Project description:To study the role of distinct ATRX aberrations in neuroblastoma we created isogenic ATRX aberrant models using CRISPR-Cas9 in several neuroblastoma cell lines and one tumoroid. We created ATRX knock-out models, ATRX in-frame exon 2-10 deletions and ATRX in-frame exon 2-13 deletions. Additionally, we included patient-derived models data (i.e. cell line data and one tumoroid).
Project description:We report on the characterization of ATRX in-frame fusion neuroblastoma and identify that ATRX IFF proteins re-locate from H3K9me3 enriched regions to active chromatin, such as the promoter of neural repressor REST. We further identify that REST is upregulated in ATRX IFF NB and that several neurogenesis and REST target genes are transcriptionally downregulated. Through ChIP-seq analysis, we observe that REST is bound to ATRX IFF Down genes, which have higher levels of H3K27me3. We further show that ATRX in-frame fusion neuroblastoma cells are sensitive to EZH2 inhibitors through de-repression of H3K27me3 bound neuronal function genes, includiing a subset of REST targets.
Project description:Age and stage of disease at diagnosis is associated with outcome in neuroblastoma. A previous study identified ATRX point mutations and in-frame deletions in older patients with stage 4 disease. To validate the frequency of ATRX mutations and assess the relation of mutations and known prognostic variables, we collaborated with the Children’s Oncology Group and sequenced the entire ATRX genomic locus in 475 neuroblastoma tumor samples to validate the frequency of ATRX mutations and assess the relation of mutations and known prognostic variables. Older age at diagnosis, stage 4 disease, and unfavorable histology were significantly associated with mutations in the ATRX gene; MYCN amplification was mutually exclusive from ATRX mutations. To directly test if ATRX mutations and MYCN amplification are incompatible in neuroblastoma, we mutated the ATRX gene in MYCN amplified neuroblastoma cell lines and ectopically expressed MYCN in ATRX mutant neuroblastoma cell lines. Both approaches showed that ATRX and MYCN amplification are incompatible in neuroblastoma in culture and in vivo. To gain a better understanding of the underlying molecular and cellular mechanisms of this incompatibility, we performed a series of experiments including telomere analysis, epigenetic profiling, electron microscopic analysis and metabolic profiling. We discovered that induction of MYCN expression in ATRX mutant neuroblastomas cells leads to metabolic reprogramming, mitochondrial dysfunction, increased reactive oxygen species and replicative stress. We propose that this leads to synthetic lethality in ATRX mutant neuroblastomas because of the underlying replicative stress in those cells as a result of dysfunction of this essential histone chaperone.
Project description:Here, we report that ATRX co-localizes with the H3K9-methyl transferase SETDB1 (also known as ESET), the co-repressor TRIM28 (also known as KAP1), and the transcription factor ZNF274 at 3â exons of Zinc Finger Genes (ZNFs) containing an atypical H3K9me3/H3K36me3 chromatin signature. Disruption of ATRX and ZNF274 leads to a significant reduction of H3K9me3, particularly at the 3â ZNF exons and other atypical chromatin regions, higher percentages of DNA damage, and defects in cell cycle. Taken together, our studies suggest that ATRX binds the 3â exons of ZNFs to maintain genomic stability through the regulation of their H3K9me3 levels XL-MNase ChIP-seq of ATRX was performed in the erythroleukemic cell line K562 and the Neuroblastoma cell line LAN6. Two independent replicates using different ATRX antibodies were performed in K562. Additionally, Native ChIP-seq of H3K9me3 in LAN6, ATRX WT and ATRX KO K562 cells was performed. Input samples were sequenced as control.
Project description:Alterations in the tumor suppressor ATRX are recurrently observed in several cancer types including sarcomas, which are mesenchymal neoplasms. ATRX has multiple epigenetic functions including heterochromatin formation and maintenance and regulation of transcription through modulation of chromatin accessibility. Here, we show in murine mesenchymal progenitor cells (MPCs) that Atrx deficiency aberrantly activated mesenchymal differentiation programs. This includes adipogenic pathways where ATRX loss induced expression of adipogenic transcription factors (Pparγ and Cebpα) and enhanced adipogenic differentiation in response to differentiation stimuli. These changes are linked to loss of heterochromatin near mesenchymal lineage genes together with increased chromatin accessibility and gains of active chromatin marks at putative enhancer elements and promoters. Finally, we observed depletion of H3K9me3 at transposable elements, which are derepressed including near mesenchymal genes where they could serve as regulatory elements. Our results demonstrate ATRX functions to buffer against differentiation in mesenchymal progenitor cells, which has implications for understanding ATRX loss of function in sarcomas.
Project description:Alterations in the tumor suppressor ATRX are recurrently observed in several cancer types including sarcomas, which are mesenchymal neoplasms. ATRX has multiple epigenetic functions including heterochromatin formation and maintenance and regulation of transcription through modulation of chromatin accessibility. Here, we show in murine mesenchymal progenitor cells (MPCs) that Atrx deficiency aberrantly activated mesenchymal differentiation programs. This includes adipogenic pathways where ATRX loss induced expression of adipogenic transcription factors (Pparγ and Cebpα) and enhanced adipogenic differentiation in response to differentiation stimuli. These changes are linked to loss of heterochromatin near mesenchymal lineage genes together with increased chromatin accessibility and gains of active chromatin marks at putative enhancer elements and promoters. Finally, we observed depletion of H3K9me3 at transposable elements, which are derepressed including near mesenchymal genes where they could serve as regulatory elements. Our results demonstrate ATRX functions to buffer against differentiation in mesenchymal progenitor cells, which has implications for understanding ATRX loss of function in sarcomas.
Project description:Alterations in the tumor suppressor ATRX are recurrently observed in several cancer types including sarcomas, which are mesenchymal neoplasms. ATRX has multiple epigenetic functions including heterochromatin formation and maintenance and regulation of transcription through modulation of chromatin accessibility. Here, we show in murine mesenchymal progenitor cells (MPCs) that Atrx deficiency aberrantly activated mesenchymal differentiation programs. This includes adipogenic pathways where ATRX loss induced expression of adipogenic transcription factors (Pparγ and Cebpα) and enhanced adipogenic differentiation in response to differentiation stimuli. These changes are linked to loss of heterochromatin near mesenchymal lineage genes together with increased chromatin accessibility and gains of active chromatin marks at putative enhancer elements and promoters. Finally, we observed depletion of H3K9me3 at transposable elements, which are derepressed including near mesenchymal genes where they could serve as regulatory elements. Our results demonstrate ATRX functions to buffer against differentiation in mesenchymal progenitor cells, which has implications for understanding ATRX loss of function in sarcomas.
Project description:Alterations in the tumor suppressor ATRX are recurrently observed in several cancer types including sarcomas, which are mesenchymal neoplasms. ATRX has multiple epigenetic functions including heterochromatin formation and maintenance and regulation of transcription through modulation of chromatin accessibility. Here, we show in murine mesenchymal progenitor cells (MPCs) that Atrx deficiency aberrantly activated mesenchymal differentiation programs. This includes adipogenic pathways where ATRX loss induced expression of adipogenic transcription factors (Pparγ and Cebpα) and enhanced adipogenic differentiation in response to differentiation stimuli. These changes are linked to loss of heterochromatin near mesenchymal lineage genes together with increased chromatin accessibility and gains of active chromatin marks at putative enhancer elements and promoters. Finally, we observed depletion of H3K9me3 at transposable elements, which are derepressed including near mesenchymal genes where they could serve as regulatory elements. Our results demonstrate ATRX functions to buffer against differentiation in mesenchymal progenitor cells, which has implications for understanding ATRX loss of function in sarcomas.
Project description:Alterations in the tumor suppressor ATRX are recurrently observed in several cancer types including sarcomas, which are mesenchymal neoplasms. ATRX has multiple epigenetic functions including heterochromatin formation and maintenance and regulation of transcription through modulation of chromatin accessibility. Here, we show in murine mesenchymal progenitor cells (MPCs) that Atrx deficiency aberrantly activated mesenchymal differentiation programs. This includes adipogenic pathways where ATRX loss induced expression of adipogenic transcription factors (Pparγ and Cebpα) and enhanced adipogenic differentiation in response to differentiation stimuli. These changes are linked to loss of heterochromatin near mesenchymal lineage genes together with increased chromatin accessibility and gains of active chromatin marks at putative enhancer elements and promoters. Finally, we observed depletion of H3K9me3 at transposable elements, which are derepressed including near mesenchymal genes where they could serve as regulatory elements. Our results demonstrate ATRX functions to buffer against differentiation in mesenchymal progenitor cells, which has implications for understanding ATRX loss of function in sarcomas.