1,720,997 research outputs found
Silencing CD34 antigen in human hematopoietic stem cells
No full textCD34 is a highly glycosylated transmembrane protein strongly expressed on hematopoietic stem/progenitor cells (HSPCs); despite its importance as a marker of HSPCs, its function is still poorly understood, even if a role in cell adhesion has been demonstrated. In order to characterize the function of CD34 antigen in human HSPCs, we evaluated by small interfering RNAs (siRNAs) mediated gene silencing the role of CD34 antigen in HSPCs differentiation. By using the Nucleofection Amaxa technology for siRNA transfection in HSPCs, we obtained a rapid and effective down-regulation of the CD34 antigen. In this paper, we have demonstrated that CD34 silencing in HSPCs enhances their granulocyte and megakaryocyte differentiation and reduces erythroid maturation as shown by clonogenic assay, morphological analysis and expression of differentiation markers. In agreement with these results, the gene expression profile of HSPCs-silenced cells reveals the up-regulation of genes involved in granulocyte and megakaryocyte commitment and the down-regulation of erythroid genes. These data indicate that CD34 transmembrane protein promotes the differentiation of CD34+ hematopoietic progenitors towards the erythroid lineage at the expense of granulocyte and megakaryocyte ones
Eosinophils, but not neutrophils, exibit an efficient DNA repair machinary and high nucleolar activity
Full text linkBACKGROUND AND OBJECTIVES: Traditionally eosinophils have been considered terminally differentiated cells that play a role in host protection against parasites. However, there is some evidence showing that eosinophils are, in fact, multifunctional leukocytes involved in inflammatory responses, as well as in tissue homeostasis. We characterized the transcriptome profile of human eosinophils, and, for the purpose of comparison, the transcriptome profile of neutrophils, monocytes and hematopoietic progenitor cells. Moreover, we studied the activation of selected cellular processes for which a significant differential expression was demonstrated. DESIGN AND METHODS: We profiled gene expression using Affymetrix GeneChips. DNA repair capacity was tested using the comet assay. Nucleoli and their activity were characterized by transmission electron microscopy analysis, silver staining of nucleolus regions (AgNOR) and RNA staining. RESULTS: Gene expression profiling showed that eosinophils appear hierarchically closer to monocytes than to neutrophils. Gene ontology mapping of differentially expressed genes revealed that eosinophils express categories very similar to those expressed by monocytes, related to DNA repair and nucleolar functions. Moreover, our data show that eosinophils and monocytes maintain the ability to repair both double and single strand DNA breaks, whereas neutrophils lack this capacity. Furthermore, eosinophils exhibit nucleolar activity, which is lacking in neutrophils, but resembles that in monocytes. INTERPRETATION AND CONCLUSIONS: The presence of large, active nucleoli in eosinophils, coupled to marked activity of DNA repair systems, suggests that eosinophils are not terminally differentiated cells. Indeed, their transcriptome profile and functional properties are more similar to those of non-terminally differentiated cells such as monocytes, rather than to neutrophils
c-Myb supports erythropoiesis by transactivating KLF1 and LMO2 expression
No full textThe c-Myb transcription factor is highly expressed in immature hematopoietic cells and down-regulated during
differentiation. c-myb is essential for the hematopoietic development, as c-myb-/- mice die at E15 due to failure of fetal
hepatic erythropoiesis. To gain further insights into the role of c-myb during the hematopoietic lineage commitment, we
studied the effects of c-Myb silencing in human CD34+ hematopoietic stem/progenitor cells. c-Myb silencing in CD34+
cells was performed by transfection of siRNAs using the Amaxa Nucleofector® Technology. In order to keep c-Myb
expression silenced for all the commitment phase of CD34+ cells, each sample was nucleofected 3 times, once a day.
Moreover, to exclude non-specific effects of siRNA nucleofection, for each experiment, together with the sample
transfected with the siRNAs targeting c-Myb, one sample electroporated without siRNAs and one transfected with a
non-targeting siRNA were performed. c-Myb silencing effects on CD34+ cells differentiation ability were studied by
methylcellulose and collagen-based clonogenic assays and by morphological and immunophenotypic analyses after
liquid culture. Furthermore, we investigated by microarray analysis the changes in gene expression induced by c-Myb
silencing. Methylcellulose assay revealed a remarkable increase of the percentage of monocyte (CFU-M) colonies and a
decrease of the erythroid ones (BFU-E) in c-Myb-silenced CD34+ cells. Moreover, collagen-based clonogenic assay
demonstrated that c-Myb silencing strongly enhances the megakaryocyte commitment of CD34+ cells. In agreement
with these data, flow cytometric analysis showed an increase in mono-macrophage and megakaryocyte fractions in cmyb-silenced
cells, while the erythroid population was strongly decreased. Morphological evaluation of May
Grunwald-Giemsa stained cytospins further supported the conclusion that c-myb silencing forces the CD34+ cells
commitment towards the macrophage and megakaryocyte lineages at the expense of the erythroid one. Gene expression
profiling of c-Myb silenced CD34+ cells enabled us to identify new putative targets which can account for c-Myb
knockdown effects. Indeed, Chromatin Immunoprecipitation and Luciferase reporter assay demonstrated that c-Myb
binds to KLF1 and LMO2 promoters and transactivates their expression. Functional rescue experiments showed that the
retroviral vector-mediated overexpression of KLF1 and LMO2 transcription factors in c-Myb silenced cells is able to
rescue, at least in part, the impaired erythroid differentiation. Our data collectively demonstrate that c-Myb plays a
pivotal role in human primary hematopoietic stem/progenitor cells lineage commitment, by enhancing erythropoiesis at
the expense of megakaryocyte diffentiation. In particular, we identified c-Myb-driven KLF1 and LMO2 transactivation
as the molecular mechanism through which c-Myb regulates erythroid versus megakaryocyte lineage fate decision
Role of CD34 antigen in myeloid differentiation of human hematopoietic progenitor cells
No full textCD34 is a transmembrane protein that is strongly expressed on hematopoietic stem/progenitor cells (HSCs); despite its importance as a marker of HSCs, its function is still poorly understood, although a role in cell adhesion has been demonstrated. To characterize the function of CD34 antigen on human HSCs, we examined, by both inhibition and overexpression, the role of CD34 in the regulation of HSC lineage differentiation. Our results demonstrate that CD34 silencing enhances HSC granulocyte and megakaryocyte differentiation and reduces erythroid maturation. In agreement with these results, the gene expression profile of these cells reveals the upregulation of genes involved in granulocyte and megakaryocyte differentiation and the downregulation of erythroid genes. Consistently, retroviral-mediated CD34 overexpression leads to a remarkable increase in erythroid progenitors and a dramatic decrease in granulocyte progenitors, as evaluated by clonogenic assay. Together, these data indicate that the CD34 molecule promotes the differentiation of CD34+ hematopoietic progenitors toward the erythroid lineage, which is achieved, at least in part, at the expense of granulocyte and megakaryocyte lineages
Signal control of hematopoietic stem cell fate: Wnt, Notch, and Hedgehog as the usual suspects
No full textPurpose of review: Hematopoietic homeostasis depends on appropriate self-renewal and differentiation capacity of hematopoietic stem cells. The characterization of the key extracellular signals that integrate with intracellular molecular machinery to regulate hematopoietic stem cells fate choice is crucial to move toward hematopoietic stem cell clinical application. Recent Findings: Several factors have been described as positive and negative regulators of hematopoietic stem cell self-renewal and differentiation. Most of the hematopoietic cytokines studied promote either survival or differentiation or both in hematopoietic stem cells ex vivo, whereas morphogens (Wnt, Notch, and Hedgehog) may signify a class of hematopoietic stem cell regulators that support expansion of the hematopoietic stem cell pool by a combination of survival and induced self-renewal. Summary: Although Wnt, Notch, and Hedgehog signaling pathways have been implicated in self-renewal and proliferation in vivo, modulation of these pathways alone does not result in substantive expansion of hematopoietic stem cells ex vivo. In addition to these signaling pathways, Bcl-2 family members may have an important role in inducing survival in hematopoietic stem cells both in vivo and ex vivo. Understanding the complex relationship between these unique signaling pathways is essential to achieve successful ex-vivo expansion toward enhanced hematopoietic stem cell transplantation-based therapies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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