Abnormal Localization of Neutrophil Elastase in Patients with Severe Congenital Neutropenia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1279-1279
Author(s):  
Takashi Sato ◽  
Masakazu Habara ◽  
Hiroki Kihara ◽  
Hiroshi Kawaguchi ◽  
Mizuka Miki ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Dimensional Analysis ◽  
Protein Trafficking ◽  
Neutrophil Elastase ◽  
Plasma Membranes ◽  
Normal Subjects ◽  
Precursor Cells ◽  
Proteinase 3 ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia

Abstract Mutations in the ELA2 gene encoding neutrophil elastase (NE) in patients with severe congenital neutropenia (SCN) are involved in the pathogenesis of this disorder, possibly due to the abnormal protein trafficking and accelerated apoptosis of myeloid cells. In this study we precisely examined the localization of NE in neutrophils and myeloid precursor cells in bone marrow in patients with SCN using immunofluorescence microscopy equipped with three-dimensional analysis program. Three patients with SCN were enrolled in this study. All patients with SCN showed heterozygous mutation in the ELA2 gene. In normal subjects the pattern of localization of NE in mature neutrophils was almost similar to those of myeloperoxidase (MPO), proteinase 3, lysosomal associated membrane protein 2 (LAMP2). Administration of G-CSF to normal subjects did not affect the pattern of the localization of these proteins in neutrophils. In contrast, mature neutrophils elicited by the administration of G-CSF in patients with SCN NE predominantly localized to the plasma membranes. A small part of NE was detected in the cytoplasmic compartment. The pattern of localization of NE was significantly different from those of MPO, proteinase 3, and LAMP2 in SCN patients, suggesting the abnormal traffic of NE to granules. Adaptor proteins 3 (AP3) specifically shuttles transmembrane cargo proteins from the trans-Golgi to lysosomes. AP3 of myeloid progenitor cells enriched for CD33-positive cells in normal bone marrow was localized in both cytoplasm and plasma membranes. The localization pattern of AP3 was completely consistent with those of NE, MPO, and LAMP2. The localization of AP3 of promyelocytes in patients with SCN was observed in both plasma membranes and cytoplasm. This finding was completely similar to that in normal myeloid precursor cells. However, the localization of NE of promyelocytes in SCN patients was predominantly in plasma membrane. The figures merged apparently presented the different localization of NE and AP3. This result was confirmed by the 3-dimensional analysis with histogram. The localizations of other constituents of primary granules, MPO, poteinase 3, and LAMP2, were consistent with those of AP3. These observations suggest that the mislocalization of NE in myeloid precursor cells in SCN patients does not result from a generalized impairment of protein trafficking but is specific to the mutant NE. The abnormal localization of NE may be involved in the pathogenesis of SCN associated with ELA2 mutation.

Small Molecule Inhibitor of Neutrophil Elastase Normalizes Myeloid Differentiation and Improves Impaired Cell Survival Triggered by Elastase Mutations In Patients with Severe Congenital Neutropenia and Acute Myeloid Leukemia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 386-386
Author(s):  
Andrew A. Aprikyan ◽  
Vahagn Makaryan ◽  
Maxim Totrov ◽  
Ruben Abagyan ◽  
David C. Dale
Keyword(s):  
Bone Marrow ◽  
Small Molecule ◽  
Neutrophil Elastase ◽  
Myeloid Leukemia ◽  
Small Molecule Inhibitor ◽  
Myeloid Differentiation ◽  
Severe Congenital Neutropenia ◽  
Wild Type ◽  
Congenital Neutropenia ◽  
Molecule Inhibitor

Abstract Abstract 386 Heterozygous mutations in the neutrophil elastase gene ELANE have been identified as the primary cause of severe congenital neutropenia (SCN) associated with recurring severe infections and evolution to acute myeloid leukemia (AML). As of today, more than 50 substitution, truncation, insertion and deletion mutations have been identified. Animal studies based on knock-in or knockout of ELANE in mice failed to produce severe neutropenia phenotype. We and others previously reported that expression of various mutants but not wild type neutrophil elastase (NE) in human but not murine cells triggers accelerated apoptosis. We also reported that expression of mutant NE (del.145-152), identified in SCN patients one of whom evolved to develop MDS/AML, in human promyelocytic tet-off HL60 cells causes both accelerated apoptosis and characteristic block of myeloid differentiation similar to that seen in bone marrow of SCN patients. Examination of the tertiary structure of NE revealed that most of the mutations leave the active site of the mutant protease intact. We identified a small molecule inhibitor of neutrophil elastase, a derivative of L-malic acid (Merck, USA), that blocked the proteolytic activity of NE by approximately 80% and was capable of restoring impaired myeloid differentiation and normalizing production of myeloid cells expressing del145-152 NE mutant. It is important to note that block of proteolytic activity of NE with the NE-SMI had no adverse effect on control human myeloid progenitor cells expressing wild type NE, thus confirming the gain-of-function effect of NE mutants. More than 20% of SCN patients with NE mutations evolve to develop AML. Molecular modeling and analysis of the tertiary structures of NE available through the Protein Database revealed that 16 different mutations identified in AML patients affect predominantly the N95 or N144 glycosylation sites or the binding pocket of the protease suggesting that altered substrate specificity of the mutant enzyme is the cause of accelerated apoptosis and block of myeloid differentiation in SCN/AML. We sought to obtain bone marrow samples from 2 unrelated SCN/AML patients both on G-CSF treatment harboring either C122Y or insPQ94. Bone marrow purified CD34+ and/or CD34-/CD33+ myeloid progenitors from the patients showed basal level of apoptosis in a range of 20–25%, which gradually increased reaching 40–50% apoptosis by 3 days of culture. Importantly, treatment of primary bone marrow-derived cells with NE-SMI substantially reduced accelerated apoptosis to near initial rate with approximately up to 2-fold reduction of apoptosis by 3 days of culture as determined by flow cytometry. Thus, our findings demonstrate that 1) small molecule inhibitor of neutrophil elastase is effective in blocking accelerated apoptosis triggered by three different NE mutations identified in SCN patients evolved to develop MDS/AML and 2) the small molecule inhibitor of NE is a promising therapeutic agent that should be considered for testing in clinical trials in SCN/AML patients. Disclosures: Dale: Amgen: Consultancy, Research Funding; Merck: Patents & Royalties, Research Support.

scholarly journals Neutrophil Elastase Defects in Congenital Neutropenia

2021 ◽  
Vol 12 ◽  
Author(s):  
Zuzanna Rydzynska ◽  
Bartlomiej Pawlik ◽  
Damian Krzyzanowski ◽  
Wojciech Mlynarski ◽  
Joanna Madzio
Keyword(s):  
Bone Marrow ◽  
Neutrophil Elastase ◽  
Genetic Background ◽  
Biological Role ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Maturation Arrest

Severe congenital neutropenia (SCN) is a rare hematological condition with heterogenous genetic background. Neutrophil elastase (NE) encoded by ELANE gene is mutated in over half of the SCN cases. The role of NE defects in myelocytes maturation arrest in bone marrow is widely investigated; however, the mechanism underlying this phenomenon has still remained unclear. In this review, we sum up the studies exploring mechanisms of neutrophil deficiency, biological role of NE in neutrophil and the effects of ELANE mutation and neutropenia pathogenesis. We also explain the hypotheses presented so far and summarize options of neutropenia therapy.

scholarly journals Efficient Correction of HAX1 Mutations in Primary HSPCs of Severe Congenital Neutropenia Patients Using CRISPR/CAS9 GENE-Editing

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 22-22
Author(s):  
Malte U Ritter ◽  
Benjamin Secker ◽  
Masoud Nasri ◽  
Maksim Klimiankou ◽  
Benjamin Dannenmann ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Bone Marrow ◽  
Stem Cell ◽  
Protein Expression ◽  
Healthy Donor ◽  
Live Cell Imaging ◽  
Gene Editing ◽  
Cell Imaging ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia

Patients with the rare pre-leukemia bone marrow failure syndrome severe congenital neutropenia (CN) have markedly reduced numbers of neutrophils in peripheral blood (<500/μl), leading to frequent infections and requiring chronic granulocyte stimulating factor (G-CSF) treatment. Approximately 7 % of CN patients carry homozygous loss-of-function mutations in the HAX1 gene. 25 % of HAX1-CN patients develop MDS or AML. The only curative therapy for CN patients with overt MDS/AML is hematopoietic stem cell transplantation with its associated risks. A clinical need for gene therapy for CN patients is imminent. Here, we describe for the first time the application of CRISPR/Cas9 gene-editing in combination with recombinant adeno associated virus 6 (rAAV6)-based delivery of the template for homology-directed repair (HDR) for the mutated HAX1 gene in primary bone marrow mononuclear CD34+ cells (HSPCs) of HAX1-CN patients. We selected HAX1 mutation p.W44X as the most frequently described mutation in HAX1-CN. We established the delivery of the chemically modified sgRNA in combination with SpCas9 V3 in primary HSPCs using electroporation. The HDR template was generated by PCR from healthy donor HSPCs and cloned into pRC6 vector for the production of high titer rAAV6 (>12x1012 viral copies per ml). Our gene-editing protocol produced on average 79,7 % (± 8,62 %) of total editing (TE) in healthy donor HSPCs (n=6). When we transduced healthy donor HSPCs with rAAV6 containing the template at MOI 105 after electroporation with CRISPR/Cas9 RNP, we achieved 38,1 % (± 1,3 %) knock-in (KI) efficiency and 82,3 % (± 8,2 %) TE (n=2). We further applied this approach to primary HSPCs from 5 CN patients harboring the p.W44X HAX1 mutation. We achieved 84,4 % (± 4,2 %) TE and 65,8 % (± 7,12 %) KI. Too proof, that our editing reintroduced HAX1 protein expression, we performed Western Blot analysis of edited cells (n=2) and were able to detect relevant amounts of HAX1 protein. To assess the effect of HAX1 correction on the neutropenic phenotype in vitro, we performed a liquid culture differentiation assay of edited HSPCs to neutrophils. HSPCs from the same patients that were edited in the AAVS1 safe harbor were used as isogenic controls. In the AAVS1 locus the editing efficiency was 76,74 % (± 17,07 %) total indels. By morphological assessment of Wright-Giemsa stained cytospins of edited cells derived on day 14 of differentiation revealed significant (p = 0,005) increases of mature neutrophils for all five edited HAX1-CN patient samples, as compared to the respective controls. This phenotype correction was also observed in flow cytometry by a significant (p = 0,011) increase of mature CD34-CD45+ CD15+CD16+ neutrophils (n=5). To investigate if the HAX1 mutation correction and reinforced expression of HAX1 protein improved the sensitivity of HSPCs to oxidative stress as described by Klein et al. 2007, we performed live-cell imaging of caspase3/7 activation. Live-cell imaging revealed a substantial reduction of H2O2-induced apoptosis in corrected HAX1-CN patients derived HSPCs (n=3). Furthermore, the corrected differentiated cells were investigated for functional hallmarks of granulocytes. We could observe that HAX1 gene-edited HSPCs showed comparable chemotaxis, phagocytosis and no defects in ROS production to isogenic control edited cells. Taken together, we established a protocol for efficient selection-free correction of HAX1 p.W44X mutation in primary HSPCs using CRISPR/Cas9 and rAVV6 HDR repair templates. Our gene-editing reintroduced HAX1 protein expression in primary HSPCs from HAX1-CN patients. Neutrophils derived from corrected cells showed functional improvements in survival to oxidative stress and general neutrophil functions. We believe that these results are enticing to be investigated further for potential clinical translation as an autologous stem cell therapy for HAX1-CN patients. Disclosures No relevant conflicts of interest to declare.

Diversity and Molecular Modeling of Neutrophil Elastase Mutations in Patients with Severe Congenital Neutropenia and Acute Myelogenous Leukemia.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1454-1454
Author(s):  
Andrew A.G. Aprikyan ◽  
Steve Stein ◽  
Nara A. Markosyan ◽  
Maxim Totrov ◽  
Ruben Abagyan ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Neutrophil Elastase ◽  
Apoptotic Cell ◽  
Myelogenous Leukemia ◽  
Congenital Neutropenia ◽  
Deletion Mutations ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells ◽  
Acute Myelogenous

Abstract Severe congenital neutropenia (SCN) is an inheritable hematopoietic disorder that is characterized by extremely low levels of neutrophils in peripheral circulation and maturation arrest of bone marrow myeloid progenitor cells at the promyelocytic stage of differentiation. SCN patients have recurring severe infections and approximately 10% of these patients evolve to develop acute myelogenous leukemia. Recently we reported that an impaired cell survival and cell cycle arrest of bone marrow myeloid progenitor cells was observed in SCN patients compared with controls. We also reported various heterozygous mutations in the neutrophil elastase (NE) gene encoding a serine protease in approximately 80% of SCN patients. We hypothesized that mutations in the NE gene trigger apoptotic cell death of myeloid progenitor cells and subsequent severe neutropenia. Mutational analysis of 15 families with one or more affected family members revealed that mutant NE was present only in affected but not in healthy members of these families suggesting the causative role for mutant NE in pathogenesis of SCN. Sequencing analysis revealed that none of SCN patients negative for NE mutations examined had mutations in the Gfi-1 or WAS gene. Sequencing DNA samples of SCN and SCN/AML patients revealed 40 mutations that are distributed primarily throughout the exons 2 through 5 of the NE gene and result in substitution, deletion, insertion, or truncation mutations. Molecular modeling of the tertiary structure of NE revealed that all these mutations can be grouped into three major categories. The first category includes 19 substitution and insertion mutations that are grouped around the N-glycosylation sites of the neutrophil elastase and may lead to abnormal targeting and subcellular localization of the mutant protease. The second group includes 9 substitution and deletion mutations that alter the side loop of the NE that is necessary for proper oligomerization of neutrophil elastase. The third category includes 12 substitution, truncation, and deletion mutations that either alter or completely eliminate the carboxy-terminus of the mutant protein leading to conformational changes of the binding pocket of the NE, and subsequently to altered substrate specificity and/or an acquired resistance to elastase inhibitors. SCN patients that evolved to develop AML had either substitution, deletion, or truncation mutations from each of the three categories described above. Most mutations are clearly non-conservative, have destabilizing effect on oligomeric structure of mutant protein, and alter dramatically the affinity of mutant NE to various factors participating in its processing and intracellular transport. Flow cytometry analysis of annexin V-labeled cells revealed that expression of representative mutant but not normal NE from each of the three categories of NE mutations in human promyelocytic HL-60 cells triggered apoptotic cell death similar to that observed in bone marrow progenitor cells in SCN patients. These data indicate that impaired cell survival and block of differentiation in SCN is due to heterozygous mutations in the neutrophil elastase gene. Current studies focused on design and screen of specific protease inhibitors capable of blocking the pro-apoptotic effect of mutant neutrophil elastase.

A Model of Severe Congenital Neutropenia Reveals Signaling Pathways Mediating Mutant Elastase-Triggered Agranulocytosis.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3070-3070
Author(s):  
Andrew A. Aprikyan ◽  
Tomas Vaisar ◽  
Vahagn Makaryan ◽  
Jay Heinecke
Keyword(s):  
Bone Marrow ◽  
Signaling Pathways ◽  
Myelogenous Leukemia ◽  
Severe Neutropenia ◽  
Myeloid Differentiation ◽  
Cellular Model ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Histone H2b ◽  
Maturation Arrest

Abstract Severe congenital neutropenia (SCN; Kostmann’s syndrome or infantile genetic agranulocytosis) defines an inheritable hematopoietic disorder of impaired neutrophil production due to a “maturation arrest” at the promyelocytic stage of differentiation in the bone marrow. SCN patients have recurring severe infections and often develop acute myelogenous leukemia. We and others reported accelerated apoptosis and cell cycle arrest of bone marrow-derived myeloid progenitor cells in SCN patients with autosomal dominant and autosomal recessive inheritance. Heterozygous mutations in the neutrophil elastase (NE) gene encoding a serine protease, are present in a majority of SCN patients, but not in healthy members of the family, thus indicating a key role of mutant NE in pathogenesis of this disorder. To date, there are no animal or cellular models of SCN as both the knock-in of mutant NE as well as the knock-out of normal NE failed to result in neutropenia phenotype in mice. The molecular mechanisms of mutant NE-mediated severe neutropenia remain largely unknown. We hypothesized that mutations in NE expose the protease to a new range of substrates. To explore this proposal, we established a cellular model of SCN based on tetracycline-regulated expression of mutant NE in human promyelocytic tet-off HL-60 cells that very closely recapitulated the human phenotype. Mutant NE expression resulted in a characteristic block of myeloid differentiation - the cellular hallmark of SCN. Expression of the mutant product was associated with a significant reduction in phosphatidylinosytol-3-kinase and phosphorylated PKB/Akt levels and an imbalance of anti-apoptotic Bcl-2 and pro-apoptotic Bax. These alterations contributed to observed dissipation of mitochondrial membrane potential as determined by FACS analysis, aberrant release of cytochrome C, and accelerated apoptosis. Marked changes in actin cytoskeleton that made the cells more rigid appeared to stem from a reduced level of alpha-actinin and elevated level of Rho GTPase. Immunoprecipitation of cell lysates with elastase-specific monoclonal antibodies followed by mass spectrometric analysis revealed that NE interacted with histone H2B, one of the key components of the nucleosome core of the chromatin. Interestingly, the expression level of histone H2B was substantially reduced in cells expressing mutant NE, therefore supporting the notion of altered substrate specificity of mutant NE. Thus, these observations provide the first evidence that mutant NE affects specific signaling pathways that lead to alterations in cytoskeleton and chromatin reorganization, subsequent apoptosis, and a block of myeloid differentiation in SCN. This cellular model of SCN should provide an invaluable tool for screening potential therapeutic agents capable of preventing maturation arrest and leukemogenesis in subjects suffering from severe congenital neutropenia.

Stable Long-Term Risk of Leukemia in Patients with Severe Congenital Neutropenia Maintained On G-CSF Therapy.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3206-3206 ◽  
Author(s):  
Philip S. Rosenberg ◽  
Cornelia Zeidler ◽  
Audrey Anna Bolyard ◽  
Blanche P. Alter ◽  
Mary Ann Bonilla ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cumulative Incidence ◽  
Bone Marrow Failure ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Hazard Curve ◽  
Number Of Patients ◽  
Increasing Trend

Abstract Abstract 3206 Poster Board III-143 BACKGROUND G-CSF therapy reduces sepsis mortality in patients with severe congenital neutropenia (SCN), but effective therapy has revealed a high syndromic predisposition to myelodysplastic syndrome and acute myeloid leukemia (MDS/AML), particularly in patients who require higher doses of G-CSF. Although the long-term risk of MDS/AML after 10 or more years on therapy remains uncertain, prior data on the limited number of patients with long-term follow-up suggested the hazard rate might be as high as 8%/year after 12 years on G-CSF. METHODS We updated prospective follow-up of 374 well-characterized patients with SCN on long-term G-CSF enrolled in the Severe Chronic Neutropenia International Registry (Blood. 2006 Jun 15; 107(12):4628-35). We ascertained event-free time, deaths from sepsis, and MDS/AML events that accrued since our previous report. Follow-up was censored for patients who received a bone marrow transplant. RESULTS The update yielded 3590 person-years of follow-up versus 2043 in the prior report; among patients treated for 10 or more years, there were 849 person-years versus just 67 previously. In all, there were 61 MDS/AML events and 29 deaths from sepsis, versus prior totals of 44 and 19, respectively. After including up-to-date follow-up, the estimated annual hazard of death from sepsis remained qualitatively stable, at 0.81%/year (95% Confidence Interval, CI: 0.56 – 1.16%/year). Similarly, during the first five years after the start of G-CSF therapy, the updated estimate of the hazard curve for MDS/AML showed the same increasing trend as the previous estimate. However, in contrast to the prior estimate that showed a subsequent increasing trend over time (with a large margin of error), the updated hazard curve attained a plateau: after 10 years on G-CSF, the estimated hazard of MDS/AML was 2.3%/year (95% CI: 1.7 – 2.9%/year). Although this aspect of the natural history appears less dire than first suggested, after 15 years on G-CSF, the cumulative incidence was 10% (95% CI: 6 – 14%) for death from sepsis and 22% (95% CI: 17 – 28%) for MDS/AML. Furthermore, for the subset of patients who failed to achieve at 6 months an absolute neutrophil count at or above the median value for the cohort (2188 cells/μL) despite doses of G-CSF at or above the median (8 μg/kg/day), the cumulative incidence after 15 years on G-CSF was 18% (95% CI: 7 – 28%) for death from sepsis and 34% (95% CI: 21 – 47%) for MDS/AML. With additional follow-up, the association of G-CSF dose at 6 months with the relative hazard of MDS/AML became more strongly statistically significant (P = 0.003 versus P = 0.024; the hazard of MDS/AML increased by 1.24-fold (95% CI: 1.08-1.43-fold) per doubling of the dose of G-CSF). CONCLUSIONS For SCN patients maintained on G-CSF therapy, the hazard of MDS/AML over the long-term falls significantly below the range suggested by preliminary data. The updated hazard estimate of 2.3%/year after 10 years on G-CSF (which includes both MDS and AML events) is similar to that for other inherited bone marrow failure syndromes with a high intrinsic risk of AML, notably Fanconi anemia and dyskeratosis congenita. Nonetheless, the cumulative incidence of both MDS/AML and sepsis death rises to very high levels, and the data continue to support the hypothesis that SCN patients with higher G-CSF requirements are also at higher risk of leukemia. Disclosures Boxer: Amgen Inc.: Equity Ownership. Dale:Amgen Inc.: Consultancy, Honoraria, Research Funding, Speaker.

A Microrna Feed-Forward Loop Amplifies GFI1N382S Transcriptional Reprogramming In Severe Congenital Neutropenia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2239-2239
Author(s):  
Chinavenmeni Subramani Velu ◽  
Avedis Kazanjian ◽  
Clemencia Colmenares ◽  
H. Leighton Grimes
Keyword(s):  
Bone Marrow ◽  
Target Genes ◽  
Bone Marrow Cells ◽  
Transcriptional Repressor ◽  
Dominant Negative ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Feed Forward ◽  
Marrow Cells ◽  
Myeloid Progenitors

Abstract Abstract 2239 The Growth factor independent -1 (Gfi1) transcriptional repressor regulates both hematopoietic stem cell self renewal and myeloid differentiation. Humans with severe congenital neutropenia (SCN) display mutations in GFI1 that generate dominant negative acting proteins. Moreover, GFI1-mutant SCN patients and Gfi1-/- mice display a unique accumulation of myeloid progenitors. Recently we showed that Gfi1 regulation of HoxA9, Pbx1 and Meis1 underlies these phenomena, in that the Gfi1-Hox transcriptional circuit controls the accumulation of myeloid progenitors in vivo. We have also shown that Gfi1 regulates miR-21 during myelopoiesis, and that miR-21 is deregulated by Gfi1N382S expression. Our new data link these concepts by demonstrating that forced expression of miR-21 in bone marrow cells results in the accumulation of myeloid progenitors in transplant recipients. Moreover, miR-21 directly targets the Ski oncoprotein, and Ski-/- bone marrow cells show an accumulation of myeloid progenitors. Thus, Gfi1-/-, miR-21 overexpressing-, and Ski-/- myeloid progenitors accumulate in the marrow. Strikingly, Ski is dramatically reduced in miR-21 overexpressing Lin- bone marrow cells. Nearly undetectable Ski expression in Gfi1-/- bone marrow cells can be completely rescued by antagonizing miR-21 activity. Since Ski is a corepressor and Gfi1 is a transcriptional repressor, we next tested whether the two proteins physically interact. Indeed, endogenous Ski and Gfi1 can be coimmunoprecipitated. Synthetic Ski and Gfi1 proteins reveal that the interaction is mediated through Ski carboxy-terminal and Gfi1 zinc-finger domains. Chromatin immunoprecipitation reveals Ski and Gfi1 co-occupy several Gfi1 target genes (including HoxA9), which are derepressed upon Gfi1 or Ski knockdown. However, while Gfi1 binds and regulates the miR-21 gene, Ski is not bound to the miR-21 gene, and Ski knockdown has no effect upon miR-21 levels. Thus, the data point to a novel feed-forward transcriptional circuit. Gfi1N382S deregulation of miR-21 amplifies the dominant-negative effect of Gfi1N382S through miR-21 targeting of Ski, leading to further derepression of Gfi1-Ski target genes. Disclosures: No relevant conflicts of interest to declare.

Myelopoiesis From Induced Pluripotent Stem Cells Reveals The Role Of Elastase Activity In The Pathogenesis Of Severe Congenital Neutropenia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 442-442
Author(s):  
Ramesh C Nayak ◽  
Lisa Trump ◽  
H. Leighton Grimes ◽  
Carolyn Lutzko ◽  
Jose A. Cancelas
Keyword(s):  
Stem Cell ◽  
Neutrophil Elastase ◽  
Embryoid Body ◽  
Point Mutations ◽  
Annexin V ◽  
High Dose ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Elastase Activity ◽  
Induced Pluripotent

Severe congenital neutropenia (SCN) is a hereditary neutropenia characterized by granulocytic precursor differentiation arrest in which the pathogenic mechanism is poorly understood. Over half of SCN patients associate with autosomal dominant point mutations in the gene encoding neutrophil elastase (ELANE). High-dose G-CSF therapy succeeds in increasing neutrophil counts in many SCN patients, but the molecular explanation for high dose G-CSF rescue is unknown. Mutations in the G-CSF receptor (CSF3R) associated with a dramatic risk for transformation provides a cautionary note for high dose G-CSF treatment. The pathogenic mechanism of ELANE mutations is incompletely understood due to the lack of disease recapitulation in murine models of ELANE-mutant hematopoiesis and the difficulty to obtain primary, relevant myeloid cell populations from patients. Using induced pluripotent stem cell (iPSC) derived myelopoietic cultures from peripheral blood mononuclear cells of patients with ELANE exon 3 point mutations (Q97P and I118N), we designed experiments to recapitulate G-CSF signaling in SCN myelopoiesis. The patient-derived iPSC lines were characteristically similar to human embryonic stem cell lines and normal blood-derived iPSC lines with expression of SSEA-4, Tra-1-60, Tra-1-81, and CD9 pluripotency markers >85% in all lines as determined by FACS analysis at passage 10-15. All iPSC retained a normal karyotype and ELANE locus mutations of the original specimens. Both SCN iPSC lines and control iPSC lines (normal and immune-mediated congenital neutropenia) show functional G-CSF (50 ng/mL)-induced differentiation into the myeloid lineage. However, G-CSF failed to induce terminal granulocytic differentiation of SCN iPSC derived myeloid progenitors resulting in differentiation arrest at the promyelocyte/myelocyte stage. The hematopoietic cells derived from SCN iPSC line show reduced frequency of CFU-G and CFU-GM (CFU-G+CFU-GM, 22±1.15 in 104 embryoid body cells from non SCN iPSC vs 4±2 in 104 embryoid body cells from ELANE mutated SCN iPSC). Moreover, SCN iPSC promyelocytes show significantly increased apoptosis over controls as determined by Annexin-V analysis (31% Annexin-V+ in SCN iPSC derived promyelocyte vs 3% in control iPSC). Surviving SCN promyelocytes showed decreased reactive oxygen species activity and no phagocytic activity. In contrast, suprapharmacological doses of G-CSF (1000 ng/mL) rescued SCN iPSC-derived differentiation. It has been shown that NE, expressed in promyelocytes, can cleave recombinant G-CSF and CSF3R. We evaluated the possibility that inadequate G-CSF signaling in SCN iPSC was due to abnormal elastase activity. To this end, we supplemented 50 ng/mL G-CSF cultures with a specific, cell-permeant neutrophil elastase inhibitor (Sivelastat, 230 nM) to find rescued granulocyte differentiation arrest (31% neutrophil in myeloid differentiation culture of SCN iPSC derived hematopoietic progenitors in presence of Sivelastat vs 2% mature neutrophils without Sivelastat). In conclusion, SCN modeling through patient iPSC derived myelopoiesis and G-CSF driven granulocytic recapitulation unveil a mechanism of resistance to G-CSF therapy with important translational implications for therapy. Combination of low-dose G-CSF and NE inhibitory therapy may result in an efficacious, safer approach in SCN therapy. Disclosures: No relevant conflicts of interest to declare.

Successful Hematopoietic Stem Cell Transplantation Using an Immunosuppressive Conditioning Regimen in Ten Patients with Severe Congenital Neutropenia: A Single-Institute Experience

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3688-3688
Author(s):  
Yoko Mizoguchi ◽  
Mizuka Miki ◽  
Aya Furue ◽  
Shiho Nishimura ◽  
Maiko Shimomura ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Stem Cell Transplantation ◽  
Acute Gvhd ◽  
Conditioning Regimen ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Hematopoietic Stem ◽  
Engraftment Failure

Abstract Severe congenital neutropenia (SCN) is a rare heterogeneous genetic disorder characterized by severe chronic neutropenia, with absolute neutrophil counts below 0.5×109/L, and by recurrent bacterial infections from early infancy. Granulocyte colony-stimulating factor (G-CSF) is widely used for the treatment of neutropenia in patients with SCN. However, the long-term G-CSF therapy has a relative risk of developing myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). The only curative treatment available for SCN patients is hematopoietic stem cell transplantation (HSCT). Recently, HSCTs with reduced intensity conditioning (RIC) regimens have been applied to the treatment of SCN patients without malignant transformation who have become G-CSF refractory. However, the optimal conditions of HSCT for SCN patients have not been established. In this study, we conducted bone marrow cell transplantations (BMT) in ten patients with SCN using an immunosuppressive conditioning regimen to minimize early and late transplant-related morbidity in Hiroshima University Hospital. Ten patients with a total of 11 HSCT procedures in our institution (performed from 2007 to 2015) were enrolled in this study. Four of the ten patients had experienced engraftment failure of the initial HSCT and three of them were referred to our hospital for re-transplantation. Heterozygous mutation inthe ELANE gene was identified in nine of ten patients. These nine patients received BMT less than 10 years of age. All ten patients had recurrently experienced moderate to severe bacterial or fungal infection before HSCT and received temporal or regular administration of G-CSF. Bone marrow cells (BM) were obtained from five HLA-matched related (MRD), three HLA-matched unrelated (MUD), and three HLA-mismatched unrelated (7/8) donors (MMUD), respectively. The conditioning regimen basically consisted of fludarabine (100 to 125 mg/m2), cyclophosphamide (100 to 150 mg/kg), melphalan (70 to 90 mg/m2), total body irradiation (3 to 3.6 Gy), and/or anti-thymocyte globulin (10 to 12 mg/kg). Short-term methotrexate and tacrolimus were administered for the prophylaxis of graft-versus-host disease (GVHD). Engraftment of neutrophils was successfully observed within 24 days of post-transplantation in all patients. All patients achieved complete chimerism at the time of engraftment. Two patients who underwent BMT from MRD and one patient who underwent BMT from MUD showed the gradual decrease of donor-derived cells. Donor lymphocyte infusion treatment successfully achieved the complete chimerism or stable mixed chimerism in these 3 patients. Although 3 patients experienced the acute GVHD (Grade I-II), the addition of glucocorticoids to tacrolimus prevented the extension of acute GVHD. Only one patient developed mild chronic GVHD presenting limited type of skin involvement. All patients are alive for 9 months to 9 years after HSCT with no signs of severe infections or transplantation-related morbidity. Our results demonstrate that BMT together with a sufficient immunosuppressive conditioning regimen may be a feasible and effective treatment for SCN patients, irrespective of initial engraftment failure. Although our results through the small number of cohort is limited to conclude, the BMT with the optimal donors may lead to the increased opportunity for lower risk of SCN patients especially at younger age as a curative treatment. The further analyses of accumulated cases are necessary to assess the efficacy, safety, and less late adverse effects related to HSCT including fertility. Disclosures No relevant conflicts of interest to declare.

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