ABSTRACT
N6-methyladenosine (m6A) is the most abundant RNA modification, but little is known about its role in mammalian hematopoietic development. Here, we show that conditional deletion of the m6A writer METTL3 in murine fetal liver resulted in hematopoietic failure and perinatal lethality. Loss of METTL3 and m6A activated an aberrant innate immune response, mediated by the formation of endogenous double-stranded RNAs (dsRNAs). The aberrantly formed dsRNAs were long, highly m6A modified in their native state, characterized by low folding energies, and predominantly protein coding. We identified coinciding activation of pattern recognition receptor pathways normally tasked with the detection of foreign dsRNAs. Disruption of the aberrant immune response via abrogation of downstream Mavs or Rnasel signaling partially rescued the observed hematopoietic defects in METTL3-deficient cells in vitro and in vivo. Our results suggest that m6A modification protects against endogenous dsRNA formation and a deleterious innate immune response during mammalian hematopoietic development.
Subject(s)
Adenosine/chemistry , Hematopoiesis/genetics , Hematopoiesis/immunology , Immunity, Innate/genetics , RNA, Double-Stranded/metabolism , Animals , Biomarkers , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Bone Marrow Failure Disorders/pathology , Cell Differentiation/genetics , Disease Models, Animal , Epigenesis, Genetic , Gene Expression , Hematopoietic Stem Cells , Immunophenotyping , Methylation , Methyltransferases/genetics , Methyltransferases/metabolism , Mice , Mice, Knockout , RNA, Double-Stranded/chemistryABSTRACT
Human telomere biology disorders (TBD)/short telomere syndromes (STS) are heterogeneous disorders caused by inherited loss-of-function mutations in telomere-associated genes. Here, we identify 3 germline heterozygous missense variants in the RPA1 gene in 4 unrelated probands presenting with short telomeres and varying clinical features of TBD/STS, including bone marrow failure, myelodysplastic syndrome, T- and B-cell lymphopenia, pulmonary fibrosis, or skin manifestations. All variants cluster to DNA-binding domain A of RPA1 protein. RPA1 is a single-strand DNA-binding protein required for DNA replication and repair and involved in telomere maintenance. We showed that RPA1E240K and RPA1V227A proteins exhibit increased binding to single-strand and telomeric DNA, implying a gain in DNA-binding function, whereas RPA1T270A has binding properties similar to wild-type protein. To study the mutational effect in a cellular system, CRISPR/Cas9 was used to knock-in the RPA1E240K mutation into healthy inducible pluripotent stem cells. This resulted in severe telomere shortening and impaired hematopoietic differentiation. Furthermore, in patients with RPA1E240K, we discovered somatic genetic rescue in hematopoietic cells due to an acquired truncating cis RPA1 mutation or a uniparental isodisomy 17p with loss of mutant allele, coinciding with stabilized blood counts. Using single-cell sequencing, the 2 somatic genetic rescue events were proven to be independently acquired in hematopoietic stem cells. In summary, we describe the first human disease caused by germline RPA1 variants in individuals with TBD/STS.
Subject(s)
Bone Marrow Failure Disorders/pathology , Gain of Function Mutation , Heterozygote , Myelodysplastic Syndromes/pathology , Replication Protein A/genetics , Telomere Shortening , Telomere/genetics , Adolescent , Adult , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Cell Differentiation , Child , Female , Humans , Infant, Newborn , Male , Middle Aged , Myelodysplastic Syndromes/etiology , Myelodysplastic Syndromes/metabolism , Young AdultABSTRACT
We report 5 children with bone marrow failure (BMF) after primary varicella zoster virus (VZV) infection or VZV vaccination, highlighting the highly variable course. Two patients were treated with intravenous immunoglobulins; one had a slow hematologic recovery, and the other was rescued by allogeneic hematopoietic stem cell transplantation (HSCT). Of the 2 patients treated with immunosuppressive therapy with antithymocyte globulin and cyclosporine, one had a complete response, and the other was transplanted for nonresponse. One patient underwent a primary allograft. All patients are alive. This study demonstrated that VZV-associated BMF is a life-threatening disorder that often requires HSCT.
Subject(s)
Hematopoietic Stem Cell Transplantation , Varicella Zoster Virus Infection , Humans , Male , Female , Child , Hematopoietic Stem Cell Transplantation/adverse effects , Child, Preschool , Herpesvirus 3, Human , Bone Marrow Failure Disorders/etiology , Vaccination/adverse effects , Bone Marrow Diseases/etiology , Chickenpox Vaccine/adverse effects , Adolescent , Immunoglobulins, Intravenous/therapeutic use , InfantABSTRACT
Inborn errors of immunity (IEI) are a genetically heterogeneous group of disorders with a broad clinical spectrum. Identification of molecular and functional bases of these disorders is important for diagnosis, treatment, and an understanding of the human immune response. We identified 6 unrelated males with neutropenia, infections, lymphoproliferation, humoral immune defects, and in some cases bone marrow failure associated with 3 different variants in the X-linked gene TLR8, encoding the endosomal Toll-like receptor 8 (TLR8). Interestingly, 5 patients had somatic variants in TLR8 with <30% mosaicism, suggesting a dominant mechanism responsible for the clinical phenotype. Mosaicism was also detected in skin-derived fibroblasts in 3 patients, demonstrating that mutations were not limited to the hematopoietic compartment. All patients had refractory chronic neutropenia, and 3 patients underwent allogeneic hematopoietic cell transplantation. All variants conferred gain of function to TLR8 protein, and immune phenotyping demonstrated a proinflammatory phenotype with activated T cells and elevated serum cytokines associated with impaired B-cell maturation. Differentiation of myeloid cells from patient-derived induced pluripotent stem cells demonstrated increased responsiveness to TLR8. Together, these findings demonstrate that gain-of-function variants in TLR8 lead to a novel childhood-onset IEI with lymphoproliferation, neutropenia, infectious susceptibility, B- and T-cell defects, and in some cases, bone marrow failure. Somatic mosaicism is a prominent molecular mechanism of this new disease.
Subject(s)
Bone Marrow Failure Disorders/pathology , Gain of Function Mutation , Immunologic Deficiency Syndromes/pathology , Inflammation/pathology , Mosaicism , Pancytopenia/pathology , Toll-Like Receptor 8/genetics , Adolescent , Adult , B-Lymphocytes/pathology , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Cell Differentiation , Child , Child, Preschool , Cytokines/metabolism , Female , Follow-Up Studies , Humans , Immunologic Deficiency Syndromes/etiology , Immunologic Deficiency Syndromes/metabolism , Infant , Inflammation/etiology , Inflammation/metabolism , Lymphocyte Activation , Male , Pancytopenia/etiology , Pancytopenia/metabolism , Pedigree , Prognosis , T-Lymphocytes/immunology , Young AdultABSTRACT
Peripheral blood cytopenia, a frequent presenting symptom in pediatric patients, can be caused by bone marrow failure (BMF). Timely identification of patients with non-reversible BMF is of crucial importance to reduce the risks of invasive infections and bleeding complications. Most pediatric patients with severe persistent cytopenia, independent of the underlying cause, are offered allogeneic hematopoietic stem cell transplantation (HSCT) as curative therapy. Here we report on our management guidelines and HSCT outcomes of pediatric BMF patients to pinpoint improvements and future challenges. We formulated recommendations based on this 50 years' experience, which were implemented at our center in 2017. By analysis of the HSCT cohort of 2017-2023, the 5-year outcome data is presented and compared to historical outcome data. In addition, outcomes of patients transplanted for identified inherited bone marrow failure syndromes (IBMFS) are compared to severe aplastic anemia (SAA) outcomes to underline the often multiorgan disease in IBMFS with implications for long-term survival. Survival of pediatric patients with irreversible BMF has improved tremendously. SAA patients transplanted after 2017 had a superior 5-year overall (OS) and event-free survival (EFS) of 97% and 85% compared to 68% and 59% in the cohort transplanted before 2017 (p = 0.0011 and p = 0.017). A similar trend was seen for BMF, with an OS and EFS of 89% for those transplanted after 2017 compared to 62% and 59% (p > 0.05). This improvement is mainly related to better survival in the first months after HSCT. The long-term survival after HSCT is lower in IBMFS patients as compared to SAA patients due to secondary malignancies and multiorgan toxicity. Conclusion: Unbiased protocolized in-depth diagnostic strategies are crucial to increase the frequency of identifiable causes within the heterogeneous group of pediatric BMF. A comprehensive approach to identify the cause of BMF can prevent treatment delay and be useful to tailor treatment and follow-up protocols. What is Known: ⢠Irreversible BMF in pediatric patients can be caused by a wide spectrum of underlying diseases including (pre)malignant disease, IBMFS and AA. Identifying the exact underlying cause of BMF is crucial for tailored therapy, however often challenging and time-consuming. ⢠Frontline allogeneic HSCT is offered to most pediatric patients with severe BMF as curative treatment. What is New: ⢠Protocolized unbiased diagnostics, short time to treatment (< 3 months) and maximal supportive care until curative treatment can prevent complications with a negative effect on survival such as infection and bleeding. ⢠Personalized follow-up protocols for IBMFS patients are essential to prevent a second decline in survival due to long-term treatment toxicity and extra-hematological disease complications.
Subject(s)
Anemia, Aplastic , Hematopoietic Stem Cell Transplantation , Child , Humans , Congenital Bone Marrow Failure Syndromes/etiology , Anemia, Aplastic/diagnosis , Anemia, Aplastic/therapy , Bone Marrow Failure Disorders/diagnosis , Bone Marrow Failure Disorders/etiology , Hematopoietic Stem Cell Transplantation/adverse effects , Hematopoietic Stem Cell Transplantation/methodsABSTRACT
Hypoplastic bone marrow failure is a diagnostic feature of multiple haematological disorders, which also share a substantial overlap of clinical symptoms. Hence, discrimination of underlying disorders in patients presenting with hypoplastic bone marrow failure remains a major challenge in the clinic. Recent next-generation sequencing (NGS) studies have broadened our understanding of the varying molecular mechanisms and advanced diagnostics of disorders exhibiting hypoplastic bone marrow failure. In this article, we present a literature review of NGS studies of haematological disorders associated with hypoplastic bone marrow failure and highlight the relevance of NGS for improved clinical diagnostics and decision-making.
Subject(s)
Bone Marrow Failure Disorders/diagnosis , Bone Marrow Failure Disorders/etiology , Bone Marrow/pathology , Disease Susceptibility , High-Throughput Nucleotide Sequencing , Animals , Biomarkers , Biopsy , Diagnosis, Differential , Genetic Predisposition to Disease , Humans , Molecular Diagnostic Techniques , PhenotypeABSTRACT
In the event of a high-dose radiation exposure accident, adipose-derived stem cell (ADSC) transplantation might be used as an emergency medical treatment to compensate for bone marrow failure. To investigate the possible course of that treatment, we examined whether transplantation of ADSCs into whole-body X-ray irradiated mice would provide resistance to radiation damage. ADSCs were obtained from a primary culture of adipocytes from adipose tissue of syngeneic mice. The ADSCs were transplanted via an intravenous (i.v.) route after whole-body irradiation (6 Gy, X-rays) of the ICR mice. Fifty days after transplantation, the survival rate of the transplanted group was 40% higher than the control group, and the difference in survival rates was maintained in the following 200 days. After 400 days, however, the difference in survival rates became smaller and disappeared after 650 days. The results indicate that ADSC transplantation may reduce lethality from acute radiation bone marrow injury for several hundred days.
Subject(s)
Adipocytes/transplantation , Adipose Tissue/cytology , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/therapy , Radiation Injuries, Experimental/etiology , Radiation Injuries, Experimental/therapy , Stem Cell Transplantation/methods , Whole-Body Irradiation/adverse effects , X-Rays/adverse effects , Adipocytes/cytology , Animals , Bone Marrow Failure Disorders/mortality , Cells, Cultured , Female , Mice, Inbred ICR , Radiation Dosage , Radiation Injuries, Experimental/mortality , Survival Rate , Time FactorsABSTRACT
We studied the possibility of using sodium deoxyribonucleate (Derinat) for improving the efficiency of co-transplantation of mesenchymal (MSC) and hematopoietic stem cells (HSC) to female F1(CBA×C57BL/6) mice with bone marrow aplasia caused by exposure to γ-radiation. It was found that immunomodulator Derinat enhanced the effect of co-transplantation, in particular, triple post-irradiation administration of Derinat accelerated hematopoiesis recovery judging from the parameters of peripheral blood, total cellularity of the bone marrow and spleen, and animal survival. Single or double administration of Derinat prior to irradiation was ineffective. The optimal result was obtained when the following scheme was applied: MSCâHSC with an interval of 48 h starting during the first hours after irradiation and triple administration of Derinat (in 10-15 min, 3 and 7 days after irradiation) in a dose of 3 mg/mouse.
Subject(s)
DNA/pharmacology , Hematopoietic Stem Cell Transplantation , Mesenchymal Stem Cell Transplantation , Radiation Injuries, Experimental/therapy , Animals , Bone Marrow Cells/drug effects , Bone Marrow Cells/physiology , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/therapy , Combined Modality Therapy , DNA/chemistry , DNA/therapeutic use , Female , Gamma Rays/adverse effects , Hematopoiesis/drug effects , Hematopoiesis/physiology , Hematopoietic Stem Cell Transplantation/methods , Mesenchymal Stem Cell Transplantation/methods , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Radiation Injuries, Experimental/etiology , Recovery of Function/drug effects , Sodium/chemistry , Sodium/pharmacology , Whole-Body Irradiation/adverse effectsABSTRACT
The International Paroxysmal Nocturnal Hemoglobinuria (PNH) Registry (NCT01374360) was initiated to optimize patient management by collecting data regarding disease burden, progression, and clinical outcomes. Herein, we report updated baseline demographics, clinical characteristics, disease burden data, and observed trends regarding clone size in the largest cohort of Registry patients. Patients with available data as of July 2017 were stratified by glycosylphosphatidylinositol (GPI)-deficient granulocyte clone size (< 10%, ≥ 10%-< 50%, and ≥ 50%). All patients were untreated with eculizumab at baseline, defined as date of eculizumab initiation or date of Registry enrollment (if never treated with eculizumab). Outcomes assessed in the current analysis included proportions of patients with high disease activity (HDA), history of major adverse vascular events (MAVEs; including thrombotic events [TEs]), bone marrow failure (BMF), red blood cell (RBC) transfusions, and PNH-related symptoms. A total of 4439 patients were included, of whom 2701 (60.8%) had available GPI-deficient granulocyte clone size data. Among these, median clone size was 31.8% (1002 had < 10%; 526 had ≥ 10%-< 50%; 1173 had ≥ 50%). There were high proportions of patients with HDA (51.6%), history of MAVEs (18.8%), BMF (62.6%), RBC transfusion (61.3%), and impaired renal function (42.8%). All measures except RBC transfusion history significantly correlated with GPI-deficient granulocyte clone size. A large proportion of patients with GPI-deficient granulocyte clone size < 10% had hemolysis (9.7%), MAVEs (10.2%), HDA (9.1%), and/or PNH-related symptoms. Although larger GPI-deficient granulocyte clone sizes were associated with higher disease burden, a substantial proportion of patients with smaller clone sizes had history of MAVEs/TEs.
Subject(s)
Hemoglobinuria, Paroxysmal/diagnosis , Hemoglobinuria, Paroxysmal/epidemiology , Adult , Bone Marrow Failure Disorders/diagnosis , Bone Marrow Failure Disorders/epidemiology , Bone Marrow Failure Disorders/etiology , Cost of Illness , Erythrocyte Transfusion/statistics & numerical data , Female , Granulocytes/pathology , Hemoglobinuria, Paroxysmal/pathology , Hemoglobinuria, Paroxysmal/therapy , Humans , Internationality , Male , Middle Aged , Quality of Life , Registries , Severity of Illness Index , Young AdultSubject(s)
Bone Marrow Failure Disorders/genetics , Exome Sequencing , Fanconi Anemia/genetics , Genomic Instability/genetics , Mutation , Bone Marrow Failure Disorders/etiology , Cell Movement/genetics , Child , Fanconi Anemia/complications , Gene Ontology , Humans , Mitosis/genetics , Protein Transport/genetics , Thumb/abnormalitiesSubject(s)
Bone Marrow Failure Disorders/etiology , Hematopoietic Stem Cell Transplantation/methods , Immunotherapy, Adoptive/adverse effects , Multiple Myeloma/therapy , Adult , Antigens, CD19/therapeutic use , Bone Marrow Failure Disorders/therapy , Cryopreservation , Humans , Male , Pancytopenia/etiology , Receptors, Chimeric Antigen , Stem Cells/cytology , Transplantation, Autologous , Treatment OutcomeABSTRACT
Hematopoietic cell transplantation (HCT) is the only readily available cure for many life-threatening pediatric nonmalignant diseases (NMD), but most patients lack a matched related donor and are at higher risk for graft-versus-host disease (GVHD). Use of abatacept (Aba) to target donor T-cell activation has been safe and effective in preventing GVHD after unrelated donor (URD) HCT for malignant diseases (Aba2 trial). Our primary objective was to evaluate the tolerability of Aba added to standard GVHD prophylaxis (cyclosporine and mycophenolate mofetil) in pediatric patients with NMD undergoing URD HCT. In this single-arm, single-center phase 1 trial, 10 patients receiving reduced intensity or nonmyeloablative conditioning underwent URD HCT. Immune reconstitution was assessed longitudinally via flow cytometry and compared to pediatric patients on Aba2. Nine patients successfully engrafted, with 1 primary graft rejection in the setting of inadequate cell dose; secondary graft rejection occurred in 1 patient with concurrent cytomegalovirus viremia. Two deaths occurred, both unrelated to Aba. One patient developed probable posttransplant lymphoproliferative disease, responsive to rituximab and immune suppression withdrawal. No patients developed severe acute or chronic GVHD, and 8 patients were off systemic immunosuppression at 1 year. Immune reconstitution did not appear to be impacted by Aba, and preservation of naïve relative to effector memory CD4+ T cells was seen akin to Aba2. Thus, 4 doses of Aba were deemed tolerable in pediatric patients with NMD following URD HCT, with encouraging preliminary efficacy and supportive immune correlatives in this NMD cohort.
Subject(s)
Graft vs Host Disease , Hematopoietic Stem Cell Transplantation , Pancytopenia , Humans , Child , Abatacept/therapeutic use , Hematopoietic Stem Cell Transplantation/adverse effects , Graft vs Host Disease/etiology , Graft vs Host Disease/prevention & control , Graft vs Host Disease/pathology , Pancytopenia/etiology , Unrelated Donors , Bone Marrow Failure Disorders/etiologyABSTRACT
Hypoplastic myelodysplastic syndrome (hMDS) and aplastic anemia (AA) are rare hematopoietic disorders characterized by pancytopenia with hypoplastic bone marrow (BM). hMDS and idiopathic AA share overlapping clinicopathological features, making a diagnosis very difficult. The differential diagnosis is mainly based on the presence of dysgranulopoiesis, dysmegakaryocytopoiesis, an increased percentage of blasts, and abnormal karyotype, all favouring the diagnosis of hMDS. An accurate diagnosis has important clinical implications, as the prognosis and treatment can be quite different for these diseases. Patients with hMDS have a greater risk of neoplastic progression, a shorter survival time and a lower response to immunosuppressive therapy compared with patients with AA. There is compelling evidence that these distinct clinical entities share a common pathophysiology based on the damage of hematopoietic stem and progenitor cells (HSPCs) by cytotoxic T cells. Expanded T cells overproduce proinflammatory cytokines (interferonγ and tumor necrosis factorα), resulting in decreased proliferation and increased apoptosis of HSPCs. The antigens that trigger this abnormal immune response are not known, but potential candidates have been suggested, including Wilms tumor protein 1 and human leukocyte antigen class I molecules. Our understanding of the molecular pathogenesis of these BM failure syndromes has been improved by nextgeneration sequencing, which has enabled the identification of a large spectrum of mutations. It has also brought new challenges, such as the interpretation of variants of uncertain significance and clonal hematopoiesis of indeterminate potential. The present review discusses the main clinicopathological differences between hMDS and acquired AA, focuses on the molecular background and highlights the importance of molecular testing.
Subject(s)
Anemia, Hemolytic, Autoimmune/etiology , Bone Marrow Failure Disorders/etiology , Myelodysplastic-Myeloproliferative Diseases/etiology , Anemia, Hemolytic, Autoimmune/genetics , Bone Marrow Failure Disorders/genetics , Humans , Immunity/genetics , Immunity/immunology , Myelodysplastic-Myeloproliferative Diseases/genetics , PrognosisABSTRACT
Inflammation is associated with bone marrow failure syndromes, but how specific molecules impact the bone marrow microenvironment is not well elucidated. We report a novel role for the miR-145 target, Toll/interleukin-1 receptor domain containing adaptor protein (TIRAP), in driving bone marrow failure. We show that TIRAP is overexpressed in various types of myelodysplastic syndromes (MDS) and suppresses all three major hematopoietic lineages. TIRAP expression promotes up-regulation of Ifnγ, leading to myelosuppression through Ifnγ-Ifnγr-mediated release of the alarmin, Hmgb1, which disrupts the bone marrow endothelial niche. Deletion of Ifnγ blocks Hmgb1 release and is sufficient to reverse the endothelial defect and restore myelopoiesis. Contrary to current dogma, TIRAP-activated Ifnγ-driven bone marrow suppression is independent of T cell function or pyroptosis. In the absence of Ifnγ, TIRAP drives myeloproliferation, implicating Ifnγ in suppressing the transformation of MDS to acute leukemia. These findings reveal novel, noncanonical roles of TIRAP, Hmgb1, and Ifnγ in the bone marrow microenvironment and provide insight into the pathophysiology of preleukemic syndromes.
Subject(s)
Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Endothelium/metabolism , HMGB1 Protein/metabolism , Interferon-gamma/metabolism , Membrane Glycoproteins/genetics , Myelopoiesis/genetics , Receptors, Interleukin-1/genetics , Animals , Biomarkers , Bone Marrow Failure Disorders/pathology , Cellular Microenvironment/genetics , Disease Susceptibility , Gene Expression , Hematopoiesis/genetics , Membrane Glycoproteins/metabolism , Mesenchymal Stem Cells/metabolism , Mice , Myeloproliferative Disorders/etiology , Myeloproliferative Disorders/metabolism , Myeloproliferative Disorders/pathology , Receptors, Interleukin-1/metabolismABSTRACT
U2AF1 is involved in the recognition of the 3' splice site during pre-mRNA splicing. Mutations in U2AF1 are frequently observed in myelodysplastic syndromes. However, the role of wild-type U2AF1 in normal hematopoiesis has remained elusive. Using a novel conditional U2af1 knockout allele, we have found that deletion of U2af1 results in profound defects in hematopoiesis characterized by pancytopenia, ablation of hematopoietic stem/progenitor cells (HSPC) leading to bone marrow failure and early lethality in mice. U2af1 deletion impairs HSPC function and repopulation capacity. U2af1 deletion also causes increased DNA damage and reduced survival in hematopoietic progenitors. RNA sequencing analysis reveals significant alterations in the expression of genes related to HSC maintenance, cell proliferation, and DNA damage response-related pathways in U2af1-deficient HSPC. U2af1 deficiency also induces splicing alterations in genes important for HSPC function. This includes altered splicing and perturbed expression of Nfya and Pbx1 transcription factors in U2af1-deficient HSPC. Collectively, these results suggest an important role for U2af1 in the maintenance and function of HSPC in normal hematopoiesis. A better understanding of the normal function of U2AF1 in hematopoiesis is important for development of appropriate therapeutic approaches for U2AF1 mutant induced hematologic malignancies.
Subject(s)
Bone Marrow Failure Disorders/pathology , Hematopoiesis , Hematopoietic Stem Cells/pathology , Mutation , Splicing Factor U2AF/physiology , Animals , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Cell Survival , Hematopoietic Stem Cells/metabolism , Mice , Mice, Inbred C57BL , Mice, KnockoutABSTRACT
Fanconi anemia (FA) is a devastating hereditary disease characterized by bone marrow failure (BMF) and acute myeloid leukemia (AML). As FA-deficient cells are hypersensitive to DNA interstrand crosslinks (ICLs), ICLs are widely assumed to be the lesions responsible for FA symptoms. Here, we show that FA-mutated cells are hypersensitive to persistent replication stress and that FA proteins play a role in the break-induced-replication (BIR)-like pathway for fork restart. Both the BIR-like pathway and ICL repair share almost identical molecular mechanisms of 53BP1-BRCA1-controlled signaling response, SLX4- and FAN1-mediated fork cleavage and POLD3-dependent DNA synthesis, suggesting that the FA pathway is intrinsically one of the BIR-like pathways. Replication stress not only triggers BMF in FA-deficient mice, but also specifically induces monosomy 7, which is associated with progression to AML in patients with FA, in FA-deficient cells.
Subject(s)
DNA Replication , Fanconi Anemia Complementation Group Proteins/physiology , Fanconi Anemia/genetics , Aneuploidy , Animals , Bone Marrow Failure Disorders/etiology , Cell Line, Transformed , Chickens , Chromosome Breakage , Chromosome Deletion , Chromosomes, Human, Pair 7/genetics , DNA Polymerase III/physiology , DNA Replication/genetics , Disease Progression , Fanconi Anemia/metabolism , Fanconi Anemia Complementation Group Proteins/deficiency , Fanconi Anemia Complementation Group Proteins/genetics , Female , HCT116 Cells , HEK293 Cells , Humans , Hydroxyurea/pharmacology , Leukemia, Myeloid, Acute/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Models, Genetic , Species Specificity , Tumor Suppressor p53-Binding Protein 1/physiology , Ubiquitin-Protein Ligases/physiologyABSTRACT
Severe aplastic anemia (SAA) is an acquired, T cell-driven bone marrow (BM) failure disease characterized by elevated interferon gamma (IFNγ), loss of hematopoietic stem cells (HSCs), and altered BM microenvironment, including dysfunctional macrophages (MΦs). T lymphocytes are therapeutic targets for treating SAA, however, the underlying mechanisms driving SAA development and how innate immune cells contribute to disease remain poorly understood. In a murine model of SAA, increased beta-chemokines correlated with disease and were partially dependent on IFNγ. IFNγ was required for increased expression of the chemokine receptor CCR5 on MΦs. CCR5 antagonism in murine SAA improved survival, correlating with increased platelets and significantly increased platelet-biased CD41hi HSCs. T cells are key drivers of disease, however, T cell-specific CCR5 expression and T cell-derived CCL5 were not necessary for disease. CCR5 antagonism reduced BM MΦs and diminished their expression of Tnf and Ccl5, correlating with reduced frequencies of IFNγ-secreting BM T cells. Mechanistically, CCR5 was intrinsically required for maintaining BM MΦs during SAA. Ccr5 expression was significantly increased in MΦs from aged mice and humans, relative to young counterparts. Our data identify CCR5 signaling as a key axis promoting the development of IFNγ-dependent BM failure, particularly relevant in aging where Ccr5 expression is elevated.
Subject(s)
Aging , Anemia, Aplastic/complications , Bone Marrow Failure Disorders/pathology , Interferon-gamma/metabolism , Macrophages/immunology , Receptors, CCR5/physiology , T-Lymphocytes/immunology , Anemia, Aplastic/pathology , Animals , Bone Marrow Failure Disorders/etiology , Bone Marrow Failure Disorders/metabolism , Chemokines/metabolism , Disease Models, Animal , Gene Expression Regulation , Hematopoietic Stem Cells/immunology , Hematopoietic Stem Cells/metabolism , Hematopoietic Stem Cells/pathology , Mice , Mice, Inbred C57BL , Mice, KnockoutABSTRACT
Bone marrow failure has many different etiologies, including genetic defects which manifest with specific syndromes, as well as acquired conditions as a result of insults to the bone marrow leading to aplasia. The clinical picture is varied and clues for the underlying cause may or may not be evident at the time of presentation, frequently leading to a complex workup with a battery of tests often done to rule out genetic defects. The treatment approach for bone marrow failure is very dependent on the underlying cause, which makes it all the more critical to have an accurate diagnosis. First line management essentially consists of either hematopoietic stem cell transplant or immunosuppressive therapy. In this review authors will provide a broad look at the causes of bone marrow failure, the stepwise diagnostic algorithm and the approach to decision making for treatment. Fine details of each cause, and of each treatment modality are beyond the scope of this review which aims to provide an overview.
Subject(s)
Bone Marrow Failure Disorders/diagnosis , Bone Marrow Failure Disorders/therapy , Androgens/therapeutic use , Benzoates/therapeutic use , Bone Marrow , Bone Marrow Failure Disorders/etiology , Bone Marrow Transplantation , Child , Hematopoietic Stem Cell Transplantation , Humans , Hydrazines/therapeutic use , Immunosuppression Therapy , Immunosuppressive Agents/therapeutic use , Pyrazoles/therapeutic useABSTRACT
Fanconi anemia (FA), a chromosomal instability syndrome, is caused by inherited pathogenic variants in any of 22 FANC genes, which cooperate in the FA/BRCA pathway. This pathway regulates the repair of DNA interstrand crosslinks (ICLs) through homologous recombination. In FA proper repair of ICLs is impaired and accumulation of toxic DNA double strand breaks occurs. To repair this type of DNA damage, FA cells activate alternative error-prone DNA repair pathways, which may lead to the formation of gross structural chromosome aberrations of which radial figures are the hallmark of FA, and their segregation during cell division are the origin of subsequent aberrations such as translocations, dicentrics and acentric fragments. The deficiency in DNA repair has pleiotropic consequences in the phenotype of patients with FA, including developmental alterations, bone marrow failure and an extreme risk to develop cancer. The mechanisms leading to the physical abnormalities during embryonic development have not been clearly elucidated, however FA has features of premature aging with chronic inflammation mediated by pro-inflammatory cytokines, which results in tissue attrition, selection of malignant clones and cancer onset. Moreover, chromosomal instability and cell death are not exclusive of the somatic compartment, they also affect germinal cells, as evidenced by the infertility observed in patients with FA.
Subject(s)
Chromosomal Instability , DNA Repair , Fanconi Anemia/genetics , Aging/genetics , BRCA1 Protein/physiology , BRCA2 Protein/physiology , Bone Marrow Failure Disorders/etiology , Cell Cycle , Chromatids/ultrastructure , Chromosome Aberrations , Chromosomes, Human/ultrastructure , DNA Breaks, Double-Stranded , DNA End-Joining Repair , Fanconi Anemia/complications , Fanconi Anemia/diagnosis , Fanconi Anemia Complementation Group C Protein/deficiency , Fanconi Anemia Complementation Group C Protein/genetics , Fanconi Anemia Complementation Group C Protein/physiology , Humans , Infertility/genetics , Neoplastic Syndromes, Hereditary/genetics , Phenotype , Protein Processing, Post-Translational , UbiquitinationABSTRACT
Spinal cord injury (SCI) causes immune dysfunction, increasing the risk of infectious morbidity and mortality. Since bone marrow hematopoiesis is essential for proper immune function, we hypothesize that SCI disrupts bone marrow hematopoiesis. Indeed, SCI causes excessive proliferation of bone marrow hematopoietic stem and progenitor cells (HSPC), but these cells cannot leave the bone marrow, even after challenging the host with a potent inflammatory stimulus. Sequestration of HSPCs in bone marrow after SCI is linked to aberrant chemotactic signaling that can be reversed by post-injury injections of Plerixafor (AMD3100), a small molecule inhibitor of CXCR4. Even though Plerixafor liberates HSPCs and mature immune cells from bone marrow, competitive repopulation assays show that the intrinsic long-term functional capacity of HSPCs is still impaired in SCI mice. Together, our data suggest that SCI causes an acquired bone marrow failure syndrome that may contribute to chronic immune dysfunction.