Project description:Somatic DNMT3A R882 codon mutations drive the most common form of clonal haematopoiesis (CH) and are associated with increased acute myeloid leukaemia (AML) risk. Preventing expansion of DNMT3A-R882-mutant haematopoietic stem/progenitor cells (HSPCs) may therefore avert progression to AML. To identify DNMT3A-R882-mutant-specific vulnerabilities, we conducted a genome-wide CRISPR screen on primary mouse Dnmt3aR882H/+ HSPCs. Amongst the 640 vulnerability genes identified, many were involved in mitochondrial metabolism and metabolic flux analysis confirmed enhanced oxidative phosphorylation usage in Dnmt3aR882H/+ vs Dnmt3a+/+ (WT) HSPCs. We selected citrate/malate transporter Slc25a1 and complex I component Ndufb11, for which pharmacological inhibitors are available, for downstream studies. In vivo administration of SLC25A1 inhibitor CTPI2 and complex I inhibitors IACS-010759 and metformin, suppressed post-transplantation clonal expansion of Dnmt3aR882H/+, but not WT, LT-HSCs. The effect of metformin was recapitulated using a primary human DNMT3A-R882 CH sample. Notably, analysis of 412,234 UK Biobank participants revealed that individuals taking metformin had markedly lower prevalence of DNMT3A-R882-mutant CH, after controlling for potential confounders including glycated haemoglobin, diabetes and body mass index. Collectively, our data propose that modulation of mitochondrial metabolism as a therapeutic strategy for prevention of DNMT3A-R882-mutant AML.
Project description:Somatic DNMT3A R882 codon mutations drive the most common form of clonal haematopoiesis (CH) and are associated with increased acute myeloid leukaemia (AML) risk. Preventing expansion of DNMT3A-R882-mutant haematopoietic stem/progenitor cells (HSPCs) may therefore avert progression to AML. To identify DNMT3A-R882-mutant-specific vulnerabilities, we conducted a genome-wide CRISPR screen on primary mouse Dnmt3aR882H/+ HSPCs. Amongst the 640 vulnerability genes identified, many were involved in mitochondrial metabolism and metabolic flux analysis confirmed enhanced oxidative phosphorylation usage in Dnmt3aR882H/+ vs Dnmt3a+/+ (WT) HSPCs. We selected citrate/malate transporter Slc25a1 and complex I component Ndufb11, for which pharmacological inhibitors are available, for downstream studies. In vivo administration of SLC25A1 inhibitor CTPI2 and complex I inhibitors IACS-010759 and metformin, suppressed post-transplantation clonal expansion of Dnmt3aR882H/+, but not WT, LT-HSCs. The effect of metformin was recapitulated using a primary human DNMT3A-R882 CH sample. Notably, analysis of 412,234 UK Biobank participants revealed that individuals taking metformin had markedly lower prevalence of DNMT3A-R882-mutant CH, after controlling for potential confounders including glycated haemoglobin, diabetes and body mass index. Collectively, our data propose that modulation of mitochondrial metabolism as a therapeutic strategy for prevention of DNMT3A-R882-mutant AML.
Project description:Clonal hematopoiesis (CH) reflects clonal expansion of blood stem and progenitor cells with somatic mutations. We leveraged multi-modality single-cell sequencing to capture mutation status together with the transcriptome and methylome of CD34+ hematopoietic progenitor cells from five individuals with DNMT3A R882-mutated CH.
Project description:DNA methyltransferases DNMT3A- and DNMT3B-mediated de novo DNA methylation critically regulates epigenomic and transcriptomic patterning during development. The hotspot DNMT3A mutations at the site of Arg822 (R882) promote macro-oligomer formation, leading to aberrant DNA methylation that in turn contributes to pathogenesis of acute myeloid leukemia (AML). However, the molecular basis underlying the hotspot mutation-induced functional mis-regulation of DNMT3A remains unclear. Here, we report the crystal structure of DNMT3A methyltransferase (MTase) domain, revealing a molecular basis for its DNMT3B-distinct oligomerization behavior. Introducing DNMT3B-converting mutations to DNMT3A R882 mutants also led to structure determination of R882H- and R882C-mutated DNMT3A, which show enhanced intermolecular contacts than wild-type DNMT3A. Consistently, our in vitro and genomic DNA methylation analyses reveal that the DNMT3B-converting mutations eliminate the gain-of-function effect of the DNMT3A R882 mutations in cells. Together, this study provides mechanistic insights into DNMT3A R882 mutation-triggered aberrant oligomerization and DNA hypomethylation in AML, with important implications in cancer therapy.
Project description:This data presents the transcriptomes of bulk mature colonies derived from single human haematopoietic stem cells / multipotent progenitors (HSC/MPPs) and granulocyte macrophage progenitors (GMPs) purified from one indiviual with age related clonal haematopoisesis. The profiled colonies contain mature monocytes, as measured by conventional cell surface markers (CD14+, CD15-, GlyA-), but no other mature blood cell types. This dataset is part of a larger study, the main objective of which is to understand the functional effects conferred by somatic DNMT3A R882H mutation on human haematopoietic stem cell differentiation capacity. In clonal haematopoiesis, DNMT3A R882H and DNMT3A WT HSPCs co-exist in the same individual. We compared the transcriptional differences between mature monocytic colonies derived from DNMT3A R882H and WT HSPCs in vitro. Analysis of this dataset shows that, in this individual, DNMT3A R882H HSPCs produce less mature monocytes than their WT counterparts over the same culture time.
Project description:Somatic mutations in cancer genes have been ubiquitously detected in clonal expansions across healthy human tissue, including in clonal hematopoiesis. However, mutated and wildtype cells are morphologically and phenotypically similar, limiting the ability to link genotypes with cellular phenotypes. To overcome this limitation, we leveraged multi-modality single-cell sequencing, capturing the mutation with transcriptomes and methylomes in progenitors from individuals with DNMT3A R882 mutated clonal hematopoiesis. DNMT3A mutations resulted in myeloid over lymphoid bias, and in expansion of immature myeloid progenitors primed toward megakaryocytic-erythroid fate. We observed dysregulated expression of lineage and leukemia stem cell markers. DNMT3A R882 led to preferential hypomethylation of polycomb repressive complex 2 targets and a specific sequence motif. Notably, the hypomethylation motif is enriched in binding motifs of key hematopoietic transcription factors, serving as a potential mechanistic link between DNMT3A R882 mutations and aberrant transcriptional phenotypes. Thus, single-cell multi-omics pave the road to defining the downstream consequences of mutations that drive human clonal mosaicism.
Project description:Although the majority of acute myeloid leukemia (AML) patients initially respond to chemotherapy, most of them subsequently relapse due to persistent, chemoresistant disease. However, the mechanistic basis by which AML cells persist during chemotherapy has not been fully delineated. Recurrent somatic mutations in the DNA methyltransferase 3A gene (DNMT3A), most frequently at arginine 882 (DNMT3Amut), are commonly observed in AML patients, and are also detected in elderly subjects with clonal hematopoiesis in the absence of leukemic transformation. DNMT3Amut AML patients have an inferior outcome when treated with standard dose daunorubicin-based induction chemotherapy, suggesting that DNMT3Amut AML cells can persist following chemotherapy and drive relapse. DNMT3Amut cells show impaired nucleosome eviction and chromatin remodeling in response to DNA damage in the setting of anthracycline exposure. This defect leads to an inability to sense and repair DNA damage, which results in the accumulation of single-stranded DNA breaks and increased mutagenesis. Our studies identify a critical role for DNMT3A R882 mutations in driving AML chemoresistance, and highlight the importance of chromatin remodeling in the response to cytotoxic chemotherapy.
Project description:Although the majority of acute myeloid leukemia (AML) patients initially respond to chemotherapy, most of them subsequently relapse due to persistent, chemoresistant disease. However, the mechanistic basis by which AML cells persist during chemotherapy has not been fully delineated. Recurrent somatic mutations in the DNA methyltransferase 3A gene (DNMT3A), most frequently at arginine 882 (DNMT3Amut), are commonly observed in AML patients, and are also detected in elderly subjects with clonal hematopoiesis in the absence of leukemic transformation. DNMT3Amut AML patients have an inferior outcome when treated with standard dose daunorubicin-based induction chemotherapy, suggesting that DNMT3Amut AML cells can persist following chemotherapy and drive relapse. DNMT3Amut cells show impaired nucleosome eviction and chromatin remodeling in response to DNA damage in the setting of anthracycline exposure. This defect leads to an inability to sense and repair DNA damage, which results in the accumulation of single-stranded DNA breaks and increased mutagenesis. Our studies identify a critical role for DNMT3A R882 mutations in driving AML chemoresistance, and highlight the importance of chromatin remodeling in the response to cytotoxic chemotherapy.