The EMT regulator Zeb2/Sip1 is essential for murine embryonic hematopoietic stem/progenitor cell differentiation and mobilization

Abstract

IntroductionZeb2 (also known as Sip1 and Zfhx1b) is a DNA-binding transcriptional regulator of the family of zinc-finger E-box-binding (ZEB) proteins. 1,2 Its expression and functioning during development have been associated with epithelial-to-mesenchymal transitions (EMTs). 3 EMTs encompass a series of events in which polarized epithelial cells become round in shape, lose their cell-cell contacts, and acquire the motile, migratory properties of mesenchymal cells. 4 This physiologic process is essential for many developmental processes, including mesoderm formation during gastrulation and neural crest delamination and migration. Similar EMT-like changes in cellular morphology can be observed during tumor progression, allowing tumor cells to acquire the capacity to invade the surrounding tissue and ultimately metastasize to a distant site. Subsequent tissue colonization occurs via a reverse transitional mechanism called the mesenchymal-to-epithelial transition. Given the importance of EMT and the mesenchymal-to-epithelial transition in developmental processes and disease, numerous studies have identified several EMT-inducing or EMT-regulating transcription factors, including Zeb2. 5 Recent studies of neoplastic tissues have demonstrated the existence of cancer stem cells (CSCs), tumor-initiating cells with a self-renewal capacity that exhibit an ability to induce new tumors when transplanted into nude and/or syngeneic mouse strains. 6 The existence of CSCs was initially discovered in leukemia samples, but they have also been identified in various solid tumor types. The origin of CSCs was until now unclear, but compelling results from Mani et al 7 now link EMT processes with the formation of CSCs. EMT induction in an immortalized human mammary epithelial cell line resulted in the acquisition of mesenchymal traits, the expression of stem cell markers, and an enhanced capacity to form mammospheres, a property previously and exclusively associated with mammary epithelial stem cells. 7 Suppression of the miR-200 family members, which together with miR-205 have previously been shown to negatively regulate Zeb family members, 8 not only elevates Zeb1 and/or Zeb2 expression, but also several stem cell factors (including Bmi), resulting in increased stemness and metastasisinitiating capacity. 9 These findings illustrate a potential direct link between EMT induction and the acquisition of stem cell properties.It is in this context that we analyzed the role of the EMT inducer Zeb2 in the formation of tissue-specific stem cells in vivo, specifically within the hematopoietic system. Mature blood cells arise from HSCs that are capable of generating every hematopoietic cell type, including the various lymphoid and myeloid lineages. Each HSC has the capacity to generate large numbers of mature hematopoietic cells throughout its life, and the HSC pool size in adults is regulated by finely tuned self-renewal and differentiation The online version of this article contains a data supplement.The publication costs of this article wer...

The Role of EMT Modulators in Hematopoiesis and Leukemic Transformation

“…Moderate to high Zeb2 expression is reported in all hematopoietic cells with highest levels in stem (HSC) and progenitor (HPC) populations (Goossens et al, 2011) and lowest expression in mature T cells (Postigo & Dean, 2000). Through the use of a conditional Zeb2 knockout mouse (Higashi et al, 2002) model we could show that it is not essential for the initial formation of HSCs in the embryo but it is crucial for HSC differentiation and mobilization/homing (Goossens et al, 2011).…”

“…Through the use of a conditional Zeb2 knockout mouse (Higashi et al, 2002) model we could show that it is not essential for the initial formation of HSCs in the embryo but it is crucial for HSC differentiation and mobilization/homing (Goossens et al, 2011). Hematopoietic-specific Zeb2 loss-of-function resulted in embryonic lethality resulting from bleedings occurring in the developing brain.…”

The transcription factors ZEB2 and T-bet cooperate to program cytotoxic T cell terminal differentiation in response to LCMV viral infection

“…For simplicity, the Zeb2 flox/flox ; GzmB-cre + mice will be referred to as Zeb2 −/− mice and Zeb2 flox/flox ; GzmB-cre − or Zeb +/+ ; GzmB-cre + littermate controls will be referred to as WT mice. It was important to use a conditional knock-out strategy because Zeb2 −/− mice show embryonic lethality and Zeb2 is expressed in many cell types, including hematopoietic stem cells, NK cells, monocytes, and mast cells (Tylzanowski et al, 2003;van Grunsven et al, 2006;Goossens et al, 2011;Barbu et al, 2012;Best et al, 2013). Zeb2 was efficiently deleted in ∼85-90% of the polyclonal CD44 hi CD8 + T cells using this system (unpublished data).…”

Loss of autocrine endothelial-derived VEGF significantly reduces hemangiosarcoma development in conditional p53-deficient mice

“…17,27 To more specifically study the effects of p53 deletion on the endothelium, Tie2-Cre transgenic mice, 22 in which Cre recombinase is active in both the endothelium and the hematopoietic system, 28 were crossed with conditional p53 fl/fl mice. 23 The resultant Tie2-Cre, p53 fl/fl mice developed tumors by the average age of 25 wk (Fig.…”