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At least 19 recordsLinked to original sources
PubMed2002

RP59, a marker for osteoblast recruitment, is also detected in primitive mesenchymal cells, erythroid cells, and megakaryocytes.

We recently described a novel protein in bone marrow of rats, RP59, as a marker for cells with the capacity to differentiate into osteoblasts. In this work, its expression pattern was further investigated to learn about the origin and biological relevance of RP59 expressing marrow cells. As revealed by in situ hybridization and by immunohistochemistry of yolk sac embryos, RP59 was found in the cells of the primitive ectoderm and primitive streak as well as in blood islands and extraembryonal mesoderm. Later, RP59 occurred in fetal liver cells and in circulating blood. From the time around birth, it was found in bone marrow and spleen cells. In addition, in vitro-formed blood vessels contained RP59-positive cells in the lumen. Endothelial cells and the vast majority of cells outside the blood vessels were not labeled. Concerning more mature hematopoietic cell types, RP59 was observed in megakaryocytes and nucleated erythroblasts, but absent from lymphoid cells. In conclusion, RP59 was induced in early mesoderm. It was maintained in the erythroid and megakaryotic lineages and, as earlier described, in young osteoblasts.

Animals↗
PubMed2000

HS1 interacts with Lyn and is critical for erythropoietin-induced differentiation of erythroid cells.

Erythroid cells terminally differentiate in response to erythropoietin binding its cognate receptor. Previously we have shown that the tyrosine kinase Lyn associates with the erythropoietin receptor and is essential for hemoglobin synthesis in three erythroleukemic cell lines. To understand Lyn signaling events in erythroid cells, the yeast two-hybrid system was used to analyze interactions with other proteins. Here we show that the hemopoietic-specific protein HS1 interacted directly with the SH3 domain of Lyn, via its proline-rich region. A truncated HS1, bearing the Lyn-binding domain, was introduced into J2E erythroleukemic cells to determine the impact upon responsiveness to erythropoietin. Truncated HS1 had a striking effect on the phenotype of the J2E line-the cells were smaller, more basophilic than the parental proerythoblastoid cells and had fewer surface erythropoietin receptors. Moreover, basal and erythropoietin-induced proliferation and differentiation were markedly suppressed. The inability of cells containing the truncated HS1 to differentiate may be a consequence of markedly reduced levels of Lyn and GATA-1. In addition, erythropoietin stimulation of these cells resulted in rapid, endosome-mediated degradation of endogenous HS1. The truncated HS1 also suppressed the development of erythroid colonies from fetal liver cells. These data show that disrupting HS1 has profoundly influenced the ability of erythroid cells to terminally differentiate.

Adaptor Proteins, Signal Transducing↗
PubMed1999

The beta-globin promoter is important for recruitment of erythroid Krüppel-like factor to the locus control region in erythroid cells.

Erythroid Krüppel-like factor (EKLF), which binds to the CACCC box in the beta-globin promoter, is required for the expression of the beta-globin gene in adult erythroid cells. It was recently demonstrated that EKLF is also required for the activity of the beta-globin locus control region (LCR) 5'HS3. Some evidence suggests that the LCR and the beta-globin promoter interact in adult erythroid cells, and the network of protein-protein interactions that exists between these two elements may regulate how EKLF is recruited to the LCR. In this report, we use the PIN*POINT assay to study the role of the promoter on the recruitment of EKLF to 5'HS2 and 5'HS3 of the LCR. We find that recruitment of EKLF to 5'HS2 requires the TATA box, but recruitment to 5'HS3 depends on the CACCC and TATA boxes of the beta-globin promoter. Furthermore, recruitment of EKLF to 5'HS3 only occurred in beta-globin-expressing murine erythroid leukemia cells, whereas recruitment of EKLF to 5'HS2 occurred in both gamma-globin-expressing K562 cells and murine erythroid leukemia cells. Unlike EKLF, Sp1, which also binds to CACCC boxes, is not recruited to 5'HS3. We have also examined how one 5'HS affects the recruitment of EKLF to another 5'HS. We have found that the recruitment of EKLF to 5'HS3 depends on the presence of 5'HS2 in cis, but the recruitment to 5'HS2 does not depend on 5'HS3. Based on these results, we present a model that illustrates how EKLF may be recruited to the beta-globin locus.

Animals↗
PubMed1996

Cytokine gene expression in erythroid cells.

Erythroid nuclear cells have been shown to exert regulatory effects on immunopoiesis. We have reported that some of these influences might be mediated via soluble factors secreted by nuclear erythroid cells. In this report we describe our estimate of the cytokine gene expression in cells isolated from individual erythroid colonies by Reverse transcription-Polymerase chain reaction. We found in erythroid cells, originated from the bone marrow precursors obtained from phenylhydrazine-treated mouse, the expression of the following cytokine genes: IL-1 alpha and IL-1 beta, IL-4, IL-6, GM-CSF, gamma-IFN and TGF-beta. In contrast, the erythroid cells derived from newborn mouse spleen precursor cells expressed IL-1 alpha, IL-1 beta, IL-4, IL-6 and GM-CSF mRNAs but not gamma-IFN and TGF-beta mRNAs. No detectable levels of IL-2, IL-3 and IL-5 mRNAs were expressed in nuclear erythroid cells. These data provide evidence of the expression of mRNAs coding in the set of immunoregulatory cytokines in immature erythroid progenitor cells in mouse.

Animals↗
PubMed1977

Changes in the composition of plasma membrane proteins during differentiation of embryonic chick erythroid cell.

Erythroid cells which are homogeneous with regard to stage of maturation are naturally available from the circulation of chick embryos at various times of development. This provides a convenient system for examining the changes in plasma membrane protein composition during red cell maturation. Plasma membranes are isolated from chick embryonic erythroid cells at various stages of maturation. Extensive characterization of the isolated membranes show that they are pure and their proteins undegraded. Analyses by sodium dodecyl sulfate/polyacrylamide gel electrophoresis show that both qualitative and quantitative changes occur in membrane protein composition during the early stage of erythroid differentiation. Specific proteins of red cell membrane such as "spectrin" and band three proteins are present in low levels in early erythroblasts but increase in their relative amounts with maturation. A steady-state membrane protein composition seems to be established by the late polychromatophilic erythroblast stage.

Age Factors↗
PubMed2006

Stem cell-derived erythroid cells mediate long-term systemic protein delivery.

We demonstrate here the capacity of erythroid cells to mediate long-term, systemic and therapeutic protein delivery in vivo. By targeting human factor IX (hFIX) expression to late-stage erythropoiesis, we achieve long-term hFIX secretion at levels significantly higher (>tenfold) than those obtained with an archetypal ubiquitous promoter in a mouse model of hemophilia B. Erythroid cell-derived hFIX is biologically active, resulting in phenotypic correction of the bleeding disorder. In addition to achieving high expression levels and resistance to transcriptional silencing, red cell-mediated protein delivery offers multiple advantages including immune tolerance induction, reduction of the risk of insertional oncogenesis and relative ease of application by either engrafting transduced hematopoietic stem cells or transfusing ex vivo-generated, stem cell-derived erythroid cells.

Animals↗
PubMed2000

Regulation of functional activity of bone marrow hemopoietic stem cells by erythroid cells in mice.

Transplantation of erythroid and bone marrow cells to irradiated mice stimulated exogenous colony formation. Pretreatment of erythroid cells with specific rabbit antiserum to erythroblasts abolished this effect. The reverse transcriptase polymerase chain reaction revealed the presence of mRNA for interleukin-1alpha, interleukin-1beta, interleukin-3, interleukin-6, and granulocyte-macrophage colony-stimulating factor in erythroid cells. Granulocyte-macrophage colony-stimulating factor was found in the conditioned medium from erythroid cells. Thus, erythroid cells stimulated colony-forming activity of bone marrow cells, which was probably mediated via cytokine synthesis (e.g., granulocyte-macrophage colony-stimulating factor).

Animals↗
PubMed2002

Iron targeting to mitochondria in erythroid cells.

Immature erythroid cells have an exceptionally high capacity to synthesize haem that is, at least in part, the result of the unique control of iron metabolism in these cells. In erythroid cells the vast majority of Fe released from endosomes must cross both the outer and the inner mitochondrial membranes to reach ferrochelatase, which inserts Fe into protoporphyrin IX. Based on the fact that Fe is specifically targeted into erythroid mitochondria, we have proposed that a transient mitochondria-endosome interaction is involved in Fe transfer to ferrochelatase [Ponka (1997) Blood 89, 1-25]. In this study, we examined whether the inhibition of endosome mobility within erythroid cells would decrease the rate of (59)Fe incorporation into haem. We found that, in reticulocytes, the myosin light-chain kinase inhibitor, wortmannin, and the calmodulin antagonist, W-7, caused significant inhibition of (59)Fe incorporation from (59)Fe-transferrin-labelled endosomes into haem. These results, together with confocal microscopy studies using transferrin and mitochondria labelled by distinct fluorescent markers, suggest that, in erythroid cells, endosome mobility, and perhaps their contact with mitochondria, plays an important role in a highly efficient utilization of iron for haem synthesis.

Animals↗
PubMed2006

Sox6 cell-autonomously stimulates erythroid cell survival, proliferation, and terminal maturation and is thereby an important enhancer of definitive erythropoiesis during mouse development.

Erythropoiesis, the essential process of hematopoietic stem cell development into erythrocytes, is controlled by lineage-specific transcription factors that determine cell fate and differentiation and by the hormone erythropoietin that stimulates cell survival and proliferation. Here we identify the Sry-related high-mobility-group (HMG) box transcription factor Sox6 as an important enhancer of definitive erythropoiesis. Sox6 is highly expressed in proerythroblasts and erythroblasts in the fetal liver, neonatal spleen, and bone marrow. Mouse fetuses and pups lacking Sox6 develop erythroid cells slowly and feature misshapen, short-lived erythrocytes. They compensate for anemia by elevating the serum level of erythropoietin and progressively enlarging their erythropoietic tissues. Erythroid-specific inactivation of Sox6 causes the same phenotype, demonstrating cell-autonomous roles for Sox6 in erythroid cells. Sox6 potentiates the ability of erythropoietin signaling to promote proerythroblast survival and has an effect additive to that of erythropoietin in stimulating proerythroblast and erythroblast proliferation. Sox6 also critically facilitates erythroblast and reticulocyte maturation, including hemoglobinization, cell condensation, and enucleation, and ensures erythrocyte cytoskeleton long-term stability. It does not control adult globin and erythrocyte cytoskeleton genes but acts by stabilizing filamentous actin (F-actin) levels. Sox6 thus enhances erythroid cell development at multiple levels and thereby ensures adequate production and quality of red blood cells.

Actins↗
PubMed2005

AKT induces erythroid-cell maturation of JAK2-deficient fetal liver progenitor cells and is required for Epo regulation of erythroid-cell differentiation.

AKT serine threonine kinase of the protein kinase B (PKB) family plays essential roles in cell survival, growth, metabolism, and differentiation. In the erythroid system, AKT is known to be rapidly phosphorylated and activated in response to erythropoietin (Epo) engagement of Epo receptor (EpoR) and to sustain survival signals in cultured erythroid cells. Here we demonstrate that activated AKT complements EpoR signaling and supports erythroid-cell differentiation in wild-type and JAK2-deficient fetal liver cells. We show that erythroid maturation of AKT-transduced cells is not solely dependent on AKT-induced cell survival or proliferation signals, suggesting that AKT transduces also a differentiation-specific signal downstream of EpoR in erythroid cells. Down-regulation of expression of AKT kinase by RNA interference, or AKT activity by expression of dominant negative forms, inhibits significantly fetal liver-derived erythroid-cell colony formation and gene expression, demonstrating that AKT is required for Epo regulation of erythroid-cell maturation.

Animals↗
PubMed1990

Detection in non-erythroid cells of a factor with the binding characteristics of the erythroid cell transcription factor EF1.

The erythroid transcription factor erythroid factor-1 (EF1) plays a critical role in the transcription of erythroid-specific genes. Here we report the presence of a factor with the mobility and sequence-specific DNA-binding characteristics of EF1 at low abundance in a wide variety of non-erythroid cell types. This is the first report of an EF1-like activity in non-erythroid cells and indicates that this factor may play a role in the regulation of genes expressed in such cells.

Animals↗
PubMed1977

Cell cycle time of erythroid cells in mice with normal and stimulated erythropoiesis.

The cell cycle time of erythroid cells was determined in normal mice and in polycythaemic mice after stimulation of erythropoiesis by exogenous erythropoietin. The method employed was 3HTdR autoradiography of bone marrow cells. After 21 or 38 hours of administratering the erythropoietin 3HTdR was injected into the animals. The cell cycle time was calculated from the curves of changes in the labelling indices of proerythroblasts and basophilic erythroblasts at one hour intervals. The cell cycle time in normal animals was 8.5 hours. Twenty-two to twenty-five hours after stimulation with 1.5 units of erythropoietin, the cell cycle was 7.8 hours. Thirty-nine to forty-two hours after injection, at the time when the number of nucleated erythroid cells was within normal limits, the cell cycle time was 7.7 hours. Under the used experimental conditions, the cell cycle time of early erythroid cells was not significantly changed in comparison with the values obtained in non-treated animals. This is in contrast to the results reported when extreme stimulation of erythropoiesis with endogenous erythropoietin was used.

Animals↗
PubMed1980

Binding of merocyanine 540 to normal and leukemic erythroid cells.

Normal erythroid cells and both uninduced and induced erythroleukemia cells were stained with the leukemia-specific fluorescent probe merocyanine 540 and its analogs. The external membranes of normal intact cells bound the dye, but this general low-affinity binding was completely abolished by the addition of competing serum. In contrast, erythroleukemia cells bound the dye even in the presence of serum; binding was not affected by reversing the sign of the charge carried by MC540, but was abolished upon removal of certain hydrophobic side chains. When the erythroleukemia cells were induced to differentiate, the distribution of dye-binding regions was altered by the cell such that staining became localized to one region of the membrane. Concomitantly, conconavalin A binding sites were redistributed and became localized in the same region of the membrane as the merocyanine binding sites. Merocyanine 540 is thus shown to bind to a hematopoietic surface feature whose topological distribution is subject to cellular control during differentiation. This leukemia-specific marker may be one of several eliminated during enucleation of mammalian erythroid cells.

Animals↗
PubMed1977

Purification of a putative precursor of globin messenger RNA from mouse nucleated erythroid cells.

Nucleated erythroid cells were incubated for 10 min in the presence of [5-3H]uridine, and the total RNA was isolated by three different extraction procedures. RNA containing globin messenger RNA sequences was purified from other cellular RNAs by selective hybridization to globin complementary DNA cellulose. Depending upon the extraction procedure employed, 0.4-0.6% of the radioactively-labeled total cellular RNA applied to the column annealed to globin complementary DNA cellulose. The annealed RNA was treated with formaldehyde and analyzed by formaldehyde/polyacrylamide gel electrophoresis. Mature globin mRNA and an RNA migrating at approximately 15 S were observed. No globin mRNA containing sequences larger than 20 S were present. The 15S RNA was partially resolved from mature globin mRNA by neutral sucrose density gradient centrifugation. The RNA isolated from the heavy region of this gradient migrated as 15 S in the formaldehyde/polyacrylamide gels and retained its ability to quantitatively anneal to globin complementary DNA cellulose. On the basis of these observations, we conclude that nucleated erythroid cells obtained from the spleens of anemic mice have a 15S RNA which contains globin mRNA sequences. The 15S RNA is not an aggregate and is a good candidate for a globin mRNA precursor.

Animals↗