Gfi-1 restricts proliferation and preserves functional integrity of haematopoietic stem cells. Nature 431:1002-07
ABSTRACT Haematopoietic stem cells (HSCs) sustain blood production throughout life. HSCs are capable of extensive proliferative expansion, as a single HSC may reconstitute lethally irradiated hosts. In steady-state, HSCs remain largely quiescent and self-renew at a constant low rate, forestalling their exhaustion during adult life. Whereas nuclear regulatory factors promoting proliferative programmes of HSCs in vivo and ex vivo have been identified, transcription factors restricting their cycling have remained elusive. Here we report that the zinc-finger repressor Gfi-1 (growth factor independent 1), a cooperating oncogene in lymphoid cells, unexpectedly restricts proliferation of HSCs. After loss of Gfi-1, HSCs display elevated proliferation rates as assessed by 5-bromodeoxyuridine incorporation and cell-cycle analysis. Gfi-1-/- HSCs are functionally compromised in competitive repopulation and serial transplantation assays, and are rapidly out-competed in the bone marrow of mouse chimaeras generated with Gfi-1-/- embryonic stem cells. Thus, Gfi-1 is essential to restrict HSC proliferation and to preserve HSC functional integrity.
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- "The transcription factor Gfi1 is expressed in multiple tissues, including haematopoietic progenitors and stem cells, lymphoid and myeloid cells (Karsunky et al., 2002; Hock et al., 2004; Yücel et al., 2004; Rosenbauer and Tenen, 2007; Wilson et al., 2010a; Lancrin et al., 2012). We have previously identified an enhancer that is located around 35 kb upstream of Gfi1 (referred to as the Gfi1-35 enhancer) within an intron of the neighbouring gene Evi5 (Wilson et al., 2010a). "
ABSTRACT: Comprehensive analysis of cis-regulatory elements is key to understanding the dynamic gene regulatory networks that control embryonic development. While transgenic animals represent the gold standard assay, their generation is costly, entails significant animal usage, and in utero development complicates time-course studies. As an alternative, embryonic stem (ES) cells can readily be differentiated in a process that correlates well with developing embryos. Here, we describe a highly effective platform for enhancer assays using an Hsp68/Venus reporter cassette that targets to the Hprt locus in mouse ES cells. This platform combines the flexibility of Gateway® cloning, live cell trackability of a fluorescent reporter, low background and the advantages of single copy insertion into a defined genomic locus. We demonstrate the successful recapitulation of tissue-specific enhancer activity for two cardiac and two haematopoietic enhancers. In addition, we used this assay to dissect the functionality of the highly conserved Ets/Ets/Gata motif in the Scl+19 enhancer, which revealed that the Gata motif is not required for initiation of enhancer activity. We further confirmed that Gata2 is not required for endothelial activity of the Scl+19 enhancer using Gata2(-/-) Scl+19 transgenic embryos. We have therefore established a valuable toolbox to study gene regulatory networks with broad applicability.Biology Open 11/2013; 2(11):1229-38. DOI:10.1242/bio.20136296 · 2.42 Impact Factor
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- "To inquire into molecular mechanisms that may be involved in the poor proliferative and differentiation potentials of ALL-lymphoid progenitors, the transcription of some genes relevant to the quiescence status of hematopoietic primitive cells was evaluated. Of note, transcriptional repressor growth factor independence-1 (Gfi-1), formerly identified as a bifunctional regulator of hematopoietic differentiation   , was highly displayed by ALL progenitor cells. Its nuclear distribution suggests a possible biological role in the pathogenesis of this disease. "
ABSTRACT: Acute lymphoblastic leukemia (ALL) is the most frequent malignancy of childhood. Substantial progress on understanding the cell hierarchy within ALL bone marrow (BM) has been recorded in the last few years, suggesting that both primitive cell fractions and committed lymphoid blasts with immature stem cell-like properties contain leukemia-initiating cells. Nevertheless, the biology of the early progenitors that initiate the lymphoid program remains elusive. The aim of the present study was to investigate the ability of lymphoid progenitors from B-cell precursor ALL BM to proliferate and undergo multilineage differentiation. By phenotype analyses, in vitro proliferation assays, and controlled culture systems, the lymphoid differentiation potentials were evaluated in BM primitive populations from B-cell precursor ALL pediatric patients. When compared to their normal counterparts, functional stem and progenitor cell contents were substantially reduced in ALL BM. Moreover, neither B nor NK or dendritic lymphoid-cell populations developed recurrently from highly purified ALL-lymphoid progenitors, and their proliferation and cell cycle status revealed limited proliferative capacity. Interestingly, a number of quiescence-associated transcription factors were elevated, including the transcriptional repressor Gfi-1, which was highly expressed in primitive CD34(+) cells. Together, our findings reveal major functional defects in the primitive hematopoietic component of ALL BM. A possible contribution of high levels of Gfi-1 expression in the regulation of the stem/progenitor cell biology is suggested.Clinical and Developmental Immunology 10/2013; 2013(3-4):349067. DOI:10.1155/2013/349067 · 2.93 Impact Factor
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- "Several TFs have been implicated in HSC self-renewal. Specifically, deletions of Etv6 (Hock et al., 2004b), PU.1 (Burda et al., 2010), Gfi1 (Hock et al., 2004a), or Gata2 (Rodrigues et al., 2005) result in adult HSC defects, whereas loss of Sox17 causes defects in fetal-liver HSCs (Kim et al., 2007). Gain-of-function studies have identified factors such as HoxB4, HoxA9, PU.1, Erdr1, and cFos that expand HSC activity (Deneault et al., 2009). "
ABSTRACT: Definitive hematopoiesis emerges during embryogenesis via an endothelial-to-hematopoietic transition. We attempted to induce this process in mouse fibroblasts by screening a panel of factors for hemogenic activity. We identified a combination of four transcription factors, Gata2, Gfi1b, cFos, and Etv6, that efficiently induces endothelial-like precursor cells, with the subsequent appearance of hematopoietic cells. The precursor cells express a human CD34 reporter, Sca1, and Prominin1 within a global endothelial transcription program. Emergent hematopoietic cells possess nascent hematopoietic stem cell gene-expression profiles and cell-surface phenotypes. After transgene silencing and reaggregation culture, the specified cells generate hematopoietic colonies in vitro. Thus, we show that a simple combination of transcription factors is sufficient to induce a complex, dynamic, and multistep developmental program in vitro. These findings provide insights into the specification of definitive hemogenesis and a platform for future development of patient-specific stem and progenitor cells, as well as more-differentiated blood products.Cell stem cell 06/2013; 13(2). DOI:10.1016/j.stem.2013.05.024 · 22.15 Impact Factor