Recently, we developed isogenic CRISPR-edited DIPG cell lines that are wild- type for histone H3.3 that can be compared to their matched K27M lines. Here we show via ATAC-seq analysis that H3.3K27M glioma cells have unique accessible chromatin at regions corresponding to neurogenesis, NOTCH, and neuronal development pathways and associated genes that are overexpressed in H3.3K27M compared to our isogenic wild-type cell line. As to mechanisms, accessible enhancers and super-enhancers corresponding to increased gene expression in H3.3K27M cells were also mapped to genes involved in neurogenesis and NOTCH signaling, suggesting that these pathways are key to DIPG tumor maintenance. Motif analysis implicates specific transcription factors as central to the neuro-oncogenic K27M signaling pathway including, in particular, ASCL1 and NEUROD1. Conclusions: Altogether our findings indicate that H3.3K27M causes chromatin to take on a more accessible configuration at key regulatory regions for NOTCH and neurogenesis genes resulting in increased oncogenic gene expression, which is at least partially reversible upon editing K27M back to wild- type.
2022-04-24 | GSE201265 | GEO