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PubMed1994

Transferrin binding capacity as a marker of differentiation and maturation of rat erythroid cells fractionated by counter current distribution in aqueous polymer two-phase systems.

Rat bone marrow cell populations, containing different proportions of erythroid cells, have been fractionated by counter-current distribution in the non-charge-sensitive dextran/polyethyleneglycol two-phase systems on the basis of hydrophobic cell surface properties. Cell fractions with a low distribution coefficient, which contain non-erythroid cells and early erythoblasts, showed a low transferrin binding capacity and a low haemoglobin/cell ratio whereas cell fractions with a high distribution coefficient, which contain intermediate-late erythroblasts and mature red cells, showed an elevated transferrin binding capacity and the highest haemoglobin/cell ratio. These results support transferrin binding capacity as a good marker parameter for the erythroid bone marrow cell differentiation and maturation processes.

Animals↗
PubMed1997

A "knockdown" mutation created by cis-element gene targeting reveals the dependence of erythroid cell maturation on the level of transcription factor GATA-1.

The hematopoietic-restricted transcription factor GATA-1 is required for both mammalian erythroid cell and megakaryocyte differentiation. To define the mechanisms governing its transcriptional regulation, we replaced upstream sequences including a DNase I hypersensitive (HS) region with a neomycin-resistance cassette by homologous recombination in mouse embryonic stem cells and generated mice either harboring this mutation (neoDeltaHS) or lacking the selection cassette (DeltaneoDeltaHS). Studies of the consequences of these targeted mutations provide novel insights into GATA-1 function in erythroid cells. First, the neoDeltaHS mutation leads to a marked impairment in the rate or efficiency of erythroid cell maturation due to a modest (4- to 5-fold) decrease in GATA-1 expression. Hence, erythroid differentiation is dose-dependent with respect to GATA-1. Second, since expression of GATA-1 from the DeltaneoDeltaHS allele in erythroid cells is largely restored, transcription interference imposed by the introduced cassette must account for the "knockdown" effect of the mutation. Finally, despite the potency of the upstream sequences in conferring high-level, developmentally appropriate expression of transgenes in mice, other cis-regulatory elements within the GATA-1 compensate for its absence in erythroid cells. Our work illustrates the usefulness of targeted mutations to create knockdown mutations that may uncover important quantitative contributions of gene function not revealed by conventional knockouts.

Alleles↗
PubMed1984

Haemoglobin and globin synthesis in the isolated primitive and definitive erythroid cells of chicken embryos. Evidence for a non-clonal mechanism at the haemoglobin switch.

Primitive and definitive erythroid cells of chicken embryos aged 4-8 days, were separated by unit gravity sedimentation and pulse labelled with [3H]- and [14C]leucine. The haemoglobin and globin synthesis in the cell populations was analysed by chromatofocussing, isoelectric focussing, urea starch gel electrophoresis, and immunofluorescence or radioimmunoassay, using globin specific antibodies. We found that both embryonic and adult alpha globins are present in primitive erythroid cells, but relatively more of the adult alpha-type globins are synthesized in the late primitive erythroid cells. In young definitive erythroid cells exclusively adult alpha-type globins are synthesized. From these findings we conclude that a command to synthesize adult alpha globin is perceived in both cell types at the time of the switch. This supports an environmental model rather than a clonal model of haemoglobin switching.

Animals↗
PubMed1992

The quantitative alteration of 5s rRNA during the development of mammalian erythroid cells and its effect on DNA synthesis in SP2/0 mouse myeloma cells.

Mouse myeloma cells (SP2/0) were incubated with 125I-5s rRNA from rabbit reticulocytes and processed for autoradiography. The results indicated that 5s rRNA could pass into the nuclei of mouse myeloma cells. In a separate experiment, SP2/0 were incubated with cold 5s rRNA, then with 3H-TdR and processed for autoradiography. It was found that in the mouse myeloma cells, DNA synthesis and cell division were obviously suppressed. In another series of experiments, rRNA was extracted from rabbit bone marrow, reticulocytes and erythroid cells and from rat embryonic liver and erythroid cells. The rRNA was analyzed by agarose electrophoresis. It was found that the amount of 5s rRNA in various stages of erythroid development changed along with the denucleating process. Thus it seems likely that 5s rRNA from mammalian erythroid cells could play a role in reversing the malignant phenotype of tumor cells and denucleation of mammalian erythroid cells through inhibiting DNA synthesis.

Animals↗
PubMed2001

Dynamics of ankyrin-containing complexes in chicken embryonic erythroid cells: role of phosphorylation.

Chicken erythroid ankyrin undergoes a fairly rapid cycle of cytoskeletal association, dissociation, and turnover. In addition, the cytoskeletal association of ankyrin is regulated by phosphorylation. Treatment of erythroid cells with serine and threonine phosphatase inhibitors stimulated the hyperphosphorylation of the 225- and 205-kDa ankyrin isoforms, and dissociated the bulk of these isoforms from cytoskeletal spectrin. In vitro binding studies have shown that this dissociation of ankyrin from spectrin in vivo can be attributed to a reduced ability of hyperphosphorylated ankyrin to bind spectrin. Interestingly, a significant fraction of detergent insoluble ankyrin accumulates in a spectrin-independent pool. At least some of this spectrin-independent pool of ankyrin is complexed with the AE1 anion exchanger, and the solubility properties of this pool are also regulated by phosphorylation. Treatment of cells with serine and threonine phosphatase inhibitors had no effect on ankyrin/AE1 complex formation. However, these inhibitors were sufficient to shift ankyrin/AE1 complexes from the detergent insoluble to the soluble pool. These analyses, which are the first to document the in vivo consequences of ankyrin phosphorylation, indicate that erythroid ankyrin-containing complexes can undergo dynamic rearrangements in response to changes in phosphorylation.

Animals↗
PubMed1979

Ultrastructural studies on erythropoiesis in the avian thymus. II. A stereological analysis of the lymphoid and erythroid cells.

The cortex of enlarging thymic lobes from adult haemorrhaged Quelea quelea were found to be similar to those of wild birds where the thymic enlargement was occurring naturally. A detailed stereological analysis of cells broadly designated as lymphoid, and the construction of models to account for the results, indicates that the enlarging thymic lobe contains both large and small blast cells, a heterogenous group of medium lymphocytes, erythroid cells, and two types of very small lymphocytes. The distinction between early erythroid cells and some lymphocytes, despite this detailed analysis is very difficult, but it is possible in enlarging thymic lobes that up to 42% of the lymphoid cells may have erythroid characteristics.

Animals↗
PubMed1993

[Transient pure red cell aplasia in an adult with acute parvovirus B19 infection: observation of PVB19 DNA by polymerase chain reaction, viral antibody and erythroid cells in the bone marrow].

A 35-year-old female was referred to our hospital for fever and anemia. Physical examination was unremarkable. Complete blood count revealed microcytic hypochromic anemia and reticulocytopenia. The bone marrow cellularity was normal. Some giant pronormoblasts were seen but other erythroid cells were absent. No stainable iron was seen. Parvovirus B19 (PVB19) DNA was detectable by polymerase chain reaction. Anti-PVB19 IgM-antibody was also positive in the serum on admission. Antibodies against rubella, measles, mumps, EB virus and HBs were negative and HBs antigen was also negative. Thus the diagnosis of iron deficiency anemia complicated with pure red cell aplasia secondary to PVB19 infection was made. The PVB19 DNA was still positive on days 6 and 11, suggesting that PVB19 virus persists as long as 3 weeks after the onset of PVB19 infection. However, the erythroid cells had recovered by day 6 after admission suggesting that the development of IgM antibody successfully protected the erythroid cells from infection by the residual PVB19. Hence, careful observation for PVB19 DNA and the antibody may be necessary if immunodeficient patients developed anemia of unknown etiology.

Acute Disease↗
PubMed1994

The LIM protein RBTN2 and the basic helix-loop-helix protein TAL1 are present in a complex in erythroid cells.

Chromosomal translocations in T-cell acute leukemias can activate genes encoding putative transcription factors such as the LIM proteins RBTN1 and RBTN2 and the DNA-binding basic helix-loop-helix transcription factor TAL1 associated with T-cell acute lymphocytic leukemia. While not expressed in normal T cells, RBTN2 and TAL1 are coexpressed in erythroid cells and are both important for erythroid differentiation. We demonstrate, using anti-RBTN2 and anti-TAL1 antisera, that the LIM protein RBTN2 is not phosphorylated and is complexed with the TAL1 phosphoprotein in the nucleus of erythroid cells. A complex containing both RBTN1 and TAL1 also occurs in a T-cell acute leukemia cell line. Since both RBTN2 and TAL1 are crucial for normal erythropoiesis, these data have important implications for transcription networks therein. Further, since both proteins can be involved in leukemogenesis, these data provide a direct link between proteins activated by chromosomal translocations in T-cell acute leukemia.

Adaptor Proteins, Signal Transducing↗
PubMed1975

Maturation of membrane function: transport of amino acid by rat erythroid cells.

The membrane changes which occur during cellular maturation of erythroid cells have been investigated. The transport of alpha-aminoisobutyric acid, alanine, and N-methylated-alpha-aminoisobutyric acid have been studied in the erythroblastic leukemic cell, the reticulocyte, and the erythrocyte of the Long-Evans rat. The dependence of amino acid transport on extracellular sodium concentration was investigated. Erythrocytes were found to transport these amino acids only by Na-independent systems. The steady state distribution ratio was less than 1. Reticulocytes were found to transport alpha-aminoisobutyric acid and alanine by Na-dependent systems, but only small amounts of N-methylated-alpha-aminoisobutyric acid. Small amounts of these amino acids were transported by Na-independent systems. The steady state distribution ratio was greater than one for Na-dependent transport. The erythroblastic leukemia cell, a model immature erythroid cell, showed marked Na-dependence (greater than 90%) for alpha-aminoisobutyric acid and alanine transport, and greater than 80% for the Na-dependent transport of N-methyl-alpha-aminoisobutyric acid. The steady state distribution ratio for the Na-dependent transport was greater than 4. In the erythroblastic leukemic cell, at least three Na-dependent systems are present: one includes alanine and alpha-aminoisobutyric acid, but excludes N-methyl-alpha-aminoisobutyric acid; one is for alpha-aminoisobutyric acid, alanine and also N-methyl-alpha-aminoisobutyric acid; and one is for N-methyl-alpha-aminoisobutyric acid alone. In the reticulocyte, the number of Na-dependent systems are reduced to two: one for alpha-aminoisobutyric acid and alanine; one for N-methyl-alpha-aminoisobutyric acid. In the erythrocytes, no Na-dependent transport was found. Therefore, maturation of the blast cell to the mature erythrocyte is characterized by a systematic loss in the specificity and number of transport system for amino acids.

Alanine↗
PubMed1978

Studies on nucleoli of pigeon erythroid cells.

In order to provide more information on nucleolar changes occurring during cell differentiation and maturation, pigeon erythroid cells have been studied by means of a simple light microscopic cytochemical procedure for the demonstration of the RNA containing structures and with conventional transmission electron microscopy. Nucleoli with more or less distinct nucleolonemata present in early erythroblasts were replaced by ring-shaped nucleoli and, finally, by micronucleoli in more mature erythroid cells. In contrast to the previously studied chick embryos, chickens and hens which possess micronucleoli in almost all mature erythrocytes, mature pigeon erythrocytes are mostly without any nucleoli. The ultrastructural organization of nucleoli with more or less distinct nucleolonemata and ring-shaped nucleoli do not show differences, in comparison with such forms of nucleoli in other cells. Micronucleoli in pigeon erythroblasts are characterized by degranulation, suggesting the inhibition of the formation of the nucleolar granular components. Some nucleoli show a segregation of the nucleolar components, indicating the inactivation of the nucleolar RNA polymerase, and occasionally chromatin retraction from the nucleolar body, suggesting the loss of the template. In mature erythrocytes, micronucleoli consist mainly of fibrillar components, and the perinucleolar chromatin is partially retracted from the nucleolar body of such nucleoli.

Animals↗
PubMed1993

Optimal erythroid cell production during erythropoietin treatment of mice occurs by exploiting the splenic microenvironment.

In this study, quantitative effects on erythroid cell production by a prolonged recombinant human erythropoietin (rhEpo) treatment of mice are presented. Epo treatments, given subcutaneously (s.c.) twice per day in doses of 0.5 to 500 U per day, were performed under steady-state production conditions. We found striking differences between the behavior of the different erythroid cell compartments (burst-forming unit erythroid [BFU-E], colony-forming unit erythroid [CFU-E] and erythroid precursors), as well as between the microenvironments of bone marrow and spleen. Whereas the total-body BFU-E was not changed by Epo, a redistribution of BFU-E from marrow to spleen occurred, resulting in decreasing marrow and increasing splenic BFU-E numbers. Splenic BFU-E produced CFU-E as much as 8 times more efficiently than marrow BFU-E at 50 U of Epo. At low Epo doses (to 1 U/day) no difference was found. The CFU-E in the spleen produced erythroblasts at a higher efficiency at all Epo doses (1.5 to 5 times). It seems as if this efficiency was higher at low Epo doses. Because of the migration phenomenon and the excellent microenvironment in the spleen, at the highest Epo concentrations nearly 70% of all erythroid cells reside in the spleen. Even at the highest Epo doses, granuloid cell production was not affected. Similar to the BFU-E, total-body granuloid cells remained constant (despite a shift of granulocyte-macrophage progenitors [CFU-GM]) from marrow to spleen; however, these cells did not flourish in the spleen. Under these conditions, 90% of the granuloid precursors were still localized in the marrow. Erythropoietin did not change the transit time of erythroid cells at high Epo doses.

Animals↗
PubMed1981

Evidence for increased proteolysis in intact beta thalassemia erythroid cells.

Much excess alpha chain is synthesized, but little accumulates in the erythroid cells of patients with homozygous beta thalassemia. To determine if the proteases known to exist in erythroid cells play a role in the destruction or alteration of any of this excess alpha chain, thalassemic and nonthalassemic erythroid cells were incubated for 90 minutes with 3H-leucine. The cells were then washed, and incubated twice for 15 minutes in 100 volumes of cold leucine-rich media, a procedure which eliminates almost all intracellular TCA soluble radioactivity. After these incubations levels of TCA soluble and TCA precipitable radioactivity in the cell lysates were determined, and the cells incubated for 120 minutes more in two volumes of leucine-rich media. At the end of this incubation, total TCA soluble and precipitable radioactivity was again determined in the cell lysate, and also in the two hour incubation media. The total increase in TCA soluble radioactivity in the cells and their media was divided by the 0 time TCA precipitable radioactivity, to determine the percent proteolysis labelled globin chains. In five control patients percent proteolysis ranged from 0 to 3.10 (mean = 1.50); in four severe and three mild thalassemia patients percent proteolysis ranged from 5.80 to 14.1 (mean = 11.0). The difference between the control and thalassemic groups was significant at a p of less than 0.001. This data is the first direct evidence that more proteolysis takes place in intact thalassemic cells than in non-thalassemic cells.

Adolescent↗
PubMed1989

Comparative ultrastructure of maturing toad (Bufo ictericus) and rabbit (Oryctolagus cuniculus) erythroid cells with regard to hemoglobin biosynthesis.

1. Toad and rabbit maturing erythroid cells were comparatively analysed with regard to their ultrastructural modifications involved in hemoglobin (Hb) biosynthesis. 2. The mitochondrial inner membrane differentiates to a lamellated body that, successively, gives rise to prehemosomal vesicles, prohemosomes, and to hemoglobinized organelles called hemosomes. 3. The prehemosomal vesicle involves ferruginous inclusions, taken as iron sources for heme biosynthesis, as well as the polypeptide globin chains, assembling themselves in the course of volume reduction. 4. From the prohemosomal stage onwards, where possibly heme biosynthesis occurs, hemosomes are formed; these organelles are presumably sites where the final Hb biosynthesis could take place. 5. All development stages leading to hemosome formation are similar in toad and rabbit erythroid cells, except that, in the toad, the structural prohemosome characteristics persist in hemosomes. 6. Through toad erythroid cell fractionation and electrophoresis of the organelle lysate supernatant, a wide and a weak cytoplasmic Hb bands were obtained; the latter coincides with the intraorganellar Hb band.

Animals↗
PubMed1983

Stimulation of adenylate cyclase activity by catecholamines and prostaglandins E during differentiation of rabbit bone marrow erythroid cells.

After fractionation of rabbit bone marrow into erythroid cells at different developmental stages adenylate cyclase activity of membrane ghosts was assayed in the presence of sodium fluoride, catecholamines or prostaglandins E. Both basal and fluoride-stimulated adenylate cyclase decreased continuously during differentiation. Only catecholamines having beta 2-adrenergic activity stimulated adenylate cyclase and their effect was restricted to the most immature cells, the proerythroblasts and, to a lesser extent, the basophilic erythroblasts. Thus, uncoupling of beta-adrenergic receptors occurs early in erythroblast development and hormone responsiveness is lost before the final cell division. Prostaglandin E receptors and adenylate cyclase remain coupled throughout erythroid cell development.

Adenylyl Cyclases↗
PubMed2001

Detection of fetal erythroid cells from maternal blood using fluorescence in situ hybridization and liquid culture.

Fetal nucleated erythrocytes circulating in maternal blood are a potential source of fetal DNA for noninvasive prenatal genetic diagnosis. However, the estimated ratio of fetal to maternal cells is extremely small. In order to enrich these cells, we performed direct culture using a two-phase liquid system. Mononuclear cells were obtained from maternal blood samples at 8-10(+3) weeks of gestation and cultured in the first phase. After 4-5 days, the nonadherent cells were harvested and recultured with erythropoietin in the second phase for another 3-5 days. We examined cellular morphology, and counted the number of benzidine- positive cells and the percentage of glycophorin A/CD71 positive erythroid cells. We also did Kleihauer-Betke stain for Hb F, polymerase chain reaction (PCR) for SRY/DYZ1, chromosome analysis, and fluorescence in situ hybridization (FISH). The number of total erythroid cells reached about 0.1 x 10(6)-1.0 x 10(6)/mL with a purity of 84.0-97.3%. Hb F stain showed total erythroid cells of approximately 0.4 x 10(4)-9.8 x 10(4)/mL. Male DNA was detected in one case by PCR. In this case, the XY karyotype was confirmed by FISH and amniocentesis. This approach provides enriched source of fetal cells for further prenatal genetic analysis without complicated separation or sorting procedures.

Cell Culture Techniques↗
PubMed1997

Development of erythroid cells from mouse embryonic stem cells in culture: potential use for erythroid transcription factor study.

We developed an efficient differentiation induction system from mouse embryonic stem (ES) cells into blood cells by coculture on a novel stromal cell line named OP9, in order to analyze molecular mechanisms of hematopoietic cell development and differentiation. ES cells could give rise to adult type definitive erythrocytes, myeloid and B lineage cells via multipotential hematopoietic precursor cells, when the cells were simply cocultured with the OP9 stromal cells. The temporal pattern of the appearance of erythroid lineage cells during the differentiation induction was very similar to that detected in mouse ontogeny. This differentiation induction method should facilitate to dissect the function of erythroid transcription factors during erythroid lineage cell development.

Animals↗
PubMed1981

Synthesis of 2,3-bisphosphoglycerate synthase in erythroid cells.

Antiserum prepared from a rabbit which was immunized with human erythrocyte glycerate-2,3-P2 synthase was found to react with glycerate-2,3-P2 synthase in rabbit erythroid cells. By using this antiserum, it was proved that the specific activity of this enzyme was unchanged during the development of the rabbit erythroid cells. This leads us to conclude that the increased activity of glycerate-2,3-P2 synthase in developing erythroid cells (Narita, H., Ikura, K., Yanagawa, S., Sasaki, R., Chiba, H., Saimyoji, H., and Kumagai, N. (1980) J. Biol. Chem. 255, 5230-5235) is due to the accumulation of enzyme protein. There is at least a 16-fold increase in the level of this protein during development from bone marrow erythroid cells to erythrocytes. The synthesis of glycerate-2,3-P2 synthase was shown to occur in rabbit reticulocytes and bone marrow erythroid cells. These cells were incubated for protein synthesis and the protein synthesized was precipitated with the anti-glycerate-2,3-P2 synthase antiserum and separated on sodium dodecyl sulfate-polyacrylamide gels. The immunoprecipitated product was shown to produce fragments of the same molecular weight after digestion with V8 protease as did the pure glycerate-2,3-P2 synthase. The proportion of glycerate-2,3-P2 synthase synthesis in reticulocytes (0.04% of total protein synthesis) was comparable to the level of this protein in the cells (0.07% of the total protein).

Animals↗
PubMed1983

An electron-microscope autoradiographic study of transferrin endocytosis by immature erythroid cells.

The receptor-mediated endocytosis of 125I-transferrin by immature erythroid cells was studied using the technique of quantitative electron microscope autoradiography. Morphometric analysis of the grain distribution in erythroid cells from the foetal rat liver revealed that the 125I-transferrin radioactivity was localized mainly to intracellular vesicles (61%) and the cell membrane (25%) after 20 min incubation at 37 degrees C. No activity was found associated with the nucleus or mitochondria and only a small amount with the cytosol (13%). In erythroid cells which possessed a prominent Golgi complex, most of the autoradiographic grains were associated with vesicles located in this region, giving rise to a polar distribution of the 125I-transferrin. Uptake of transferrin was found to be maximal at the basophilic normoblast stage of development and then declined progressively during maturation to the reticulocyte. The kinetics of endocytosis of 125I-transferrin by rabbit reticulocytes was also studied by electron microscope autoradiography. Up to 30% of the cell-bound transferrin was internalized almost immediately upon incubation at 37 degrees C. After 30 sec incubation, 42% of the cell-bound 125I-transferrin was estimated to be internal and this rose to almost 70% at steady state between the binding and release of transferrin after 12 min incubation.

Animals↗