Converting cell fates: generating hematopoietic stem cellsde novovia transcription factor reprogramming

Acetylation of histones is a key epigenetic modification involved in transcriptional regulation. The addition of acetyl groups to histone tails generally reduces histone-DNA interactions in the nucleosome leading to increased accessibility for transcription factors and core transcriptional machinery to bind their target sequences. There are approximately 30 histone acetyltransferases and their corresponding complexes, each of which affect the expression of a subset of genes. Because cell identity is determined by gene expression profile, it is unsurprising that the HATs responsible for inducing expression of these genes play a crucial role in determining cell fate. Here, we explore the role of HATs in the maintenance and differentiation of various stem cell types. Several HAT complexes have been characterized to play an important role in activating genes that allow stem cells to self-renew. Knockdown or loss of their activity leads to reduced expression and or differentiation while particular HATs drive differentiation towards specific cell fates. In this study we review functions of the HAT complexes active in pluripotent stem cells, hematopoietic stem cells, muscle satellite cells, mesenchymal stem cells, neural stem cells, and cancer stem cells.

Download Full-text

Live imaging of Runx1 expression in the dorsal aorta tracks the emergence of blood progenitors from endothelial cells

Blood ◽

10.1182/blood-2010-01-264382 ◽

2010 ◽

Vol 116 (6) ◽

pp. 909-914 ◽

Cited By ~ 114

Author(s):

Enid Yi Ni Lam ◽

Christopher J. Hall ◽

Philip S. Crosier ◽

Kathryn E. Crosier ◽

Maria Vega Flores

Keyword(s):

Endothelial Cells ◽

Transcription Factor ◽

Fluorescent Protein ◽

Living Organism ◽

Time Lapse ◽

Dorsal Aorta ◽

Transgenic Zebrafish ◽

Hematopoietic Stem ◽

Green Fluorescent

Abstract Blood cells of an adult vertebrate are continuously generated by hematopoietic stem cells (HSCs) that originate during embryonic life within the aorta-gonad-mesonephros region. There is now compelling in vivo evidence that HSCs are generated from aortic endothelial cells and that this process is critically regulated by the transcription factor Runx1. By time-lapse microscopy of Runx1-enhanced green fluorescent protein transgenic zebrafish embryos, we were able to capture a subset of cells within the ventral endothelium of the dorsal aorta, as they acquire hemogenic properties and directly emerge as presumptive HSCs. These nascent hematopoietic cells assume a rounded morphology, transiently occupy the subaortic space, and eventually enter the circulation via the caudal vein. Cell tracing showed that these cells subsequently populated the sites of definitive hematopoiesis (thymus and kidney), consistent with an HSC identity. HSC numbers depended on activity of the transcription factor Runx1, on blood flow, and on proper development of the dorsal aorta (features in common with mammals). This study captures the earliest events of the transition of endothelial cells to a hemogenic endothelium and demonstrates that embryonic hematopoietic progenitors directly differentiate from endothelial cells within a living organism.

Download Full-text

The homeodomain transcription factor PITX2 is required for specifying correct cell fates and establishing angiogenic privilege in the developing cornea

Developmental Dynamics ◽

10.1002/dvdy.24165 ◽

2014 ◽

Vol 243 (11) ◽

pp. 1391-1400 ◽

Cited By ~ 20

Author(s):

Philip J. Gage ◽

Chen Kuang ◽

Amanda L. Zacharias

Keyword(s):

Transcription Factor ◽

Cell Fates ◽

Homeodomain Transcription Factor

Download Full-text

A Novel, Myeloid Transcription Factor, C/EBPε, Is Upregulated During Granulocytic, But Not Monocytic, Differentiation

Blood ◽

10.1182/blood.v90.7.2591.2591_2591_2600 ◽

1997 ◽

Vol 90 (7) ◽

pp. 2591-2600 ◽

Cited By ~ 9

Author(s):

Roberta Morosetti ◽

Dorothy J. Park ◽

Alexey M. Chumakov ◽

Isabelle Grillier ◽

Masaaki Shiohara ◽

...

Keyword(s):

Stem Cells ◽

Transcription Factor ◽

Hematopoietic Stem Cells ◽

Cell Line ◽

Cell Lines ◽

Myeloid Leukemia ◽

Leukemia Cell ◽

Rt Pcr ◽

Hematopoietic Stem ◽

Nb4 Cells

Human C/EBPε is a newly cloned CCAAT/enhancer-binding transcription factor. Initial studies indicated it may be an important regulator of human myelopoiesis. To elucidate the range of expression of C/EBPε, we used reverse transcription-polymerase chain reaction (RT-PCR) analysis and examined its expression in 28 hematopoietic and 14 nonhematopoietic cell lines, 16 fresh myeloid leukemia samples, and normal human hematopoietic stem cells and their mature progeny. Prominent expression of C/EBPε mRNA occurred in the late myeloblastic and promyelocytic cell lines (NB4, HL60, GFD8), the myelomonoblastic cell lines (U937 and THP-1), the early myeloblast cell lines (ML1, KCL22, MDS92), and the T-cell lymphoblastic leukemia cell lines CEM and HSB-2. For the acute promyelocytic leukemia cell line NB4, C/EBPε was the only C/EBP family member that was easily detected by RT-PCR. No C/EBPε mRNA was found in erythroid, megakaryocyte, basophil, B lymphoid, or nonhematopoietic cell lines. Most acute myeloid leukemia samples (11 of 12) from patients expressed C/EBPε. Northern blot and RT-PCR analyses showed that C/EBPε mRNA decreased when the HL60 and KG-1 myeloblast cell lines were induced to differentiate toward macrophages. Similarly, Western blot analysis showed that expression of C/EBPε protein was either unchanged or decreased slightly as the promyelocytic cell line NB4 differentiated down the macrophage-like pathway after treatment with a potent vitamin D3 analog (KH1060). In contrast, C/EBPε protein levels increased dramatically as NB4 cells were induced to differentiate down the granulocytic pathway after exposure to 9-cis retinoic acid. Furthermore, very early, normal hematopoietic stem cells (CD34+/CD38−), purified from humans had very weak expression of C/EBPε mRNA, but levels increased as these cells differentiated towards granulocytes. Likewise, purified granulocytes appeared to express higher levels of C/EBPε mRNA than purified macrophages. Addition of phosphothiolated antisense, but not sense oligonucleotides to C/EBPε, decreased clonal growth of HL-60 and NB4 cells by about 50% compared with control cultures. Taken together, our results indicate that expression of C/EBPε is restricted to hematopoietic tissues, especially myeloid cells as they differentiate towards granulocytes and inhibition of its expression in HL-60 and NB4 myeloblasts and promyelocytes decreased their proliferative capacity. Therefore, this transcriptional factor may play an important role in the process of normal myeloid development.

Download Full-text

The megakaryocytic transcription factor ARID3A suppresses leukemia pathogenesis

Blood ◽

10.1182/blood.2021012231 ◽

2021 ◽

Author(s):

Oriol Alejo-Valle ◽

Karoline Weigert ◽

Raj Bhayadia ◽

Michelle Ng ◽

Hasan Issa ◽

...

Keyword(s):

Transcription Factor ◽

Transcriptional Repression ◽

Reverse Genetics ◽

Erythroid Differentiation ◽

Chromosome 21 ◽

Hematopoietic Stem ◽

Megakaryocytic Differentiation ◽

Megakaryoblastic Leukemia ◽

Multiple Routes ◽

Induced Apoptosis

Given the plasticity of hematopoietic stem/progenitor cells, multiple routes of differentiation must be blocked during acute myeloid leukemia pathogenesis - the molecular basis of which is incompletely understood. Here we report that post-transcriptional repression of the transcription factor ARID3A by miR-125b is a key event in megakaryoblastic leukemia (AMKL) pathogenesis. AMKL is frequently associated with trisomy 21 and GATA1 mutations (GATA1s), and children with Down syndrome are at a high risk of developing this disease. We show that chromosome 21-encoded miR-125b synergizes with Gata1s to drive leukemogenesis in this context. Leveraging forward and reverse genetics, we uncover Arid3a as the main miR-125b target behind this synergy. We demonstrate that, during normal hematopoiesis, this transcription factor promotes megakaryocytic differentiation in concert with GATA1 and mediates TGFβ-induced apoptosis and cell cycle arrest in complex with SMAD2/3. While Gata1s mutations perturb erythroid differentiation and induce hyperproliferation of megakaryocytic progenitors, intact ARID3A expression assures their megakaryocytic differentiation and growth restriction. Upon knockdown, these tumor suppressive functions are revoked, causing a dual megakaryocytic/erythroid differentiation blockade and subsequently AMKL. Inversely, restoring ARID3A expression relieves the megakaryocytic differentiation arrest in AMKL patient-derived xenografts. This work illustrates how mutations in lineage-determining transcription factors and perturbation of post-transcriptional gene regulation can interplay to block multiple routes of hematopoietic differentiation and cause leukemia. In AMKL, surmounting this differentiation blockade through restoration of the tumor suppressor ARID3A represents a promising strategy for treating this lethal pediatric disease.

Download Full-text

Gata2 is required for HSC generation and survival

Journal of Experimental Medicine ◽

10.1084/jem.20130751 ◽

2013 ◽

Vol 210 (13) ◽

pp. 2843-2850 ◽

Cited By ~ 119

Author(s):

Emma de Pater ◽

Polynikis Kaimakis ◽

Chris S. Vink ◽

Tomomasa Yokomizo ◽

Tomoko Yamada-Inagawa ◽

...

Keyword(s):

Endothelial Cells ◽

Transcription Factor ◽

Developmental Stages ◽

Vascular Endothelial ◽

Vascular Integrity ◽

Hematopoietic Stem ◽

Vascular Endothelial Cadherin ◽

Umbilical Arteries ◽

Specific Deletion

Knowledge of the key transcription factors that drive hematopoietic stem cell (HSC) generation is of particular importance for current hematopoietic regenerative approaches and reprogramming strategies. Whereas GATA2 has long been implicated as a hematopoietic transcription factor and its dysregulated expression is associated with human immunodeficiency syndromes and vascular integrity, it is as yet unknown how GATA2 functions in the generation of HSCs. HSCs are generated from endothelial cells of the major embryonic vasculature (aorta, vitelline, and umbilical arteries) and are found in intra-aortic hematopoietic clusters. In this study, we find that GATA2 function is essential for the generation of HSCs during the stage of endothelial-to-hematopoietic cell transition. Specific deletion of Gata2 in Vec (Vascular Endothelial Cadherin)-expressing endothelial cells results in a deficiency of long-term repopulating HSCs and intra-aortic cluster cells. By specific deletion of Gata2 in Vav-expressing hematopoietic cells (after HSC generation), we further show that GATA2 is essential for HSC survival. This is in contrast to the known activity of the RUNX1 transcription factor, which functions only in the generation of HSCs, and highlights the unique requirement for GATA2 function in HSCs throughout all developmental stages.

Download Full-text

Transcription factor Etv6 regulates functional differentiation of cross-presenting classical dendritic cells

Journal of Experimental Medicine ◽

10.1084/jem.20172323 ◽

2018 ◽

Vol 215 (9) ◽

pp. 2265-2278 ◽

Cited By ~ 10

Author(s):

Colleen M. Lau ◽

Ioanna Tiniakou ◽

Oriana A. Perez ◽

Margaret E. Kirkling ◽

George S. Yap ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

Transcription Factor ◽

T Cell ◽

Cd8 T Cells ◽

Functional Differentiation ◽

Specific Gene ◽

Hematopoietic Stem

An IRF8-dependent subset of conventional dendritic cells (cDCs), termed cDC1, effectively cross-primes CD8+ T cells and facilitates tumor-specific T cell responses. Etv6 is an ETS family transcription factor that controls hematopoietic stem and progenitor cell (HSPC) function and thrombopoiesis. We report that like HSPCs, cDCs express Etv6, but not its antagonist, ETS1, whereas interferon-producing plasmacytoid dendritic cells (pDCs) express both factors. Deletion of Etv6 in the bone marrow impaired the generation of cDC1-like cells in vitro and abolished the expression of signature marker CD8α on cDC1 in vivo. Moreover, Etv6-deficient primary cDC1 showed a partial reduction of cDC-specific and cDC1-specific gene expression and chromatin signatures and an aberrant up-regulation of pDC-specific signatures. Accordingly, DC-specific Etv6 deletion impaired CD8+ T cell cross-priming and the generation of tumor antigen–specific CD8+ T cells. Thus, Etv6 optimizes the resolution of cDC1 and pDC expression programs and the functional fitness of cDC1, thereby facilitating T cell cross-priming and tumor-specific responses.

Download Full-text

Functional Studies of MLL-AF4 and a Murinized pSer-variant thereof: MLL-AF4 Impairs the Ribosome Biosynthesis Pathway

10.21203/rs.3.rs-743930/v1 ◽

2021 ◽

Author(s):

Anna Lena Siemund ◽

Eric Kowarz ◽

Rolf Marschalek

Keyword(s):

Transcription Factor ◽

Fusion Protein ◽

Mammalian Cells ◽

Biological Activities ◽

Intracellular Localization ◽

Biological Behavior ◽

Hematopoietic Stem ◽

Functional Studies ◽

Pol I ◽

Transcription Factor Complex

Abstract Background: Recent pathomolecular studies on the MLL-AF4 fusion protein revealed that the murinized version of MLL-AF4, the MLL-Af4 fusion protein, was able to induce leukemia when expressed in murine or human hematopoietic stem/progenitor cells (1). In parallel, a group from Japan demonstrated that the pSer domain of the AF4 protein, as well as the pSer domain of the MLL-AF4 fusion is able to bind the Pol I transcription factor complex SL1 (2).Here, we investigated the human MLL-AF4 and a pSer-murinized version thereof for their functional properties in mammalian cells. Gene expression profiling studies were complemented by intracellular localization studies and functional experiments concerning the biological activities in the nuecleolus.Results: Based on our results, we have to conclude that MLL-AF4 is predominantly localizing in the nucleolus, thereby interfering withPol I transcription, and subsequently,also ribosomebiogenesis. The murinized pSer-variant is more localizing in the nucleus, which may explain their different biological behavior. Of note, AF4-MLL is cooperating at the molecular level with MLL-AF4, but not with the pSer-murinized version of it.Conclusion: This study provides new insights and a molecular explanation for the known differences between hMLL-hAF4 (not leukemogenic) and hMLL-mAf4 (leukemogenic). While the human pSer domain is able to efficiently recruit the SL1 transcription factor complex, the murine counterpart is not. This has several consequences for our understanding of t(4;11) leukemia which is by far the most frequent leukemia in infants, childhood and adults suffering from MLL-r acute leukemia.

Download Full-text

Asymmetric organelle inheritance predicts human blood stem cell fate

Blood ◽

10.1182/blood.2020009778 ◽

2021 ◽

Author(s):

Dirk Loeffler ◽

Florin Schneiter ◽

Weijia Wang ◽

Arne Wehling ◽

Tobias Kull ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Division ◽

Cell Fate ◽

Human Blood ◽

Asymmetric Cell Division ◽

Cell Fates ◽

Hematopoietic Stem ◽

Stem Cell Fate ◽

Blood Stem Cells

Understanding human hematopoietic stem cell fate control is important for their improved therapeutic manipulation. Asymmetric cell division, the asymmetric inheritance of factors during division instructing future daughter cell fates, was recently described in mouse blood stem cells. In human blood stem cells, the possible existence of asymmetric cell division remained unclear due to technical challenges in its direct observation. Here, we use long-term quantitative single-cell imaging to show that lysosomes and active mitochondria are asymmetrically inherited in human blood stem cells and that their inheritance is a coordinated, non-random process. Furthermore, multiple additional organelles, including autophagosomes, mitophagosomes, autolysosomes and recycling endosomes show preferential asymmetric co-segregation with lysosomes. Importantly, asymmetric lysosomal inheritance predicts future asymmetric daughter cell cycle length, differentiation and stem cell marker expression, while asymmetric inheritance of active mitochondria correlates with daughter metabolic activity. Hence, human hematopoietic stem cell fates are regulated by asymmetric cell division, with both mechanistic evolutionary conservation and differences to the mouse system.

Download Full-text