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| 3. |
- Armstrong, Scott A, et al.
(författare)
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FLT3 mutations in childhood acute lymphoblastic leukemia.
- 2004
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 103:9, s. 3544-3546
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Tidskriftsartikel (refereegranskat)abstract
- Activating mutations of the FLT3 receptor tyrosine kinase are common in acute myelogenous leukemia (AML) but are rare in adult acute lymphoblastic leukemia (ALL). We have recently shown that FLT3 is highly expressed and often mutated in ALLs with rearrangement of the mixed lineage leukemia (MLL) gene on chromosome 11q23. Because hyperdiploid ALL samples also show high-level expression of FLT3, we searched for the presence of FLT3 mutations in leukemic blasts from 71 patients with ALL. The data show that approximately 25% (6 of 25) of hyperdiploid ALL samples possess FLT3 mutations, whereas only 1 of 29 TEL/AML1-rearranged samples harbored mutations (P =.04, Fisher exact test). Three mutations are novel in-frame deletions within a 7-amino acid region of the receptor juxtamembrane domain. Finally, 3 samples from patients whose disease would relapse harbored FLT3 mutations. These data suggest that patients with hyperdiploid or relapsed ALL might be considered candidates for therapy with newly described small-molecule FLT3 inhibitors.
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| 4. |
- Barragan, A, et al.
(författare)
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The duffy-binding-like domain 1 of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a heparan sulfate ligand that requires 12 mers for binding
- 2000
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Ingår i: Blood. - 0006-4971 .- 1528-0020. ; 95, s. 3594-
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Tidskriftsartikel (refereegranskat)abstract
- The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), present on the surfaces of parasitized red blood cells (pRBC), mediates rosetting, a virulent phenotype. Here, we show that pRBC specifically bind heparan sulfate (HS) and heparin onto their surfaces and that the rosetting ligand PfEMP1 specifically adheres to heparin-Sepharose when extracted from the surfaces of radioiodinated infected RBC. An analysis of the binding properties of the different regions of PfEMP1 provides evidence that the Duffy-binding-like domain-1 (DBL-1) is the predominant ligand involved in HS and heparin binding. Soluble DBL-1 requires a minimal heparin fragment size of a 12-mer ( approximately 4 kd) for binding and is critically dependent on N-sulfation. A 12-mer is also the minimal heparin fragment that disrupts naturally formed rosettes. DBL-1 binds specifically to erythrocytes and also to HS from endothelial cells and human aorta but not to chondroitin sulfate A, suggesting that different PfEMP1s mediate adhesion to distinct glycosaminoglycans in individual malaria parasites. Present data suggest that HS on endothelial cells may also be involved in the sequestration of pRBC. Elucidation of these binding mechanisms opens up new possibilities for therapeutic strategies targeting adhesive interactions of pRBC.
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| 5. |
- Björnsson, Jon Mar, et al.
(författare)
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Proliferation of primitive myeloid progenitors can be reversibly induced by HOXA10
- 2001
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Ingår i: Blood. - 1528-0020 .- 0006-4971. ; 98:12, s. 3301-3308
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies show that several Hox transcription factors are important for regulation of proliferation and differentiation in hematopoiesis. Among these is HOXA10, which is selectively expressed at high levels in the most primitive subpopulation of human CD34(+) bone marrow cells. When overexpressed, HOXA10 increases the proliferation of early progenitor cells and can lead to the development of myeloid leukemia. To study the effects of HOXA10 on primitive hematopoietic progenitors in more detail, transgenic mice were generated with regulatable HOXA10 expression. The transgenic mouse model, referred to as tetO-HOXA10, contains the HOXA10 gene controlled by a tetracycline-responsive element and a minimal promoter. Thus, the expression of HOXA10 is inducible and reversible depending on the absence or presence of tetracycline or its analog, doxycycline. A retroviral vector containing the tetracycline transactivator gene (tTA) was used to induce expression of the HOXA10 gene In bone marrow cells from the transgenic mice. Reverse transcription-polymerase chain reaction analysis confirmed regulatable HOXA10 expression in several transgenic lines. HOXA10 induction led to the formation of hematopoietic colonies containing blastlike cells and megakaryocytes. Moreover, the induction of HOXA10 resulted in significant proliferative advantage of primitive hematopoietic progenitors (spleen colony-forming units [CFU-S-12]), which was reversible on withdrawal of induction. Activation of HOXA10 expression in tet0-HOXA10 mice will therefore govern proliferation of primitive myeloid progenitors in a regulated fashion. This novel animal model can be used to identify the target genes of HOXA10 and better clarify, the specific role of HOXA10 in normal and malignant hematopoiesis.
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| 6. |
- Björnsson, Jon Mar, et al.
(författare)
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Reduced proliferative capacity of hematopoietic stem cells deficient in hoxb3 and hoxb4
- 2003
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Ingår i: Blood. - 0006-4971 .- 1528-0020. ; 23:11, s. 3872-3883
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Tidskriftsartikel (refereegranskat)abstract
- Several homeobox transcription factors, such as HOXB3 and HOXB4, have been implicated in regulation of hematopoiesis. In support of this, studies show that overexpression of HOXB4 strongly enhances hematopoietic stem cell regeneration. Here we find that mice deficient in both Hoxb3 and Hoxb4 have defects in endogenous hematopoiesis with reduced cellularity in hematopoietic organs and diminished number of hematopoietic progenitors without perturbing lineage commitment. Analysis of embryonic day 14.5 fetal livers revealed a significant reduction in the hematopoietic stem cell pool, suggesting that the reduction in cellularity observed postnatally is due to insufficient expansion during fetal development. Primitive Lin(-) Scal(+) c-kit(+) hematopoietic progenitors lacking Hoxb3 and Hoxb4 displayed impaired proliferative capacity in vitro. Similarly, in vivo repopulating studies of Hoxb3/Hoxb4-deficient hematopoietic cells resulted in lower repopulating capability compared to normal littermates. Since no defects in homing were observed, these results suggest a slower regeneration of mutant HSC. Furthermore, treatment with cytostatic drugs demonstrated slower cell cycle kinetics of hematopoietic stem cells deficient in Hoxb3 and Hoxb4, resulting in increased tolerance to antimitotic drugs. Collectively, these data suggest a direct physiological role of Hoxb4 and Hoxb3 in regulating stem cell regeneration and that these genes are required for maximal proliferative response.
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| 7. |
- Brogren, Helén, 1977, et al.
(författare)
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Platelets synthesize large amounts of active plasminogen activator inhibitor 1
- 2004
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 104:13, s. 3943-8
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have suggested that plasminogen activator inhibitor 1 (PAI-1) released from platelets convey resistance of platelet-rich blood clots to thrombolysis. However, the majority of PAI-1 in platelets is inactive and therefore its role in clot stabilization is unclear. Because platelets retain mRNA and capacity for synthesis of some proteins, we investigated if platelets can de novo synthesize PAI-1 with an active configuration. PAI-1 mRNA was quantified with real-time polymerase chain reaction and considerable amounts of PAI-1 mRNA were detected in all platelet samples. Over 24 hours, the amount of PAI-1 protein as determined by an enzyme-linked immunosorbent assay increased by 25% (P = .001). Metabolic radiolabeling with (35)S-methionine followed by immunoprecipitation confirmed an ongoing PAI-1 synthesis, which could be further stimulated by thrombin and inhibited by puromycin. The activity of the newly formed PAI-1 was investigated by incubating platelets in the presence of tissue-type plasminogen activator (tPA). This functional assay showed that the majority of the new protein was in an active configuration and could complex-bind tPA. Thus, there is a continuous production of large amounts of active PAI-1 in platelets, which could be a mechanism by which platelets contribute to stabilization of blood clots.
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| 8. |
- Bruce, Lesley J, et al.
(författare)
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Absence of CD47 in protein 4.2-deficient hereditary spherocytosis in man : an interaction between the Rh complex and the band 3 complex.
- 2002
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 100:5, s. 1878-1885
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Tidskriftsartikel (refereegranskat)abstract
- We present data on a patient of South Asian origin with recessive hereditary spherocytosis (HS) due to absence of protein 4.2 [4.2 (-) HS]. Protein 4.2 cDNA sequence analysis showed the presence of a novel 41-bp frameshift deletion that predicts a truncated peptide designated protein 4.2 Hammersmith. Quantitative reverse transcription-polymerase chain reaction indicated that the mutant mRNA was unstable. Sequencing of protein 4.2 genomic DNA revealed that the deletion stems from aberrant splicing. The proband was homozygous for a G>T substitution at position 1747 (cDNA numbering) that activates a cryptic acceptor splice site within exon 11 of the protein 4.2 gene (EPB42). The proband's mother was found to be heterozygous for this substitution. Unlike protein 4.2 null mice, the proband's red cells showed no evidence for abnormal cation permeability. Quantitation of red cell membrane proteins was carried out by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blotting, and flow cytometric measurement. CD47, a protein associated with the Rh complex, was markedly reduced to about 1% (in the proband) and 65% (in the mother) that found in healthy controls. The Rh-associated glycoprotein migrated with a higher than normal apparent molecular weight on SDS-PAGE. There was no obvious reduction in Rh polypeptides. These observations indicate that protein 4.2 and CD47 interact in the human red cell membrane. They provide further evidence for an association between the band 3 complex (band 3, ankyrin, protein 4.2, glycophorin A) and the Rh complex (Rh-associated glycoprotein, Rh polypeptides, glycophorin B, CD47, LW) and define a point of attachment between the Rh complex and the red cell cytoskeleton.
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| 9. |
- Brun, Ann, et al.
(författare)
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Hoxb4-deficient mice undergo normal hematopoietic development but exhibit a mild proliferation defect in hematopoietic stem cells
- 2004
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 103:11, s. 4126-4133
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Tidskriftsartikel (refereegranskat)abstract
- Enforced expression of Hoxb4 dramatically increases the regeneration of murine hematopoietic stem cells (HSCs) after transplantation and enhances the repopulation ability of human severe combined immunodeficiency (SCID) repopulating cells. Therefore, we asked what physiologic role Hoxb4 has in hematopoiesis. A novel mouse model lacking the entire Hoxb4 gene exhibits significantly reduced cellularity in spleen and bone marrow (BM) and a subtle reduction in red blood cell counts and hemoglobin values. A mild reduction was observed in the numbers of primitive progenitors and stem cells in adult BM and fetal liver, whereas lineage distribution was normal. Although the cell cycle kinetics of primitive progenitors was normal during endogenous hematopoiesis, defects in proliferative responses of BM Lin(-) Sca1(+) c-kit(+) stem and progenitor cells were observed in culture and in vivo after the transplantation of BM and fetal liver HSCs. Quantitative analysis of mRNA from fetal liver revealed that a deficiency of Hoxb4 alone changed the expression levels of several other Hox genes and of genes involved in cell cycle regulation. In summary, the deficiency of Hoxb4 leads to hypocellularity in hematopoietic organs and impaired proliferative capacity. However, Hoxb4 is not required for the generation of HSCs or the maintenance of steady state hematopoiesis.
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| 10. |
- Carlsson, G, et al.
(författare)
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Kostmann syndrome: severe congenital neutropenia associated with defective expression of Bcl-2, constitutive mitochondrial release of cytochrome c, and excessive apoptosis of myeloid progenitor cells
- 2004
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 103:9, s. 3355-3361
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Tidskriftsartikel (refereegranskat)abstract
- Kostmann syndrome, or severe congenital neutropenia (SCN), is an autosomal recessive disorder of neutrophil production. To investigate the potential role of apoptosis in SCN, bone marrow aspirates and biopsies were obtained from 4 patients belonging to the kindred originally described by Kostmann and 1 patient with SCN of unknown inheritance. An elevated degree of apoptosis was observed in the bone marrow of these patients, and a selective decrease in B-cell lymphoma-2 (Bcl-2) expression was seen in myeloid progenitor cells. Furthermore, in vitro apoptosis of bone marrow-derived Kostmann progenitor cells was increased, and mitochondrial release of cytochrome c was detected in CD34+ and CD33+ progenitors from patients, but not in controls. Administration of granulocyte colony-stimulating factor (G-CSF) restored Bcl-2 expression and improved survival of myeloid progenitor cells. In addition, cytochrome c release was partially reversed upon incubation of progenitor cells with G-CSF. In sum, these studies establish a role for mitochondria-dependent apoptosis in the pathogenesis of Kostmann syndrome and yield a tentative explanation for the beneficial effect of growth factor administration in these patients. (Blood. 2004;103:3355-3361)
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