Identification of a Novel Acetyl-CoA Binding Protein (EST1) Which Epigenetically Regulates the Expression of Erythroid-Specific Genes

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4761-4761
Author(s):  
Tohru Fujiwara ◽  
Tsuyoshi Ikura ◽  
Satoshi Ichikawa ◽  
Shinichiro Takahashi ◽  
Kazumichi Furuyama ◽  
...  
Keyword(s):  
Western Blot ◽  
Protein Complex ◽  
Es Cells ◽  
Differential Expression Analysis ◽  
Erythroid Differentiation ◽  
Dominant Negative ◽  
Erythroid Cells ◽  
Wild Type ◽  
Acetyl Coa ◽  
In Erythroid Cells

Abstract (Introduction) Embryonic stem (ES) cells that lack 5-aminolevulinate synthase-2 (ALAS2) gene provide a valuable model in dissecting molecular events in which heme is required during erythroid differentiation. Recently, we identified a novel acetyltransferase-like gene (EST1) through differential expression analysis between wild-type and heme-deficient erythroblasts as a potential downstream target gene of heme (BBRC2006;340:105–110, ASH 2007). EST1 belongs to the GNAT (GCN5-related N-acetyltransferase) superfamily since it contains the highly conserved amino acid residues (motif A), known as acetyl-CoA binding domain. Since the GNAT superfamily contains a wide variety of acetyltransferases with different substrates or with unknown functions, probing how EST1 might be required for biological events in erythroid cells, could be informative. Here, we investigated the role of EST1 during erythroid differentiation. (Methods) EST1 was constitutively expressed using Flag/HA-tagged retroviral vector into mouse erythroleukemia (MEL) cell line. EST1 protein complex was purified by affinity chromatography from nuclear extract of EST1-expessed MEL cells. To obtain dominant-negative EST1-expressing cells, both Arg-62 and Gly-65 within EST1 were substituted to glutamic acid, and similarly transduced into MEL cells. These mutations have been widely applied for abolishment of acetyl-CoA binding activity. For depletion of endogenous EST1, siRNAs specific for EST1 were introduced into Hepa1c1c7 cells (Results) Although recombinant EST1 protein did not have acetylase activity for free histones in vitro (ASH 2007), EST1 protein forms a multimeric protein complex. Western blot analysis using FLAG-eluted polypeptides revealed the presence of GCN5, TRRAP, SPT3 and GATA-1, implying that this protein complex might participate in the transcriptional regulation of erythroid-specific genes. Following EST1 depletion in Hepa1c1c cells, a significant decrease in the acetylation of H3 and a mild decrease in that of H4, were observed by Western blot analyses. Similarly, a significant decrease in the acetylation of H3 and a mild decrease in that of H4 were also observed in dominant-negative than in wild-type EST1-expressing MEL cells. Furthermore, the level of bmajor and ALAS2 mRNA were significantly lower in dominant-negative than in wild-type EST1-expressing MEL cells upon treatment with 1.5% DMSO for both 48h and 72h. We are currently exploring mechanisms of how EST1 participates in the regulation of histone modification in erythroid cells. (Conclusion) EST1 may epigenetically regulate a subset of erythroid-specific genes under control of heme. Further elucidation of the function of the EST1 gene would enhance our understanding of the transcriptional network involving erythroid differentiation.

Analyses of Heme-Regulated Genes during Erythoid Differentiation.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2660-2660
Author(s):  
Tohru Fujiwara ◽  
Yoko Okitsu ◽  
Tsuyoshi Ikura ◽  
Shinichiro Takahashi ◽  
Kazumichi Furuyama ◽  
...  
Keyword(s):  
Es Cells ◽  
Erythroid Differentiation ◽  
Surface Expression ◽  
Nuclear Extract ◽  
Luciferase Assay ◽  
Wild Type ◽  
Acetyl Coa ◽  
Cis Element

Abstract (Introduction) During erythroid differentiation, the level of erythroid-specific genes increases synchronizing with the intracellular heme content. In addition, heme has been shown to play a role in transcription and protein synthesis. Based on these evidences, it is possible that heme widely regulates the expression of erythroid specific genes. With this hypothesis, we compared the gene expression profile between wild-type and heme-deficient erythroblasts generated from wild-type and ALAS2 (−) ES cells in in vitro, and identified 4 heme-regulated erythroid-specific genes (UCP2, CNBP, NuSAP and unknown EST1), (BBRC2006;340:105–110). Among them, unknown EST1 is consisted of 110 a.a. with a conserved acetyl-CoA binding domain, which was characteristic of GNAT (GCN5-related N-acetyltransferase) superfamily. Thus, it is likely that EST1 is a novel acetyltransferase. In the present study, we focused two genes, EST1 and NuSAP, and investigated their function during erythoid differentiation. (Methods) First, the expression and regulation of NuSAP gene during erythroid differentiation was examined. For the expression analysis, in vivo erythroblasts were fractionated according to the surface expression of TER119/CD71, and the level of expression of NuSAP mRNA was examined by quantitative RT-PCR. For the promoter analysis, the promoter region of mouse NuSAP gene was cloned, and the regulatory cis-element was determined by luciferase assay and EMSA. Next, for defining the properties of EST1, EST1 was constitutively expressed using Flag/HA tagged retroviral vector into mouse erythroleukemia (MEL) cell line, and nuclear extract of EST1-expessed MEL cells was purified by affinity chromatography, which was loaded on an SDS/PAGE gel and subjected to electrophoresis. In addition, for in vitro histone acetyltransferase (HAT) assay, free histone and purified EST1 protein were incubated with [3H]acetyl-CoA, and acetyltransferase activity was measured by scintigraphy. (Results) (1) NuSAP mRNA was more significantly abundant in the subset corresponding to immature erythroblasts (TER119+CD71high) than mature erythroblasts (TER119+CD71low), and it was significantly increased in TER119+ cells from in vivo phlebotomized mice compared with control mice. Furthermore, during erythroid maturation of MEL cells by dimethylsulfoxide, NuSAP mRNA was increased at 24–72 hrs. Promoter analyses of NuSAP gene demonstrated that duplicated CCAAT boxes located at −81/−85 and −30/−34 were essential for promoter activity, which was trans-activated by NF-YA. These results suggested that NuSAP might contribute to the expansion of immature erythroblast pool under the control of NF-Y. (2) By the gel electrophoresis, it was revealed that EST1 protein forms a multimeric protein complex. Furthermore, whereas recombinant EST1 protein did not show HAT activity, EST1 complex could acetylate free histones in vitro, suggesting that EST1 might be a component of HAT complex. (Conclusion) The novel functions of EST1 and NuSAP suggest that heme regulates erythroid differentiation by controlling the expression of variety of genes.

Regulation of hemoglobin synthesis and proliferation of differentiating erythroid cells by heme-regulated eIF-2α kinase

Blood ◽  
2000 ◽  
Vol 96 (9) ◽  
pp. 3241-3248 ◽  
Author(s):  
John S. Crosby ◽  
Peter J. Chefalo ◽  
Irene Yeh ◽  
Shong Ying ◽  
Irving M. London ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Erythroid Differentiation ◽  
Dominant Negative ◽  
Erythroid Cells ◽  
3T3 Cells ◽  
Binding Domains ◽  
Inhibition Of Protein Synthesis ◽  
Nih 3T3 ◽  
Hemoglobin Production

Abstract Protein synthesis in reticulocytes depends on the availability of heme. In heme deficiency, inhibition of protein synthesis correlates with the activation of heme-regulated eIF-2α kinase (HRI), which blocks the initiation of protein synthesis by phosphorylating eIF-2α. HRI is a hemoprotein with 2 distinct heme-binding domains. Heme negatively regulates HRI activity by binding directly to HRI. To further study the physiological function of HRI, the wild-type (Wt) HRI and dominant-negative inactive mutants of HRI were expressed by retrovirus-mediated transfer in both non-erythroid NIH 3T3 and mouse erythroleukemic (MEL) cells. Expression of Wt HRI in 3T3 cells resulted in the inhibition of protein synthesis, a loss of proliferation, and eventually cell death. Expression of the inactive HRI mutants had no apparent effect on the growth characteristics or morphology of NIH 3T3 cells. In contrast, expression of 3 dominant-negative inactive mutants of HRI in MEL cells resulted in increased hemoglobin production and increased proliferative capacity of these cells upon dimethyl-sulfoxide induction of erythroid differentiation. These results directly demonstrate the importance of HRI in the regulation of protein synthesis in immature erythroid cells and suggest a role of HRI in the regulation of the numbers of matured erythroid cells.

Identification of Novel Heme-Regulated Genes during Erythroid Differentiation.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1580-1580
Author(s):  
Tohru Fujiwara ◽  
Hideo Harigae ◽  
Shinichiro Takahashi ◽  
Kazumichi Furuyama ◽  
Mitsuo Kaku ◽  
...  
Keyword(s):  
Translational Control ◽  
Promoter Analysis ◽  
Transcription Initiation ◽  
Transmembrane Domain ◽  
Expression Profiles ◽  
Es Cells ◽  
Oxygen Carrier ◽  
Erythroid Differentiation ◽  
Content Increase ◽  
Wild Type

Abstract (Introduction) During erythroid differentiation, a large amount of heme is synthesized for hemoglobin formation. Besides its fundamental role as an oxygen carrier, heme is known to play a key role in transcriptional regulation of certain genes and in translational control of protein synthesis. Since it is known that both the level of erythroid-specific genes and heme content increase together during erythroid differentiation, heme may likely regulate the expression of erythroid-specific genes. It is also possible that heme might regulate even a wider variety of genes than hemoglobin synthesis in cells undergoing erythroid differentiation. With this view in mind, we have searched for novel genes that are under the control of heme. For this purpose, we used the wild-type and heme-deficient erythroblasts generated from the wild-type and ALAS2 (-) ES cells in vitro and compared their gene expression profiles. By this approach, we have identified and reported four novel erythroid-specific genes previously (ASH meeting 2003). In the present study, we have further investigated the mechanisms of heme-mediated regulation of these genes. (Methods) cDNA sequences of these genes were determined by 5′RACE and data-base search. In order to generate erythroblasts containing various amounts of heme, ALAS2 (-) ES subclones, which had been partially rescued by human ALAS2 cDNA driven under the erythroid-specific promoter, were established and induced to undergo erythroid differentiation. Correlation between the level of expression of these genes and intracellular heme content was examined. In addition, the promoter region of one of these genes, NuSAP, was cloned, and its cis-element, through which heme regulates the expression, was determined by promoter analysis and EMSA. (Results) The level of expression of all these genes was closely correlated with intracellular heme content in the partially rescued ALAS2 (-) erythroblasts, indicating that expression of these genes is clearly under the control of heme. The results of 5′-RACE and database search have allowed us to identify that these genes consist of uncoupling protein2 (UCP2), nucleolar spindle-associated protein (NuSAP) and two as yet uncharacterized genes (EST1 and 2). While EST1 consists of 110 a.a. with a GK motif which is characteristic of acetyltransferase, EST2 consists of 972 a.a, with nucleotide sequence indicative of a serine/threonine kinase with a putative transmembrane domain. In order to determine the heme regulatory motif, we also performed the promoter analysis of the NuSAP gene. The results showed that CCAAT box, located 34 nucleotides upstream from the transcription initiation site, was essential for the promoter activity, and the binding activity of a protein complex to this element was enhanced in DMSO-treated MEL cells, suggesting that heme regulates the expression of the NuSAP gene through this motif. (Conclusion) These results demonstrate that expression of a wide variety of genes, which may have quite different functions from hemoglobin formation, may also be regulated by heme in erythroid cells undergoing cell differentiation.

Klf1 Regulatory Networks in Primary Erythroid Cells.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1462-1462
Author(s):  
Michael Tallack ◽  
Thomas Whitington ◽  
Brooke Gardiner ◽  
Eleanor Wainwright ◽  
Janelle Keys ◽  
...  
Keyword(s):  
Regulatory Networks ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Es Cells ◽  
Erythroid Differentiation ◽  
Erythroid Cell ◽  
Gene Promoters ◽  
Erythroid Cells ◽  
Red Cell Membrane ◽  
Sequencing Platform

Abstract Abstract 1462 Poster Board I-485 Klf1/Eklf regulates a diverse suite of genes to direct erythroid cell differentiation from bi-potent progenitors. To determine the local cis-regulatory contexts and transcription factor networks in which Klf1 works, we performed Klf1 ChIP-seq using the SOLiD deep sequencing platform. We mapped more than 10 million unique 35mer tags and found ∼1500 sites in the genome of primary fetal liver erythroid cells are occupied by endogenous Klf1. Many reside within well characterised erythroid gene promoters (e.g. b-globin) or enhancers (e.g. E2f2 intron 1), but some are >100kb from any known gene. We tested a number of Klf1 bound promoter and intragenic sites for activity in erythroid cell lines and zebrafish. Our data suggests Klf1 directly regulates most aspects of terminal erythroid differentiation including synthesis of the hemoglobin tetramer, construction of a deformable red cell membrane and cytoskeleton, bimodal regulation of proliferation, and co-ordination of anti-apoptosis and enucleation pathways. Additionally, we suggest new mechanisms for Klf1 co-operation with other transcription factors such as those of the gata, ets and myb families based on over-representation and spatial constraints of their binding motifs in the vicinity of Klf1-bound promoters and enhancers. Finally, we have identified a group of ∼100 Klf1-occupied sites in fetal liver which overlap with Klf4-occupied sites in ES cells defined by Klf4 ChIP-seq. These sites are associated with genes controlling the cell cycle and proliferation and are Klf4-dependent in skin, gut and ES cells, suggesting a global paradigm for Klfs as regulators of differentiation in many, if not all, cell types. Disclosures No relevant conflicts of interest to declare.

Heme Oxygenase 1 Plays An Unexpected Role During Erythroid Differentiation

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 344-344
Author(s):  
Daniel Garcia Santos ◽  
Matthias Schranzhofer ◽  
José Artur Bogo Chies ◽  
Prem Ponka
Keyword(s):  
Red Blood Cells ◽  
Heme Oxygenase ◽  
Blood Cells ◽  
Erythroid Differentiation ◽  
Heme Biosynthesis ◽  
Erythroid Cell ◽  
Heme Oxygenase 1 ◽  
Erythroid Cells ◽  
Wild Type ◽  
Protein Levels

Abstract Abstract 344 Red blood cells (RBC) are produced at a rate of 2.3 × 106 cells per second by a dynamic and exquisitely regulated process known as erythropoiesis. During this development, RBC precursors synthesize the highest amounts of total organismal heme (75–80%), which is a complex of iron with protoporphyrin IX. Heme is essential for the function of all aerobic cells, but if left unbound to protein, it can promote free radical formation and peroxidation reactions leading to cell damage and tissue injury. Therefore, in order to prevent the accumulation of ‘free' heme, it is imperative that cells maintain a balance of heme biosynthesis and catabolism. Physiologically, the only enzyme capable of degrading heme are heme oxyganase 1 & 2 (HO). Red blood cells contain the majority of heme destined for catabolism; this process takes place in splenic and hepatic macrophages following erythrophagocytosis of senescent RBC. Heme oxygenase, in particular its heme-inducible isoform HO1, has been extensively studied in hepatocytes and many other non-erythroid cells. In contrast, virtually nothing is known about the expression of HO1 in developing RBC. Likewise, it is unknown whether HO1 plays any role in erythroid cell development under physiological or pathophysiological conditions. Using primary erythroid cells isolated from mouse fetal livers (FL), we have shown that HO1 mRNA and protein are expressed in undifferenetiated FL cells and that its levels, somewhat surprisingly, increase during erythropoietin-induced erythroid differentiation. This increase in HO1 can be prevented by succinylacetone (SA), an inhibitor of heme synthesis that blocks 5-aminolevulinic acid dehydratase, the second enzyme in the heme biosynthesis pathway. Moreover, we have found that down-regulation of HO1 via siRNA increases globin protein levels in DMSO-induced murine erythroleukemic (MEL) cells. Similarly, compared to wild type mice, FL cells isolated from HO1 knockout mice (FL/HO1−/−) exhibited increased globin and transferrin receptor levels and a decrease in ferritin levels when induced for differentiation with erythropoietin. Following induction, compared to wild type cells, FL/HO1−/− cells showed increased iron uptake and its incorporation into heme. We therefore conclude that the normal hemoglobinization rate appears to require HO1. On the other hand, MEL cells engineered to overexpress HO1 displayed reduced globin mRNA and protein levels when induced to differentiate. This finding suggests that HO1 could play a role in some pathophysiological conditions such as unbalanced globin synthesis in thalassemias. Disclosures: No relevant conflicts of interest to declare.

GATA-1 Forms Distinct Activating and Repressive Complexes in Erythroid Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 356-356
Author(s):  
John Strouboulis ◽  
Patrick Rodriguez ◽  
Edgar Bonte ◽  
Jeroen Krijgsveld ◽  
Katarzyna Kolodziej ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Chromatin Remodeling ◽  
Gene Activation ◽  
Erythroid Differentiation ◽  
Specific Gene ◽  
Erythroid Cells ◽  
In Erythroid Cells

Abstract GATA-1 is a key transcription factor essential for the differentiation of the erythroid, megakaryocytic and eosinophilic lineages. GATA-1 functions in erythropoiesis involve lineage-specific gene activation and repression of early hematopoietic transcription programs. GATA-1 is known to interact with other transcription factors, such as FOG-1, TAL-1 and Sp1 and also with CBP/p300 and the SWI/SNF chromatin remodeling complex in vitro. Despite this information the molecular basis of its essential functions in erythropoiesis remains unclear. We show here that GATA-1 is mostly present in a high (> 670kDa) molecular weight complex that appears to be dynamic during erythroid differentiation. In order to characterize the GATA-1 complex(es) from erythroid cells, we employed an in vivo biotinylation tagging approach in mouse erythroleukemic (MEL) cells1. Briefly, this involved the fusion of a small (23aa) peptide tag to GATA-1 and its specific, efficient biotinylation by the bacterial BirA biotin ligase which is co-expressed with tagged GATA-1 in MEL cells. Nuclear extracts expressing biotinylated tagged GATA-1 were bound directly to streptavidin beads and co-purifying proteins were identified by mass spectrometry. In addition to the known GATA-1-interacting transcription factors FOG-1, TAL-1 and Ldb-1, we describe novel interactions with the essential hematopoietic transcription factor Gfi-1b and the chromatin remodeling complexes MeCP1 and ACF/WCRF. Significantly, GATA-1 interaction with the repressive MeCP1 complex requires FOG-1. We also show in erythroid cells that GATA-1, FOG-1 and MeCP1 are stably bound to repressed genes representing early hematopoietic (e.g. GATA-2) or alternative lineage-specific (e.g. eosinophilic) transcription programs, whereas the GATA-1/Gfi1b complex is bound to repressed genes involved in cell proliferation. In contrast, GATA-1 and TAL-1 are bound to the active erythroid-specific EKLF gene. Our findings on GATA-1 complexes provide novel insight as to the critical roles that GATA-1 plays in many aspects of erythropoiesis by revealing the GATA-1 partners in the execution of specific functions.

A Differentiation Block in Erythroid Cells Lacking Erythroid Krupple-Like Factor (EKLF).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 526-526
Author(s):  
Patrick G. Gallagher ◽  
Murat O. Arcasoy ◽  
Serena E. Vayda ◽  
Holly K. Dressman ◽  
James J. Bieker ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Flow Cytometry ◽  
Fetal Liver ◽  
Erythroid Differentiation ◽  
Erythroid Cells ◽  
Wild Type ◽  
Fetal Liver Cells ◽  
Differentiation Block ◽  
Microarray Analyses ◽  
Deficient Mice

Abstract Mice deficient in the erythroid specific zinc-finger transcription factor EKLF die ~d14-15 of gestation of severe anemia, attributed to decreased expression of β-globin. The morphology of fetal-liver derived erythroid cells in EKLF-deficient mice does not mimic that seen in thalassemia, but instead shows hemolysis with uniform, nucleated erythroid progenitor cells. This has led to the hypothesis that a block in erythroid differentiation contributes to the anemia in EKLF-deficient mice. To address this, we performed microarray analyses with Affymetrix GeneChip Mouse Genome 430 2.0 arrays and RNA from d13.5 fetal livers of wild type (WT) and EKLF-deficient mice. Three independent EKLF +/+ and −/− RNA samples were analyzed. Numerous genes were down regulated including AHSP, pyruvate kinase, ankyrin, β spectrin and band 3. Verification of reduced expression of selected genes demonstrated that expression levels of many genes identified as down regulated via microarray analyses were minimally reduced in EKLF −/− RNA (<20%) compared to normal (Rh 30, protein 4.2, protein 4.9, p55, AQP1, and ALAS-E). Flow cytometry of WT d14.5 fetal liver cells using TER 119 and CD71 was performed. In WT fetal livers, this identifies 5 populations, designated R1-R5, with R1/R2 composed of primitive progenitors and proerythroblasts and R3, R4, and R5 composed of more mature erythroblasts (Blood102:3938, 2003). In EKLF −/− fetal livers, R3, R4, and R5, populations involved in terminal erythroid differentiation, were completely absent, suggesting many of the genes identified by microarray analyses were differentially expressed because of a bias introduced by a differentiation block to more mature erythroid cells. Confirming this hypothesis, we demonstrated that genes with <20% difference in expression between WT and EKLF-deficient fetal liver mRNA had 4-fold or higher levels in wild type R3+R4+R5 RNA compared to R1+R2 RNA. To better understand how differentially expressed genes were integrated into specific regulatory and signaling pathway networks, we used Ingenuity Pathway Analysis. A subset of focus genes incorporated into a biological network with highly a significant scores (>40) was generated containing 35 focus genes. The biological function of this network involved cell cycle and DNA replication. At the central nodes of this network were E2F1 and E2F2, transcription factors involved in cell cycle control. Cell cycle analysis demonstrated that EKLF-deficient R1 cells exhibited a significant delay exiting G0+G1 and entering S phase and both R1 and R2 cells exhibited a defect in exiting S and entering G2+M. Colony assays with R1 and R2 cells revealed that EKLF-deficient fetal liver cells had decreased frequency of CFU-E, but similar absolute numbers of CFU-E as WT. As predicted by the cell cycle defect, EKLF−/− FL cells were severely (~10 fold) deficient in their ability to generate BFU-E. Flow cytometry with annexin V revealed no difference between WT and EKLF-deficient cells indicated that apoptosis was not contributing to the differentiation block. These results support the hypothesis that the failure of definitive erythropoiesis in EKLF deficient mice is due to decreased expression of many erythroid genes involved in erythroid differentiation, stabilization of α-globin protein, membrane stability, and glycolysis, not simply decreased transcription of the β-globin gene.

A Mouse Model for Diamond-Blackfan Anemia Demonstrates a Dominant Negative Effect of a Point Mutation in the RPS19 Gene

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 38-38 ◽  
Author(s):  
Emily E. Devlin ◽  
Lydie DaCosta ◽  
Mohandas Narla ◽  
Gene Elliott ◽  
David M. Bodine
Keyword(s):  
Mouse Model ◽  
Macrocytic Anemia ◽  
Dominant Negative ◽  
Poly I:C ◽  
Dominant Negative Effect ◽  
Erythroid Cells ◽  
Wild Type ◽  
Erythroid Progenitors ◽  
Diamond Blackfan Anemia ◽  
Negative Effect

Abstract Diamond-Blackfan Anemia (DBA) is associated with mutations in several ribosomal protein genes, including Ribosomal Protein S19 (RPS19), which is mutated in approximately 25% of patients. Most RPS19 mutations are deletions of all or part of the RPS19 gene and are predicted to cause DBA by a haploinsufficiency mechanism. However, approximately 30% of RPS19 mutations are missense mutations in the RPS19 coding sequence, which we hypothesize act through a dominant negative mechanism. To test for a dominant negative effect, we generated a transgenic mouse model expressing a common and penetrant mutation at codon 62 that replaces an Arginine with a Tryptophan (R62W). The constructs contain the ubiquitous actin promoter linked to the wild-type or R62W human RPS19 cDNA followed by the 3′ region of the Gamma globin gene to provide RNA stability and intron splicing to facilitate RNA transport to the cytoplasm. The constructs are flanked by chicken HS4 barrier elements to ensure transgene expression regardless of the location in the genome. Eight lines of wild-type RPS19 transgenic mice were fertile, expressed RPS19 in all tissues, and had normal hematology. Twelve RPS19R62W founder animals were generated, six of which died before they reached 2 months of age. Two of these animals were analyzed and found to have a macrocytic anemia. None of the other 6 founder animals transmitted the RPS19R62W transgene to F1 pups or d13.5 embryos, suggesting either that the RPS19R62W transgene was not present in the germ line and/or that expression of the RPS19R62W protein may cause early lethality. Supporting this hypothesis, embryonic stem cells (ES) expressing wild-type RPS19 were viable, while ES cells expressing RPS19R62W were not viable. To circumvent potential embryonic lethality, we generated conditional RPS19R62W transgenic mice with stop sequences flanked by lox P sites inserted between the promoter and the RPS19 gene. In the presence of Cre recombinase, lox P sites are combined, excising the sequences between them. Adult mice carrying the conditional RPS19R62W transgene and the interferon inducible Mx1-Cre gene were treated with poly (I:C) to induce excision of the stop sequence. Following poly (I:C) administration, hematocrits dropped significantly in RPS19R62W/Mx1-Cre animals compared to controls, but rebounded to normal within two weeks, due to incomplete stop sequence excision and expansion of unexcised cells in the bone marrow. Colony-forming cell assays indicate that RPS19R62W-expressing bone marrow contains 2 to 3 fold fewer BFU-E and CFU-E (p<0.05) and similar numbers of CFU-GM compared to wild-type animals. The decrease in erythroid progenitors was variable, indicating different levels of excision as well as penetrance. When RPS19R62W mice were crossed to Prion-Cre mice, which express Cre at the early embryonic stage, small, anemic d13.5 embryos and occasional small, adult animals with macrocytic anemia were observed. Day 13.5 RPS19R62W/Prion-Cre fetal livers had reduced overall numbers of erythroid cells, and reduced numbers of BFU-E and CFU-E. The decrease in erythroid progenitors was variable, especially in the line carrying 1 copy of the transgene compared to the line carrying 4 copies of the transgene. FACS analysis of d13.5 fetal liver and adult RPS19R62W/Prion-Cre erythroid cells revealed a relative accumulation of erythroid progenitor cells and a relative decrease in the number of terminally differentiating erythroid cells, suggesting that terminal erythroid differentiation is delayed. These findings are consistent with the reticulocytopenia observed in adult RPS19R62W/Prion-Cre mice. In summary we have successfully generated a mouse model of DBA caused by ectopic expression of mutant human RPS19R62W. The development of a severe anemia following conditional expression of mutant RPS19 suggests that the R62W missense mutation has a dominant negative effect that delays erythropoiesis causing an overall reduction in erythroid cells.

Elucidation of the Role of LMO2 (LIM-only protein 2) in Erythroid Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3443-3443
Author(s):  
AI Inoue ◽  
Tohru Fujiwara ◽  
Yoko Okitsu ◽  
Noriko Fukuhara ◽  
Yasushi Onishi ◽  
...  
Keyword(s):  
Dna Binding ◽  
Cord Blood ◽  
Western Blotting ◽  
Target Genes ◽  
K562 Cells ◽  
Erythroid Differentiation ◽  
Dependent Manner ◽  
Erythroid Cells ◽  
In Erythroid Cells

Abstract Abstract 3443 Background: Developmental control mechanisms often utilize multimeric complexes containing transcription factors, coregulators, and additional non-DNA binding components. It is challenging to ascertain how such components contribute to complex function at endogenous loci. LMO2 (LIM-only protein 2) is a non-DNA binding transcriptional coregulator, and is an important regulator of hematopoietic stem cell development and erythropoiesis, as mice lacking this gene show defects in blood formation as well as fetal erythropoiesis (Warren et al. Cell. 1994). In the context of erythropoiesis, LMO2 has been demonstrated to be a part of multimetric complex, including master regulators of hematopoiesis (GATA-1 and SCL/TAL1), chromatin looping factor LDB1 and hematopoietic corepressor ETO2 (referred as GATA-SCL/TAL1 complex). As LMO2 controls hematopoiesis, its dysregulation is leukemogenic, and its influence on GATA factor function is still not evident, we investigated here the transcriptional regulatory mechanism via LMO2 in erythroid cells. Methods: For LMO2 knockdown, anti-LMO2 siRNA (Thermo Scientific Dharmacon) and pGIPZ lentiviral shRNAmir system (Open Biosystems) were used. Western blotting and Quantitative ChIP analysis were performed using antibodies for GATA-1, LMO2 (abcam), GATA-2, TAL1 and LDB1 (Santa Cruz). To obtain human primary erythroblasts, CD34-positive cells isolated from cord blood were induced in liquid suspension culture. For transcription profiling, human whole expression array was used (Agilent), and the data was analyzed with GeneSpring GX software. To induce erythroid differentiation of K562 cells, hemin was treated at a concentration of 30 uM for 24h. Results: siRNA-mediated LMO2 knockdown in hemin-treated K562 cells results in significantly decreased ratio of benzidine-staining positive cells, suggesting that LMO2 has an important role in the erythroid differentiation of K562 cells. Next, we conducted microarray analysis to characterize LMO2 target gene ensemble in K562 cells. In contrast to the predominantly repressive role of LMO2 in murine G1E-ER-GATA-1 cells (Fujiwara et al. PNAS. 2010), the analyses (n = 2) demonstrated that 177 and 78 genes were upregulated and downregulated (>1.5-fold), respectively, in the LMO2-knockdowned K562 cells. Downregulated gene ensemble contained prototypical erythroid genes such as HBB and SLC4A1 (encodes erythrocyte membrane protein band 3). To test what percentages of LMO2-regulated genes could be direct target genes of GATA-1 in K562 cells, we merged the microarray results with ChIP-seq profile (n= 5,749, Fujiwara et al. Mol Cell. 2009), and demonstrated that 26.4% and 23.1% of upregulated and downregulated genes, respectively, contained significant GATA-1 peaks in their loci. Furthermore, whereas LMO2 knockdown in K562 cells did not affect the expression of GATA-1, GATA-2 and SCL/TAL1 based on quantitative RT-PCR as well as Western blotting, the knockdown resulted in the significantly decreased chromatin occupancy of GATA-1, GATA-2, SCL/TAL1 and LDB1 at beta-globin locus control region and SLC4A1 locus. We subsequently analyzed the consequences of LMO2 knockdown in primary erythroblasts. Endogeneous LMO2 expression was upregulated along with the differentiation of cord blood cell-derived primary erythroblasts. shRNA-mediated knockdown of LMO2 in primary erythroblasts resulted in significant downregulation of HBB, HBA and SLC4A1. Conclusion: Our results suggest that LMO2 contributes to the expression of GATA-1 target genes in a context-dependent manner, through modulating the assembly of the components of GATA-SCL/TAL1 complex at endogeneous loci. Disclosures: No relevant conflicts of interest to declare.

Functional Analysis of FOXO3A Involved in Erythroid Differentiation

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4731-4731
Author(s):  
Hai Wang ◽  
Yadong Yang ◽  
Hongzhu QU ◽  
Xiuyan Ruan ◽  
Zhaojun Zhang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Conflicts Of Interest ◽  
Es Cells ◽  
Embryonic Stem ◽  
Erythroid Differentiation ◽  
Expression Level ◽  
Homologous Gene ◽  
Erythroid Cells ◽  
Hematopoietic Stem ◽  
Central Node

Abstract Abstract 4731 FOX (Forkhead box) proteins are a family of transcription factors that emerged as playing an important role in the embryonic development, cell cycle, carbohydrate and fatty acid metabolism and immune response. It was found that FOXO3A (also known as FOXO3) involved in erythroid differentiation, yet the mechanism for regulating hematopoietic stem cells (HSCs) differentiation is unknown. We analyzed the dynamics of genome-wide transcriptome (mRNA-Seq) of human undifferentiated embryonic stem cells (HESC), erythroid cells derived from ES cells (ESER), human fetal erythroid liver cells (FLER) and peripheral CD34+derived erythroid cells (PBER) using high throughput sequencing technology. The transcriptome analysis showed that FOXO3 was barely expression in HESC while was observably up-regulated in ESER. However, FOXO3 was down-regulated in FLER and PBER compare with ESER, the erythroid cells at early developmental stage. We presumed that FOXO3 plays an important role in primitive erythropoiesis and built up the interactions network in which FOXO3 acts as a central node by Gene Ontology (GO), correlation analysis and Ingenuity Pathways Analysis (IPA). In addition, we analyzed the profiles of histone methylation in the four types of cells by ChIP-Seq to study the chromatin conformation in the vicinity of FOXO3. More histone 3 lysine 4 (H3K4) trimethylation was found near the promoter region of FOXO3 in ESER compared with the other cells, which is coincided with the mRNA-seq results. We performed a series of experiment to identify the roles of FOXO3 in regulating erythroid differentiation. The results showed that the expression level of ε and γ globin were up-regulated in FOXO3-over-expressed 293T and Hela cells and the expression level of FOXO1 and CAT in predicted network were increased by quantitative real-time PCR detection. In addition, when FOXO3 knocked down in K562 cells, the expression level of ε and γ globin were down-regulated. The expression level of CAT, BCL2L1 and other factors in predicted network, were also decreased. These results indicate FOXO3 plays an important role in globin expression and identify the credibility of our predicted networks in which FOXO3 acts as a central node. FOXO3 binding sites (GTAAACA or ATAAACA) were predicted on the upstream of CAT and BCL2L1. We are trying to prove CAT or BCL2L1 is a direct FOXO3 target in vitro and in vivo. In conclusion, we have demonstrated FOXO3 plays a key role in erythroid differentiation and globin expression. We will further determine the enriched profiles of FOXO3 by ChIP-seq in HESC, ESER, FLER and PBER to find more targets of FOXO3. Since the zebrafish is a powerful model system for investigating vertebrate hematopoiesis. We will identify the role of Foxo3b, the homologous gene of human FOXO3, in erythroid differentiation and study the dynamic transcriptomes of Foxo3b morphants in zebrafish. We are trying to make a whole picture to elaborate the molecular mechanism of FOXO3 involved in regulation of erythroid differentiation. Disclosures: No relevant conflicts of interest to declare.

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