A Functional Screen to Identify Novel Effectors of Hematopoietic Stem Cell Activity

Molecular Genetics of Stem Cells Laboratory, Institute of Research in Immunology and Cancer (IRIC), University of Montreal, Montreal, Quebec H3C 3J7, Canada.
Cell (Impact Factor: 32.24). 05/2009; 137(2):369-79. DOI: 10.1016/j.cell.2009.03.026
Source: PubMed


Despite tremendous progress made toward the identification of the molecular circuitry that governs cell fate in embryonic stem cells, genes controlling this process in the adult hematopoietic stem cell have proven to be more difficult to unmask. We now report the results of a novel gain-of-function screening approach, which identified a series of 18 nuclear factors that affect hematopoietic stem cell activity. Overexpression of ten of these factors resulted in an increased repopulating activity compared to unmanipulated cells. Interestingly, at least four of the 18 factors, Fos, Tcfec, Hmgb1, and Sfpi1, show non-cell-autonomous functions. The utilization of this screening method together with the creation of a database enriched for potential determinants of hematopoietic stem cell self-renewal will serve as a resource to uncover regulatory networks in these cells.

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    • "SOX4 is upregulated in various types of human solid tumors and is a frequent target of retroviral insertional mutagenesis in many murine B cell lymphoma and myeloid leukemia models (Jafarnejad et al., 2013). Its overexpression is associated with clonal dominance of HSC (Kustikova et al., 2007), stem/progenitor cell repopulation advantage (Deneault et al., 2009), a block in differentiation of myeloid progenitor 32DCl3 cells (Boyd et al., 2006), and induction of myeloid leukemia (Du et al., 2005; Kvinlaug et al., 2011). However , the precise role of Sox4 gene in AML and how it is involved in specific AML subtypes is poorly understood. "
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    ABSTRACT: Mutation or epigenetic silencing of the transcription factor C/EBPα is observed in ∼10% of patients with acute myeloid leukemia (AML). In both cases, a common global gene expression profile is observed, but downstream targets relevant for leukemogenesis are not known. Here, we identify Sox4 as a direct target of C/EBPα whereby its expression is inversely correlated with C/EBPα activity. Downregulation of Sox4 abrogated increased self-renewal of leukemic cells and restored their differentiation. Gene expression profiles of leukemia-initiating cells (LICs) from both Sox4 overexpression and murine C/EBPα mutant AML models clustered together but differed from other types of AML. Our data demonstrate that Sox4 overexpression resulting from C/EBPα inactivation contributes to the development of leukemia with a distinct LIC phenotype.
    Cancer cell 10/2013; 25(2). DOI:10.1016/j.ccr.2013.09.018 · 23.52 Impact Factor
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    • "The most significant motif is a putative binding site of EGR1, which was previously demonstrated to regulate HSC quiescence and retention in bone marrow (BM) (Min et al., 2008). The second motif is a predicted binding site for SOX4, which is reported to enhance murine HSC reconstitution potential (Deneault et al., 2009). The third motif is a predicted binding site for aryl hydrocarbon receptor (AHR), which is striking in light of a recent report demonstrating ex vivo expansion of HSCs using a purine derivative that acts as an AHR agonist (Boitano et al., 2010). "
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    ABSTRACT: This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited. SUMMARY Hematopoietic stem cells (HSCs) maintain blood homeostasis and are the functional units of bone marrow transplantation. To improve the molecular understanding of HSCs and their proximal progenitors, we performed transcriptome analysis within the context of the ImmGen Consortium data set. Gene sets that define steady-state and mobilized HSCs, as well as hematopoietic stem and progenitor cells (HSPCs), were determined. Genes involved in transcriptional regulation, including a group of putative transcriptional repressors, were identified in multipotent progenitors and HSCs. Proximal promoter analyses combined with ImmGen module analysis identified candi-date regulators of HSCs. Enforced expression of one predicted regulator, Hlf, in diverse HSPC subsets led to extensive self-renewal activity ex vivo. These analyses reveal unique insights into the mechanisms that control the core properties of HSPCs.
    Stem Cell Reports 09/2013; 1(3):266-280. DOI:10.1016/j.stemcr.2013.07.004 · 5.37 Impact Factor
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    • "Hematopoietic-specific knockout of PRDM16 results in reduced numbers of phenotypic and functional HSCs due to increased apoptosis and cell cycle activity (Aguilo et al., 2011; Chuikov et al., 2010). In contrast, overexpression of Prdm16 in HSCs causes an expansion of HSCs in vitro that upon transplantation generates a myeloproliferative disorder (Deneault et al., 2009). PRDM3/EVI1–MDS1/MECOM is the fusion protein created by intergenic splicing of EVI1 with MDS1 (Fears et al., 1996). "
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    ABSTRACT: Hematopoietic stem cells (HSC)(1) supply organisms with life-long output of mature blood cells. To do so, the HSC pool size has to be maintained by HSC self-renewing divisions. PRDM3 and PRDM16 have been documented to regulate HSC self-renewal, maintenance and function. We found Prdm11 to have similar expression patterns in the hematopoietic stem and progenitor cell (HSPC) compartments as Prdm3 and Prdm16. Therefore, we undertook experiments to test if PRDM11 regulates HSC self-renewal, maintenance and function by investigating the Prdm11(-/-) mice. Our data shows that phenotypic HSPCs are intact in bone marrow (BM) of one-year-old Prdm11(-/-) mice. In addition, Prdm11(-/-) mice were able to fully regenerate the hematopoietic system upon BM transplantation (BMT) into lethally irradiated mice with a mild drop in lymphoid output only. Taken together, this suggests that PRDM11, in contrast to PRDM3 and PRDM16, is not directly involved in regulation of HSPCs in mice.
    Stem Cell Research 08/2013; 11(3):1129-1136. DOI:10.1016/j.scr.2013.07.009 · 3.69 Impact Factor
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