ABSTRACT
In childhood acute lymphoblastic leukemia (ALL), TP53 gene mutation is associated with chemoresistance in a certain population of relapsed cases. To directly verify the association of TP53 gene mutation with chemoresistance of relapsed childhood ALL cases and improve their prognosis, the development of appropriate human leukemia models having TP53 mutation in the intrinsic gene is required. Here, we sought to introduce R248Q hotspot mutation into the intrinsic TP53 gene in an ALL cell line, 697, by applying a prime editing (PE) system, which is a versatile genome editing technology. The PE2 system uses an artificial fusion of nickase Cas9 and reverse-transcriptase to directly place new genetic information into a target site through a reverse transcriptase template in the prime editing guide RNA (pegRNA). Moreover, in the advanced PE3b system, single guide RNA (sgRNA) matching the edited sequence is also introduced to improve editing efficiency. The initially obtained MDM2 inhibitor-resistant PE3b-transfected subline revealed disrupted p53 transactivation activity, reduced p53 target gene expression, and acquired resistance to chemotherapeutic agents and irradiation. Although the majority of the subline acquired the designed R248Q and adjacent silent mutations, the insertion of the palindromic sequence in the scaffold hairpin structure of pegRNA and the overlap of the original genomic DNA sequence were frequently observed. Targeted next-generation sequencing reconfirmed frequent edit errors in both PE2 and PE3b-transfected 697 cells, and it revealed frequent successful edits in HEK293T cells. These observations suggest a requirement for further modification of the PE2 and PE3b systems for accurate editing in leukemic cells.
Subject(s)
Gene Editing , Mutation , Precursor Cell Lymphoblastic Leukemia-Lymphoma , Tumor Suppressor Protein p53 , Humans , Tumor Suppressor Protein p53/genetics , Gene Editing/methods , Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics , Precursor Cell Lymphoblastic Leukemia-Lymphoma/pathology , Precursor Cell Lymphoblastic Leukemia-Lymphoma/therapy , Cell Line, Tumor , Drug Resistance, Neoplasm/genetics , CRISPR-Cas Systems/genetics , RNA, Guide, CRISPR-Cas Systems/genetics , Proto-Oncogene Proteins c-mdm2/geneticsABSTRACT
DDX41 mutation has been observed in myeloid malignancies including myelodysplastic syndromes and acute myeloid leukemia, but the underlying causative mechanisms of these diseases have not been fully elucidated. The DDX41 protein is an ATP-dependent RNA helicase with roles in RNA metabolism. We previously showed that DDX41 is involved in ribosome biogenesis by promoting the processing of newly transcribed pre-ribosomal RNA. To build on this finding, in this study, we leveraged ribosome profiling technology to investigate the involvement of DDX41 in translation. We found that DDX41 knockdown resulted in both translationally increased and decreased transcripts. Both gene set enrichment analysis and gene ontology analysis indicated that ribosome-associated genes were translationally promoted after DDX41 knockdown, in part because these transcripts had significantly shorter transcript length and higher transcriptional and translational levels. In addition, we found that transcripts with 5'-terminal oligopyrimidine motifs tended to be translationally upregulated when the DDX41 level was low. Our data suggest that a translationally regulated feedback mechanism involving DDX41 may exist for ribosome biogenesis.
Subject(s)
Leukemia, Myeloid, Acute , Myelodysplastic Syndromes , Myeloproliferative Disorders , Humans , Ribosome Profiling , DEAD-box RNA Helicases/genetics , Myelodysplastic Syndromes/genetics , Myeloproliferative Disorders/genetics , Leukemia, Myeloid, Acute/geneticsABSTRACT
The impact of gene-editing technology has rapidly expanded into developmental engineering. Using this technology, gene targeting in mice can be performed within 2-3 months, which is a much shorter timespan than that required while using embryonic stem cell-based conventional methods, which require nearly two years. In addition, genome-editing technology omits several skillful laborious steps. This review describes the prominent merits of gene targeting using this recently established and still ongoing technology in the field of hematology. In addition, the experience of the authors is reviewed to identify and characterize genes involved in the loss of the long arm of chromosome 7 in myeloid malignancies and highlight the significance of establishing the mouse model of human diseases.
Subject(s)
Gene Editing , Hematologic Diseases , Humans , Mice , Animals , Hematologic Diseases/genetics , Hematologic Diseases/therapy , TechnologyABSTRACT
Myeloid malignancies with DDX41 mutations are often associated with bone marrow failure and cytopenia before overt disease manifestation. However, the mechanisms underlying these specific conditions remain elusive. Here, we demonstrate that loss of DDX41 function impairs efficient RNA splicing, resulting in DNA replication stress with excess R-loop formation. Mechanistically, DDX41 binds to the 5' splice site (5'SS) of coding RNA and coordinates RNA splicing and transcriptional elongation; loss of DDX41 prevents splicing-coupled transient pausing of RNA polymerase II at 5'SS, causing aberrant R-loop formation and transcription-replication collisions. Although the degree of DNA replication stress acquired in S phase is small, cells undergo mitosis with under-replicated DNA being remained, resulting in micronuclei formation and significant DNA damage, thus leading to impaired cell proliferation and genomic instability. These processes may be responsible for disease phenotypes associated with DDX41 mutations.
Subject(s)
RNA Splice Sites , RNA Splicing , Cell Line , RNA Splicing/genetics , Mutation , DNA ReplicationABSTRACT
Revertant (somatic) mosaicism is a spontaneous correction of a causative mutation in patients with congenital diseases. A relatively frequent event, revertant mosaicism may bring favorable outcomes that ameliorate disorders, and is therefore called "natural gene therapy." However, it has been revealed recently that "overcorrection" of inherited bone marrow failure in patients with sterile alpha motif domain containing 9 (SAMD9)/9L syndromes by revertant mosaicism induces myelodysplastic syndrome (MDS) with monosomy 7 that occasionally proceeds to acute myelogenous leukemia (AML). In this review, we interpret very complex mechanisms underlying MDS/AML in patients with SAMD9/9L syndromes. This includes multiple myeloid tumor suppressors on the long arm of chromosome 7, all of which act in a haploinsufficient fashion, and a difference in sensitivity to interferon between cells carrying a mutation and revertants. Overcorrection of mutants by somatic mosaicism is likely a novel mechanism in carcinogenesis.
Subject(s)
Carcinogenesis/genetics , Leukemia, Myeloid, Acute/genetics , Mutation/genetics , Animals , Chromosome Deletion , Chromosomes, Human, Pair 7/genetics , Humans , Intracellular Signaling Peptides and Proteins/genetics , Mosaicism , Myelodysplastic Syndromes/genetics , Tumor Suppressor Proteins/geneticsABSTRACT
Epigenetic regulation is essential for the maintenance of the hematopoietic system, and its deregulation is implicated in hematopoietic disorders. In this study, UTX, a demethylase for lysine 27 on histone H3 (H3K27) and a component of COMPASS-like and SWI/SNF complexes, played an essential role in the hematopoietic system by globally regulating aging-associated genes. Utx-deficient (UtxΔ/Δ) mice exhibited myeloid skewing with dysplasia, extramedullary hematopoiesis, impaired hematopoietic reconstituting ability, and increased susceptibility to leukemia, which are the hallmarks of hematopoietic aging. RNA-sequencing (RNA-seq) analysis revealed that Utx deficiency converted the gene expression profiles of young hematopoietic stem-progenitor cells (HSPCs) to those of aged HSPCs. Utx expression in hematopoietic stem cells declined with age, and UtxΔ/Δ HSPCs exhibited increased expression of an aging-associated marker, accumulation of reactive oxygen species, and impaired repair of DNA double-strand breaks. Pathway and chromatin immunoprecipitation analyses coupled with RNA-seq data indicated that UTX contributed to hematopoietic homeostasis mainly by maintaining the expression of genes downregulated with aging via demethylase-dependent and -independent epigenetic programming. Of note, comparison of pathway changes in UtxΔ/Δ HSPCs, aged muscle stem cells, aged fibroblasts, and aged induced neurons showed substantial overlap, strongly suggesting common aging mechanisms among different tissue stem cells.
Subject(s)
Aging/genetics , Gene Expression Regulation/genetics , Hematopoiesis/genetics , Hematopoietic System/physiology , Histone Code/genetics , Histone Demethylases/physiology , Animals , Cellular Senescence/genetics , DNA Breaks, Double-Stranded , DNA Repair , Female , Genetic Predisposition to Disease , Hematopoiesis, Extramedullary , Histone Demethylases/deficiency , Histone Demethylases/genetics , Immune Reconstitution , Jumonji Domain-Containing Histone Demethylases/metabolism , Leukemia, Experimental/genetics , Leukemia, Experimental/virology , Male , Mice , Mice, Knockout , Moloney murine leukemia virus/physiology , Myeloid Cells/pathology , Radiation Chimera , Reactive Oxygen Species/metabolism , Recombinant Proteins/metabolism , Transcription Factors/metabolism , Virus IntegrationABSTRACT
Autosomal dominant sterile α motif domain containing 9 (Samd9) and Samd9L (Samd9/9L) syndromes are a large subgroup of currently established inherited bone marrow failure syndromes that includes myelodysplasia, infection, growth restriction, adrenal hypoplasia, genital phenotypes, and enteropathy (MIRAGE), ataxia pancytopenia, and familial monosomy 7 syndromes. Samd9/9L genes are located in tandem on chromosome 7 and have been known to be the genes responsible for myeloid malignancies associated with monosomy 7. Additionally, as IFN-inducible genes, Samd9/9L are crucial for protection against viruses. Samd9/9L syndromes are caused by gain-of-function mutations and develop into infantile myelodysplastic syndromes associated with monosomy 7 (MDS/-7) at extraordinarily high frequencies. We generated mice expressing Samd9LD764N, which mimic MIRAGE syndrome, presenting with growth retardation, a short life, bone marrow failure, and multiorgan degeneration. In hematopoietic cells, Samd9LD764N downregulates the endocytosis of transferrin and c-Kit, resulting in a rare cause of anemia and a low bone marrow reconstitutive potential that ultimately causes MDS/-7. In contrast, in nonhematopoietic cells we tested, Samd9LD764N upregulated the endocytosis of EGFR by Ship2 phosphatase translocation to the cytomembrane and activated lysosomes, resulting in the reduced expression of surface receptors and signaling. Thus, Samd9/9L is a downstream regulator of IFN that controls receptor metabolism, with constitutive activation leading to multiorgan dysfunction.
Subject(s)
ErbB Receptors/metabolism , Gain of Function Mutation , Myeloproliferative Disorders/metabolism , Tumor Suppressor Proteins/metabolism , Animals , Chromosome Deletion , Chromosomes, Human, Pair 7/genetics , Chromosomes, Human, Pair 7/metabolism , Disease Models, Animal , ErbB Receptors/genetics , Humans , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/metabolism , Mice , Mice, Transgenic , Myeloproliferative Disorders/genetics , Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases/genetics , Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases/metabolism , Syndrome , Tumor Suppressor Proteins/geneticsABSTRACT
Exposure to high-doses of ionizing radiation has been reported to be associated with the risk of stroke. However, risks associated with lower dose exposures remain unclear, and there is little information available for the risk modification according to the dose-rate. There are few studies using animal models which might be able to provide complementary information on this association. In this study, the male stroke-prone spontaneously hypertensive rat (SHRSP) was used as a model animal. The rats were acutely irradiated with doses between 0 and 1.0 Gy or chronically irradiated with a cumulative dose of 0.5 or 1.0 Gy (at a dose rate of 0.05 or 0.1 Gy/day, respectively). The onset time of stroke related symptoms in SHRSP was used as an endpoint for evaluating the effects of low dose and the low dose-rate gamma-ray exposures. With respect to acute exposure, the time to the onset of stroke in the irradiated rats suggested the presence of a threshold around 0.1 Gy. For the low dose-rate chronically exposed, no significant increase in stroke symptom was observed. These findings are novel and demonstrate that the SHRSP system can be used to determine the association between the risk of stroke and radiation exposure with high sensitivity. Moreover, these studies provide important information regarding the association between the low dose and low dose-rate radiation exposure and circulatory diseases, especially stroke.
Subject(s)
Radiation, Ionizing , Stroke/pathology , Animals , Disease Models, Animal , Dose-Response Relationship, Radiation , Kaplan-Meier Estimate , Male , Proportional Hazards Models , Time FactorsABSTRACT
Karyotype is an important prognostic factor in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL), but the underlying pharmacogenomics remain unknown. Asparaginase is an integral component in current chemotherapy for childhood BCP-ALL. Asparaginase therapy depletes serum asparagine. Normal hematopoietic cells can produce asparagine by asparagine synthetase (ASNS) activity, but ALL cells are unable to synthesize adequate amounts of asparagine. The ASNS gene has a typical CpG island in its promoter. Thus, methylation of the ASNS CpG island could be one of the epigenetic mechanisms for ASNS gene silencing in BCP-ALL. To gain deep insights into the pharmacogenomics of asparaginase therapy, we investigated the association of ASNS methylation status with asparaginase sensitivity. The ASNS CpG island is largely unmethylated in normal hematopoietic cells, but it is allele-specifically methylated in BCP-ALL cells. The ASNS gene is located at 7q21, an evolutionally conserved imprinted gene cluster. ASNS methylation in childhood BCP-ALL is associated with an aberrant methylation of the imprinted gene cluster at 7q21. Aberrant methylation of mouse Asns and a syntenic imprinted gene cluster is also confirmed in leukemic spleen samples from ETV6-RUNX1 knockin mice. In 3 childhood BCP-ALL cohorts, ASNS is highly methylated in BCP-ALL patients with favorable karyotypes but is mostly unmethylated in BCP-ALL patients with poor prognostic karyotypes. Higher ASNS methylation is associated with higher L-asparaginase sensitivity in BCP-ALL through lower ASNS gene and protein expression levels. These observations demonstrate that silencing of the ASNS gene as a result of aberrant imprinting is a pharmacogenetic mechanism for the leukemia-specific activity of asparaginase therapy in BCP-ALL.
Subject(s)
Asparaginase/therapeutic use , Aspartate-Ammonia Ligase/genetics , Pharmacogenomic Variants/genetics , Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/drug therapy , Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/genetics , Animals , Child , Chromosome Aberrations , DNA Methylation/genetics , Genomic Imprinting/genetics , Humans , MiceABSTRACT
In this work, we utilized spontaneously hypertensive rats (SHR) and Wister Kyoto rats (WKY), from which the SHR was established, to evaluate the effects of whole-body acute radiation on the cardiovascular system at doses from 0 to 4 Gy. In the irradiated SHR, the systolic blood pressure (SBP) increased with increasing dose, while body weight gain decreased with increasing radiation dose. Furthermore, pathological observations of SHR demonstrated that the number of rats with cystic degeneration in the liver increased with increasing dose. The effects observed among SHR, such as increased SBP and retardation of body weight gain, appear very similar to those observed in Japanese atomic bomb survivors. In contrast, the SBP among WKY did not change relative to dose; the body weight, however, did change, as in the SHR. Therefore, the association between radiation exposure and SBP, but not between radiation exposure and retardation of body weight gain, may be affected by genetic background, as evident from strain difference. These results suggest that the SHR and WKY animal models may be useful for studying radiation effects on non-cancer diseases including circulatory diseases, chronic liver disease and developmental retardation.
Subject(s)
Blood Pressure/genetics , Blood Pressure/radiation effects , Body Weight/genetics , Body Weight/radiation effects , Genetic Background , Animals , Liver/pathology , Liver/radiation effects , Male , Rats , Rats, Inbred SHRABSTRACT
Versican is a large chondroitin sulfate/dermatan sulfate proteoglycan in the extracellular matrix, and is expressed at high levels in tissues during development and remodeling in pathological conditions. Its core protein is cleaved at a region close to the N-terminal end of CSß domain by several members of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family, i.e., ADAMTS-1, 4, 5, 9, 15, and 20. Here, using a CRISPR/Cas9 system, we generated knock-in mice (V1R), which express an ADAMTS cleavage-resistant versican. Some V1R homozygote mice, termed R/R, exhibit syndactyly and organ hemorrhage. In wound healing experiments, R/R wound shows accumulation of versican and activated TGFß-signaling in the early stage, leading to faster healing than wild type wound. Immunostaining for Ki67, CD31, smooth muscle α-actin, periostin demonstrates higher levels of overall cell proliferation and an increased number of endothelial cells and myofibroblasts. Immunostaining for CD11b and qRT-PCR for macrophage markers revealed increased levels of inflammatory cell infiltration, especially those of M1 macrophages. Cultured R/R dermal fibroblasts revealed increased deposition of versican, type I and III collagens, and hyaluronan, and upregulation of Smad2/3 signaling. Taken together, these results demonstrate that the cleavage site determines versican turnover and that versican plays a central role in the provisional matrix during the wound repair.
Subject(s)
ADAMTS Proteins/metabolism , Hemorrhage/genetics , Syndactyly/genetics , Versicans/chemistry , Versicans/genetics , Wound Healing , Animals , CRISPR-Cas Systems , Cell Proliferation , Cells, Cultured , Extracellular Matrix/metabolism , Gene Knock-In Techniques , Male , Mice , Signal Transduction , Transforming Growth Factor beta/metabolism , Versicans/metabolismABSTRACT
Fifty years after its discovery, the enigma of monosomy 7 (-7) is eventually unraveling. The key to understanding -7 is "haploinsufficiency" mechanism, through which the function of myeloid tumor-suppressor genes is lost via the deletion/mutation of one allele. In this century, powerful tools such as microarray-CGH and next generation sequencing have enabled the search for tumor-suppressor genes on chromosome 7. Five genes (Samd9, Samd9-like (Samd9L), Ezh2, MLL3, and CUX1) have been identified and their myeloid tumor suppression potential has been verified using mouse models. Mice lacking one Samd9L gene developed MDS at an advanced age, whereas mice children harboring a gain-of-function mutation of Samd9 or Samd9L gene suffer from bone marrow failure, which is frequently followed by childhood MDS with -7, suggesting that these tumor-suppressor genes are the key to understanding not only MDS with -7 but also MDS in general. However, lack of Ezh2 and MLL3, which encode epigenetic regulators, contribute to the promotion of the progression of myeloid tumor cells that harbor abnormalities in the p53 or Ras pathways.
Subject(s)
Myelodysplastic Syndromes/genetics , Myeloproliferative Disorders/genetics , Animals , Chromosome Deletion , Chromosomes, Human, Pair 7/genetics , DNA-Binding Proteins , Enhancer of Zeste Homolog 2 Protein , Genes, Tumor Suppressor , Homeodomain Proteins , Humans , Intracellular Signaling Peptides and Proteins , Mice , Nuclear Proteins , Proteins , Repressor Proteins , Transcription Factors , Tumor Suppressor Proteins/geneticsABSTRACT
Host restriction factors constitute a formidable barrier for viral replication to which many viruses have evolved counter-measures. Human SAMD9, a tumor suppressor and a restriction factor for poxviruses in cell lines, is antagonized by two classes of poxvirus proteins, represented by vaccinia virus (VACV) K1 and C7. A paralog of SAMD9, SAMD9L, is also encoded by some mammals, while only one of two paralogs is retained by others. Here, we show that SAMD9L functions similarly to SAMD9 as a restriction factor and that the two paralogs form a critical host barrier that poxviruses must overcome to establish infection. In mice, which naturally lack SAMD9, overcoming SAMD9L restriction with viral inhibitors is essential for poxvirus replication and pathogenesis. While a VACV deleted of both K1 and C7 (vK1L-C7L-) was restricted by mouse cells and highly attenuated in mice, its replication and virulence were completely restored in SAMD9L-/- mice. In humans, both SAMD9 and SAMD9L are poxvirus restriction factors, although the latter requires interferon induction in many cell types. While knockout of SAMD9 with Crispr-Cas9 was sufficient for abolishing the restriction for vK1L-C7L- in many human cells, knockout of both paralogs was required for abolishing the restriction in interferon-treated cells. Both paralogs are antagonized by VACV K1, C7 and C7 homologs from diverse mammalian poxviruses, but mouse SAMD9L is resistant to the C7 homolog encoded by a group of poxviruses with a narrow host range in ruminants, indicating that host species-specific difference in SAMD9/SAMD9L genes serves as a barrier for cross-species poxvirus transmission.
Subject(s)
Host Specificity/genetics , Poxviridae Infections/genetics , Poxviridae/genetics , Poxviridae/pathogenicity , Proteins/physiology , Tumor Suppressor Proteins/physiology , Animals , Cells, Cultured , Chlorocebus aethiops , HEK293 Cells , HeLa Cells , Humans , Intracellular Signaling Peptides and Proteins , Mammals , Mice , Mice, Knockout , NIH 3T3 Cells , Poxviridae Infections/transmission , Poxviridae Infections/virology , Proteins/genetics , Sequence Homology , Tumor Suppressor Proteins/genetics , Vaccinia virus/genetics , Vaccinia virus/pathogenicity , Vero CellsABSTRACT
Chronic myelomonocytic leukemia (CMML) is a hematological malignancy characterized by uncontrolled proliferation of dysplastic myelomonocytes and frequent progression to acute myeloid leukemia (AML). We identified mutations in the Cbl gene, which encodes a negative regulator of cytokine signaling, in a subset of CMML patients. To investigate the contribution of mutant Cbl in CMML pathogenesis, we generated conditional knockin mice for Cbl that express wild-type Cbl in a steady state and inducibly express CblQ367P , a CMML-associated Cbl mutant. CblQ367P mice exhibited sustained proliferation of myelomonocytes, multilineage dysplasia, and splenomegaly, which are the hallmarks of CMML. The phosphatidylinositol 3-kinase (PI3K)-AKT and JAK-STAT pathways were constitutively activated in CblQ367P hematopoietic stem cells, which promoted cell cycle progression and enhanced chemokine-chemokine receptor activity. Gem, a gene encoding a GTPase that is upregulated by CblQ367P , enhanced hematopoietic stem cell activity and induced myeloid cell proliferation. In addition, Evi1, a gene encoding a transcription factor, was found to cooperate with CblQ367P and progress CMML to AML. Furthermore, targeted inhibition for the PI3K-AKT and JAK-STAT pathways efficiently suppressed the proliferative activity of CblQ367P -bearing CMML cells. Our findings provide insights into the molecular mechanisms underlying mutant Cbl-induced CMML and propose a possible molecular targeting therapy for mutant Cbl-carrying CMML patients.
Subject(s)
Cell Cycle , Hematopoietic Stem Cells , Leukemia, Myelogenous, Chronic, BCR-ABL Positive , Mutation, Missense , Myelopoiesis , Proto-Oncogene Proteins c-cbl , Up-Regulation , Amino Acid Substitution , Animals , Gene Expression Regulation, Enzymologic , Hematopoietic Stem Cells/metabolism , Hematopoietic Stem Cells/pathology , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , Leukemia, Myeloid, Acute/genetics , Leukemia, Myeloid, Acute/metabolism , Leukemia, Myeloid, Acute/pathology , Mice , Mice, Transgenic , Monocytes/metabolism , Monocytes/pathology , Monomeric GTP-Binding Proteins/biosynthesis , Monomeric GTP-Binding Proteins/genetics , Phosphatidylinositol 3-Kinases/genetics , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-cbl/biosynthesis , Proto-Oncogene Proteins c-cbl/genetics , Signal TransductionABSTRACT
Polycomb repressive complex 2 (PRC2) catalyzes the monomethylation, dimethylation, and trimethylation of histone H3 Lys27 (H3K27) and acts as a central epigenetic regulator that marks the repressive chromatin domain. Embryonic ectoderm development (EED), an essential component of PRC2, interacts with trimethylated H3K27 (H3K27me3) through the aromatic cage structure composed of its three aromatic amino acids, Phe97, Trp364, and Tyr365. This interaction allosterically activates the histone methyltransferase activity of PRC2 and thereby propagates repressive histone marks. In this study, we report the analysis of knock-in mice harboring the myeloid disorder-associated EED Ile363Met (I363M) mutation, analogous to the EED aromatic cage mutants. The I363M homozygotes displayed a remarkable and preferential reduction of H3K27me3 and died at midgestation. The heterozygotes increased the clonogenic capacity and bone marrow repopulating activity of hematopoietic stem/progenitor cells (HSPCs) and were susceptible to leukemia. Lgals3, a PRC2 target gene encoding a multifunctional galactose-binding lectin, was derepressed in I363M heterozygotes, which enhanced the stemness of HSPCs. Thus, our work provides in vivo evidence that the structural integrity of EED to H3K27me3 propagation is critical, especially for embryonic development and hematopoietic homeostasis, and that its perturbation increases the predisposition to hematologic malignancies.
Subject(s)
Galectin 3/genetics , Leukemia/genetics , Polycomb Repressive Complex 2/chemistry , Animals , Embryonic Development/genetics , Epigenesis, Genetic/genetics , Galectin 3/chemistry , Genetic Predisposition to Disease , Hematopoietic Stem Cells/chemistry , Hematopoietic Stem Cells/metabolism , Histone-Lysine N-Methyltransferase/chemistry , Histone-Lysine N-Methyltransferase/genetics , Humans , Mice , Polycomb Repressive Complex 2/geneticsABSTRACT
Polycomb repressive complex 2 (PRC2) participates in transcriptional repression through methylation of histone H3K27. The WD-repeat protein embryonic ectoderm development (EED) is a non-catalytic but an essential component of PRC2 and its mutations were identified in hematopoietic malignancies. To clarify the role(s) of EED in adult hematopoiesis and leukemogenesis, we generated Eed conditional knockout (Eed(Δ/Δ)) mice. Eed(Δ/Δ) mice died in a short period with rapid decrease of hematopoietic cells. Hematopoietic stem/progenitor cells (HSPCs) were markedly decreased with impaired bone marrow (BM) repopulation ability. Cell cycle analysis of HSPCs demonstrated increased S-phase fraction coupled with suppressed G0/G1 entry. Genes encoding cell adhesion molecules are significantly enriched in Eed(Δ/Δ) HSPCs, and consistently, Eed(Δ/Δ) HSPCs exhibited increased attachment to a major extracellular matrix component, fibronectin. Thus, EED deficiency increases proliferation on one side but promotes quiescence possibly by enhanced adhesion to the hematopoietic niche on the other, and these conflicting events would lead to abnormal differentiation and functional defect of Eed(Δ/Δ) HSPCs. In addition, Eed haploinsufficiency induced hematopoietic dysplasia, and Eed heterozygous mice were susceptible to malignant transformation and developed leukemia in cooperation with Evi1 overexpression. Our results demonstrated differentiation stage-specific and dose-dependent roles of EED in normal hematopoiesis and leukemogenesis.
Subject(s)
Haploinsufficiency , Hematopoiesis , Leukemia/metabolism , Polycomb Repressive Complex 2/genetics , Polycomb Repressive Complex 2/physiology , Animals , Antigens, CD34/metabolism , Cell Adhesion , Cell Cycle , Cell Differentiation , Cell Proliferation , Cell Transformation, Neoplastic , Extracellular Matrix/metabolism , Female , Fetal Blood/cytology , Fibronectins/chemistry , Fibronectins/metabolism , Flow Cytometry , Gene Transfer Techniques , Hematologic Neoplasms/genetics , Hematologic Neoplasms/metabolism , Hematopoietic Stem Cells/cytology , Heterozygote , Histones , Leukemia/genetics , Male , Mice , Mice, Inbred C57BL , RNA, Small Interfering/metabolismABSTRACT
The DDX41 gene, encoding a DEAD-box type ATP-dependent RNA helicase, is rarely but reproducibly mutated in myeloid diseases. The acquired mutation in DDX41 is highly concentrated at c.G1574A (p.R525H) in the conserved motif VI located at the C-terminus of the helicase core domain where ATP interacts and is hydrolyzed. Therefore, it is likely that the p.R525H mutation perturbs ATPase activity in a dominant-negative manner. In this study, we screened for the DDX41 mutation of CD34-positive tumor cells based on mRNA sequencing and identified the p.R525H mutation in three cases among 23 patients. Intriguingly, these patients commonly exhibited acute myeloid leukemia (AML) with peripheral blood cytopenias and low blast counts, suggesting that the mutation inhibits the growth and differentiation of hematopoietic cells. Data from cord blood cells and leukemia cell lines suggest a role for DDX41 in preribosomal RNA processing, in which the expression of the p.R525H mutant causes a certain ribosomopathy phenotype in hematopoietic cells by suppressing MDM2-mediated RB degradation, thus triggering the inhibition of E2F activity. This study uncovered a pathogenic role of p.R525H DDX41 in the slow growth rate of tumor cells. Age-dependent epigenetic alterations or other somatic changes might collaborate with the mutation to cause AML.
Subject(s)
DEAD-box RNA Helicases/genetics , Genetic Predisposition to Disease , Leukemia, Myeloid, Acute/genetics , Mutation , Aged , Aged, 80 and over , Amino Acid Substitution , Animals , Biomarkers , Bone Marrow Transplantation , Chromosome Aberrations , Codon , DEAD-box RNA Helicases/metabolism , DNA Mutational Analysis , Disease Models, Animal , Female , Gene Expression , Hematopoietic Stem Cells/metabolism , Humans , Leukemia, Myeloid, Acute/diagnosis , Leukemia, Myeloid, Acute/metabolism , Male , Mice , Middle Aged , Protein Binding , Protein TransportABSTRACT
E2A-PBX1 is a chimeric gene product detected in t(1;19)-bearing acute lymphoblastic leukemia (ALL) with B-cell lineage. To investigate the leukemogenic process, we generated conditional knock-in (cKI) mice for E2A-PBX1, in which E2A-PBX1 is inducibly expressed under the control of the endogenous E2A promoter. Despite the induced expression of E2A-PBX1, no hematopoietic disease was observed, strongly suggesting that additional genetic alterations are required to develop leukemia. To address this possibility, retroviral insertional mutagenesis was used. Virus infection efficiently induced T-cell, B-cell, and biphenotypic ALL in E2A-PBX1 cKI mice. Inverse PCR identified eight retroviral common integration sites, in which enhanced expression was observed in the Gfi1, Mycn, and Pim1 genes. In addition, it is of note that viral integration and overexpression of the Zfp521 gene was detected in one tumor with B-cell lineage; we previously identified Zfp521 as a cooperative gene with E2A-HLF, another E2A-involving fusion gene with B-lineage ALL. The cooperative oncogenicity of E2A-PBX1 with overexpressed Zfp521 in B-cell tumorigenesis was indicated by the finding that E2A-PBX1 cKI, Zfp521 transgenic compound mice developed B-lineage ALL. Moreover, upregulation of ZNF521, the human counterpart of Zfp521, was found in several human leukemic cell lines bearing t(1;19). These results indicate that E2A-PBX1 cooperates with additional gene alterations to develop ALL. Among them, enhanced expression of ZNF521 may play a clinically relevant role in E2A fusion genes to develop B-lineage ALL.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/metabolism , DNA-Binding Proteins/metabolism , Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics , Precursor Cell Lymphoblastic Leukemia-Lymphoma/metabolism , Proto-Oncogene Proteins/metabolism , Animals , B-Lymphocytes/metabolism , B-Lymphocytes/pathology , Basic Helix-Loop-Helix Transcription Factors/genetics , Cell Line, Tumor , Cell Transformation, Neoplastic , DNA-Binding Proteins/genetics , Disease Models, Animal , Gene Knock-In Techniques , Humans , Mice , Mutagenesis, Insertional , Pre-B-Cell Leukemia Transcription Factor 1 , Promoter Regions, Genetic/genetics , Proto-Oncogene Proteins/genetics , Real-Time Polymerase Chain Reaction , Transcription Factors/geneticsABSTRACT
Resistin-like molecule ß (RELMß) reportedly has multiple functions including local immune responses in the gut. In this study, we investigated the possible contribution of RELMß to non-alcoholic steatohepatitis (NASH) development. First, RELMß knock-out (KO) mice were shown to be resistant to methionine-choline deficient (MCD) diet-induced NASH development. Since it was newly revealed that Kupffer cells in the liver express RELMß and that RELMß expression levels in the colon and the numbers of RELMß-positive Kupffer cells were both increased in this model, we carried out further experiments using radiation chimeras between wild-type and RELMß-KO mice to distinguish between the contributions of RELMß in these two organs. These experiments revealed the requirement of RELMß in both organs for full manifestation of NASH, while deletion of each one alone attenuated the development of NASH with reduced serum lipopolysaccharide (LPS) levels. The higher proportion of lactic acid bacteria in the gut microbiota of RELMß-KO than in that of wild-type mice may be one of the mechanisms underlying the lower serum LPS level the former. These data suggest the contribution of increases in RELMß in the gut and Kupffer cells to NASH development, raising the possibility of RELMß being a novel therapeutic target for NASH.