Search

Supplementary Figure 4 from Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Supplementary Figure 5 from Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Supplementary Figure 2 from Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Supplementary Figure 3 from Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Supplementary Figure 1 from Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Recurring chromosomal translocations observed in human leukemia often result in the expression of fusion proteins that are DNA-binding transcription factors. These altered proteins acquire new dimerization properties that result in the assembly of inappropriate multimeric transcription complexes that deregulate hematopoietic programs and induce leukemogenesis. Recently, we reported that the fusion protein AML1/MDS1/EVI1 (AME), a product of a t(3;21)(q26;q22) associated with chronic myelogenous leukemia and acute myelogenous leukemia, displays a complex pattern of self-interaction. Here, we show that the 8th zinc finger motif of MDS1/EVI1 is an oligomerization domain involved not only in interaction of AME with itself but also in interactions with the parental proteins, RUNX1 and MDS1/EVI1, from which AME is generated. Because the 8th zinc finger motif is also present in the oncoprotein EVI1, we have evaluated the effects of the interaction between RUNX1 and EVI1 in vitro and in vivo. We found that in vitro, this interaction alters the ability of RUNX1 to bind to DNA and to regulate a reporter gene, whereas in vivo, the expression of the isolated 8th zinc finger motif of EVI1 is sufficient to block the granulocyte colony-stimulating factor–induced differentiation of 32Dcl3 cells, leading to cell death. As EVI1 is not detected in normal bone marrow cells, these data suggest that its inappropriate expression could contribute to hematopoietic transformation in part by a new mechanism that involves EVI1 association with key hematopoietic regulators, leading to their functional impairment. [Cancer Res 2007;67(12):5658–66]

Janus-activated kinase 2 (JAK2) mutations are common in myeloproliferative disorders; however, although they are detected in virtually all polycythemia vera patients, they are found in ∼50% of essential thrombocythemia (ET) patients, suggesting that converging pathways/abnormalities underlie the onset of ET. Recently, the chromosomal translocation 3;21, leading to the fusion gene AML1/MDS1/EVI1 (AME), was observed in an ET patient. After we forced the expression of AME in the bone marrow (BM) of C57BL/6J mice, all the reconstituted mice died of a disease with symptoms similar to ET with a latency of 8 to 16 months. Peripheral blood smears consistently showed an elevated number of dysplastic platelets with anisocytosis, degranulation, and giant size. Although the AME-positive mice did not harbor Jak2 mutations, the BM of most of them had significantly higher levels of activated Stat3 than the controls. With combined biochemical and biological assays we found that AME binds to the Stat3 promoter leading to its up-regulation. Signal transducers and activators of transcription 3 (STAT3) analysis of a small group of ET patients shows that in about half of the patients, there is STAT3 hyperactivation independently of JAK2 mutations, suggesting that the hyperactivation of STAT3 by JAK2 mutations or promoter activation may be a critical step in development of ET. [Cancer Res 2009;69(1):262–71]

Recurring chromosomal translocations observed in human leukemia often result in the expression of fusion proteins that are DNA-binding transcription factors. These altered proteins acquire new dimerization properties that result in the assembly of inappropriate multimeric transcription complexes that deregulate hematopoietic programs and induce leukemogenesis. Recently, we reported that the fusion protein AML1/MDS1/EVI1 (AME), a product of a t(3;21)(q26;q22) associated with chronic myelogenous leukemia and acute myelogenous leukemia, displays a complex pattern of self-interaction. Here, we show that the 8th zinc finger motif of MDS1/EVI1 is an oligomerization domain involved not only in interaction of AME with itself but also in interactions with the parental proteins, RUNX1 and MDS1/EVI1, from which AME is generated. Because the 8th zinc finger motif is also present in the oncoprotein EVI1, we have evaluated the effects of the interaction between RUNX1 and EVI1 in vitro and in vivo. We found that in vitro, this interaction alters the ability of RUNX1 to bind to DNA and to regulate a reporter gene, whereas in vivo, the expression of the isolated 8th zinc finger motif of EVI1 is sufficient to block the granulocyte colony-stimulating factor–induced differentiation of 32Dcl3 cells, leading to cell death. As EVI1 is not detected in normal bone marrow cells, these data suggest that its inappropriate expression could contribute to hematopoietic transformation in part by a new mechanism that involves EVI1 association with key hematopoietic regulators, leading to their functional impairment. [Cancer Res 2007;67(12):5658–66]

EVI1 is an aggressive nuclear oncoprotein deregulated by recurring chromosomal abnormalities in myelodysplastic syndrome (MDS). The expression of the corresponding gene is a very poor prognostic marker for MDS patients and is associated with severe defects of the erythroid lineage. We have recently shown that the constitutive expression of EVI1 in murine bone marrow results in a fatal disease with features characteristic of MDS, including anemia, dyserythropoiesis, and dysmegakaryopoiesis. These lineages are regulated by the DNA-binding transcription factor GATA1. EVI1 has two zinc finger domains containing seven motifs at the N terminus and three motifs at the C terminus. Supported by results of assays utilizing synthetic DNA promoters, it was earlier proposed that erythroid-lineage repression by EVI1 is based on the ability of this protein to compete with GATA1 for DNA-binding sites, resulting in repression of gene activation by GATA1. Here, however, we show that EVI1 is unable to bind to classic GATA1 sites. To understand the mechanism utilized by EVI1 to repress erythropoiesis, we used a combination of biochemical assays, mutation analyses, and in vitro bone marrow differentiation. The results indicate that EVI1 interacts directly with the GATA1 protein rather than the DNA sequence. We further show that this protein-protein interaction blocks efficient recognition or binding to DNA by GATA1. Point mutations that disrupt the geometry of two zinc fingers of EVI1 abolish the protein-protein interaction, leading to normal erythroid differentiation of normal murine bone marrow in vitro.

Twenty-eight myelodysplastic syndromes (MDS) patients were treated with arsenic trioxide (ATO) and thalidomide. Seven patients responded including one complete hematologic and cytogenetic response and one with regression in spleen size. Two trilineage responses were seen in patients with inv(3)(q21q26.2). Three of five patients who had high pre-therapy EVI1 levels showed unexpectedly good responses while two died early in the first cycle. In vitro studies using 32Dcl3 cells forced to express EVI1 confirmed increased sensitivity of these cells to ATO. Both low/high risk MDS may benefit significantly from therapy with ATO/thalidomide, and those with high pre-therapy EVI1 expression may be uniquely sensitive.

Objective: To investigate the growth-inhibitory effect of Rep proteins on cells. Methods: We generated Rep-expressing plasmids that containing wild-type rep genes or mutant rep genes with point mutations in their ATP-binding sites. We obtained several HeLa cell clones expressing Rep proteins constitutively by the regulator plasmid. The expression of each Rep protein was detected by Western blotting with an anti-Rep monoclonal antibody. Results: Clones that expressed Rep52 and Rep40 grew more slowly than those which exhibited no detectable expression of Rep or mutant Rep protein. In contrast, clone w-33, which proliferated as quickly as control HeLa cells, expressed only Rep40. By comparing the expression levels of Rep proteins in these clones, we found that the ratio of Rep40 to Rep52 gradually increased in the faster growing clones. Conclusion: These results suggest that while Rep52 expression retards cell proliferation, Rep40 promotes recovery from Rep52-induced HeLa cell growth inhibition.

In this globalization era, it is an important strategy to focus on the core status of bilingual art teachers in the internationalization of higher education. And it is necessary to prepare a thorough, detailed, well-designed assessment criterion for teachers, especially for teachers specialized in art, as their competency relates directly to whether the fine art culture can be inherited and whether the cultural communication can be achieved. Based on the positive psychological capital of students majoring in art, this research investigates art teachers' bilingual teaching attitude, and how to construct the competency of art teachers via bilingual teaching. Educational modernization and internationalization are two megatrends of education development in the world. The internationalization of higher education presages of a possibility that the open-ended, innovative, quality-oriented education will become the basic trend of higher education, which requires teachers to evolve in their roles, from the tutor of students acquiring knowledge into their designer of the future life. As the implementation of the National Medium-term or Long-term Program of Development for Education goes further and further, the deterioration of the problems arising from the process of education internationalization also speeds up day by day on both dimensions of depth and breadth. On the micro level, the study of education internationalization mostly focuses on bilingual education. Ever since the Ministry of Education of People's Republic of China issued A Number of Opinions on Strengthening Undergraduate Teaching of Higher Education and Enhancing Education Quality, documents like Opinions on the Implementation of Undergraduate Teaching Quality and Reform Project in Higher Education have been published in succession to encourage colleges and universities "to proactively hire foreign scholars and experts to engage in the teaching of professional courses in bilingual manner, and to encourage or support overseas graduates to return and to teach professional courses in English, eventually to enhance undergraduate students' English competency for special academic purposes." The nation has also approved of 403 courses as Bilingual Teaching Demonstration Courses. It vigorously pursues bilingual education not only to enhance students' English skills, but also to hope that college or university students can master the most updated knowledge in their majors and reach the cutting-edge of the specialized science and technology. Speaking of further objectives, one, among others, is to enhance the self-confidence of students via bilingual learning and to help them obtain inner peace and ability to hold hopes and positive expectations for the future. As a result, they will be able to deal with the complicated international competition and to improve the international competitiveness of our country's higher education. And the core personnel in charge of cultivating the positive psychological capital of students is the teachers working in the forefront of colleges and universities. Their sense of identity with the bilingual teaching and their competency in the teaching methods take the pivotal role here. This article attempts to study the attitudes and methods employed by art teachers based on the model of the students' positive psychological capital. As for students of art majors, the talented ones in this field feel the pressing urge of internationalization. Art teachers' attitudes towards or ideas of internationalization and their international knowledge, experience and methods will directly influence the planning and implementing of the art courses' international strategy. Their competency is in direct relation to the inheritance of the fine art culture as well as the realization of the cultural communication. Not only should art talents acquire adequate

RUNX1 (AML1, CBFalpha2, PEBP2alphaB) is a transcription factor essential for the establishment of the hematopoietic stem cell. It is generally thought that RUNX1 exists as a monomer that regulates hematopoietic differentiation by interacting with tissue-specific factors and its DNA consensus through its N terminus. RUNX1 is frequently altered in human leukemia by gene fusions or point mutations. In general, these alterations do not affect the N terminus of the protein, and it is unclear how they consistently lead to hematopoietic transformation and leukemia. Here we report that RUNX1 homodimerizes through a mechanism involving C terminus-C terminus interaction. This RUNX1-RUNX1 interaction regulates the activity of the protein in reporter gene assays and modulates its ability to induce hematopoietic differentiation of hematopoietic cell lines. The promoters of genes regulated by RUNX1 often contain multiple RUNX1 binding sites. This arrangement suggests that RUNX1 could homodimerize to bring and hold together distant chromatin sites and factors and that if the dimerization region is removed by gene fusions or is altered by point mutations, as observed in leukemia, the ability of RUNX1 to regulate differentiation could be impaired.

This paper, as an attempt to find a solution to the problem of ‘Identity Crisis’ brought about by the traditional spoon-feeding Education Mode, explores to construct a new mode of vocal music teaching characterized by an interaction on an equal and democratic footing between learners and the teacher in light of Habermas’ Communicative Action theory. This new mode, taking into consideration students’ personalities and characteristics, can help to cultivate their innovative spirit and practical ability, hence enhancing the expressiveness of the teaching content and bettering teaching effect and the quality of vocal music talents.

AML1/MDS1/EVI1 (AME) is a chimeric transcription factor produced by the (3;21)(q26;q22) translocation. This chromosomal translocation is associated with de novo and therapy-related acute myeloid leukemia and with the blast crisis of chronic myelogenous leukemia. AME is obtained by in-frame fusion of the AML1 and MDS1/EVI1 (ME) genes. The mechanisms by which AME induces a neoplastic transformation in bone marrow cells are unknown. AME interacts with the corepressors CtBP and HDAC1, and it was shown that AME is a repressor in contrast to the parent transcription factors AML1 and ME, which are transcription activators. Studies with murine bone marrow progenitors indicated that the introduction of a point mutation that destroys the CtBP-binding consensus impairs but does not abolish the disruption of cell differentiation and replication associated with AME expression, suggesting that additional events are required. Several chimeric proteins, such as AML1/ETO, BCR/ABL, and PML/RARa, are characterized by the presence of a self-interaction domain critical for transformation. We report that AME is also able to oligomerize and displays a complex pattern of self-interaction that involves at least three oligomerization regions, one of which is the distal zinc finger domain. Although the deletion of this short domain does not preclude the self-interaction of AME, it significantly reduces the differentiation defects caused in vitro by AME in primary murine bone marrow progenitors. The addition of a point mutation that inhibits CtBP binding completely abrogates the effects of AME on differentiation, suggesting that AME induces hematopoietic differentiation defects through at least two separate but cooperating pathways.

EVI1 is an oncogene frequently associated with chronic and acute myeloid leukemia. In hematopoietic cells, EVI1 impairs several pathways including proliferation, differentiation, and apoptosis. Interferon-alpha (IFN-alpha) is a powerful cytokine that controls the immune response and limits the expansion of several tissues including bone marrow. These properties contribute to the effectiveness of IFN-alpha in the treatment of many neoplastic disorders especially chronic myeloid leukemia. We report here that in murine hematopoietic progenitors the expression of EVI1 completely abrogates the antiproliferative and apoptotic effects of IFN-alpha. EVI1 does not repress the JAK/STAT signaling pathway or the activation of many IFN-responsive genes. On the contrary, EVI1 prolongs the phosphorylation of STAT1 and the activation of an IFN-dependent reporter gene. However, EVI1 specifically represses the IFN-dependent induction of the tumor suppressor PML and blocks the apoptotic pathways activated by PML. We show that the position of the ISRE, which is located within the first exon of PML, is critical to block PML induction by IFN-alpha. The relocation of the ISRE to a position upstream of the transcription start site is sufficient to re-establish the response to IFN in the presence of EVI1. Our data suggest that stabilized STAT1 phosphorylation and prolonged binding of the STAT1 complex to the first exon could impair PML transcription and inhibit the activation of PML-dependent apoptotic pathways resulting in loss of IFN response. These results point to a novel mechanism utilized by an oncogene to escape normal cell response to growth-controlling cytokines.

The myelodysplastic syndromes (MDS) continue to pose conceptual and practical conundrums because of their heterogeneity and therapeutic challenges. They are not restricted to the presence of clonal cells that are prone to excessive proliferation and premature apoptosis. In MDS the bone marrow microenvironment also is abnormal and exhibits an excess of proinflammatory cytokines, especially tumor necrosis factor (TNF), neoangiogenesis, and poorly defined immune defects. Thalidomide, a drug with anti-TNF, antiangiogenic, and immunomodulatory activities, and other agents with anti-TNF effects, such as pentoxifylline, etanercept, and infliximab, have produced hematologic improvement in 20% to 40% of patients. These agents may provide effective therapy for a subset of lower-risk MDS patients, even if the drugs target the bone marrow microenvironment predominantly. However, in higher-risk MDS patients, especially those with more than 10% blasts, it is important to eliminate abnormal cell clones; drugs used for this purpose have included arsenic trioxide, topotecan, the farnesyl transferase inhibitor tipifarnib, and demethylating agents, such as 5-azacytidine and decitabine. To increase the therapeutic index, a combination strategy may be preferable for higher-risk MDS patients, in whom the seed (clone) and the soil (bone marrow microenvironment) must be targeted simultaneously. The challenge is to recognize the subset that is likely to respond to a given drug so that patients can be preselected for therapy.

GATA1, founding member of the GATA transcription factor family, is essential for cell maturation and differentiation within the erythroid and megakaryocyte (MK) lineages. Disruption of DNA- or protein-binding capacity of GATA1 causes severe hematopoietic dysfunction and plays a role in blood disorders such as thrombocytopenia, anemia or leukemia. GATA1 expression seems to be related to the MK commitment both in mice and in humans; indeed, similarly to the murine myeloid M1 cell line, in which the enforced expression of GATA1 induces the c-Mpl appearance and MK differentiation, transduction of human hematopoietic stem cells with a GATA1 highly expressing vector results in self-renewal block and in the exclusive generation of Meg-E lineages. More recently, a role for GATA1 also in myeloproliferative disorders (MPDs) was indicated by the “GATA1-low” mouse model which develop a disease closely resembling the human idiopathic myelofibrosis. Interestingly, patients affected by myelofibrosis was also shown to express decreased GATA1 levels by immunostaining of BM sections. In this study, we investigated by Real Time PCR the levels of GATA1 in a myeloproliferative disorders such as essential thrombocytemia (ET) tipically characterized by a neoplastic megakaryocitic proliferation. We have studied BM samples of 40 newly diagnosed patients (M:F ratio 1:1 - median age 53 years, range 18–84) affected by ET, as for the PVSG group criteria. These patients were selected from a cohort of 65 ET patients considering a similar erythroid/myeloid ratio at the FACS analysis to reduce a possible bias for the RT-PCR results due to the erythroid compartment interference. The median platelets count of the selected patients was 670,000/mL (range 493,000–1,400,000/mL), myelofibrotic index 0/1, and 18 out of 40 patients (45%) showed mild splenomegaly both at the physical examination and US scan (median spleen vol 550 ml - range 430–1400 mL). No chromosomal abnormalities were detected by cytogenetic analysis. JAK2 sequencing in 21/40 patients indicated that 9/21 patients (43%) were positive for the JAK2 V617F genomic mutation. At the end of observation time (median 18 mo.) no patients had evidence or signs of thrombotic or hemorrhagic complications. BM cells from six healthy donors were used as normal controls in the study. The relative GATA1 quantification was calculated in according to the DCt method with GAPDH as internal control. The results showed a significant increase of GATA1 expression in BM cells from ET patients (median DCt + 6,11 ; range −0,41/+18,11) compared to the controls (median DCt + 0,172 ; range −4,03/+1,7) (p < 0,003). Interestingly, the GATA1 overexpression is not a mere consequence of the proliferation and activation of MKs, indeed samples from three patients affected by idiopathic thrombocytopenic purpura, whose BM smears had the typical secondary megakaryocytic hyperplasia, showed GATA1 levels much lower than the ET patients (median DCt − 0,6 ; range − 3,21/−0,9). No significant difference in GATA1 level was found between patients harbouring a JAK mutation (median DCt +5,86 ; range 0,85/16,12) and those with wild type alleles (median DCt +4,75 ; range −0,41/10,21). In conclusion, our results suggest that GATA1 overexpression could be a trigger for MK neoplastic commitment and proliferation and, consequently, seems to have a central role for ET pathogenesis both in JAK2 mutated and in JAK2 WT patients.

The molecular etiology of subgroups of essential thrombocythemia (ET), as well as some other myeloproliferative disorders (MPDs) has been recently better understood by the identification of an activating somatic point mutation (Valine 617 to Phenylalanine) in Jak2 detected in patients with MPDs. Approximately 23%–57% of ET patients harbor this mutation, which is thought to be one of the dominant factors contributing to the disease. However, the pathways disrupted in at least half of ET patients who have wild type Jak2 are not known. The fusion gene AML1/MDS1/EVI1 (AME), a product of the t(3;21)(q26;q22) translocation, is associated with several hematopoietic disorders, primarily chronic myelogenous leukemia and acute myeloid leukemia, and to a lesser extent with ET. We have investigated the role of AME by generating C57BL/6J mice that express this fusion oncogene in their bone marrow after bone marrow infection and transplantation. After a latency of 12 ± 1.8 months, all the reconstituted mice invariably developed an ET-like disease. The disease was fatal and the animals died of anemia probably caused by bleeding. Until 1–2 weeks before death, at which time the mice were severely cytopenic, the peripheral blood hemoglobin and leukocyte counts of the reconstituted AME mice were normal. The only striking difference was the platelet counts, which were consistently above the normal range (1456–3153 and 940–1608 K/ml for AME and control mice, respectively, p=0.00029). Platelets appeared dysplastic with anisocytosis, various degrees of degranulation, and giant size. The bone core biopsies of AME mice were especially remarkable for large and giant megakaryocytes with a tendency for clustering. Touch preparations of the biopsies showed progressive maturation in the granulocytic and erythroid precursor cell lines, a normal myeloid to erythroid ratio and no evidence of dyshematopoiesis. These finding coupled with markedly increased levels of TPO but normal concentrations of c-Mpl and Epo-R are concordant with the morphologic and laboratory features of patients with ET. The sequence analysis of exon 12 of Jak2 demonstrated no guanine-to-thymine transversion at nucleotide 1849 in all AME mice tested. These data are valuable because they provide a novel mouse model for understanding the deregulated pathways in ET patients with wild-type Jak2.

RUNX1 also known as AML1 is a transcription factor essential for normal hematopoiesis, platelet production and thymocyte development. RUNX1 is the most frequent target of chromosomal translocations and acquired or inherited point mutations associated with human leukemia. RUNX1 is a DNA-binding transcription factor that can act both as an activator and a repressor of gene expression depending probably on the association of RUNX1 with co-activator or corepressors in large transcription complexes at promoter sites. The C-terminus of RUNX1 contains an inhibitory region, ID, which represses positive regulation of RUNX1-dependent genes. Thus, this region could potentially act as a switch and co-operate with RUNX1-interacting transcription factors in the choice between gene activation or gene repression. Here we have examined the role of ID in gene regulation by RUNX1. We found that this region is a homo-dimerization motif that controls RUNX1-RUNX1 interaction in vitro and in vivo. The association of RUNX1 with itself through this domain appears to reduce the positive transactivating potential of RUNX1 and, if provided in trans, this domain can repress by itself the activity of RUNX1 in reporter gene assays. Our studies suggest that RUNX1 autoregulates itself through its ability to form a homodimer. Data will be shown on the effects of the ID region in hematopoietic differentiation of cell lines. The results indicate that the ID region plays critical role in RUNX1 activity and is essential to control the correct execution of hematopoietic programs. It is of importance that aside from the t(12;21), all chromosomal translocations and virtually all point mutations associated with leukemia profoundly affect the integrity of the C-terminus including the ID region. These studies suggest a novel pathway involved in RUNX1 leukemogenesis and provide new targets for the management of RUNX1-leukemia. Kislay Sinha and Donglan Li contributed equally to this study.

EVI1 is an aggressive nuclear oncoprotein deregulated by recurring chromosomal abnormalities in acute myeloid leukemia and myelodysplastic syndrome. This protein has two Zn finger domains containing 7 motifs at the N-terminus and 3 motifs at the C-terminus. The expression of this gene is a very poor prognostic marker and is associated with diseases characterized by erythroid and megakaryocytic defects. We have recently shown that the forced expression of EVI1 in murine bone marrow results in a fatal disease with features characteristic of MDS, including fatal dyserythropoiesis, dysmegakaryopoiesis, and anemia. These lineages are regulated by the transcription factor GATA-1, a DNA-binding protein that in addition to erythrocytes and megakaryocytes exerts a strict control also on the differentiation of mast cells and eosinophils, on the basis of its expression and association with specific partners. In the present study, we used biochemical assays and in vitro culture to show that GATA-1 and the N-terminus of EVI1 are involved in the formation of a protein complex that is unable to regulate efficiently GATA-1-dependent promoters in reporter gene assays. EMSA studies with a GATA-1-specific probe indicate that EVI1 does not recognize and bind to the DNA probe but disrupts the DNA-binding of GATA-1. By deletion analysis and point mutations, we mapped the interaction between the proteins to two motifs in the proximal Zn finger domain of EVI1 and to the C-terminus Zn finger of GATA-1. Cys to Ala mutations in the two EVI1 motifs abrogate the interaction and restore the response of a promoter in reporter gene assays. We propose that the association between EVI1 and the DNA-binding motif of GATA-1 impairs efficient promoter binding by GATA-1 and the regulation of erythroid and megakaryocytic lineage. There studies suggest that the interaction surface between the two proteins could be an attractive target for the development of competing small molecules as a treatment in EVI1-associated leukemia.

Myelodysplasia is a hematological disease in which genomic abnormalities accumulate in a hematopoietic stem cell leading to severe pancytopenia, multilineage differentiation impairment, and bone marrow (BM) apoptosis. Mortality in the disease results from pancytopenia or transformation to acute myeloid leukemia. There are frequent cytogenetic abnormalities, including deletions of chromosomes 5, 7, or both. Recurring chromosomal translocations in myelodysplasia are rare, but the most frequent are the t(3;3)(q21;q26) and the inv(3)(q21q26), which lead to the inappropriate activation of the EVI1 gene located at 3q26. To better understand the role of EVI1 in this disease, we have generated a murine model of EVI1-positive myelodysplasia by BM infection and transplantation. We find that EVI1 induces a fatal disease of several stages that is characterized by severe pancytopenia. The disease does not progress to acute myeloid leukemia. Comparison of in vitro and in vivo results suggests that EVI1 acts at two levels. The immediate effects of EVI1 are hyperproliferation of BM cells and downregulation of EpoR and c-Mpl, which are important for terminal erythroid differentiation and platelet formation. These defects are not fatal, and the mice survive for about 10 months with compensated hematopoiesis. Over this time, compensation fails, and the mice succumb to fatal peripheral cytopenia.