Human Epo Gene Research Articles

Asialo-rhuEPO as a Potential Neuroprotectant for Ischemic Stroke Treatment.

Neuroprotective drugs to protect the brain against cerebral ischemia and reperfusion (I/R) injury are urgently needed. Mammalian cell-produced recombinant human erythropoietin (rhuEPOM) has been demonstrated to have excellent neuroprotective functions in preclinical studies, but its neuroprotective properties could not be consistently translated in clinical trials. The clinical failure of rhuEPOM was thought to be mainly due to its erythropoietic activity-associated side effects. To exploit its tissue-protective property, various EPO derivatives with tissue-protective function only have been developed. Among them, asialo-rhuEPO, lacking terminal sialic acid residues, was shown to be neuroprotective but non-erythropoietic. Asialo-rhuEPO can be prepared by enzymatic removal of sialic acid residues from rhuEPOM (asialo-rhuEPOE) or by expressing human EPO gene in glycoengineered transgenic plants (asialo-rhuEPOP). Both types of asialo-rhuEPO, like rhuEPOM, displayed excellent neuroprotective effects by regulating multiple cellular pathways in cerebral I/R animal models. In this review, we describe the structure and properties of EPO and asialo-rhuEPO, summarize the progress on neuroprotective studies of asialo-rhuEPO and rhuEPOM, discuss potential reasons for the clinical failure of rhuEPOM with acute ischemic stroke patients, and advocate future studies needed to develop asialo-rhuEPO as a multimodal neuroprotectant for ischemic stroke treatment.

Integration of CRISPR/Cas12a and Multiplexed RPA for Fast Detection of Gene Doping.

Fast and on-site detection is important for an effective antigene-doping strategy. However, the current gene doping (GD) evaluation methods require sophisticated instruments and laborious procedures, limiting their field applications. This study proposes a CRISPR/Cas12a-based detection platform (termed CasGDP) combining CRISPR/Cas12a and multiplexed Recombinase Polymerase Amplification (RPA) for rapid evaluation of GD. CasGDP showed high specificity for identifying the putative target genes such as EPO, IGF-1, and GH-1. By using fluorescence as the readout, the method achieved a limit-of-detection of 0.1 nM and 1 aM for unamplified and amplified target plasmids, respectively. Additionally, an in vitro GD cell model was successfully established with the human EPO gene (hEPO). The results indicated that the hEPO gene transfection promoted the hEPO protein expression. Furthermore, trace amounts of EPO transgene spiked in human serum were efficiently measured by CasGDP with fluorescence- and lateral flow device (LFD)-based readouts in 40 min. Finally, we designed a multiplexed microfluidic device and realized simultaneous detection of the three transgenes via LFD embedded in the device. To our knowledge, this is the first work that combines the CRISPR-based system and multiplexed RPA for GD detection. We anticipate CasGDP to be widely used as a rapid, sensitive, and robust tool for GD evaluation.

Proof of Gene Doping in a Mouse Model with a Human Erythropoietin Gene Transferred Using an Adenoviral Vector.

Despite the World Anti-Doping Agency (WADA) ban on gene doping in the context of advancements in gene therapy, the risk of EPO gene-based doping among athletes is still present. To address this and similar risks, gene-doping tests are being developed in doping control laboratories worldwide. In this regard, the present study was performed with two objectives: to develop a robust gene-doping mouse model with the human EPO gene (hEPO) transferred using recombinant adenovirus (rAdV) as a vector and to develop a detection method to identify gene doping by using this model. The rAdV including the hEPO gene was injected intravenously to transfer the gene to the liver. After injection, the mice showed significantly increased whole-blood red blood cell counts and increased expression of hematopoietic marker genes in the spleen, indicating successful development of the gene-doping model. Next, direct and potentially indirect proof of gene doping were evaluated in whole-blood DNA and RNA by using a quantitative PCR assay and RNA sequencing. Proof of doping could be detected in DNA and RNA samples from one drop of whole blood for approximately a month; furthermore, the overall RNA expression profiles showed significant changes, allowing advanced detection of hEPO gene doping.

Regulated Basal, Inducible, and Tissue-Specific Human Erythropoietin Gene Expression in Transgenic Mice Requires Multiple cis DNA Sequences

Erythropoietin (Epo) gene expression in kidney and liver is inducible by anemia. To localize the sequences necessary for regulated expression of the Epo gene, we constructed transgenic mice containing five human Epo gene constructs and examined Epo expression under basal conditions and with anemia. Mice containing the Epo gene with 0.3 kb of 5' flanking sequence, 0.7 kb of 3' flanking sequence, and either all introns or only intron I alone were polycythemic, had Epo expression in various tissues (including non-Epo-producing tissues), and induction only in liver. In contrast, mice containing the Epo gene with 8.5 kb of 3' flanking sequence and either 9.5 or 22 kb of 5' flanking sequence had basal expression at low levels in appropriate tissues and were less likely to be markedly polycythemic. Mice with the smaller of these two constructs had induction only in the liver, whereas those with the larger construct had induction in the kidney and liver. These studies indicate that sequences sufficient for induction in the liver are located in close proximity to the Epo gene, including the immediate 5' and 3' flanking sequence and the first intron. They also indicate that sequences required for induction in the kidney are located more than 9.5 kb 5' to the gene. Furthermore, comparison of these and prior transgenic studies suggest that sequences that limit the basal expression of the Epo gene are located downstream of the gene. We conclude that multiple cis DNA sequences are required for regulated Epo gene expression.

Erythropoietin promotes survival and regeneration of insect neurons in vivo and in vitro

In addition to its function as a regulator of hematopoiesis, the cytokine erythropoietin (Epo) initiates adaptive cellular responses to both moderate environmental challenges and tissue damaging insults in various non-hematopoietic mammalian tissues. Epo's neuroprotective and neuroregenerative functions mediated through janus kinases (JAK)/signal transducers and activators of transcription (STAT) transduction pathways and regulation of Epo and Epo receptor expression in the nervous system by hypoxia inducible factor (HIF) have been documented in a variety of in vitro and in vivo studies and homologs of the human Epo gene are present in fish, amphibians and mammals. The present study reproduces the hallmarks of Epo-mediated mammalian neuroprotection in the grasshopper nervous system. Recombinant human Epo (rhEpo) increases the survival of dissociated grasshopper brain neurons under normoxic and hypoxic conditions and promotes the regeneration of neurites in vitro. In addition, reestablishment of sound source localization after unilateral tympanic nerve crush injury was accelerated and more complete after application of rhEpo, demonstrating in vivo support of auditory receptor cell axon regeneration. Immunoblots of central nervous tissue extracts from mouse, grasshopper, crayfish and leech labeled protein bands of ∼38 kDa, fitting to the molecular weight of Epo reported in earlier studies. These results indicate that a ligand/receptor system that shares structural and functional similarities with mammalian Epo and Epo receptor exerts neuroprotective and neuroregenerative effects in insects. With both upstream (HIF system) and downstream (JAK/STAT pathway) elements of the mammalian Epo system being present in insects and other invertebrates, Epo-like signaling involved in tissue protection appears to be an ancient beneficial function shared by vertebrates and invertebrates.

Characterization of Tissue-Specific HIF-1 and HIF-2 Regulatory Elements of the Erythropoietin Gene

Hypoxia regulates erythropoiesis and other essential processes via hypoxia-inducible transcription factors (HIFs). HIFs are heterodimers that consist of an α subunit (3 isotypes with significant homology; HIF-1α, HIF-2α, HIF-3α), and a common b-subunit; HIF-1 and HIF-2, in some instances exhibiting tissue- and gene-specific gene regulation. Erythropoietin (EPO) was the first identified HIF-1 target gene with the defined HIF-1 binding sequence. However, subsequent works suggested that HIF-2 also regulates EPO transcription and that there are other regulatory elements of EPO gene (i.e. Kidney Inducible Element KIE, Negative Regulatory Element NRE, and Negative Regulatory Liver specific Element NRLE). In silico analysis of the human EPO genome found two additional potential HIF-binding elements in the KIE and NRE regions. The comparative analysis of phylogenically conserved sequences of human, mouse, dog, and rat Epo genes further refined these mouse Epo gene HIF-binding elements as mKIE, mNRE1, mNRE2, and mNRLE2.We treated mice in hypoxia chamber (8% O2) and monitored changes of Epo mRNA levels in liver, kidney, brain, spleen, and bone marrow. All tested tissues increased Epo transcription during hypoxia. Bone marrow, spleen, kidney, and brain showed a peak of induction of Epo transcript at 3 hours of hypoxia treatment, while liver reached the highest level at 6 hours. Mice were sacrificed and organs were harvested, and in vivo chromatin immunoprecipitation (ChIPs) was performed with antibodies against HIF-1α and HIF- 2α and tissue-specific binding regions were defined. The results from these studies are summarized below.HIF-1mKIErnNREmNRE2mNRLE2NormHypNormHypNormHypNormHypLiver−+−−+−??Kidney−+−−+−+−Brain−+−−−+−+BM−+−−−−−+Splsen−+−−−−−+HIF-2mKIEmNREmNRE2mNRLE2NormHypNormHypNormHypNormHypLiver−+−−−+−+Kidney+−−−+−??Brain−−−−−−−+BM−−−−−−+−Spleen−+−−−−−+“+” denotes presence and “-” absence of binding of HIF-1 and HIF-2, “?” – indicates inconclusive results. “Norm” - normoxia, “Hyp” - hypoxia.In conclusion, we demonstrate the differential hypoxia-induced binding of HIF-1 and HIF-2 at different HIF binding elements in the tissues known to express Epo. Further studies will be required to define the function of these HIF-1 and HIF-2 binding elements in tissue specific Epo expression and their role in health and disease.

Recombinant EPO production points the nephrologist should know

Why should the nephrologist be familiar with EPOs and biosimilars? The administration of recombinant human erythropoietin (rhEPO) and its analogues provides enormous benefit in the prevention and reversal of anaemia in chronic kidney disease (CKD), malignancy and AIDS, and it supports autologous blood collection. rhEPO-type substances represent the largest market of a class of biopharmaceuticals, with global estimated sales of � 10 10 euro per annum. The key process patents for the first-generation of rhEPOs have expired in the EU and other regions, opening the market for biosimilar follow-on products. In addition, confronted with imminent patent expiration, the manufacturers of the innovative compounds have developed second-generation products with improved pharmacokinetic properties. Thus, the clinician will be faced with a panoply of different erythropoiesisstimulating biopharmaceuticals, and it will be important for him to be familiar with their molecular biology. The complexities of EPO formation in mammalian cells rhEPO is produced with the use of cells transfected with either the human EPO gene or EPO cDNA (the coding sequence of the gene) linked to an expression vector (‘recombinant DNA’), which are integrated into the genome of the host cell and stably expressed over time. The present therapeutic rhEPO preparations are manufactured in mammalian host cells, because EPO is a complex glycoprotein of 165 amino acids to which four glycans (carbohydrate side chains) are attached. Transfected bacteria such as Escherichia coli are useful as hosts for the production of non-glycosylated recombinant proteins (Figure 1). Yeast and filamentous fungi glycosylate proteins differently from mammalian cells, adding for example high mannose-type N-glycans. The synthesis of human N-glycans is a complicated process. It starts in the cytosol with the addition of distinct sugar molecules to dolichol, from which the glycan is transferred to the growing polypeptide in the endoplasmic reticulum. After several sugars have been trimmed from the protein, it is folded and moved to the Golgi complex, where further mannose elimination occurs before N-acetylglucosamine, galactose and sialic acid (N-acetylneuraminic acid) are finally added.

Development of soil amoeba Dictyostelium discoideum as an expression system for recombinant human erythropoietin

Erythropoietin (EPO) is the most important biopharmaceutical product at present being produced by recombinant DNA technology from mammalian cell lines. Other available expression systems have not been useful in producing this protein due to the requirement of N-glycosylation for in vivo activity. In order to develop an alternative expression system, the human epo gene was expressed in the cellular slime mold Dictyostelium discoideum. The 2.43 kbp epo gene from the mammalian expression vector was cloned in the Dictyostelium expression cassette and used to transform cells. Positive clones were selected on the basis of antibiotic resistance. The clones were screened for the presence of the transgene. The copies of the gene inserted in the genome were identified and the transcript too was ascertained. The protein was identified by immuno-blotting and appears to be glycosylated though differently from that of humans or CHO cell lines. It has not yet been tested in bioassay.

The effect of dissolved oxygen on the production and the glycosylation profile of recombinant human erythropoietin produced from CHO cells

Human recombinant erythropoietin (rHuEPO) was produced from Chinese hamster ovary (CHO) cells transfected with the human EPO gene. The cells were grown in batch cultures in controlled bioreactors in which the set-points for dissolved oxygen varied between 3% and 200%. The cell-specific growth rate and final cell yield was significantly lower under hyperoxic conditions (200% DO). However, there was no significant difference in growth rates at other oxygen levels compared to control cultures run under a normoxic condition (50% DO). The specific productivity of EPO was significantly lower at a DO set-point of 3% and 200% but maintained a consistently high value between 10% to 100% DO. The EPO produced under all conditions as analyzed by two-dimensional electrophoresis showed a molecular weight range of 33 to 37 kDa and a low isoelectric point range of 3.5 to 5.0. This corresponds to a highly glycosylated and sialylated protein with a profile showing at least seven distinct isoforms. The glycan pattern of isolated samples of EPO was analyzed by weak anion exchange (WAX) HPLC and by normal-phase HPLC incorporating sequential digestion with exoglycosidase arrays. Assigned structures were confirmed by mass spectrometry (MALDI-MS). The most prominent glycan structures were core fucosylated tetranntenary with variable sialylation. However, significant biantennary, triantennary, and non-fucosylated glycans were also identified. Detailed analysis of these glycan structures produced under variable dissolved oxygen levels did not show consistently significant variations except for the ratio of fucosylated to non-fucosylated isoforms. Maximum core fucosylation (80%) was observed at 50% and 100% DO, whereas higher or lower DO levels resulted in reduced fucosylation. This observation of lower fucosylation at high or low DO levels is consistent with previous data reported for glycoprotein production in insect cells.

742. Human Artificial Chromosome (HAC) Vector Provides Long-Term Therapeutic Transgene Expression in Normal Human Primary Fibroblasts

Top of pageAbstract Human artificial chromosomes (HACs) are segregating freely from host chromosomes through a set of cell divisions. Accordingly, the host genome is not disrupted and the expression of the transgene could be sustained for a prolonged period without suffering the effects of its surrounding sequence on the host genome. These are the ideal properties required for vectors in gene therapy, and therefore HACs are potentially useful to ensure both safety and duration of gene expression in therapeutic gene delivery. We constructed a novel human chromosome 21-derived HAC (21|[Delta]|pqHAC) vector, which devoid of most expressed genes by telomere truncation at the genomic regions proximal to the centromere in both p and q arms, and inserted human erythropoietin (EPO) gene, which is a growth factor for erythroid cells and widely used for the clinical treatment of anemia in renal insufficiency, into the HAC (EPO-21|[Delta]|pqHAC) as a model of therapeutic transgenes. Although low transfer efficiency of intact HACs to the cells has hampered the studies using normal human primary cells, the major targets for ex vivo gene therapy, we successfully demonstrated the introduction of EPO-21|[Delta]|pqHAC vector into normal primary human fibroblasts (hPFs) with micro cell-mediated chromosome transfer (MMCT). However, the mitotic stability of EPO-21|[Delta]|pqHAC vector in normal hPFs and the growth ability of the resultant hPF clones to obtain graft cells for transplantation remained to be elucidated. Here, we studied the hPF clones harboring the EPO-21|[Delta]|pqHAC vector cytogenetically and demonstrated that the structurally defined, extra artificial chromosome was highly maintained in normal hPFs under non-selective condition at a constant copy number mostly in a single copy per cell without accompanying aberration of host chromosomes. Mitotic-loss rates were determined, and the level of stability of EPO-21|[Delta]|pqHAC vector was comparable with those reported for the other top-down and bottom-up artificial chromosomes in human fibro-sarcoma cell line HT1080 cells. These hPF clones proliferated from a single colony up to 3.8x107 cells and then their growth stopped, suggesting that cell senescence occurred and the introduction of the EPO-21|[Delta]|pqHAC vector did not cause immortalization. We also showed the long-term expression of human epo gene in the hPFs carrying the EPO-21|[Delta]|pqHAC vector. In conclusion, this study shows the potential application of the 21|[Delta]|pqHAC vector in hormone-replacement gene therapy, which might ensure safety with no lesion of host chromosomes and provides long-term therapeutic transgene expression. This also implies that utilization of the HAC vector offers novel options for ex vivo gene therapy.

Overexpression of human erythropoietin (EPO) affects plant morphologies: retarded vegetative growth in tobacco and male sterility in tobacco and Arabidopsis

Erythropoietin (EPO) is a glycoprotein used for curing human anemia by regulating the differentiation of erythroid progenitors and the production of red blood cells. To examine the expression of recombinant EPO in plants, pPEV-EP21, in which human epo cDNA under the control of the CaMV 35S promoter, was introduced into tobacco and Arabidopsis via Agrobacterium tumefaciens-mediated transformation. The RNA expression level of epo in the transgenic lines was initially estimated by Northern blot analysis. Two transgenic lines, which exhibited a high expression level of epo mRNA determined by Northern analysis, were chosen for Western blot analysis to examine the production of EPO proteins. Those two lines, EP21-12 and EP21-14, revealed detectable bands on the immunoblot. Interestingly, constitutive expression of the human epo gene affected the morphologies in transgenic plants such that vegetative growth of transgenic tobacco was retarded, and male sterility was induced in transgenic tobacco and Arabidopsis.

Autocrine stimulation by erythropoietin in transgenic mice results in erythroid proliferation without neoplastic transformation

Erythropoietin (Epo) autocrine stimulation has been implicated in erythroleukemia. To develop a model of Epo autocrine stimulation, we made transgenic mice using a construct that linked the human Epo gene to an erythroid-specific regulatory element, designated 5′HS-2, from the human β-globin locus control region. We hypothesized that Epo gene expression would be targeted to erythroid cells in these mice, resulting in autocrine stimulation of erythroid progenitor cell growth in culture, and that chronic autocrine Epo stimulation would result in erythroleukemia. Transgenic mice containing intact copies of the 5′HS-2Epo construction had elevated hematocrits, reticulocyte counts and serum Epo levels and marked splenic enlargement. Analysis of RNA isolated from organs of transgenic mice revealed constitutive Epo mRNA expression primarily in spleen, blood and bone marrow. RNA samples from anemic transgenic mice revealed Epo gene induction only in the liver. Marrow derived from 5′HS-2Epo mice grew BFU-E in the absence of exogenous Epo. Despite observation of up to 2 years, no mouse developed erythroleukemia, demonstrating that Epo autocrine stimulation alone is insufficient for progression to malignancy. These studies show that 5′HS-2 can be used to target Epo gene expression to erythroid tissue. These mice could provide a model system for studying autocrine growth regulation.

Pattern of prepro-endothelin-1 expression revealed by reporter-gene activity in kidneys of erythropoietin-overexpressing mice.

Transgenic overexpression of erythropoietin (Epo) in mice increases haematocrit to a mean of 80% in adult mice, leading to an increase in blood viscosity and volume. As a consequence, renal tissue endothelin-1 (ET-1) concentrations are significantly elevated in erythropoietin-overexpressing (Epo+) mice (mean+/-S.E.M; Epo+, 798+/-71; Epo-, 400+/-25 pg/g tissue; P<0.01). To investigate the pattern of expression of the primary translation product of the ET-1 gene, prepro-ET-1, in kidneys of (Epo+) mice, we generated crossbred mice overexpressing the human EPO gene with mice carrying a reporter gene construct expressing the LacZ gene under the control of the human prepro-ET-1 promotor sequence (LacZ+/Epo+). For comparison, we generated (LacZ+/Epo-) mice from the same strains. After Bluo-Gal staining of frozen kidney sections (n=10 in each group), intracellular blue precipitates as indicators of prepro-ET-1 promotor activity were detectable in tubular and vascular endothelium and glomerular cells in (LacZ+/Epo-) as well as (LacZ+/Epo+) mice. Comparison of the amount of blue precipitates by semiquantitative scoring showed a significant increase in reporter gene activity in tubular epithelium of (LacZ+/Epo+) mice (mean+/-S.E.M.; LacZ+/Epo+, 1.64+/-0.18; LacZ+/Epo-, 1.00+/-0.19; P<0.05). Reporter gene activity was not significantly elevated in epithelium of small intrarenal arteries of (LacZ+/Epo+) mice (mean+/-S.E.M.; LacZ+/Epo+, 0.86+/-0.14; LacZ+/Epo-, 0.38+/-0.21; P=0.08) and was similar in glomerular cells (mean+/-S.E.M.; LacZ+/Epo+, 1.28+/-0.16; LacZ+/Epo-, 1.14+/-0.21; P=0.6). The main source of elevated ET-1 tissue concentration in kidneys of (Epo+) mice therefore seems more likely to be tubular than vascular endothelium or glomerular cells.

Regulation of human erythropoietin gene induction by upstream flanking sequences in transgenic mice

Human erythropoietin (Epo) gene expression is inducible by hypoxia or anaemia in the kidney and liver. Previous transgenic mouse experiments have demonstrated that sequences required for Epo gene induction in the kidney reside in a 7 8 kb Barn HI fragment located 6 kb upstream of the gene. To sublocalize these sequences, we performed Desoxyribonuclease I (DNAse I) mapping studies using transgenic mice which carried this DNA fragment. These studies revealed a DNAse I hypersensitive site (DNAse I HS) located 4 6 kb from the upstream end of the 7.8 kb fragment in anaemic kidney and liver samples. Sequence analysis of the region encompassing the DNAse I HS revealed an element with remarkable homology to the 3' Epo gene hypoxia-inducible enhancer. This suggested the presence of an additional regulatory element that contributes to the control of hypoxia-inducible Epo gene expression in kidney and liver. We constructed transgenic mice containing the human Epo gene linked to either the 5 kb upstream or 2.5 kb downstream portion of the 7.8kb fragment. Inducible expression was limited to the liver. Thus, neither fragment was alone sufficient to confer kidney inducible expression. These findings indicate that sequences more than 8.5 kb upstream of the Epo gene are required for kidney-specific induction. They suggest that either those sequences reside in an 0.3 kb Hind III fragment located between the 5 kb and the 2.5 kb fragments or that sequences in the 5 kb or 0.3 kb fragments must interact with sequences in the 2.5 kb fragment to allow Epo gene induction in the kidney.

Erythropoietin: physiologic and pharmacologic aspects.

The purpose of this review is to give an update of the recent progress in research on erythropoietin (Epo), the hormone that regulates red blood cell production. Epo is a glycoprotein with a molecular mass of approx 30 kDa, which circulates in plasma of the human with 165 amino acids with three N-linked and one O-linked acidic oligosaccharide side chains in the molecule. Both the alpha (39% CHO) and beta (24% CHO) forms are available for clinical use, and there does not appear to be any difference in the pharmacokinetics of these two forms of Epo. Radioimmunoassays and enzyme-linked immunoabsorbant (ELISA) assays are available in a kit form. Serum levels of Epo in normal human subjects range between 1 and 27 mmu/ml or approx 5 pmol/l. It seems clear that the cells in the adult mammalian kidney which produce Epo are the interstitial cells in the peritubular capillary bed and the perivenous hepatocytes in the liver. Expression of the human Epo gene sequences that direct expression in the kidney are located 6-14 kilobases 5' to the gene; whereas the sequences that control hepatocyte-specific expression are located within 0.7 KS to the 3'-flanking region and 0.5 KS to the 5'-flanking region. The signal transduction pathways postulated to be involved in the expression of Epo are: kinases A, G and C; both a constitutive factor and a second hypoxia-inducible factor-1 (HIF-1) located in the 5' end of an hypoxia inducible enhancer region of the Epo gene; and reactive oxygen species. The primary target cell in the bone marrow acted on by Epo is the colony-forming unit erythroid (CFU-E) which has the highest number of Epo receptors. It has been postulated that Epo decreases the rate which Epo-dependent progenitor cells undergo programed cell death (apoptosis). There are two major signal transduction pathways activated by the Epo receptor: the JAK2-STAT5 pathway and the ras pathway. Both pathways involve tyrosine phosphorylation. The approved clinical uses of Epo are the anemias associated with end-stage renal disease, cancer chemotherapeutic agents, and patients with HIV infection receiving AZT. Other anemias reported to respond to Epo therapy are anemia of prematurity, rheumatoid arthritis, and myelodysplasia. Other uses of Epo under investigation are in perioperative surgery and preoperative autologous blood donation.

Negative Regulation of the Erythropoietin Gene Expression by the GATA Transcription Factors

AbstractWe examined regulation of the human erythropoietin (Epo) gene through the GATA sequence in the Epo promoter and showed that Hep3B and HepG2 cells express human GATA-2 (hGATA-2) mRNA and protein. Nuclear extracts of QT6 cells transfected with hGATA-1, 2, or 3 transcription factors showed specific binding to the GATA element in the human Epo gene promoter by gel mobility shift assay. Transient transfection of Hep3B cells with hGATA-1, 2, or 3 showed that each of these transcription factors significantly decreased the level of expression of Epo mRNA as assessed by a competitive polymerase chain reaction. Transient transfection of Hep3B cells with hGATA-1, 2, and 3 and an Epo-reporter gene (growth hormone [GH]) construct showed significant inhibition of the Epo promoter. Antisense oligonucleotide for hGATA-2 transcription factor significantly increased the Epo protein in Hep3B cells under 1% O2 for 24 hours incubation. Furthermore, transient transfection of Hep3B cells with hGATA-1, 2, and 3 and an Epo-reporter gene (luciferase) construct also showed significant inhibition of the Epo promoter. However, transfection of the mutated GATA sequence of the Epo-luciferase gene with hGATA-1, 2, and 3 interfere with the inhibition of the Epo promoter. We conclude that the hGATA-1, 2, and 3 transcription factors specifically bind to the GATA element in the human Epo gene promoter and negatively regulate Epo gene expression.

Erythropoietin: a somewhat personal history.

The existence of erythropoietin (epo) —then termed hemopoietine was postulated by Carnot and Dellandre, as long ago as 1906, but there were questions whether the experimental evidence was sufficient to indicate a humoral factor that could regulate the rate of red cell formation [I]. For more than 30 years the field of study of epo was largely in eclipse. Of the 40 years between the reemergence of the field in the 50s and the present, the years until 1987 could be described as a lag period, preceding the present-day exponential rise in both widespread interest and publications on epo. This later period, the time after the cloning and expression of the human epo gene, has seen the field become full-fledged with respect to therapeutic use, marketing, and patent litigation. It also has been a time of important advances in the study of the molecular and cellular biology of epo, its receptor, and of erythropoiesis. While this notable expansion in research is still in process, it seemed appropriate for me to agree with the suggestion of the editor of Perspectives to write a personal account of my experience that spans the period when epo was considered to be a laboratory curiosity (if it had any existence at all) to the present.

Cloning of the murine eosinophil peroxidase gene (mEPO): characterization of a conserved subgroup of mammalian hematopoietic peroxidases.

The mouse eosinophil peroxidase (mEPO) gene was cloned by screening a random-primed bone marrow cDNA library at reduced criteria using a hEPO cDNA. An mEPO cDNA was subsequently used to isolate the mEPO gene from a lambda-genomic library. The mEPO gene displays a high degree of conservation with its human homologue: the transcription units are approximately the same size, conserve the relative size and position of the 12 exons associated with each gene, and at a nucleotide level the mouse and human EPO genes are 86% identical in the protein coding regions and 66% identical in the 3'-untranslated trailer regions. This strong conservation extends to the encoded proteins which show approximately 90% amino acid identity. Expression of the mEPO gene is restricted to tissues containing eosinophil progenitor cells (e.g., bone marrow and spleen), a pattern similar to the expression of another murine eosinophil granule protein, major basic protein.

GATA transcription factors negatively regulate erythropoietin gene expression.

We examined regulation of the human erythropoietin (Epo) gene through the GATA sequence in the Epo promoter, and demonstrated that Hep3B and HepG2 cells express human GATA-2 (hGATA-2) mRNA and protein. Nuclear extracts of QT6 cells transfected with hGATA-1, -2 or -3 transcription factors revealed specific binding to the GATA element in the human Epo gene promoter by gel mobility shift assay. Transient transfection of Hep3B cells with hGATA-1, -2 or -3 demonstrated that each of these transcription factors significantly decreased the level of expression of Epo mRNA as assessed by a competitive polymerase chain reaction. Furthermore, transient transfection of Hep3B cells with hGATA-1, -2 and -3 and and Epo reporter gene construct showed significant inhibition of the Epo promoter. We conclude that the hGATA-1, -2 and -3 transcription factors specifically bind to the GATA element in the human Epo gene promoter and negatively regulate Epo gene expression.

Stimulation of Erythropoiesis by In Vivo Gene Therapy: Physiologic Consequences of Transfer of the Human Erythropoietin Gene to Experimental Animals Using an Adenovirus Vector

Erythropoietin (Epo), a 30.4-kD glycoprotein, is the principal regulator of erythropoiesis. To evaluate the concept that in vivo gene transfer might be used as an alternative to recombinant human Epo (rhEpo) in applications requiring a 1- to 3-week stimulation of erythropoiesis, the replication-deficient recombinant adenovirus AdMLP.Epo was constructed by deleting the majority of E1 from adenovirus type 5, and replacing E1 with an expression cassette containing the adenovirus type 5 major late promoter (MLP) and the human Epo gene, including the 3' cis-acting hypoxia response element. In vitro studies showed that infection of the human hepatocyte cell line Hep3B with AdMLP.Epo resulted in a 15-fold increase in Epo production in 24 hours that was enhanced to 116-fold in the presence of a hypoxic stimulus. One-time in vivo administration of AdMLP.Epo (7 x 10(9) plaque-forming units/kg) to the peritoneum of cotton rats caused a marked increase in red blood cell production, with a 2.6-fold increase in bone marrow erythroid precursors by day 4, and sevenfold increase in reticulocyte count by day 7. The hematocrit increased gradually, with a maximum of 64% +/- 4% at day 14 (compared with an untreated baseline of 46% +/- 2%), and a level of 55% +/- 1% at day 24. Furthermore, one-time subcutaneous administration of AdMLP.Epo caused an increase in hematocrit that peaked at 14 days (57% +/- 2%) and was still elevated at day 42. Hematocrit level in animals receiving subcutaneous administration of AdMLP.Epo sustained a long-term increase compared with animals receiving intraperitoneal administration. In the context of these observations, gene therapy with a single administration of an adenovirus vector containing the human EPO gene may provide a means of significantly augmenting the circulating red blood cell mass over the 1- to 3-week period necessary for many clinical applications.