GATA-2 mediated regulation of normal hematopoietic stem/progenitor cell function, myelodysplasia and myeloid leukemia

Decoding the Implications of Zinc in the Development and Therapy of Leukemia

Zinc plays a central role in the hematological development. Therapeutic interventions with zinc are shown to improve the health status of patients with malignancies by stimulating the immune system and reducing side effects. Despite the abnormal zinc homeostasis in leukemia, the role and mechanisms of zinc signaling in leukemia development remain poorly understood. Recently, some important breakthroughs are made in laboratory and clinical studies of zinc in leukemia, such as the role of zinc in regulating ferroptosis and the effects of zinc in immunotherapy. Zinc-based strategies are urgently needed to refine the current zinc intervention regimen for side-effect free therapy in chemotherapy-intolerant patients. This review provides a comprehensive overview of the role of zinc homeostasis in leukemia patients and focuses on the therapeutic potential of zinc signaling modulation in leukemia.

Multifunctional acyltransferase HBO1: a key regulatory factor for cellular functions

HBO1, also known as KAT7 or MYST2, is a crucial histone acetyltransferase with diverse cellular functions. It typically forms complexes with protein subunits or cofactors such as MEAF6, ING4, or ING5, and JADE1/2/3 or BRPF1/2/3, where the BRPF or JADE proteins serve as the scaffold targeting histone H3 or H4, respectively. The histone acetylation mediated by HBO1 plays significant roles in DNA replication and gene expression regulation. Additionally, HBO1 catalyzes the modification of proteins through acylation with propionyl, butyryl, crotonyl, benzoyl, and acetoacetyl groups. HBO1 undergoes ubiquitination and degradation by two types of ubiquitin complexes and can also act as an E3 ubiquitin ligase for the estrogen receptor α (ERα). Moreover, HBO1 participates in the expansion of medullary thymic epithelial cells (mTECs) and regulates the expression of peripheral tissue genes (PTGs) mediated by autoimmune regulator (AIRE), thus inducing immune tolerance. Furthermore, HBO1 influences the renewal of hematopoietic stem cells and the development of neural stem cells significantly. Importantly, the overexpression of HBO1 in various cancers suggests its carcinogenic role and potential as a therapeutic target. This review summarizes recent advancements in understanding HBO1's involvement in acylation modification, DNA replication, ubiquitination, immunity, and stem cell renewal.

REEP3 is a potential diagnostic and prognostic biomarker correlated with immune infiltration in pancreatic cancer

Receptor Expression-Enhancing Protein 3 (REEP3) serves as a pivotal enzyme crucial for endoplasmic reticulum (ER) clearance during mitosis and is implicated in the advancement of diverse malignancies. Nonetheless, the biological role and mechanisms of REEP3 in pancreatic cancer patients, along with its interplay with immune infiltration, remain inadequately elucidated. In this study, we initially analyzed the differential expression of REEP3 between pancreatic cancer tissues and normal pancreas tissues using the Cancer Genome Atlas (TCGA), GTEx and Gene Expression Omnibus (GEO) databases. Subsequently, we utilized Kaplan-Meier analysis, Cox regression and ROC curve to determine the predictive value of REEP3 for the clinical outcomes of pancreatic cancer patients. Functional enrichment analyses, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA), were conducted to explore the potential signaling pathways and biological functions associated with pancreatic cancer. Furthermore, we investigated the PPI network, miRNA, RBP and transcription factor interactions of REEP3 using databases such as GeneMania, STRING, StarBase, KnockTK, ENCODE, Jaspar and hTFtarget. Lastly, the "ssGSEA" algorithm and TIMER database were employed to investigate the correlation between REEP3 expression and immune infiltration as well as immune checkpoints. The expression of REEP3 in pancreatic cancer showed a significantly higher level compared to that in normal tissues. ROC curve analysis indicated that REEP3 holds substantial diagnostic potential for pancreatic cancer patients. Elevated REEP3 expression correlated with unfavorable outcomes in terms of both overall survival and relapse-free survival, establishing it as a notable adverse prognostic marker in pancreatic cancer. Moreover, both univariate and multivariate Cox regression analyses demonstrated that REEP3 maintained an independent association with overall survival. Functional enrichment analyses revealed pathways significantly linked to REEP3, including cytoplasmic translation, wound healing, viral processes, regulation of cellular component size and actin filament organization. Additionally, REEP3 expression displayed a significant positive correlation with CD8+ T cells, B cells, natural killer cells, dendritic cells and macrophages. REEP3 is a potential diagnostic, prognostic marker and immunotherapeutic target for pancreatic cancer.

GATA2 mutant variant allele frequency may reflect prognosis in Chinese adult patients with de novo cytogenetically normal acute myeloid leukemia

Exploration of variant allele frequency (VAF) of GATA2 mutations (GATA2mut) provides insights into acute myeloid leukemia (AML) prognosis. In this study, we analyzed GATA2mut and co-mutations in 166 Chinese patients with cytogenetically normal AML. This was done through targeted next-generation sequencing of 34 genes associated with myeloid leukemia. GATA2mut was identified in 17 (10%) patients being significantly correlated with co-mutations in CCAAT/enhancer-binding protein alpha (CEBPA) double mutation (P = 0.001). We observed that the N-terminal zinc finger domain (ZF1) was linked to CEBPA mutations, while the C-terminal zinc finger domain (ZF2) was associated with Wilms' tumor 1 (WT1) mutations. It was also noted that patients with GATA2mut had lower platelet counts at diagnosis (P = 0.032). In the entire cohort, GATA2mut had no significant prognostic impact on overall survival (OS) (P = 0.762) and relapse-free survival (RFS) (P = 0.369) compared to patients with GATA2wt. The OS (P = 0.737) and RFS (P = 0.894) of the ZF1 mutation were similar to those of the ZF2 mutation. Most patients with GATA2 mutations were classified in the ELN2022 favorable- and intermediate-risk groups. GATA2mut patients in the favorable-risk group were divided into GATA2High and GATA2Low groups using a median cutoff variant allele frequency (VAF) of 40.13%. GATA2High patients were associated with worse OS (P = 0.031) and RFS (P = 0.021) than GATA2Low patients. In the intermediate-risk group, the high median VAF of GATA2 (≥38.51%) had no significant effect in OS and RFS compared with the low median VAF (<38.51%). This study offers new insights on the prognosis of GATA2mut in the favorable-risk group, where VAF can be used as a guide.

The Role of Stem Cells as Therapeutics for Ischaemic Stroke

Stroke remains one of the leading causes of death and disability worldwide. Current reperfusion treatments for ischaemic stroke are limited due to their narrow therapeutic window in rescuing ischaemic penumbra. Stem cell therapy offers a promising alternative. As a regenerative medicine, stem cells offer a wider range of treatment strategies, including long-term intervention for chronic patients, through the reparation and replacement of injured cells via mechanisms of differentiation and proliferation. The purpose of this review is to evaluate the therapeutic role of stem cells for ischaemic stroke. This paper discusses the pathology during acute, subacute, and chronic phases of cerebral ischaemic injury, highlights the mechanisms involved in mesenchymal, endothelial, haematopoietic, and neural stem cell-mediated cerebrovascular regeneration, and evaluates the pre-clinical and clinical data concerning the safety and efficacy of stem cell-based treatments. The treatment of stroke patients with different types of stem cells appears to be safe and efficacious even at relatively higher concentrations irrespective of the route and timing of administration. The priming or pre-conditioning of cells prior to administration appears to help augment their therapeutic impact. However, larger patient cohorts and later-phase trials are required to consolidate these findings.

A review of the role of zinc finger proteins on hematopoiesis

The bone marrow is responsible for producing an incredible number of cells daily in order to maintain blood homeostasis through a process called hematopoiesis. Hematopoiesis is a greatly demanding process and one entirely dependent on complex interactions between the hematopoietic stem cell (HSC) and its surrounding microenvironment. Zinc (Zn2+) is considered an important trace element, playing diverse roles in different tissues and cell types, and zinc finger proteins (ZNF) are proteins that use Zn2+ as a structural cofactor. In this way, the ZNF structure is supported by a Zn2+ that coordinates many possible combinations of cysteine and histidine, with the most common ZNF being of the Cys2His2 (C2H2) type, which forms a family of transcriptional activators that play an important role in different cellular processes such as development, differentiation, and suppression, all of these being essential processes for an adequate hematopoiesis. This review aims to shed light on the relationship between ZNF and the regulation of the hematopoietic tissue. We include works with different designs, including both in vitro and in vivo studies, detailing how ZNF might regulate hematopoiesis.

Role of the pioneer transcription factor GATA2 in health and disease

The transcription factor GATA2 is involved in human diseases ranging from hematopoietic disorders, to cancer, to infectious diseases. GATA2 is one of six GATA-family transcription factors that act as pioneering transcription factors which facilitate the opening of heterochromatin and the subsequent binding of other transcription factors to induce gene expression from previously inaccessible regions of the genome. Although GATA2 is essential for hematopoiesis and lymphangiogenesis, it is also expressed in other tissues such as the lung, prostate gland, gastrointestinal tract, central nervous system, placenta, fetal liver, and fetal heart. Gene or transcriptional abnormalities of GATA2 causes or predisposes patients to several diseases including the hematological cancers acute myeloid leukemia and acute lymphoblastic leukemia, the primary immunodeficiency MonoMAC syndrome, and to cancers of the lung, prostate, uterus, kidney, breast, gastric tract, and ovaries. Recent data has also linked GATA2 expression and mutations to responses to infectious diseases including SARS-CoV-2 and Pneumocystis carinii pneumonia, and to inflammatory disorders such as atherosclerosis. In this article we review the role of GATA2 in the etiology and progression of these various diseases.

GATA2 mitotic bookmarking is required for definitive haematopoiesis

In mitosis, most transcription factors detach from chromatin, but some are retained and bookmark genomic sites. Mitotic bookmarking has been implicated in lineage inheritance, pluripotency and reprogramming. However, the biological significance of this mechanism in vivo remains unclear. Here, we address mitotic retention of the hemogenic factors GATA2, GFI1B and FOS during haematopoietic specification. We show that GATA2 remains bound to chromatin throughout mitosis, in contrast to GFI1B and FOS, via C-terminal zinc finger-mediated DNA binding. GATA2 bookmarks a subset of its interphase targets that are co-enriched for RUNX1 and other regulators of definitive haematopoiesis. Remarkably, homozygous mice harbouring the cyclin B1 mitosis degradation domain upstream Gata2 partially phenocopy knockout mice. Degradation of GATA2 at mitotic exit abolishes definitive haematopoiesis at aorta-gonad-mesonephros, placenta and foetal liver, but does not impair yolk sac haematopoiesis. Our findings implicate GATA2-mediated mitotic bookmarking as critical for definitive haematopoiesis and highlight a dependency on bookmarkers for lineage commitment.

Single-cell gene and isoform expression analysis reveals signatures of ageing in haematopoietic stem and progenitor cells

Single-cell approaches have revealed that the haematopoietic hierarchy is a continuum of differentiation, from stem cell to committed progenitor, marked by changes in gene expression. However, many of these approaches neglect isoform-level information and thus do not capture the extent of alternative splicing within the system. Here, we present an integrated short- and long-read single-cell RNA-seq analysis of haematopoietic stem and progenitor cells. We demonstrate that over half of genes detected in standard short-read single-cell analyses are expressed as multiple, often functionally distinct, isoforms, including many transcription factors and key cytokine receptors. We observe global and HSC-specific changes in gene expression with ageing but limited impact of ageing on isoform usage. Integrating single-cell and cell-type-specific isoform landscape in haematopoiesis thus provides a new reference for comprehensive molecular profiling of heterogeneous tissues, as well as novel insights into transcriptional complexity, cell-type-specific splicing events and consequences of ageing.

Dynamics of Chromatin Accessibility During Hematopoietic Stem Cell Differentiation Into Progressively Lineage-Committed Progeny

Epigenetic mechanisms regulate the multilineage differentiation capacity of hematopoietic stem cells (HSCs) into a variety of blood and immune cells. Mapping the chromatin dynamics of functionally defined cell populations will shed mechanistic insight into 2 major, unanswered questions in stem cell biology: how does epigenetic identity contribute to a cell type's lineage potential, and how do cascades of chromatin remodeling dictate ensuing fate decisions? Our recent work revealed evidence of multilineage gene priming in HSCs, where open cis-regulatory elements (CREs) exclusively shared between HSCs and unipotent lineage cells were enriched for DNA binding motifs of known lineage-specific transcription factors. Oligopotent progenitor populations operating between the HSCs and unipotent cells play essential roles in effecting hematopoietic homeostasis. To test the hypothesis that selective HSC-primed lineage-specific CREs remain accessible throughout differentiation, we used ATAC-seq to map the temporal dynamics of chromatin remodeling during progenitor differentiation. We observed epigenetic-driven clustering of oligopotent and unipotent progenitors into distinct erythromyeloid and lymphoid branches, with multipotent HSCs and MPPs associating with the erythromyeloid lineage. We mapped the dynamics of lineage-primed CREs throughout hematopoiesis and identified both unique and shared CREs as potential lineage reinforcement mechanisms at fate branch points. Additionally, quantification of genome-wide peak count and size revealed overall greater chromatin accessibility in HSCs, allowing us to identify HSC-unique peaks as putative regulators of self-renewal and multilineage potential. Finally, CRISPRi-mediated targeting of ATACseq-identified putative CREs in HSCs allowed us to demonstrate the functional role of selective CREs in lineage-specific gene expression. These findings provide insight into the regulation of stem cell multipotency and lineage commitment throughout hematopoiesis and serve as a resource to test functional drivers of hematopoietic lineage fate.

The Clinical Spectrum, Diagnosis, and Management of GATA2 Deficiency

Hereditary myeloid malignancy syndromes (HMMSs) are rare but are becoming increasingly significant in clinical practice. One of the most well-known syndromes within this group is GATA2 deficiency. The GATA2 gene encodes a zinc finger transcription factor essential for normal hematopoiesis. Insufficient expression and function of this gene as a result of germinal mutations underlie distinct clinical presentations, including childhood myelodysplastic syndrome and acute myeloid leukemia, in which the acquisition of additional molecular somatic abnormalities can lead to variable outcomes. The only curative treatment for this syndrome is allogeneic hematopoietic stem cell transplantation, which should be performed before irreversible organ damage happens. In this review, we will examine the structural characteristics of the GATA2 gene, its physiological and pathological functions, how GATA2 genetic mutations contribute to myeloid neoplasms, and other potential clinical manifestations. Finally, we will provide an overview of current therapeutic options, including recent transplantation strategies.

Distinct expression and prognostic values of GATA transcription factor family in human ovarian cancer

Accumulated studies have provided controversial evidences of expression patterns and prognostic value of the GATA family in human ovarian cancer. In the present study, we accessed the distinct expression and prognostic roles of 7 individual members of GATA family in ovarian cancer (OC) patients through Oncomine analysis, CCLE analysis, Human Protein Atlas (HPA), Kaplan–Meier plotter (KM plotter) database, cBioPortal and Metascape. Our results indicated that GATA1, GATA3, GATA4 and TRPS1 mRNA and protein expression was significantly higher in OC than normal samples. High expression of GATA1, GATA2, and GATA4 were significantly correlated with better overall survival (OS), while increased GATA3 and GATA6 expression were associated with worse prognosis in OC patients. GATA1, GATA2, GATA3 and GATA6 were closely related to the different pathological histology, pathological grade, clinical stage and TP53 mutation status of OC. The genetic variation and interaction of the GATA family may be closely related to the pathogenesis and prognosis of OC, and the regulatory network composed of GATA family genes and their neighboring genes are mainly involved in Notch signaling pathway, Th1 and Th2 cell differentiation and Hippo signaling pathway. Transcriptional GATA1/2/3/4/6 could be prognostic markers and potential therapeutic target for OC patients.

Conversion of a Non-Cancer-Selective Promoter into a Cancer-Selective Promoter

Simple Summary

The rat progression elevated gene-3 (PEG-3) promoter displays cancer-selective expression, whereas the rat growth arrest and DNA damage inducible gene-34 (GADD34) promoter lacks cancer specificity. PEG-3 and GADD34 minimal promoters display strong sequence homology except for two single point mutations. Since mutations are prevalent in many gene promoters resulting in significant alterations in promoter specificity and activity, we have explored the relevance of these two nucleotide alterations in determining cancer-selective gene expression. We demonstrate that these two point mutations are required to transform a non-cancer-specific promoter (pGADD) into a cancer-selective promoter (pGAPE). Additionally, we found GATA2 transcription factor binding sites in the GAPE-Prom, which regulates pGAPE activity selectively in cancer cells. This newly created pGAPE has all the necessary elements making it an appropriate genetic tool to noninvasively deliver imaging agents to follow tumor growth and progression to metastasis and for generating conditionally replicating adenoviruses that can express and deliver their payload exclusively in cancer.

Abstract

Progression-elevated gene-3 (PEG-3) and rat growth arrest and DNA damage-inducible gene-34 (GADD34) display significant sequence homology with regulation predominantly transcriptional. The rat full-length (FL) and minimal (min) PEG-3 promoter display cancer-selective expression in rodent and human tumors, allowing for cancer-directed regulation of transgenes, viral replication and in vivo imaging of tumors and metastases in animals, whereas the FL- and min-GADD34-Prom lack cancer specificity. Min-PEG-Prom and min-GADD34-Prom have identical sequences except for two single-point mutation differences (at −260 bp and +159 bp). Engineering double mutations in the min-GADD34-Prom produce the GAPE-Prom. Changing one base pair (+159) or both point mutations in the min-GADD34-Prom, but not the FL-GADD34-Prom, results in cancer-selective transgene expression in diverse cancer cells (including prostate, breast, pancreatic and neuroblastoma) vs. normal counterparts. Additionally, we identified a GATA2 transcription factor binding site, promoting cancer specificity when both min-PEG-Prom mutations are present in the GAPE-Prom. Taken together, introducing specific point mutations in a rat min-GADD34-Prom converts this non-cancer-specific promoter into a cancer-selective promoter, and the addition of GATA2 with existing AP1 and PEA3 transcription factors enhances further cancer-selective activity of the GAPE-Prom. The GAPE-Prom provides a genetic tool to specifically regulate transgene expression in cancer cells.

The histone lysine acetyltransferase HBO1 (KAT7) regulates hematopoietic stem cell quiescence and self-renewal

The histone acetyltransferase HBO1 (MYST2, KAT7) is indispensable for postgastrulation development, histone H3 lysine 14 acetylation (H3K14Ac), and the expression of embryonic patterning genes. In this study, we report the role of HBO1 in regulating hematopoietic stem cell function in adult hematopoiesis. We used 2 complementary cre-recombinase transgenes to conditionally delete Hbo1 (Mx1-Cre and Rosa26-CreERT2). Hbo1-null mice became moribund due to hematopoietic failure with pancytopenia in the blood and bone marrow 2 to 6 weeks after Hbo1 deletion. Hbo1-deleted bone marrow cells failed to repopulate hemoablated recipients in competitive transplantation experiments. Hbo1 deletion caused a rapid loss of hematopoietic progenitors. The numbers of lineage-restricted progenitors for the erythroid, myeloid, B-, and T-cell lineages were reduced. Loss of HBO1 resulted in an abnormally high rate of recruitment of quiescent hematopoietic stem cells (HSCs) into the cell cycle. Cycling HSCs produced progenitors at the expense of self-renewal, which led to the exhaustion of the HSC pool. Mechanistically, genes important for HSC functions were downregulated in HSC-enriched cell populations after Hbo1 deletion, including genes essential for HSC quiescence and self-renewal, such as Mpl, Tek(Tie-2), Gfi1b, Egr1, Tal1(Scl), Gata2, Erg, Pbx1, Meis1, and Hox9, as well as genes important for multipotent progenitor cells and lineage-specific progenitor cells, such as Gata1. HBO1 was required for H3K14Ac through the genome and particularly at gene loci required for HSC quiescence and self-renewal. Our data indicate that HBO1 promotes the expression of a transcription factor network essential for HSC maintenance and self-renewal in adult hematopoiesis.

Oncogene-Induced Reprogramming in Acute Lymphoblastic Leukemia: Towards Targeted Therapy of Leukemia-Initiating Cells

Simple Summary

Acute lymphoblastic leukemia is a heterogeneous disease characterized by a diversity of genetic alterations, following a sophisticated and controversial organization. In this review, we present and discuss the concepts exploring the cellular, molecular and functional heterogeneity of leukemic cells. We also review the emerging evidence indicating that cell plasticity and oncogene-induced reprogramming should be considered at the biological and clinical levels as critical mechanisms for identifying and targeting leukemia-initiating cells.

Abstract

Our understanding of the hierarchical structure of acute leukemia has yet to be fully translated into therapeutic approaches. Indeed, chemotherapy still has to take into account the possibility that leukemia-initiating cells may have a distinct chemosensitivity profile compared to the bulk of the tumor, and therefore are spared by the current treatment, causing the relapse of the disease. Therefore, the identification of the cell-of-origin of leukemia remains a longstanding question and an exciting challenge in cancer research of the last few decades. With a particular focus on acute lymphoblastic leukemia, we present in this review the previous and current concepts exploring the phenotypic, genetic and functional heterogeneity in patients. We also discuss the benefits of using engineered mouse models to explore the early steps of leukemia development and to identify the biological mechanisms driving the emergence of leukemia-initiating cells. Finally, we describe the major prospects for the discovery of new therapeutic strategies that specifically target their aberrant stem cell-like functions.

Arsenic Dispensing Powder Promotes Erythropoiesis in Myelodysplastic Syndromes via Downregulation of HIF1A and Upregulation of GATA Factors

Traditional Chinese Medicine (TCM) is a practical medicine based on thousands of years of medical practice in China. Arsenic dispensing powder (ADP) has been used as a treatment for MDS patients with a superior efficacy on anemia at Xiyuan Hospital of China Academy of Chinese Medical Sciences. In this study, we retrospectively analyzed MDS patients that received ADP treatment in the past 9 years and confirmed that ADP improves patients' anemia and prolongs overall survival in intermediate-risk MDS patients. Then, we used the MDS transgenic mice model and cell line to explore the drug mechanism. In normal and MDS cells, ADP does not show cellular toxicity but promotes differentiation. In mouse MDS models, we observed that ADP showed significant efficacy on promoting erythropoiesis. In the BFU-E and CFU-E assays, ADP could promote erythropoiesis not only in normal clones but also in MDS clones. Mechanistically, we found that ADP could downregulate HIF1A in MDS clones through upregulation of VHL, P53 and MDM2, which is involved in two parallel pathways to downregulate HIF1A. We also confirmed that ADP upregulates GATA factors in normal clones. Thus, our clinical and experimental studies indicate that ADP is a promising drug to promote erythropoiesis in both MDS and normal clones with a superior outcome than current regular therapies. ADP promotes erythropoiesis in myelodysplastic syndromes via downregulation of HIF1A and upregulation of GATA factors.

The functional interplay of transcription factors and cell adhesion molecules in experimental myelodysplasia including hematopoietic stem progenitor compartment

Myelodysplastic syndrome is a heterogenous group of disorder with clonal dysregulated hematopoiesis characterized by bone marrow failure, cytogenetic and molecular abnormalities and variable risk of progression to acute myeloid leukemia (AML). The bone marrow niche plays a major role in maintaining the homeostasis and is often injured by the chemotherapeutic drugs leading to catastrophic consequences like myelodysplastic syndrome. In the present study, we made an attempt to find out the osteoblastic niche related alterations in the myelodysplastic bone marrow through mainly flowcytometric and fluorescent microscopic studies. We have also checked the condition of the myelodysplastic bone through micro computed tomography. The results revealed that the affected osteoblasts of the myelodysplastic bone marrow compelled the hematopoietic stem cell to come out of quiescence and become actively proliferating, and in this scenario the decline in expression of cell adhesion molecules like N-Cadherin, Intercellular adhesion molecule 1 (ICAM) and upregulated focal adhesion kinase (FAK) played a major role. The hike in number of osteoclasts in myelodysplastic cases than control also shattered the balance between bone formation and resorption ratio. We have recorded a dysregulated expression of transcription factors GATA2 and CEBPα (CCAAT-enhancer-binding-protein) in the hematopoietic stem progenitor compartment of the myelodysplastic bone marrow, the main reason behind the presence of abnormal myeloblasts in myelodysplastic cases. Collectively, we can say the coordinated perturbations in the osteoblastic niche, cell adhesion molecules together with the transcription factors has resulted in the uncontrolled proliferation of hematopoietic stem cell, dysregulated myelopoiesis, early trafficking of hematopoietic progenitors to blood compartment and at the same time pancytopenic peripheral blood conditions during the progression of N-Ethyl N Nitroso Urea (ENU) induced myelodysplasia.

Myelopoiesis of the Amphibian Xenopus laevis Is Segregated to the Bone Marrow, Away From Their Hematopoietic Peripheral Liver

Across vertebrates, hematopoiesis takes place within designated tissues, wherein committed myeloid progenitors further differentiate toward cells with megakaryocyte/erythroid potential (MEP) or those with granulocyte/macrophage potential (GMP). While the liver periphery (LP) of the Xenopus laevis amphibian functions as a principal site of hematopoiesis and contains MEPs, cells with GMP potential are instead segregated to the bone marrow (BM) of this animal. Presently, using gene expression and western blot analyses of blood cell lineage-specific transcription factors, we confirmed that while the X. laevis LP hosts hematopoietic stem cells and MEPs, their BM contains GMPs. In support of our hypothesis that cells bearing GMP potential originate from the frog LP and migrate through blood circulation to the BM in response to chemical cues; we demonstrated that medium conditioned by the X. laevis BM chemoattracts LP and peripheral blood cells. Compared to LP and by examining a comprehensive panel of chemokine genes, we showed that the X. laevis BM possessed greater expression of a single chemokine, CXCL12, the recombinant form of which was chemotactic to LP and peripheral blood cells and appeared to be a major chemotactic component within BM-conditioned medium. In confirmation of the hepatic origin of the cells that give rise to these frogs' GMPs, we also demonstrated that the X. laevis BM supported the growth of their LP-derived cells.

New Insights Into the Differentiation of Megakaryocytes From Hematopoietic Progenitors

Megakaryocytes are hematopoietic cells, which are responsible for the production of blood platelets. The traditional view of megakaryopoiesis describes the cellular journey from hematopoietic stem cells, through a hierarchical series of progenitor cells, ultimately to a mature megakaryocyte. Once mature, the megakaryocyte then undergoes a terminal maturation process involving multiple rounds of endomitosis and cytoplasmic restructuring to allow platelet formation. However, recent studies have begun to redefine this hierarchy and shed new light on alternative routes by which hematopoietic stem cells are differentiated into megakaryocytes. In particular, the origin of megakaryocytes, including the existence and hierarchy of megakaryocyte progenitors, has been redefined, as new studies are suggesting that hematopoietic stem cells originate as megakaryocyte-primed and can bypass traditional lineage checkpoints. Overall, it is becoming evident that megakaryopoiesis does not only occur as a stepwise process, but is dynamic and adaptive to biological needs. In this review, we will reexamine the canonical dogmas of megakaryopoiesis and provide an updated framework for interpreting the roles of traditional pathways in the context of new megakaryocyte biology. Visual Overview- An online visual overview is available for this article.

Rapid progression to AML in a patient with germline GATA2 mutation and acquired NRAS Q61K mutation

GATA2 deficiency syndrome is caused by autosomal dominant, heterozygous germline mutations with widespread effects on immune, pulmonary and vascular systems. Patients commonly develop hematological abnormalities including bone marrow failure, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). We present a patient with GATA2 mutation and MDS who progressed to AML over four months. Whole exome and targeted deep sequencing identified a new p.Q61K NRAS mutation in the bone marrow at the time of AML development. Rapid development of AML is possible in the setting of germline GATA2 mutation despite stable MDS, supporting close monitoring and consideration of early allogeneic transplantation.

Impaired immune responses to herpesviruses and microbial ligands in patients with MonoMAC

MonoMAC is a complex primary immunodeficiency caused by mutations in the myeloid transcription factor GATA2, characterized by multilineage cytopenia with malignant complications and severe infections, including mycobacteria and herpesviruses. We describe the clinical presentation, genetics and antiviral inflammatory responses in a small case series. Two patients presented in childhood with mycobacterial infection and were diagnosed with MonoMAC germline GATA2 variants; their healthy fathers with the same mutations were also studied. Three patients were elderly individuals with acquired GATA2 mutations and malignant haematological conditions. Overall, this study demonstrates the heterogeneous clinical presentation and variation in immunodeficiency caused by GATA2 mutations.

High glucose promotes pancreatic cancer cells to escape from immune surveillance via AMPK-Bmi1-GATA2-MICA/B pathway

Background

Modulation of cell surface expression of MHC class I chain-related protein A/B (MICA/B) has been proven to be one of the mechanisms by which tumor cells escape from NK cell-mediated killing. Abnormal metabolic condition, such as high glucose, may create a cellular stress milieu to induce immune dysfunction. Hyperglycemia is frequently presented in the majority of pancreatic cancer patients and is associated with poor prognosis. In this study, we aimed to detect the effects of high glucose on NK cell-mediated killing on pancreatic cancer cells through reduction of MICA/B expression.

Methods

The lysis of NK cells on pancreatic cancer cells were compared at different glucose concentrations through lactate dehydrogenase release assay. Then, qPCR, Western Blot, Flow cytometry and Immunofluorescence were used to identify the effect of high glucose on expression of MICA/B, Bmi1, GATA2, phosphorylated AMPK to explore the underlying mechanisms in the process. Moreover, an animal model with diabetes mellitus was established to explore the role of high glucose on NK cell-mediated cytotoxicity on pancreatic cancer in vivo.

Results

In our study, high glucose protects pancreatic cancer from NK cell-mediated killing through suppressing MICA/B expression. Bmi1, a polycomb group (PcG) protein, was found to be up-regulated by high glucose, and mediated the inhibition of MICA/B expression through promoting GATA2 in pancreatic cancer. Moreover, high glucose inhibited AMP-activated protein kinase signaling, leading to high expression of Bmi1.

Conclusion

Our findings identify that high glucose may promote the immune escape of pancreatic cancer cells under hyperglycemic tumor microenvironment. In this process, constitutive activation of AMPK-Bmi1-GATA2 axis could mediate MICA/B inhibition, which may serve as a therapeutic target for further intervention of pancreatic cancer immune evasion.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1209-9) contains supplementary material, which is available to authorized users.

A new genetic tool to improve immune-compromised mouse models: Derivation and CRISPR/Cas9-mediated targeting of NRG embryonic stem cell lines

Development of human hematopoietic stem cells and differentiation of embryonic stem (ES) cells/induced pluripotent stem (iPS) cells to hematopoietic stem cells are poorly understood. NOD (Non-obese diabetic)-derived mouse strains, such as NSG (NOD-Scid-il2Rg) or NRG (NOD-Rag1-il2Rg), are the best available models for studying the function of fetal and adult human hematopoietic cells as well as ES/iPS cell-derived hematopoietic stem cells. Unfortunately, engraftment of human hematopoietic stem cells is very variable in these models. Introduction of additional permissive mutations into these complex genetic backgrounds of the NRG/NSG mice by natural breeding is a very demanding task in terms of time and resources. Specifically, since the genetic elements defining the NSG/NRG phenotypes have not yet been fully characterized, intense backcrossing is required to ensure transmission of the full phenotype. Here we describe the derivation of embryonic stem cell (ESC) lines from NRG pre-implantation embryos generated by in vitro fertilization followed by the CRISPR/CAS9 targeting of the Gata-2 locus. After injection into morula stage embryos, cells from three tested lines gave rise to chimeric adult mice showing high contribution of the ESCs (70%-100%), assessed by coat color. Moreover, these lines have been successfully targeted using Cas9/CRISPR technology, and the mutant cells have been shown to remain germ line competent. Therefore, these new NRG ESC lines combined with genome editing nucleases bring a powerful genetic tool that facilitates the generation of new NOD-based mouse models with the aim to improve the existing xenograft models.

Myeloid malignancies with somatic GATA2 mutations can be associated with an immunodeficiency phenotype

Germline mutations in GATA2 are associated with a complex immunodeficiency and cancer predisposition syndrome. Somatic GATA2^mut in myeloid malignancies may impart a similar phenotype. We reviewed adult patients with a diagnosis of GATA2^mut hematological malignancy who were referred to our HHMC for genetic testing, and identified to have somatic GATA2^mut. Nine patients with a median age of 63 years were included. Six patients (66.7%) were males. Atypical CML and acute myeloid leukemia were the most common initial presentation. The median overall VAF was 47.14%. Monocytopenia was pronounced when the GATA2^mut involved the C-terminal ZFD. GATA2 N-terminal ZFD mutations tend to be co-mutated with biCEBPA^mut. Unlike germline GATA2 mutations, monocytopenia associated with somatic GATA2 mutations often resolved at remission. We concluded that similar to germline GATA2 mutations, a subset of somatic GATA2 mutations can impart a germline phenotype.

Hematopoietic Differentiation of Human Pluripotent Stem Cells: HOX and GATA Transcription Factors as Master Regulators

Numerous human disorders of the blood system would directly or indirectly benefit from therapeutic approaches that reconstitute the hematopoietic system. Hematopoietic stem cells (HSCs), either from matched donors or ex vivo manipulated autologous tissues, are the most used cellular source of cell therapy for a wide range of disorders. Due to the scarcity of matched donors and the difficulty of ex vivo expansion of HSCs, there is a growing interest in harnessing the potential of pluripotent stem cells (PSCs) as a de novo source of HSCs. PSCs make an ideal source of cells for regenerative medicine in general and for treating blood disorders in particular because they could expand indefinitely in culture and differentiate to any cell type in the body. However, advancement in deriving functional HSCs from PSCs has been slow. This is partly due to an incomplete understanding of the molecular mechanisms underlying normal hematopoiesis. In this review, we discuss the latest efforts to generate human PSC (hPSC)-derived HSCs capable of long-term engraftment. We review the regulation of the key transcription factors (TFs) in hematopoiesis and hematopoietic differentiation, the Homeobox (HOX) and GATA genes, and the interplay between them and microRNAs. We also propose that precise control of these master regulators during the course of hematopoietic differentiation is key to achieving functional hPSC-derived HSCs.

MDS-associated mutations in germline GATA2 mutated patients with hematologic manifestations

Germline mutation in GATA2 can lead to GATA2 deficiency characterized by a complex multi-system disorder that can present with many manifestations including variable cytopenias, bone marrow failure, myelodysplastic syndrome/acute myeloid leukemia (MDS/AML), and severe immunodeficiency. Penetrance and expressivity within families is often variable. There is a spectrum of bone marrow disease in symptomatic cytopenic patients ranging from hypocellular marrows without overt dysplasia to those with definitive MDS, AML, or chronic myelomonocytic leukemia. Relatives of probands with the same mutations may demonstrate minimal disease manifestations and normal marrows. A comprehensive clinical, hematological and genetic assessment of 25 patients with germline GATA2 mutation was performed. MDS-associated mutations were identified in symptomatic GATA2 patients both with overt MDS and in those with hypocellular/aplastic bone marrows without definitive dysplasia. Healthy relatives of probands harboring the same germline GATA2 mutations had essentially normal marrows that were overall devoid of MDS-associated mutations. The findings suggest that abnormal clonal hematopoiesis is a common event in symptomatic germline mutated GATA2 patients with MDS and also in those with hypocellular marrows without overt morphologic evidence of dysplasia, possibly indicating a pre-MDS stage warranting close monitoring for disease progression.

Successful Nonmyeloablative Allogeneic Stem Cell Transplant in a Child With Emberger Syndrome and GATA2 Mutation

Emberger syndrome with underlying guanine-adenine-thymine-adenine 2 (GATA2) mutation is a rare disorder and very few successful nonmyeloablative allogeneic hematopoietic stem cell transplants (HSCTs) have been reported. We report a case of Emberger syndrome with GATA2 mutation in a 9-year-old girl who presented with congenital sensorineural deafness, warts, lymphedema, and Myelodysplastic syndrome. Her sister had died of a similar illness. She underwent a nonmyeloablative matched related donor peripheral blood HSCT with rabbit antithymoglobulin (5 mg/kg), fludarabine (160 mg/m), cyclophophamide (29 mg/kg), and total body irradiation (2 Gray). Graft versus host disease prophylaxis consisted of tacrolimus and mycophenolate moefetil. She had neutrophil engraftment on day+15 and fully donor chimerism by day+30. She developed limited chronic skin graft versus host disease on tapering off immunosuppression. She is disease free on day+475. The review of literature showed a total of 28 patients with GATA2 mutation have undergone HSCT mostly nonmyeloablative and overall survival is 75%. Nonmyeloablatove HSCT is feasible and safe for the patients with GATA2 mutation.

Germline GATA2 Mutation and Bone Marrow Failure

GATA2 deficiency is an immunodeficiency and bone marrow failure disorder caused by pathogenic variants in GATA2. It is inherited in an autosomal-dominant pattern or can be due to de novo sporadic germline mutation. Patients commonly have B-cell, dendritic cell, natural killer cell, and monocytopenias, and are predisposed to myelodysplastic syndrome, acute myeloid leukemia, and chronic myelomonocytic leukemia. Patients may suffer from disseminated human papilloma virus and mycobacterial infections, pulmonary alveolar proteinosis, and lymphedema. The bone marrow eventually takes on a characteristic hypocellular myelodysplasia with loss of monocytes and hematogones, megakaryocytes with separated nuclear lobes, micromegakaryocytes, and megakaryocytes with hypolobated nuclei.

Natural history of GATA2 deficiency in a survey of 79 French and Belgian patients

Heterozygous germline GATA2 mutations strongly predispose to leukemia, immunodeficiency, and/or lymphoedema. We describe a series of 79 patients (53 families) diagnosed since 2011, made up of all patients in France and Belgium, with a follow up of 2249 patients/years. Median age at first clinical symptoms was 18.6 years (range, 0-61 years). Severe infectious diseases (mycobacteria, fungus, and human papilloma virus) and hematologic malignancies were the most common first manifestations. The probability of remaining symptom-free was 8% at 40 years old. Among the 53 probands, 24 had missense mutations including 4 recurrent alleles, 21 had nonsense or frameshift mutations, 4 had a whole-gene deletion, 2 had splice defects, and 2 patients had complex mutations. There were significantly more cases of leukemia in patients with missense mutations (n=14 of 34) than in patients with nonsense or frameshift mutations (n=2 of 28). We also identify new features of the disease: acute lymphoblastic leukemia, juvenile myelomonocytic leukemia, fatal progressive multifocal leukoencephalopathy related to the JC virus, and immune/inflammatory diseases. A revised International Prognostic Scoring System (IPSS) score allowed a distinction to be made between a stable disease and hematologic transformation. Chemotherapy is of limited efficacy, and has a high toxicity with severe infectious complications. As the mortality rate is high in our cohort (up to 35% at the age of 40), hematopoietic stem cell transplantation (HSCT) remains the best choice of treatment to avoid severe infectious and/or hematologic complications. The timing of HSCT remains difficult to determine, but the earlier it is performed, the better the outcome.

Alterations of specific chromatin conformation affect ATRA-induced leukemia cell differentiation

Chromatin conformation plays a key role in regulating gene expression and controlling cell differentiation. However, the whole-genome chromatin conformation changes that occur during leukemia cell differentiation are poorly understood. Here, we characterized the changes in chromatin conformation, histone states, chromatin accessibility, and gene expression using an all-trans retinoic acid (ATRA)-induced HL-60 cell differentiation model. The results showed that the boundaries of topological associated domains (TADs) were stable during differentiation; however, the chromatin conformations within several specific TADs were obviously changed. By combining H3K4me3, H3K27ac, and Hi-C signals, we annotated the differential gene-regulatory chromatin interactions upon ATRA induction. The gains and losses of the gene-regulatory chromatin interactions are significantly correlated with gene expression and chromatin accessibility. Finally, we found that the loss of GATA2 expression and DNA binding are crucial for the differentiation process, and changes in the chromatin structure around the GATA2 regulate its expression upon ATRA induction. This study provided both statistical insights and experimental details regarding the relationship between chromatin conformation changes and transcription regulation during leukemia cell differentiation, and the results suggested that the chromatin conformation is a new type of potential drug target for cancer therapy.

HBV suppresses expression of MICA/B on hepatoma cells through up-regulation of transcription factors GATA2 and GATA3 to escape from NK cell surveillance

Decreased expression of NKG2D ligands on HBV-infected human hepatoma cells impairs NK cells lysis. However, which components of HBV exert this effect and the precise mechanisms need to be further investigated. In the present study, we observed that the HBx and HBc genes significantly down-regulated MICA expression. Through analysis with the chromatin immunoprecipitation assay, we found that HBV infection promotes the expression of transcription factors GATA-2 and GATA-3, which specifically suppressed MICA/B expression by directly binding to the promoter region of MICA/B. HBx protein, acting as a co-regulator, forms a tripolymer with GATA2 and GATA3, thus promotes the GATA-2 or GATA-3-mediated of MICA/B suppression. HBc protein inhibits MICA/B expression via directly binding to the CpG island in the MICA/B promoter. Thus, our study identified the novel role of transcription factors GATA-2 and GATA-3 in suppressing MICA/B expression and clarified the mechanisms of HBx and HBc in downregulation of MICA/B expression. These findings provide novel mechanisms for the contribution of HBV to hepatoma cells escape from NK cell surveillance.

Comparative study of hematopoietic stem and progenitor cells between sexes in mice under physiological conditions along time

Hematopoietic stem and progenitor cells (HSPCs) are attractive targets in regenerative medicine, although the differences in their homeostatic maintenance between sexes along time are still under debate. We accurately monitored hematopoietic stem cells (HSCs), common lymphoid progenitors (CLPs), and common myeloid progenitors (CMPs) frequencies by flow cytometry, by performing serial peripheral blood extractions from male and female B6SJL wild-type mice and found no significant differences. Only modest differences were found in the gene expression profile of Slamf1 and Gata2. Our findings suggest that both sexes could be used indistinctly to perform descriptive studies in the murine hematopoietic system, especially for flow cytometry studies in peripheral blood. This would allow diminishing the number of animals needed for the experimental procedures. In addition, the use of serial extractions in the same animals drastically decreases the number of animals needed.

GATA2 Inhibition Sensitizes Acute Myeloid Leukemia Cells to Chemotherapy

Drug resistance constitutes one of the main obstacles for clinical recovery of acute myeloid leukemia (AML) patients. Therefore, the treatment of AML requires new strategies, such as adding a third drug. To address whether GATA2 could act as a regulator of chemotherapy resistance in human leukemia cells, we observed KG1a cells and clinical patients’ AML cells with a classic drug (Cerubidine) and Gefitinib. After utilizing chemotherapy, the expression of GATA2 and its target genes (EVI, SCL and WT1) in surviving AML cells and KG1a cells were significantly enhanced to double and quadrupled compared to its original level respectively. Furthermore, with continuous chemotherapeutics, AML cells with GATA2 knockdown or treated with GATA2 inhibitor (K1747) almost eliminated with dramatically reduced expression of WT1, SCL, EVI, and significantly increased apoptotic population. Therefore, we propose that reducing GATA2 expression or inhibition of its transcription activity can relieve the drug resistance of acute myeloid leukemia cells and it would be helpful for eliminating the leukemia cells in patients.

Hematopoietic stem and progenitor cells as novel prognostic biomarkers of longevity in a murine model for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a difficult diagnosis and prognosis. In this regard, new and more reliable biomarkers for the disease are needed. We propose peripheral blood, and, more specifically, the hematopoietic stem and progenitor cells (HSPCs) as potential prognostic biomarkers in the SOD1G93A murine model of ALS. We accurately and serially studied three HSPCs-hematopoietic stem cells (HSCs), common lymphoid progenitors (CLPs), and common myeloid progenitors (CMPs)-in both control and SOD1G93A mice along the disease's progression by RT-PCR and flow cytometry analysis. We found interesting differences for every HSPC type in the transgenic mice compared with the control mice at every time point selected, as well as differences along the disease course. The results showed a maintained compensatory increase of HSCs along disease progression. However, the downregulated levels of CLPs and CMPs suggested an exit of these cell populations to the peripheral tissues, probably due to their supporting role to the damaged tissues. In addition, a positive correlation of the percentage of CLPs and CMPs with the longevity was found, as well as a positive correlation of HSCs and CMPs with motor function and weight, thus reinforcing the idea that HSPCs play a relevant role in the longevity of the SOD1G93A mice. On the basis of these results, both CLPs and CMPs could be considered prognostic biomarkers of longevity in this animal model, opening the door to future studies in human patients for their potential clinical use.

Generation and Analysis of GATA2w/eGFP Human ESCs Reveal ITGB3/CD61 as a Reliable Marker for Defining Hemogenic Endothelial Cells during Hematopoiesis

The transition from hemogenic endothelial cells (HECs) to hematopoietic stem/progenitor cells (HS/PCs), or endothelial to hematopoietic transition (EHT), is a critical step during hematopoiesis. However, little is known about the molecular determinants of HECs due to the challenge in defining HECs. We report here the generation of GATA2^w/eGFP reporter in human embryonic stem cells (hESCs) to mark cells expressing GATA2, a critical gene for EHT. We show that during differentiation, functional HECs are almost exclusively GATA2/eGFP⁺. We then constructed a regulatory network for HEC determination and also identified a panel of positive or negative surface markers for discriminating HECs from non-hemogenic ECs. Among them, ITGB3 (CD61) precisely labeled HECs both in hESC differentiation and embryonic day 10 mouse embryos. These results not only identify a reliable marker for defining HECs, but also establish a robust platform for dissecting hematopoiesis in vitro, which might lead to the generation of HSCs in vitro.

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Generation of GATA2^w/eGFP reporter in human ESCs

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GATA2/eGFP expression defines HECs and HPCs in hESC differentiation

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CD61 marks HECs and HPCs in hPSC differentiation

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CD61 defines HECs in YS and AGM E10 mouse embryo

The analysis of novel distal Cebpa enhancers and silencers using a transcriptional model reveals the complex regulatory logic of hematopoietic lineage specification

C/EBPα plays an instructive role in the macrophage-neutrophil cell-fate decision and its expression is necessary for neutrophil development. How Cebpa itself is regulated in the myeloid lineage is not known. We decoded the cis-regulatory logic of Cebpa, and two other myeloid transcription factors, Egr1 and Egr2, using a combined experimental-computational approach. With a reporter design capable of detecting both distal enhancers and silencers, we analyzed 46 putative cis-regulatory modules (CRMs) in cells representing myeloid progenitors, and derived early macrophages or neutrophils. In addition to novel enhancers, this analysis revealed a surprisingly large number of silencers. We determined the regulatory roles of 15 potential transcriptional regulators by testing 32,768 alternative sequence-based transcriptional models against CRM activity data. This comprehensive analysis allowed us to infer the cis-regulatory logic for most of the CRMs. Silencer-mediated repression of Cebpa was found to be effected mainly by TFs expressed in non-myeloid lineages, highlighting a previously unappreciated contribution of long-distance silencing to hematopoietic lineage resolution. The repression of Cebpa by multiple factors expressed in alternative lineages suggests that hematopoietic genes are organized into densely interconnected repressive networks instead of hierarchies of mutually repressive pairs of pivotal TFs. More generally, our results demonstrate that de novo cis-regulatory dissection is feasible on a large scale with the aid of transcriptional modeling. Current address: Department of Biology, University of North Dakota, 10 Cornell Street, Stop 9019, Grand Forks, ND 58202-9019, USA.

Haematopoietic and immune defects associated with GATA2 mutation

Heterozygous familial or sporadic GATA2 mutations cause a multifaceted disorder, encompassing susceptibility to infection, pulmonary dysfunction, autoimmunity, lymphoedema and malignancy. Although often healthy in childhood, carriers of defective GATA2 alleles develop progressive loss of mononuclear cells (dendritic cells, monocytes, B and Natural Killer lymphocytes), elevated FLT3 ligand, and a 90% risk of clinical complications, including progression to myelodysplastic syndrome (MDS) by 60 years of age. Premature death may occur from childhood due to infection, pulmonary dysfunction, solid malignancy and MDS/acute myeloid leukaemia. GATA2 mutations include frameshifts, amino acid substitutions, insertions and deletions scattered throughout the gene but concentrated in the region encoding the two zinc finger domains. Mutations appear to cause haplo-insufficiency, which is known to impair haematopoietic stem cell survival in animal models. Management includes genetic counselling, prevention of infection, cancer surveillance, haematopoietic monitoring and, ultimately, stem cell transplantation upon the development of MDS or another life-threatening complication.

Regulation of GATA-binding protein 2 levels via ubiquitin-dependent degradation by Fbw7: involvement of cyclin B-cyclin-dependent kinase 1-mediated phosphorylation of THR176 in GATA-binding protein 2

A GATA family transcription factor, GATA-binding protein 2 (GATA2), participates in cell growth and differentiation of various cells, such as hematopoietic stem cells. Although its expression level is controlled by transcriptional induction and proteolytic degradation, the responsible E3 ligase has not been identified. Here, we demonstrate that F-box/WD repeat-containing protein 7 (Fbw7/Fbxw7), a component of Skp1, Cullin 1, F-box-containing complex (SCF)-type E3 ligase, is an E3 ligase for GATA2. GATA2 contains a cell division control protein 4 (Cdc4) phosphodegron (CPD), a consensus motif for ubiquitylation by Fbw7, which includes Thr(176). Ectopic expression of Fbw7 destabilized GATA2 and promoted its proteasomal degradation. Substitution of threonine 176 to alanine in GATA2 inhibited binding with Fbw7, and the ubiquitylation and degradation of GATA2 by Fbw7 was suppressed. The CPD kinase, which mediates the phosphorylation of Thr(176), was cyclin B-cyclin-dependent kinase 1 (CDK1). Moreover, depletion of endogenous Fbw7 stabilized endogenous GATA2 in K562 cells. Conditional Fbw7 depletion in mice increased GATA2 levels in hematopoietic stem cells and myeloid progenitors at the early stage. Increased GATA2 levels in Fbw7-conditional knock-out mice were correlated with a decrease in a c-Kit high expressing population of myeloid progenitor cells. Our results suggest that Fbw7 is a bona fide E3 ubiquitin ligase for GATA2 in vivo.

GATA2 as a potential metastasis-driving gene in prostate cancer

Effective treatment for metastatic prostate cancer is critically needed. The present study was aimed at identifying metastasis-driving genes as potential targets for therapy (oncotargets). A differential gene expression profile of metastatic LTL-313H and non-metastatic LTL-313B prostate cancer tissue xenografts, derived from one patient's specimen, was subjected to integrative analysis using the Ingenuity Upstream Regulator Analysis tool. Six candidate master regulatory genes were identified, including GATA2, a gene encoding a pioneer factor, a special transcription factor facilitating the recruitment of additional transcription factors. Elevated GATA2 expression in metastatic prostate cancer tissues correlated with poor patient prognosis. Furthermore, GATA2 gene silencing in human prostate cancer LNCaP cells led to a marked reduction in cell migration, tissue invasion, focal adhesion disassembly and to a dramatic change in cell transcriptomes, indicating that GATA2 plays a critical role in prostate cancer metastasis. As such, GATA2 could represent a prostate cancer metastasis-driving gene and a potential target for therapy of metastatic prostate cancer.

Regulation of EPCs: The Gateway to Blood Vessel Formation

Endothelial progenitor cells (EPCs) are primitive endothelial precursors which are known to functionally contribute to the pathogenesis of disease. To date a number of distinct subtypes of these cells have been described, with differing maturation status, cellular phenotype, and function. Although there is much debate on which subtype constitutes the true EPC population, all subtypes have endothelial characteristics and contribute to neovascularisation. Vasculogenesis, the process by which EPCs contribute to blood vessel formation, can be dysregulated in disease with overabundant vasculogenesis in the context of solid tumours, leading to tumour growth and metastasis, and conversely insufficient vasculogenesis can be present in an ischemic environment. Importantly, it is widely known that transcription factors tightly regulate cellular phenotype and function by controlling the expression of particular target genes and in turn regulating specific signalling pathways. This suggests that transcriptional regulators may be potential therapeutic targets to control EPC function. Herein, we discuss the observed EPC subtypes described in the literature and review recent studies describing the role of a number of transcriptional families in the regulation of EPC phenotype and function in normal and pathological conditions.

A conserved zinc finger transcription factor GATA involving in the hemocyte production of scallop Chlamys farreri

GATA are a family of transcription factors characterized by their ability to bind to the DNA sequence "GATA", and involved in a myriad of cellular processes. GATA1/2/3 factors are known as the hematopoietic GATA factors, which play dominated roles in regulating hematopoiesis. In the present study, a gene encoding GATA transcription factor (designed as CfGATA) was cloned and characterized from the scallop Chlamys farreri. The full-length cDNA of CfGATA is of 2058 bp encoding a predicted polypeptide of 457 amino acids with two conserved zinc finger domains, which shared high similarity with other reported GATA1/2/3 proteins. The mRNA transcripts of CfGATA showed higher expression in gills, hepatopancreas, hemocytes and heart, and the CfGATA protein expressed in HEK293 cells was found to be localized specifically in the nuclei. The recombinant CfGATA protein (rCfGATA) exhibited strong ability to bind specific WGATAR DNA sequence by electrophoretic mobility shift assay in vitro. After CfGATA gene was silenced by RNA interference, the hemocyte renewal rate and circulating total hemocyte count (THC) decreased significantly, which was 7.85-fold and 19.46-fold lower than that of PBS control, respectively (P < 0.05). After LPS stimulation, the expression level of CfGATA mRNA decreased significantly in the hemocytes of PBS or EGFP dsRNA treated scallops, which was accompanied by the increase of hemocyte renewal rate and the reduced circulating THC at 24 h. In contrast, the hemocyte renewal rate and circulating THC did not change significantly in CfGATA gene interfered scallops after LPS stimulation. These results suggested that CfGATA, as a conserved GATA1/2/3 transcription factor, plays essential roles in regulating hemocyte production of scallop.

Leucine-rich repeat-containing G-protein-coupled Receptor 5 marks short-term hematopoietic stem and progenitor cells during mouse embryonic development

Lgr5 is a marker for proliferating stem cells in adult intestine, stomach, and hair follicle. However, Lgr5 is not expressed in adult hematopoietic stem and progenitor cells (HSPCs). Whether Lgr5 is expressed in the embryonic and fetal HSPCs that undergo rapid proliferation is unknown. Here we report the detection of Lgr5 expression in HSPCs in the aorta-gonad-mesonephros (AGM) and fetal liver. We also found that a portion of Lgr5(+) cells expressed the Runx1 gene that is critical for the ontogeny of HSPCs. A small portion of Lgr5(+) cells also expressed HSPC surface markers c-Kit and CD34 in AGM or CD41 in fetal liver. Furthermore, the majority of Lgr5(+) cells expressed Ki67, indicating their proliferating state. Transplantation of fetal liver-derived Lgr5-GFP(+) cells (E12.5) demonstrated that Lgr5-GFP(+) cells were able to reconstitute myeloid and lymphoid lineages in adult recipients, but the engraftment was short-term (4-8 weeks) and 20-fold lower compared with the Lgr5-GFP(-) control. Our data show that Lgr5-expressing cells mark short-term hematopoietic stem and progenitor cells, consistent with the role of Lgr5 in supporting HSPCs rapid proliferation during embryonic and fetal development.

GATA-2 inhibits transforming growth factor-β signaling pathway through interaction with Smad4

GATA-2, a member of zinc finger GATA transcription factor family, plays key role in the hematopoietic stem cells self-renewal and differentiation. The transforming growth factor-β (TGFβ) signaling pathway is a major signaling network that controls cell proliferation, differentiation and tumor suppression. Here we found that GATA-2 negatively regulated TGF-β signaling pathway in Smad4-dependent manner. GATA-2 specifically interacts with Smad4 with its N-terminal while the zinc finger domain of GATA-2 is essential for negative regulation of TGFβ. Although GATA-2 did not affect the phosphorylation of Smad2/3 and the complex Smad2/3/4 formation in response to TGFβ, the DNA binding activity of Smad4 was decreased significantly by GATA-2 overexpression. Overexpression of GATA-2 in K562 cells led to reduced TGFβ-induced erythroid differentiation while knockdown of GATA-2 enhanced TGFβ-induced erythroid differentiation. All these results suggest that GATA-2 is a novel negative regulator of TGFβ signal pathway.

Stem cell origin of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are common hematologic disorders that are characterized by decreased blood counts due to ineffective hematopoiesis. MDS is considered a 'preleukemic' disorder linked to a significantly elevated risk of developing an overt acute leukemia. Cytopenias can be observed in all three myeloid lineages suggesting the involvement of multipotent, immature hematopoietic cells in the pathophysiology of this disease. Recent studies using murine models of MDS as well as primary patient-derived bone marrow samples have provided direct evidence that the most immature, self-renewing hematopoietic stem cells (HSC), as well as lineage-committed progenitor cells, are critically altered in patients with MDS. Besides significant changes in the number and distribution of stem as well as immature progenitor cells, genetic and epigenetic aberrations have been identified, which confer functional changes to these aberrant stem cells, impairing their ability to proliferate and differentiate. Most importantly, aberrant stem cells can persist and further expand after treatment, even upon transient achievement of clinical complete remission, pointing to a critical role of these cells in disease relapse. Ongoing preclinical and clinical studies are particularly focusing on the precise molecular and functional characterization of aberrant MDS stem cells in response to therapy, with the goal to develop stem cell-targeted strategies for therapy and disease monitoring that will allow for achievement of longer-lasting remissions in MDS.

Cellular network entropy as the energy potential in Waddington's differentiation landscape

Differentiation is a key cellular process in normal tissue development that is significantly altered in cancer. Although molecular signatures characterising pluripotency and multipotency exist, there is, as yet, no single quantitative mark of a cellular sample's position in the global differentiation hierarchy. Here we adopt a systems view and consider the sample's network entropy, a measure of signaling pathway promiscuity, computable from a sample's genome-wide expression profile. We demonstrate that network entropy provides a quantitative, in-silico, readout of the average undifferentiated state of the profiled cells, recapitulating the known hierarchy of pluripotent, multipotent and differentiated cell types. Network entropy further exhibits dynamic changes in time course differentiation data, and in line with a sample's differentiation stage. In disease, network entropy predicts a higher level of cellular plasticity in cancer stem cell populations compared to ordinary cancer cells. Importantly, network entropy also allows identification of key differentiation pathways. Our results are consistent with the view that pluripotency is a statistical property defined at the cellular population level, correlating with intra-sample heterogeneity, and driven by the degree of signaling promiscuity in cells. In summary, network entropy provides a quantitative measure of a cell's undifferentiated state, defining its elevation in Waddington's landscape.

Transcriptional regulation of haematopoietic stem cells

Haematopoietic stem cells (HSCs) are a rare cell population found in the bone marrow of adult mammals and are responsible for maintaining the entire haematopoietic system. Definitive HSCs are produced from mesoderm during embryonic development, from embryonic day 10 in the mouse. HSCs seed the foetal liver before migrating to the bone marrow around the time of birth. In the adult, HSCs are largely quiescent but have the ability to divide to self-renew and expand, or to proliferate and differentiate into any mature haematopoietic cell type. Both the specification of HSCs during development and their cellular choices once formed are tightly controlled at the level of transcription. Numerous transcriptional regulators of HSC specification, expansion, homeostasis and differentiation have been identified, primarily from analysis of mouse gene knockout experiments and transplantation assays. These include transcription factors, epigenetic modifiers and signalling pathway effectors. This chapter reviews the current knowledge of these HSC transcriptional regulators, predominantly focusing on the transcriptional regulation of mouse HSCs, although transcriptional regulation of human HSCs is also mentioned where relevant. Due to the breadth and maturity of this field, we have prioritised recently identified examples of HSC transcriptional regulators. We go on to highlight additional layers of control that regulate expression and activity of HSC transcriptional regulators and discuss how chromosomal translocations that result in fusion proteins of these HSC transcriptional regulators commonly drive leukaemias through transcriptional dysregulation.

LIM-domain-only proteins in cancer

LIM-domain proteins are a large family of proteins that are emerging as key molecules in a wide variety of human cancers. In particular, all members of the human LIM-domain-only (LMO) proteins, LMO1-4, which are required for many developmental processes, are implicated in the onset or the progression of several cancers, including T cell leukaemia, breast cancer and neuroblastoma. These small proteins contain two protein-interacting LIM domains but little additional sequence, and they seem to function by nucleating the formation of new transcriptional complexes and/or by disrupting existing transcriptional complexes to modulate gene expression programmes. Through these activities, the LMO proteins have important cellular roles in processes that are relevant to cancer such as self-renewal, cell cycle regulation and metastasis. These functions highlight the therapeutic potential of targeting these proteins in cancer.