Evi-1 Is a Critical Regulator for Hematopoietic Stem Cells and Transformed Leukemic Cells

Abstract

Evi-1 has been recognized as one of the dominant oncogenes associated with murine and human myeloid leukemia. Here, we show that hematopoietic stem cells (HSCs) in Evi-1-deficient embryos are severely reduced in number with defective proliferative and repopulating capacity. Selective ablation of Evi-1 in Tie2(+) cells mimics Evi-1 deficiency, suggesting that Evi-1 function is required in Tie2(+) hematopoietic stem/progenitors. Conditional deletion of Evi-1 in the adult hematopoietic system revealed that Evi-1-deficient bone marrow HSCs cannot maintain hematopoiesis and lose their repopulating ability. In contrast, Evi-1 is dispensable for blood cell lineage commitment. Evi-1(+/-) mice exhibit the intermediate phenotype for HSC activity, suggesting a gene dosage requirement for Evi-1. We further demonstrate that disruption of Evi-1 in transformed leukemic cells leads to significant loss of their proliferative activity both in vitro and in vivo. Thus, Evi-1 is a common and critical regulator essential for proliferation of embryonic/adult HSCs and transformed leukemic cells.

Mechanisms of self-renewal in hematopoietic stem cells

“…Mouse embryos lacking Evi-1 die due to the remarkably decreased number and reconstitution capacity of HSCs. Conditional Evi-1 deletion in adult mice also showed that Evi-1 is essential for the maintenance of HSCs [98]. By knocking in an internal ribosome entry site (IRES)-GFP cassette into the Evi-1 locus, Kataoka et al demonstrated that Evi-1 was predominantly expressed in LT-HSCs, and its expression was sharply down-regulated along with differentiation, indicating that the Evi-1 expression level is a candidate HSC-specific marker.…”

EVI-1 interacts with histone methyltransferases SUV39H1 and G9a for transcriptional repression and bone marrow immortalization

“…Although we have shown that complete loss of Evi-1 slightly reduced colony-forming ability of E2A/HLF, the effect of Evi-1 deletion in E2A/HLF-immortalized cells is relatively small than that in MLL-immortalized cells. 12 It therefore seems likely that the Evi-1/HMT interaction is not a major mediator for oncogenic activity of E2A/HLF.…”

“…30 We used E2A/HLF as a control because the contribution of Evi-1 to colony-forming ability of E2A/HLF-transduced cells is relatively small. 12 Despite the efficient downregulation of Suv39h1 and G9a (Figure 6e), the HMT-knockdown cells showed equivalent colony-forming activity to that of control E2A/HLF-transduced cells (Figure 6f; Supplementary Table 2). These results indicate that both Suv39h1 and G9a are specifically required for Evi-1-mediated bone marrow immortalization.…”

“…12,14 The pCMV-Myc-SUV39H1 and pEGFPC1-G9a were gifts from M Tachibana and Y Shinkai. SUV39H1-H324K was created by PCR mutagenesis to change amino acid 324 from histidine to lysine.…”

“…9,10 Furthermore, recent gene targeting studies in mice revealed that Evi-1 has an essential function in the proliferation/maintenance of haematopoietic stem cells. 11,12 EVI-1 contains DNA-binding zinc finger motifs and belongs to the positive regulatory (PR) domain family of transcription factors, which are characterized by the presence of multiple zinc fingers and a PR domain at the N-terminus. 13 The PR domain is a subclass of the evolutionarily conserved SET domain, which has been linked to chromatin-mediated gene regulation and histone methylation.…”