LRF is an essential downstream target of GATA1 in erythroid development and regulates BIM-dependent apoptosis

ZBTB7A as a therapeutic target for cancer

ZBTB7A, alternatively referred to Pokemon, FBI-1, LRF, and OCZF, is classified as a member of POK/ZBTB protein family of transcriptional repressors. ZBTB7A binds to targeted DNA via C-terminal zinc fingers and recruits co-compression complexes through N-terminal BTB ⁄ POZ domain to impede transcription. ZBTB7A regulates a range of fundamental biological processes such as cell proliferation, differentiation and apoptosis, B- and T-lymphocyte fate determination and thymic insulin expression and self-tolerance. Accumulating evidence has demonstrated an important role of ZBTB7A in the initiation and advancement of tumors, thus making ZBTB7A emerge as an appealing target. This review examines the functions and regulatory mechanisms of ZBTB7A in a range of common solid tumors, including hepatocellular carcinoma, breast cancer, prostate cancer and lung cancer, as well as hematological malignancies. Notably, the review concludes with a summary of the recent applications of targeting ZBTB7A in clinical treatments through gene silencing, immunotherapy and chemotherapeutic approaches to halt or slow tumor progression. We focus on the functional role and regulatory mechanisms of ZBTB7A in cancer with the goal of providing new insights for the development of more effective cancer therapeutic strategies.

BIT: Bayesian Identification of Transcriptional Regulators from Epigenomics-Based Query Region Sets

Transcriptional regulators (TRs) are master controllers of gene expression and play a critical role in both normal tissue development and disease progression. However, existing computational methods for identification of TRs regulating specific biological processes have significant limitations, such as relying on distance on a linear chromosome or binding motifs that have low specificity. Many also use statistical tests in ways that lack interpretability and rigorous confidence measures. We introduce BIT, a novel Bayesian hierarchical model for in-silico TR identification. Leveraging a comprehensive library of TR ChIP-seq data, BIT offers a fully integrated Bayesian approach to assess genome-wide consistency between user-provided epigenomic profiling data and the TR binding library, enabling the identification of critical TRs while quantifying uncertainty. It avoids estimation and inference in a sequential manner or numerous isolated statistical tests, thereby enhancing accuracy and interpretability. BIT successfully identified critical TRs in perturbation experiments, functionally essential TRs in various cancer types, and cell-type-specific TRs within heterogeneous cell populations, offering deeper biological insights into transcriptional regulation.

Hydroxyurea reduces the levels of the fetal globin gene repressors ZBTB7A/LRF and BCL11A in erythroid cells in vitro

Objectives

Hydroxyurea (HU) is the most widely used therapy for adults and children with sickle cell disease (SCD). It is believed to act largely by inducing the transcription of fetal γ-globin genes to generate fetal hemoglobin (HbF), which inhibits the pathological polymerization of sickle hemoglobin (HbS). The mechanisms by which hydroxyurea elevates HbF are unclear. We explored the hypothesis that hydroxyurea induces HbF expression by inhibiting the expression of 2 γ-globin gene repressors, BCL11A and ZBTB7A (also known as LRF), which normally bind the γ-globin gene promoters to inhibit their expression after birth.

Methods

We treated immortalized murine erythroleukemia cells and normal human donor CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea and measured the effects on globin, BCL11A and ZBTB7A protein and mRNA expression.

Results

Treating murine erythroleukemia cells or human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts with hydroxyurea reduced the protein levels of BCL11A and ZBTB7A compared to the vehicle-treated control. BCL11A mRNA levels were reduced in both cell types upon hydroxyurea treatment. However, ZBTB7A mRNA levels were only reduced in human CD34+ hematopoietic stem and progenitor cell-derived erythroblasts.

Conclusions

Hydroxyurea can act in erythroid cells to reduce the levels and activity of two direct fetal γ-globin transcriptional repressors with accompanying de-repression of the γ-globin genes and induction of HbF, which may explain the mechanism of action leading to amelioration of symptoms in SCD patients treated with this drug.

Pokemon inhibits Bim transcription to promote the proliferation, anti-anoikis, invasion, histological grade, and dukes stage of colorectal neoplasms

PURPOSE

This study aims to determine whether Pokemon regulates Bim activity in colorectal carcinoma (CRC) carcinogenesis.

METHODS

Clinical tissue samples were analyzed to detect the expression and clinicopathological significance of Pokemon and Bim in CRC. Proliferation, apoptosis, and invasion assays were conducted to identify the regulatory effect of Pokemon on Bim. The combined treatment effects of Pokemon knockdown and diamminedichloroplatinum (DDP) were also examined.

RESULTS

Immunohistochemical analysis of 80 samples of colorectal epithelia (CRE), 80 cases of colorectal adenoma (CRA), and 160 of CRC samples revealed protein expression rates of 23.8%, 38.8%, and 70.6% for Pokemon, and 88.8%, 73.8%, and 31.9% for Bim, respectively. A significant negative correlation was observed between Pokemon and Bim expression across the CRE, CRA, and CRC lesion stages. In CRC, higher Pokemon and lower Bim expression correlated with higher histological grades, advanced Dukes stages, and increased cancer invasion. In both LoVo and HCT116 cells, overexpression of Pokemon significantly reduced Bim expression, leading to increased proliferation, resistance to anoikis, and cell invasion. Additionally, Pokemon overexpression significantly decreased DDP-induced Bim expression, reduction of anti-apoptosis and invasion, whereas Pokemon knockdown resulted in the opposite effects.

CONCLUSION

These findings suggest that Pokemon inhibits Bim transcription, thereby promoting CRC proliferation, resistance to apoptosis, invasion, and advancing histological grade and Dukes staging. Pokemon knockdown enhances the therapeutic efficacy of DDP in the treatment of CRC.

Landscape of driver mutations and their clinical effects on Down syndrome-related myeloid neoplasms

ABSTRACT

Transient abnormal myelopoiesis (TAM) is a common complication in newborns with Down syndrome (DS). It commonly progresses to myeloid leukemia (ML-DS) after spontaneous regression. In contrast to the favorable prognosis of primary ML-DS, patients with refractory/relapsed ML-DS have poor outcomes. However, the molecular basis for refractoriness and relapse and the full spectrum of driver mutations in ML-DS remain largely unknown. We conducted a genomic profiling study of 143 TAM, 204 ML-DS, and 34 non-DS acute megakaryoblastic leukemia cases, including 39 ML-DS cases analyzed by exome sequencing. Sixteen novel mutational targets were identified in ML-DS samples. Of these, inactivations of IRX1 (16.2%) and ZBTB7A (13.2%) were commonly implicated in the upregulation of the MYC pathway and were potential targets for ML-DS treatment with bromodomain-containing protein 4 inhibitors. Partial tandem duplications of RUNX1 on chromosome 21 were also found, specifically in ML-DS samples (13.7%), presenting its essential role in DS leukemia progression. Finally, in 177 patients with ML-DS treated following the same ML-DS protocol (the Japanese Pediatric Leukemia and Lymphoma Study Group acute myeloid leukemia -D05/D11), CDKN2A, TP53, ZBTB7A, and JAK2 alterations were associated with a poor prognosis. Patients with CDKN2A deletions (n = 7) or TP53 mutations (n = 4) had substantially lower 3-year event-free survival (28.6% vs 90.5%; P < .001; 25.0% vs 89.5%; P < .001) than those without these mutations. These findings considerably change the mutational landscape of ML-DS, provide new insights into the mechanisms of progression from TAM to ML-DS, and help identify new therapeutic targets and strategies for ML-DS.

C2H2 Zinc Finger Transcription Factors Associated with Hemoglobinopathies

In humans, specific aberrations in β-globin results in sickle cell disease and β-thalassemia, symptoms of which can be ameliorated by increased expression of fetal globin (HbF). Two recent CRISPR-Cas9 screens, centered on ∼1500 annotated sequence-specific DNA binding proteins and performed in a human erythroid cell line that expresses adult hemoglobin, uncovered four groups of candidate regulators of HbF gene expression. They are (1) members of the nucleosome remodeling and deacetylase (NuRD) complex proteins that are already known for HbF control; (2) seven C2H2 zinc finger (ZF) proteins, including some (ZBTB7A and BCL11A) already known for directly silencing the fetal γ-globin genes in adult human erythroid cells; (3) a few other transcription factors of different structural classes that might indirectly influence HbF gene expression; and (4) DNA methyltransferase 1 (DNMT1) that maintains the DNA methylation marks that attract the MBD2-associated NuRD complex to DNA as well as associated histone H3 lysine 9 methylation. Here we briefly discuss the effects of these regulators, particularly C2H2 ZFs, in inducing HbF expression for treating β-hemoglobin disorders, together with recent advances in developing safe and effective small-molecule therapeutics for the regulation of this well-conserved hemoglobin switch.

Base editing of the HBG promoter induces potent fetal hemoglobin expression with no detectable off-target mutations in human HSCs

Reactivating silenced γ-globin expression through the disruption of repressive regulatory domains offers a therapeutic strategy for treating β-hemoglobinopathies. Here, we used transformer base editor (tBE), a recently developed cytosine base editor with no detectable off-target mutations, to disrupt transcription-factor-binding motifs in hematopoietic stem cells. By performing functional screening of six motifs with tBE, we found that directly disrupting the BCL11A-binding motif in HBG1/2 promoters triggered the highest γ-globin expression. Via a side-by-side comparison with other clinical and preclinical strategies using Cas9 nuclease or conventional BEs (ABE8e and hA3A-BE3), we found that tBE-mediated disruption of the BCL11A-binding motif at the HBG1/2 promoters triggered the highest fetal hemoglobin in healthy and β-thalassemia patient hematopoietic stem/progenitor cells while exhibiting no detectable DNA or RNA off-target mutations. Durable therapeutic editing by tBE persisted in repopulating hematopoietic stem cells, demonstrating that tBE-mediated editing in HBG1/2 promoters is a safe and effective strategy for treating β-hemoglobinopathies.

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.

CK2β Regulates Hematopoietic Stem Cell Biology and Erythropoiesis

The Ser-Thr kinase CK2 plays important roles in sustaining cell survival and resistance to stress and these functions are exploited by different types of blood tumors. Yet, the physiological involvement of CK2 in normal blood cell development is poorly known. Here, we discovered that the β regulatory subunit of CK2 is critical for normal hematopoiesis in the mouse. Fetal livers of conditional CK2β knockout embryos showed increased numbers of hematopoietic stem cells associated to a higher proliferation rate compared to control animals. Both hematopoietic stem and progenitor cells (HSPCs) displayed alterations in the expression of transcription factors involved in cell quiescence, self-renewal, and lineage commitment. HSPCs lacking CK2β were functionally impaired in supporting both in vitro and in vivo hematopoiesis as demonstrated by transplantation assays. Furthermore, KO mice developed anemia due to a reduced number of mature erythroid cells. This compartment was characterized by dysplasia, proliferative defects at early precursor stage, and apoptosis at late-stage erythroblasts. Erythroid cells exhibited a marked compromise of signaling cascades downstream of the cKit and erythropoietin receptor, with a defective activation of ERK/JNK, JAK/STAT5, and PI3K/AKT pathways and perturbations of several transcriptional programs as demonstrated by RNA-Seq analysis. Moreover, we unraveled an unforeseen molecular mechanism whereby CK2 sustains GATA1 stability and transcriptional proficiency. Thus, our work demonstrates new and crucial functions of CK2 in HSPC biology and in erythropoiesis.

Transcriptional repression of lncRNA and miRNA subsets mediated by LRF during erythropoiesis

Non-coding RNA (ncRNA) species, mainly long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been currently imputed for lesser or greater involvement in human erythropoiesis. These RNA subsets operate within a complex circuit with other epigenetic components and transcription factors (TF) affecting chromatin remodeling during cell differentiation. Lymphoma/leukemia-related (LRF) TF exerts higher occupancy on DNA CpG rich sites and is implicated in several differentiation cell pathways and erythropoiesis among them and also directs the epigenetic regulation of hemoglobin transversion from fetal (HbF) to adult (HbA) form by intervening in the γ-globin gene repression. We intended to investigate LRF activity in the evolving landscape of cells' commitment to the erythroid lineage and specifically during HbF to HbA transversion, to qualify this TF as potential repressor of lncRNAs and miRNAs. Transgenic human erythroleukemia cells, overexpressing LRF and further induced to erythropoiesis, were subjected to expression analysis in high LRF occupancy genetic loci-producing lncRNAs. LRF abundance in genetic loci transcribing for studied lncRNAs was determined by ChIP-Seq data analysis. qPCRs were performed to examine lncRNA expression status. Differentially expressed miRNA pre- and post-erythropoiesis induction were assessed by next-generation sequencing (NGS), and their promoter regions were charted. Expression levels of lncRNAs were correlated with DNA methylation status of flanked CpG islands, and contingent co-regulation of hosted miRNAs was considered. LRF-binding sites were overrepresented in LRF overexpressing cell clones during erythropoiesis induction and exerted a significant suppressive effect towards lncRNAs and miRNA collections. Based on present data interpretation, LRF's multiplied binding capacity across genome is suggested to be transient and associated with higher levels of DNA methylation. KEY MESSAGES: During erythropoiesis, LRF displays extensive occupancy across genetic loci. LRF significantly represses subsets of lncRNAs and miRNAs during erythropoiesis. Promoter region CpG islands' methylation levels affect lncRNA expression. MiRNAs embedded within lncRNA loci show differential regulation of expression.

Precision Editing as a Therapeutic Approach for β-Hemoglobinopathies

Beta-hemoglobinopathies are the most common genetic disorders worldwide, caused by a wide spectrum of mutations in the β-globin locus, and associated with morbidity and early mortality in case of patient non-adherence to supportive treatment. Allogeneic transplantation of hematopoietic stem cells (allo-HSCT) used to be the only curative option, although the indispensable need for an HLA-matched donor markedly restricted its universal application. The evolution of gene therapy approaches made possible the ex vivo delivery of a therapeutic β- or γ- globin gene into patient-derived hematopoietic stem cells followed by the transplantation of corrected cells into myeloablated patients, having led to high rates of transfusion independence (thalassemia) or complete resolution of painful crises (sickle cell disease-SCD). Hereditary persistence of fetal hemoglobin (HPFH), a syndrome characterized by increased γ-globin levels, when co-inherited with β-thalassemia or SCD, converts hemoglobinopathies to a benign condition with mild clinical phenotype. The rapid development of precise genome editing tools (ZFN, TALENs, CRISPR/Cas9) over the last decade has allowed the targeted introduction of mutations, resulting in disease-modifying outcomes. In this context, genome editing tools have successfully been used for the introduction of HPFH-like mutations both in HBG1/HBG2 promoters or/and in the erythroid enhancer of BCL11A to increase HbF expression as an alternative curative approach for β-hemoglobinopathies. The current investigation of new HbF modulators, such as ZBTB7A, KLF-1, SOX6, and ZNF410, further expands the range of possible genome editing targets. Importantly, genome editing approaches have recently reached clinical translation in trials investigating HbF reactivation in both SCD and thalassemic patients. Showing promising outcomes, these approaches are yet to be confirmed in long-term follow-up studies.

Gene Therapy and Gene Editing for β-Thalassemia

After many years of intensive research, emerging data from clinical trials indicate that gene therapy for transfusion-dependent β-thalassemia is now possible. Strategies for therapeutic manipulation of patient hematopoietic stem cells include lentiviral transduction of a functional erythroid-expressed β-globin gene and genome editing to activate fetal hemoglobin production in patient red blood cells. Gene therapy for β-thalassemia and other blood disorders will invariably improve as experience accumulates over time. The best overall approaches are not known and perhaps not yet established. Gene therapy comes at a high cost, and collaboration between multiple stakeholders is required to ensure that these new medicines are administered equitably.

Structural basis for transcription factor ZBTB7A recognition of DNA and effects of ZBTB7A somatic mutations that occur in human acute myeloid leukemia

ZBTB7A belongs to a small family of transcription factors having three members in humans (7A, 7B, and 7C). They share a BTB/POZ protein interaction domain at the amino end and a zinc-finger DNA-binding domain at the carboxyl end. They control the transcription of a wide range of genes, having varied functions in hematopoiesis, oncogenesis, and metabolism (in particular glycolysis). ZBTB7A-binding profiles at gene promoters contain a consensus G(a/c)CCC motif, followed by a CCCC sequence in some instances. Structural and mutational investigations suggest that DNA-specific contacts with the four-finger tandem array of ZBTB7A are formed sequentially, initiated from ZF1-ZF2 binding to G(a/c)CCC before spreading to ZF3-ZF4, which bind the DNA backbone and the 3' CCCC sequence, respectively. Here, we studied some mutations found in t(8;21)-positive acute myeloid leukemia patients that occur within the ZBTB7A DNA-binding domain. We determined that these mutations generally impair ZBTB7A DNA binding, with the most severe disruptions resulting from mutations in ZF1 and ZF2, and the least from a frameshift mutation in ZF3 that results in partial mislocalization. Information provided here on ZBTB7A-DNA interactions is likely applicable to ZBTB7B/C, which have overlapping functions with ZBTB7A in controlling primary metabolism.

Mammalian life depends on two distinct pathways of DNA damage tolerance

DNA damage threatens genomic integrity and instigates stem cell failure. To bypass genotoxic lesions during replication, cells employ DNA damage tolerance (DDT), which is regulated via PCNA ubiquitination and REV1. DDT is conserved in all domains of life, yet its relevance in mammals remains unclear. Here, we show that inactivation of both PCNA-ubiquitination and REV1 results in embryonic and adult lethality, and the accumulation of DNA damage in hematopoietic stem and progenitor cells (HSPCs) that ultimately resulted in their depletion. Our results reveal the crucial relevance of DDT in the maintenance of stem cell compartments and mammalian life in unperturbed conditions.

Effective therapies for sickle cell disease: are we there yet?

Sickle cell disease (SCD) is a common genetic blood disorder associated with acute and chronic pain, progressive multiorgan damage, and early mortality. Recent advances in technologies to manipulate the human genome, a century of research and the development of techniques enabling the isolation, efficient genetic modification, and reimplantation of autologous patient hematopoietic stem cells (HSCs), mean that curing most patients with SCD could soon be a reality in wealthy countries. In parallel, ongoing research is pursuing more facile treatments, such as in-vivo-delivered genetic therapies and new drugs that can eventually be administered in low- and middle-income countries where most SCD patients reside.

Leukemia/lymphoma-related factor (LRF) or osteoclast zinc finger protein (OCZF) overexpression promotes osteoclast survival by increasing Bcl-xl mRNA: A novel regulatory mechanism mediated by the RNA binding protein SAM68

RANKL induces NFATc1, a key transcriptional factor to induce osteoclast-specific genes such as cathepsin K, whereas transcriptional control of osteoclast survival is not fully understood. Leukemia/lymphoma-related factor (LRF) in mouse and osteoclast zinc finger protein (OCZF) in rat are zinc finger and BTB domain-containing protein (zBTB) family of transcriptional regulators, and are critical regulators of hematopoiesis. We have previously shown that differentiation and survival were enhanced in osteoclasts from OCZF-Transgenic (Tg) mice. In the present study, we show a possible mechanism of osteoclast survival regulated by LRF/OCZF and the role of OCZF overexpression in pathological bone loss. In the in vitro cultures, LRF was highly colocalized with NFATc1 in cells of early stage in osteoclastogenesis, but only LRF expression persisted after differentiation into mature osteoclasts. LRF expression was further enhanced in resorbing osteoclasts formed on dentin slices. Osteoclast survival inhibitor such as alendronate, a bisphosphonate reduced LRF expression. Micro CT evaluation revealed that femurs of OCZF-Tg mice showed significantly lower bone volume compared to that of WT mice. Furthermore, OCZF overexpression markedly promoted bone loss in ovariectomy-induced osteolytic mouse model. The expression of anti-apoptotic Bcl-xl mRNA, which is formed by alternative splicing, was enhanced in the cultures in which osteoclasts are formed from OCZF-Tg mice. In contrast, the expression of pro-apoptotic Bcl-xs mRNA was lost in the culture derived from OCZF-Tg mice. We found that the expression levels of RNA binding splicing regulator, Src substrate associated in mitosis of 68 kDa (Sam68) protein were markedly decreased in OCZF-Tg mice-derived osteoclasts. In addition, shRNA-mediated knockdown of Sam68 expression increased the expression of Bcl-xl mRNA, suggesting that SAM68 regulates the expression of Bcl-xl. These results indicate that OCZF overexpression reduces protein levels of Sam68, thereby promotes osteoclast survival, and suggest that LRF/OCZF is a promising target for regulating pathological bone loss.

Gene Editing-Based Technologies for Beta-hemoglobinopathies Treatment

Beta (β)-thalassemia is a group of human inherited abnormalities caused by various molecular defects, which involves a decrease or cessation in the balanced synthesis of the β-globin chains in hemoglobin structure. Traditional treatment for β-thalassemia major is allogeneic bone marrow transplantation (BMT) from a completely matched donor. The limited number of human leukocyte antigen (HLA)-matched donors, long-term use of immunosuppressive regimen and higher risk of immunological complications have limited the application of this therapeutic approach. Furthermore, despite improvements in transfusion practices and chelation treatment, many lingering challenges have encouraged researchers to develop newer therapeutic strategies such as nanomedicine and gene editing. One of the most powerful arms of genetic manipulation is gene editing tools, including transcription activator-like effector nucleases, zinc-finger nucleases, and clustered regularly interspaced short palindromic repeat-Cas-associated nucleases. These tools have concentrated on γ- or β-globin addition, regulating the transcription factors involved in expression of endogenous γ-globin such as KLF1, silencing of γ-globin inhibitors including BCL11A, SOX6, and LRF/ZBTB7A, and gene repair strategies. In this review article, we present a systematic overview of the appliances of gene editing tools for β-thalassemia treatment and paving the way for patients' therapy.

ZBTB7A, a miR-144-3p targeted gene, accelerates bladder cancer progression via downregulating HIC1 expression

Background

Zinc finger and BTB domain-containing 7A (ZBTB7A) is a member of the POK family of transcription factors that plays an oncogenic or tumor-suppressive role in different cancers depending on the type and genetic context of cancer. However, the function and molecular mechanism of ZBTB7A in bladder cancer (BC) remain elusive.

Methods

The role of ZBTB7A in bladder cancer was detected by colony formation, transwell, and tumor formation assays. The expression levels of ZBTB7A, HIC1, and miR-144-3p were analyzed by qRT-PCR and Western blot. Bioinformatics analysis and a dual-luciferase reporter assay were used to assess the effect of ZBTB7A on the promoter activity of HIC1.

Results

The present study revealed that knockdown of ZBTB7A suppressed BC cell growth and migration, as indicated by an approximately 50% reduction in the number of colonies and an approximately 70% reduction in the number of migrated cells. Loss of ZBTB7A inhibited tumor growth in vivo, resulting in a 75% decrease in tumor volume and an 80% decrease in tumor weight. Further mechanistic studies revealed that ZBTB7A bound to the hypermethylated in cancer 1 (HIC1) promoter and downregulated HIC1 expression, accelerating the malignant behavior of BC. Increased expression of ZBTB7A in BC tissues was negatively corrected with the expression of HIC1. Moreover, ZBTB7A was a target of miR-144-3p, which decreased ZBTB7A expression in BC.

Conclusion

Our data demonstrate that ZBTB7A, a targeted gene of miR-144-3p, promoted tumorigenesis of BC through downregulating HIC1 expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02596-w.

Epigenomic analysis of KLF1 haploinsufficiency in primary human erythroblasts

Haploinsufficiency for the erythroid-specific transcription factor KLF1 is associated with hereditary persistence of fetal hemoglobin (HPFH). Increased HbF ameliorates the symptoms of β-hemoglobinopathies and downregulation of KLF1 activity has been proposed as a potential therapeutic strategy. However, the feasibility of this approach has been challenged by the observation that KLF1 haploinsufficient individuals with the same KLF1 variant, within the same family, display a wide range of HbF levels. This phenotypic variability is not readily explained by co-inheritance of known HbF-modulating variants in the HBB, HBS1L-MYB and/or BCL11A loci. We studied cultured erythroid progenitors obtained from Maltese individuals in which KLF1 p.K288X carriers display HbF levels ranging between 1.3 and 12.3% of total Hb. Using a combination of gene expression analysis, chromatin accessibility assays and promoter activity tests we find that variation in expression of the wildtype KLF1 allele may explain a significant part of the variability in HbF levels observed in KLF1 haploinsufficiency. Our results have general bearing on the variable penetrance of haploinsufficiency phenotypes and on conflicting interpretations of pathogenicity of variants in other transcriptional regulators such as EP300, GATA2 and RUNX1.

CRISPR-Cas9 to induce fetal hemoglobin for the treatment of sickle cell disease

Genome editing is potentially a curative technique available to all individuals with β-hemoglobinopathies, including sickle cell disease (SCD). Fetal hemoglobin (HbF) inhibits sickle hemoglobin (HbS) polymerization, and it is well described that naturally occurring hereditary persistence of HbF (HPFH) alleviates disease symptoms; therefore, reawakening of developmentally silenced HbF in adult red blood cells (RBCs) has long been of interest as a therapeutic strategy. Recent advances in genome editing platforms, particularly with the use of CRISPR-Cas9, have paved the way for efficient HbF induction through the creation of artificial HPFH mutations, editing of transcriptional HbF silencers, and modulating epigenetic intermediates that govern HbF expression. Clinical trials investigating BCL11A enhancer editing in patients with β-hemoglobinopathies have demonstrated promising results, although follow-up is short and the number of patients treated to date is low. While practical, economic, and clinical challenges of genome editing are well recognized by the scientific community, potential solutions to overcome these hurdles are in development. Here, we review the recent progress and obstacles yet to be overcome for the most effective and feasible HbF reactivation practice using CRISPR-Cas9 genome editing as a curative strategy for patients with SCD.

Comprehensive Analysis of microRNAs in Human Adult Erythropoiesis

MicroRNAs (miRNAs) are small non-coding RNAs, which play an important role in various cellular and developmental processes. The study of miRNAs in erythropoiesis is crucial to uncover the cellular pathways that are modulated during the different stages of erythroid differentiation. Using erythroid cells derived from human CD34+ hematopoietic stem and progenitor cells (HSPCs)and small RNA sequencing, our study unravels the various miRNAs involved in critical cellular pathways in erythroid maturation. We analyzed the occupancy of erythroid transcription factors and chromatin accessibility in the promoter and enhancer regions of the differentially expressed miRNAs to integrate miRNAs in the transcriptional circuitry of erythropoiesis. Analysis of the targets of the differentially expressed miRNAs revealed novel pathways in erythroid differentiation. Finally, we described the application of Clustered regularly interspaced short palindromic repeats-Cas9 (CRISPR-Cas9) based editing of miRNAs to study their function in human erythropoiesis.

β-Hemoglobinopathies: The Test Bench for Genome Editing-Based Therapeutic Strategies

Hemoglobin is a tetrameric protein composed of two α and two β chains, each containing a heme group that reversibly binds oxygen. The composition of hemoglobin changes during development in order to fulfill the need of the growing organism, stably maintaining a balanced production of α-like and β-like chains in a 1:1 ratio. Adult hemoglobin (HbA) is composed of two α and two β subunits (α2β2 tetramer), whereas fetal hemoglobin (HbF) is composed of two γ and two α subunits (α2γ2 tetramer). Qualitative or quantitative defects in β-globin production cause two of the most common monogenic-inherited disorders: β-thalassemia and sickle cell disease. The high frequency of these diseases and the relative accessibility of hematopoietic stem cells make them an ideal candidate for therapeutic interventions based on genome editing. These strategies move in two directions: the correction of the disease-causing mutation and the reactivation of the expression of HbF in adult cells, in the attempt to recreate the effect of hereditary persistence of fetal hemoglobin (HPFH) natural mutations, which mitigate the severity of β-hemoglobinopathies. Both lines of research rely on the knowledge gained so far on the regulatory mechanisms controlling the differential expression of globin genes during development.

A unified model of human hemoglobin switching through single-cell genome editing

Key mechanisms of fetal hemoglobin (HbF) regulation and switching have been elucidated through studies of human genetic variation, including mutations in the HBG1/2 promoters, deletions in the β-globin locus, and variation impacting BCL11A. While this has led to substantial insights, there has not been a unified understanding of how these distinct genetically-nominated elements, as well as other key transcription factors such as ZBTB7A, collectively interact to regulate HbF. A key limitation has been the inability to model specific genetic changes in primary isogenic human hematopoietic cells to uncover how each of these act individually and in aggregate. Here, we describe a single-cell genome editing functional assay that enables specific mutations to be recapitulated individually and in combination, providing insights into how multiple mutation-harboring functional elements collectively contribute to HbF expression. In conjunction with quantitative modeling and chromatin capture analyses, we illustrate how these genetic findings enable a comprehensive understanding of how distinct regulatory mechanisms can synergistically modulate HbF expression.

Genetic mechanisms underlying fetal hemoglobin (HbF) regulation and switching are not fully understood. Here, the authors develop a single-cell genome editing functional assay to model how effects of mutation-harbouring functional elements contribute to HbF expression.

Reactivation of a developmentally silenced embryonic globin gene

The α- and β-globin loci harbor developmentally expressed genes, which are silenced throughout post-natal life. Reactivation of these genes may offer therapeutic approaches for the hemoglobinopathies, the most common single gene disorders. Here, we address mechanisms regulating the embryonically expressed α-like globin, termed ζ-globin. We show that in embryonic erythroid cells, the ζ-gene lies within a ~65 kb sub-TAD (topologically associating domain) of open, acetylated chromatin and interacts with the α-globin super-enhancer. By contrast, in adult erythroid cells, the ζ-gene is packaged within a small (~10 kb) sub-domain of hypoacetylated, facultative heterochromatin within the acetylated sub-TAD and that it no longer interacts with its enhancers. The ζ-gene can be partially re-activated by acetylation and inhibition of histone de-acetylases. In addition to suggesting therapies for severe α-thalassemia, these findings illustrate the general principles by which reactivation of developmental genes may rescue abnormalities arising from mutations in their adult paralogues.

Zbtb46-dependent altered developmental program in embryonic stem cell-derived blood cell progenitors

Zbtb46 is a recently identified dendritic cell (DC)-specific transcription factor with poorly defined biology. Although Zbtb46 is highly expressed in conventional DCs, evidence also points to its presence in erythroid progenitors and endothelial cells suggesting that this factor might influence the early hematopoietic development. Here, we probe the effect of this transcription factor in embryonic stem cell (ESC)-derived blood cell progenitors using chemically inducible mouse cell lines. Unexpectedly, forced expression of this protein elicited a broad repressive effect at the early stage of ESC differentiation. Ectopic expression of Zbtb46 interfered with the mesoderm formation and cell proliferation was also negatively impacted. More importantly, reduced number of CD11b+ myeloid blood cells were generated from ESC-derived Flk1+ mesoderm cells in the presence of Zbtb46. Consistent with this finding, our gene expression profiling revealed that numerous myeloid and immune response related genes, including Irf8, exhibited lower expression in the Zbtb46-primed cells. Despite these repressive effects, however, Zbtb46 overexpression was associated with enhanced formation of erythroid blood cell colonies and increased adult hemoglobin (Hbb-b1) expression at the early phase of ESC differentiation. Moreover, elevated percent of CD105 (Endoglin) positive cells were detected in the Zbtb46-primed samples. In summary, our results support that Zbtb46 suppresses the ESC-derived myeloid development and diverts mesoderm cells toward erythroid developmental pathway. Moreover, our transcriptomic data provide a resource for exploration of the Zbtb46 regulatory network in ESC-derived progenitors.

ZNF410 represses fetal globin by singular control of CHD4

Known fetal hemoglobin (HbF) silencers have potential on-target liabilities for rational β-hemoglobinopathy therapeutic inhibition. Here, through transcription factor (TF) CRISPR screening, we identify zinc-finger protein (ZNF) 410 as an HbF repressor. ZNF410 does not bind directly to the genes encoding γ-globins, but rather its chromatin occupancy is concentrated solely at CHD4, encoding the NuRD nucleosome remodeler, which is itself required for HbF repression. CHD4 has two ZNF410-bound regulatory elements with 27 combined ZNF410 binding motifs constituting unparalleled genomic clusters. These elements completely account for the effects of ZNF410 on fetal globin repression. Knockout of ZNF410 or its mouse homolog Zfp410 reduces CHD4 levels by 60%, enough to substantially de-repress HbF while eluding cellular or organismal toxicity. These studies suggest a potential target for HbF induction for β-hemoglobin disorders with a wide therapeutic index. More broadly, ZNF410 represents a special class of gene regulator, a conserved TF with singular devotion to regulation of a chromatin subcomplex.

Role of ZBTB7A zinc finger in tumorigenesis and metastasis

The zinc finger and BTB (broad-complex, tramtrack and bric a brac) domain containing protein 7A (ZBTB7A) is a pleiotropic transcription factor that plays an important role in various stages of cell proliferation, differentiation, and other developmental processes. ZBTB7A is a member of the POK family that directly and specifically binds to short DNA recognition sites located near their target genes thereby acting as transcriptional activator or repressor. ZBTB7A overexpression has been associated with tumorigenesis and metastasis in various human cancer types, including breast, prostate, lung, ovarian, and colon cancer. However in some instances downregulation of ZBTB7A results in tumor progression, suggesting its role as a tumor suppressor. ZBTB7A is involved with complicated regulatory networks which include protein-protein and protein-nucleic acid interactions. ZBTB7A involvement in cancer progression and metastasis is perhaps enabled through the regulation of various signaling pathways depending on the type and genetic context of cancer. The association of ZBTB7A with other proteins affects cancer aggressiveness, therapeutic resistance and clinical outcome. This review focuses on the involvement of ZBTB7A in various signaling pathways and its role in cancer progression. We will also review the literature on ZBTB7A and cancer which could be potentially explored for its therapeutic implications.

Physiological and Aberrant γ-Globin Transcription During Development

The expression of the fetal Gγ- and Aγ-globin genes in normal development is confined to the fetal period, where two γ-globin chains assemble with two α-globin chains to form α₂γ₂ tetramers (HbF). HbF sustains oxygen delivery to tissues until birth, when β-globin replaces γ-globin, leading to the formation of α₂β₂ tetramers (HbA). However, in different benign and pathological conditions, HbF is expressed in adult cells, as it happens in the hereditary persistence of fetal hemoglobin, in anemias and in some leukemias. The molecular basis of γ-globin differential expression in the fetus and of its inappropriate activation in adult cells is largely unknown, although in recent years, a few transcription factors involved in this process have been identified. The recent discovery that fetal cells can persist to adulthood and contribute to disease raises the possibility that postnatal γ-globin expression could, in some cases, represent the signature of the fetal cellular origin.

Dual targeting of brain region-specific kinases potentiates neurological rescue in Spinocerebellar ataxia type 1

A critical question in neurodegeneration is why the accumulation of disease-driving proteins causes selective neuronal loss despite their brain-wide expression. In Spinocerebellar ataxia type 1 (SCA1), accumulation of polyglutamine-expanded Ataxin-1 (ATXN1) causes selective degeneration of cerebellar and brainstem neurons. Previous studies revealed that inhibiting Msk1 reduces phosphorylation of ATXN1 at S776 as well as its levels leading to improved cerebellar function. However, there are no regulators that modulate ATXN1 in the brainstem-the brain region whose pathology is most closely linked to premature death. To identify new regulators of ATXN1, we performed genetic screens and identified a transcription factor-kinase axis (ZBTB7B-RSK3) that regulates ATXN1 levels. Unlike MSK1, RSK3 is highly expressed in the human and mouse brainstems where it regulates Atxn1 by phosphorylating S776. Reducing Rsk3 rescues brainstem-associated pathologies and deficits, and lowering Rsk3 and Msk1 together improves cerebellar and brainstem function in an SCA1 mouse model. Our results demonstrate that selective vulnerability of brain regions in SCA1 is governed by region-specific regulators of ATXN1, and targeting multiple regulators could rescue multiple degenerating brain areas.

LRF/ZBTB7A conservation accentuates its potential as a therapeutic target for the hematopoietic disorders

Conserved sequences across species have always provided valuable insights to improve our understanding on the human genome's entity and the interplay among different loci. Lymphoma/leukemia related factor (LRF) is encoded by ZBTB7A gene and belongs to an evolutionarily conserved family of transcription factors, implicated in vital cellular functions. The present data, demonstrating the wide-spread and the high overlap of the LRF/ZBTB7A recognition sites with genomic segments identified as CpG islands in the human genome, suggest that its binding capacity strongly depends on a specific sequence-encoded feature within CpGs. We have previously shown that de-methylation of the CpG island 326 lying in the ZBTB7A gene promoter is associated with impaired pharmacological induction of fetal hemoglobin in β-type hemoglobinopathies patients. Within this context we aimed to investigate the extent of the LRF/ZBTB7A conservation among primates and mouse genome, focusing our interest also on the CpG island flanking the gene's promoter region, in an effort to further establish its epigenetic regulatory role in human hematopoiesis and pharmacological involvement in hematopoietic disorders. Comparative analysis of the human ZBTB7A nucleotide and amino acid sequences and orthologous sequences among non-human primates and mouse, exhibited high conservation scores. Pathway analysis, clearly indicated that LRF/ZBTB7A influences conserved cellular processes. These data in conjunction with the high levels of expression foremost in hematopoietic tissues, highlighted LRF/ZBTB7A as an essential factor operating indisputably during hematopoiesis.

Emerging role of ZBTB7A as an oncogenic driver and transcriptional repressor

ZBTB7A is a member of the POK family of transcription factors that possesses a POZ-domain at the N-terminus and Krüppel-like zinc-finger at the c-terminus. ZBTB7A was initially isolated as a protein that binds to the inducer of the short transcript of HIV-1 virus TAT gene promoter. The protein forms a homodimer through protein-protein interaction via the N-terminus POZ-domains. ZBTB7A typically binds to the DNA elements through its zinc-finger domains and represses transcription both by modification of the chromatin organization and through the direct recruitment of transcription factors to gene regulatory regions. ZBTB7A is involved in several fundamental biological processes including cell proliferation, differentiation, and development. It also participates in hematopoiesis, adipogenesis, chondrogenesis, cellular metabolism and alternative splicing of BCLXL, DNA repair, development of oligodendrocytes, osteoclast and unfolded protein response. Aberrant ZBTB7A expression promotes oncogenic transformation and tumor progression, but also maintains a tumor suppressive role depending on the type and genetic context of cancer. In this comprehensive review we provide information about the structure, function, targets, and regulators of ZBTB7A and its role as an oncogenic driver and transcriptional repressor in various human diseases.

The E3 ligase adaptor molecule SPOP regulates fetal hemoglobin levels in adult erythroid cells

Reactivation of fetal hemoglobin (HbF) production benefits patients with sickle cell disease and β-thalassemia. To identify new HbF regulators that might be amenable to pharmacologic control, we screened a protein domain-focused CRISPR-Cas9 library targeting chromatin regulators, including BTB domain-containing proteins. Speckle-type POZ protein (SPOP), a substrate adaptor of the CUL3 ubiquitin ligase complex, emerged as a novel HbF repressor. Depletion of SPOP or overexpression of a dominant negative version significantly raised fetal globin messenger RNA and protein levels with minimal detrimental effects on normal erythroid maturation, as determined by transcriptome and proteome analyses. SPOP controls HbF expression independently of the major transcriptional HbF repressors BCL11A and LRF. Finally, pharmacologic HbF inducers cooperate with SPOP depletion during HbF upregulation. Our study implicates SPOP and the CUL3 ubiquitin ligase system in controlling HbF production in human erythroid cells and may offer new therapeutic strategies for the treatment of β-hemoglobinopathies.

ZBTB7A links tumor metabolism to myeloid differentiation

ZBTB7A is a transcription factor that regulates all three branches of hematopoietic differentiation while repressing the expression of key glycolytic enzymes and glucose transporters. Here, we propose that ZBTB7A acts as a link between differentiation and metabolism, two interconnected cellular processes. In particular, ZBTB7A can activate or repress metabolic programs necessary for the differentiation of specific cell lineages while controlling key pathways such as Notch signaling. Finally, the dual role of ZBTB7A has implications for the treatment of myeloid malignancies, where the block of differentiation could potentially be overcome by metabolic therapies with low toxicity.

Advances in genome editing: the technology of choice for precise and efficient β-thalassemia treatment

Beta (β)-thalassemia is one of the most significant hemoglobinopathy worldwide. The high prevalence of the β-thalassemia carriers aggravates the disease burden for patients and national economies in the developing world. The survival of β-thalassemia patients solely relies on repeated transfusions, which eventually results into multi-organ damage. The fetal γ-globin genes are ordinarily silenced at birth and replaced by the adult β-globin genes. However, mutations that cause lifelong persistence of fetal γ-globin, ameliorate the debilitating effects of β-globin mutations. Therefore, therapeutically reactivating the fetal γ-globin gene is a prime focus of researchers. CRISPR/Cas9 is the most common approach to correct disease causative mutations or to enhance or disrupt the expression of proteins to mitigate the effects of the disease. CRISPR/cas9 and prime gene editing to correct mutations in hematopoietic stem cells of β-thalassemia patients has been considered a novel therapeutic approach for effective hemoglobin production. However, genome-editing technologies, along with all advantages, have shown some disadvantages due to either random insertions or deletions at the target site of edition or non-specific targeting in genome. Therefore, the focus of this review is to compare pros and cons of these editing technologies and to elaborate the retrospective scope of gene therapy for β-thalassemia patients.

ZBTB7A prevents RUNX1-RUNX1T1-dependent clonal expansion of human hematopoietic stem and progenitor cells

ZBTB7A is frequently mutated in acute myeloid leukemia (AML) with t(8;21) translocation. However, the oncogenic collaboration between mutated ZBTB7A and the RUNX1–RUNX1T1 fusion gene in AML t(8;21) remains unclear. Here, we investigate the role of ZBTB7A and its mutations in the context of normal and malignant hematopoiesis. We demonstrate that clinically relevant ZBTB7A mutations in AML t(8;21) lead to loss of function and result in perturbed myeloid differentiation with block of the granulocytic lineage in favor of monocytic commitment. In addition, loss of ZBTB7A increases glycolysis and hence sensitizes leukemic blasts to metabolic inhibition with 2-deoxy-d-glucose. We observed that ectopic expression of wild-type ZBTB7A prevents RUNX1-RUNX1T1-mediated clonal expansion of human CD34+ cells, whereas the outgrowth of progenitors is enabled by ZBTB7A mutation. Finally, ZBTB7A expression in t(8;21) cells lead to a cell cycle arrest that could be mimicked by inhibition of glycolysis. Our findings suggest that loss of ZBTB7A may facilitate the onset of AML t(8;21), and that RUNX1-RUNX1T1-rearranged leukemia might be treated with glycolytic inhibitors.

The multi-faceted functioning portrait of LRF/ZBTB7A

Transcription factors (TFs) consisting of zinc fingers combined with BTB (for broad-complex, tram-track, and bric-a-brac) domain (ZBTB) are a highly conserved protein family that comprises a multifunctional and heterogeneous group of TFs, mainly modulating cell developmental events and cell fate. LRF/ZBTB7A, in particular, is reported to be implicated in a wide variety of physiological and cancer-related cell events. These physiological processes include regulation of erythrocyte maturation, B/T cell differentiation, adipogenesis, and thymic insulin expression affecting consequently insulin self-tolerance. In cancer, LRF/ZBTB7A has been reported to act either as oncogenic or as oncosuppressive factor by affecting specific cell processes (proliferation, apoptosis, invasion, migration, metastasis, etc) in opposed ways, depending on cancer type and molecular interactions. The molecular mechanisms via which LRF/ZBTB7A is known to exert either physiological or cancer-related cellular effects include chromatin organization and remodeling, regulation of the Notch signaling axis, cellular response to DNA damage stimulus, epigenetic-dependent regulation of transcription, regulation of the expression and activity of NF-κB and p53, and regulation of aerobic glycolysis and oxidative phosphorylation (Warburg effect). It is a pleiotropic TF, and thus, alterations to its expression status become detrimental for cell survival. This review summarizes its implication in different cellular activities and the commonly invoked molecular mechanisms triggered by LRF/ZBTB7A’s orchestrated action.

ZBTB7A governs estrogen receptor alpha expression in breast cancer

ZBTB7A, a member of the POZ/BTB and Krüppel (POK) family of transcription factors, has been shown to have a context-dependent role in cancer development and progression. The role of ZBTB7A in estrogen receptor alpha (ERα)-positive breast cancer is largely unknown. Approximately 70% of breast cancers are classified as ERα-positive. ERα carries out the biological effects of estrogen and its expression level dictates response to endocrine therapies and prognosis for breast cancer patients. In this study, we find that ZBTB7A transcriptionally regulates ERα expression in ERα-positive breast cancer cell lines by binding to the ESR1 promoter leading to increased transcription of ERα. Inhibition of ZBTB7A in ERα-positive cells results in decreased estrogen responsiveness as demonstrated by diminished estrogen-response element-driven luciferase reporter activity, induction of estrogen target genes, and estrogen-stimulated growth. We also report that ERα potentiates ZBTB7A expression via a post-translational mechanism, suggesting the presence of a positive feedback loop between ZBTB7A and ERα, conferring sensitivity to estrogen in breast cancer. Clinically, we find that ZBTB7A and ERα are often co-expressed in breast cancers and that high ZBTB7A expression correlates with improved overall and relapse-free survival for breast cancer patients. Importantly, high ZBTB7A expression predicts a more favorable outcome for patients treated with endocrine therapies. Together, these findings demonstrate that ZBTB7A contributes to the transcriptional program maintaining ERα expression and potentially an endocrine therapy-responsive phenotype in breast cancer.

Genome editing for blood disorders: state of the art and recent advances

In recent years, tremendous advances have been made in the use of gene editing to precisely engineer the genome. This technology relies on the activity of a wide range of nuclease platforms - such as zinc-finger nucleases, transcription activator-like effector nucleases, and the CRISPR-Cas system - that can cleave and repair specific DNA regions, providing a unique and flexible tool to study gene function and correct disease-causing mutations. Preclinical studies using gene editing to tackle genetic and infectious diseases have highlighted the therapeutic potential of this technology. This review summarizes the progresses made towards the development of gene editing tools for the treatment of haematological disorders and the hurdles that need to be overcome to achieve clinical success.

LRF acts as an activator and repressor of the human β-like globin gene transcription in a developmental stage dependent manner

Leukemia/lymphoma-related factor (LRF; a hematopoietic transcription factor) has been suggested to repress fetal γ-globin genes in the human adult stage β-globin locus. Here, to study the role of LRF in the fetal stage β-globin locus, we knocked out its expression in erythroid K562 cells, in which the γ-globin genes are mainly transcribed. The γ-globin transcription was reduced in LRF knock-out cells, and transcription factor binding to the β-globin locus control region hypersensitive sites (LCR HSs) and active histone organization in the LCR HSs were disrupted by the depletion of LRF. In contrast, LRF loss in the adult stage β-globin locus did not affect active chromatin structure in the LCR HSs and induced the fetal γ-globin transcription. These results indicate that LRF may act as an activator and repressor of the human β-like globin gene transcription in a manner dependent on developmental stage.

Wake-up Sleepy Gene: Reactivating Fetal Globin for β-Hemoglobinopathies

Disorders in hemoglobin (hemoglobinopathies) were the first monogenic diseases to be characterized and remain among the most common and best understood genetic conditions. Moreover, the study of the β-globin locus provides a textbook example of developmental gene regulation. The fetal γ-globin genes (HBG1/HBG2) are ordinarily silenced around birth, whereupon their expression is replaced by the adult β-globin genes (HBB primarily and HBD). Over 50 years ago it was recognized that mutations that cause lifelong persistence of fetal γ-globin expression ameliorate the debilitating effects of mutations in β-globin. Since then, research has focused on therapeutically reactivating the fetal γ-globin genes. Here, we summarize recent discoveries, focusing on the influence of genome editing technologies, including CRISPR-Cas9, and emerging gene therapy approaches.

P38α/JNK signaling restrains erythropoiesis by suppressing Ezh2-mediated epigenetic silencing of Bim

While erythropoietin (EPO) constitutes the major treatment for anemia, a range of anemic disorders remain resistant to EPO treatment. The need for alternative therapeutic strategies requires the identification of mechanisms that physiologically restrain erythropoiesis. Here we show that P38α restrains erythropoiesis in mouse and human erythroblasts independently of EPO by integrating apoptotic signals during recovery from anemia. P38α deficiency promotes JNK activation through increased expression of Map3k4 via a negative feedback mechanism. JNK prevents Cdk1-mediated phosphorylation and subsequent degradation by Smurf2 of the epigenetic silencer Ezh2. Stabilized Ezh2 silences Bim expression and protects erythroblasts from apoptosis. Thus, we identify P38α/JNK signaling as a molecular brake modulating erythropoiesis through epigenetic silencing of Bim. We propose that inhibition of P38α, by enhancing erythropoiesis in an EPO-independent fashion, may provide an alternative strategy for the treatment of anemia.

Erythropoietin (EPO) stimulates erythropoiesis and is commonly used to treat anemia. Here Hu et al. find that P38α/JNK signaling restrains erythropoiesis independently of EPO by regulating epigenetic silencing of the proapoptotic protein Bim, and thus identify putative targets for the treatment of anemic disorders resistant to EPO.

FBI-1 mRNA in normal mucosa is an independent prognostic factor in colorectal cancer patients

Although several studies provide evidence that FBI-1 is an important gene regulator in colorectal cancer (CRC), it is noteworthy that, to our knowledge, no analysis of the correlation between FBI-1 expression and prognosis in CRC has been reported. Using real-time RT-PCR, we detected FBI-1 mRNA in 161 CRC patients (primary tumor, along with the corresponding normal mucosa), 36 liver metastases, and analyzed the relationship of its expression with clinicopathological features. Colon cancer cell lines were used to study FBI-1 function. Our study found that FBI-1 was significant up-regulated in tumor tissue (2.621 ± 0.157) compared with the corresponding normal mucosa (1.620 ± 0.165, P < 0.0001). FBI-1 in normal mucosa was a prognostic factor (P = 0.039, RR 0.431, 95% CI 0.194-0.958), independent of gender, age, stage, and differentiation. High levels of FBI-1 mRNA were related with good survival. Patients with complications had a higher primary tumor FBI-1 expression than those without complications (3.400 ± 0.332 vs. 2.516 ± 0.241, P = 0.032). Suppression of FBI-1 in colon cancer cell lines could repress proliferation of cancer cells. In conclusion, FBI-1 mRNA is overexpressed in CRC, and takes part in the development of CRC. FBI-1 mRNA in normal mucosa is an independent prognostic factor. Our findings give further support to the concept of "field cancerization", and hint that when we study a biomarker, we should not only focus on the tumor tissue but also the corresponding normal mucosa.

Mouse Models of Erythropoiesis and Associated Diseases

Animal models of erythropoiesis have been, and will continue to be, important tools for understanding molecular mechanisms underlying the development of this cell lineage and the pathophysiology associated with various human erythropoietic diseases. In this regard, the mouse is probably the most valuable animal model available to investigators. The physiology and short gestational period of mice make them ideal for studying developmental processes and modeling human diseases. These attributes, coupled with cutting-edge genetic tools such as transgenesis, gene knockouts, conditional gene knockouts, and genome editing, provide a significant resource to the research community to test a plethora of hypotheses. This review summarizes the mouse models available for studying a wide variety of erythroid-related questions, as well as the properties inherent in each one.

Recent progress in understanding and manipulating haemoglobin switching for the haemoglobinopathies

The major β-haemoglobinopathies, sickle cell disease and β-thalassaemia, represent the most common monogenic disorders worldwide and a steadily increasing global disease burden. Allogeneic haematopoietic stem cell transplantation, the only curative therapy, is only applied to a small minority of patients. Common clinical management strategies act mainly downstream of the root causes of disease. The observation that elevated fetal haemoglobin expression ameliorates these disorders has motivated longstanding investigations into the mechanisms of haemoglobin switching. Landmark studies over the last decade have led to the identification of two potent transcriptional repressors of γ-globin, BCL11A and ZBTB7A. These regulators act with additional trans-acting epigenetic repressive complexes, lineage-defining factors and developmental programs to silence fetal haemoglobin by working on cis-acting sequences at the globin gene loci. Rapidly advancing genetic technology is enabling researchers to probe deeply the interplay between the molecular players required for γ-globin (HBG1/HBG2) silencing. Gene therapies may enable permanent cures with autologous modified haematopoietic stem cells that generate persistent fetal haemoglobin expression. Ultimately rational small molecule pharmacotherapies to reactivate HbF could extend benefits widely to patients.

Concise Review: Epigenetic Regulation of Hematopoiesis: Biological Insights and Therapeutic Applications

Hematopoiesis is the process of blood cell formation starting from hematopoietic stem/progenitor cells (HSPCs). The understanding of regulatory networks involved in hematopoiesis and their impact on gene expression is crucial to decipher the molecular mechanisms that control hematopoietic development in physiological and pathological conditions, and to develop novel therapeutic strategies. An increasing number of epigenetic studies aim at defining, on a genome‐wide scale, the cis‐regulatory sequences (e.g., promoters and enhancers) used by human HSPCs and their lineage‐restricted progeny at different stages of development. In parallel, human genetic studies allowed the discovery of genetic variants mapping to cis‐regulatory elements and associated with hematological phenotypes and diseases. Here, we summarize recent epigenetic and genetic studies in hematopoietic cells that give insights into human hematopoiesis and provide a knowledge basis for the development of novel therapeutic approaches. As an example, we discuss the therapeutic approaches targeting cis‐regulatory regions to reactivate fetal hemoglobin for the treatment of β‐hemoglobinopathies. Epigenetic studies allowed the definition of cis‐regulatory sequences used by human hematopoietic cells. Promoters and enhancers are targeted by transcription factors and are characterized by specific histone modifications. Genetic variants mapping to cis‐regulatory elements are often associated with hematological phenotypes and diseases. In some cases, these variants can alter the binding of transcription factors, thus changing the expression of the target genes. Targeting cis‐regulatory sequences represents a promising therapeutic approach for many hematological diseases. Stem Cells Translational Medicine2017;6:2106–2114

BH3-only protein BIM: An emerging target in chemotherapy

BH3-only proteins constitute major proportion of pro-apoptotic members of B-cell lymphoma 2 (Bcl-2) family of apoptotic regulatory proteins and participate in embryonic development, tissue homeostasis and immunity. Absence of BH3-only proteins contributes to autoimmune disorders and tumorigenesis. Bim (Bcl-2 Interacting Mediator of cell death), most important member of BH3-only proteins, shares a BH3-only domain (9-16 aa) among 4 domains (BH1-BH4) of Bcl-2 family proteins and highly pro-apoptotic in nature. Bim initiates the intrinsic apoptotic pathway under both physiological and patho-physiological conditions. Reduction in Bim expression was found to be associated with tumor promotion and autoimmunity, while overexpression inhibited tumor growth and drug resistance as cancer cells suppress Bim expression and stability. Apart from its role in normal homeostasis, Bim has emerged as a central player in regulation of tumorigenesis, therefore gaining attention as a plausible target for chemotherapy. Regulation of Bim expression and stability is complicated and regulated at multiple levels viz. transcriptional, post-transcriptional, post-translational (preferably by phosphorylation and ubiquitination), epigenetic (by promoter acetylation or methylation) including miRNAs. Furthermore, control over Bim expression and stability may be exploited to enhance chemotherapeutic efficacy, overcome drug resistance and select anticancer drug regimen as various chemotherapeutic agents exploit Bim as an executioner of cell death. Owing to its potent anti-tumorigenic activity many BH3 mimetics e.g. ABT-737, ABT-263, obatoclax, AT-101and A-1210477 have been developed and entered in clinical trials. It is more likely that in near future strategies commanding Bim expression and stability ultimately lead to Bim based therapeutic regimen for cancer treatment.

Six2 is involved in GATA1-mediated cell apoptosis in mouse embryonic kidney-derived cell lines

Six2 (Sine oculis homeobox 2), a homeodomain transcription factor, plays a crucial role in the regulation of mammalian nephrogenesis. It is also implicated in numerous biological functions, such as cell proliferation, apoptosis, and migration. However, the underlying regulatory mechanisms of Six2 remain largely unknown. In this study, we predicted that CRX, GATA1, HOXD8, and POU2F2 might target, binding to the promoter region of Six2 (~2000 bp) by bioinformatics analysis. Among the four genes, the predicted binding sequence of GATA1 is most highly conserved across species. Luciferase assays demonstrated that knockdown of GATA1 decreased the activity of Six2 promoter and qPCR result of Six2 expression was in consistent with this in 293T cells. Mutation of GATA1 binding sites of mSix2 promoter led to obvious decrease of the mSix2 promoter activity. Furthermore, knockdown of GATA1 decreased Six2 expression in mk3 cells and increased cell apoptosis of mk3 and mk4 compared with corresponding control cells, but this up-regulation can be rescued by Six2 overexpression. Our findings indicated that GATA1 may be a potential regulator of Six2-maintained population of nephron progenitor cells.

Zbtb7a induction in alveolar macrophages is implicated in anti-HLA-mediated lung allograft rejection

Chronic rejection significantly limits long-term success of solid organ transplantation. De novo donor-specific antibodies (DSAs) to mismatched donor human leukocyte antigen after human lung transplantation predispose lung grafts to chronic rejection. We sought to delineate mediators and mechanisms of DSA pathogenesis and to define early inflammatory events that trigger chronic rejection in lung transplant recipients and obliterative airway disease, a correlate of human chronic rejection, in mouse. Induction of transcription factor zinc finger and BTB domain containing protein 7a (Zbtb7a) was an early response critical in the DSA-induced chronic rejection. A cohort of human lung transplant recipients who developed DSA and chronic rejection demonstrated greater Zbtb7a expression long before clinical diagnosis of chronic rejection compared to nonrejecting lung transplant recipients with stable pulmonary function. Expression of DSA-induced Zbtb7a was restricted to alveolar macrophages (AMs), and selective disruption of Zbtb7a in AMs resulted in less bronchiolar occlusion, low immune responses to lung-restricted self-antigens, and high protection from chronic rejection in mice. Additionally, in an allogeneic cell transfer protocol, antigen presentation by AMs was Zbtb7a-dependent where AMs deficient in Zbtb7a failed to induce antibody and T cell responses. Collectively, we demonstrate that AMs play an essential role in antibody-induced pathogenesis of chronic rejection by regulating early inflammation and lung-restricted humoral and cellular autoimmunity.

Erythropoietin signaling regulates heme biosynthesis

Heme is required for survival of all cells, and in most eukaryotes, is produced through a series of eight enzymatic reactions. Although heme production is critical for many cellular processes, how it is coupled to cellular differentiation is unknown. Here, using zebrafish, murine, and human models, we show that erythropoietin (EPO) signaling, together with the GATA1 transcriptional target, AKAP10, regulates heme biosynthesis during erythropoiesis at the outer mitochondrial membrane. This integrated pathway culminates with the direct phosphorylation of the crucial heme biosynthetic enzyme, ferrochelatase (FECH) by protein kinase A (PKA). Biochemical, pharmacological, and genetic inhibition of this signaling pathway result in a block in hemoglobin production and concomitant intracellular accumulation of protoporphyrin intermediates. Broadly, our results implicate aberrant PKA signaling in the pathogenesis of hematologic diseases. We propose a unifying model in which the erythroid transcriptional program works in concert with post-translational mechanisms to regulate heme metabolism during normal development.

DOI:http://dx.doi.org/10.7554/eLife.24767.001

Heme is an iron-containing compound that is important for all living things, from bacteria to humans. Our red blood cells use heme to carry oxygen and deliver it throughout the body. The amount of heme that is produced must be tightly regulated. Too little or too much heme in a person’s red blood cells can lead to blood-related diseases such as anemia and porphyria. Yet, while scientists knew the enzymes needed to make heme, they did not know how these enzymes were controlled.

Now, Chung et al. show that an important signaling molecule called erythropoietin controls how much heme is produced when red blood cells are made. The experiments used a combination of red blood cells from humans and mice as well as zebrafish, which are useful model organisms because their blood develops in a similar way to humans. When Chung et al. inhibited components of erythropoietin signaling, heme production was blocked too and the red blood cells could not work properly.

These new findings pave the way to look at human patients with blood-related disorders to determine if they have defects in the erythropoietin signaling cascade. In the future, this avenue of research might lead to better treatments for a variety of blood diseases in humans.

DOI:http://dx.doi.org/10.7554/eLife.24767.002

KLF1 directly activates expression of the novel fetal globin repressor ZBTB7A/LRF in erythroid cells

Genes encoding the human β-like hemoglobin proteins undergo a developmental switch from fetal γ-globin to adult β-globin expression around the time of birth. β-hemoglobinopathies, such as sickle-cell disease and β-thalassemia, result from mutations affecting the adult β-globin gene. The only treatment options currently available carry significant adverse effects. Analyses of heritable variations in fetal hemoglobin (HbF) levels have provided evidence that reactivation of the silenced fetal γ-globin genes in adult erythroid cells is a promising therapy. The γ-globin repressor BCL11A has become the major focus, with several studies investigating its regulation and function as a first step to inhibiting its expression or activity. However, a second repression mechanism was recently shown to be mediated by the transcription factor ZBTB7A/LRF, suggesting that understanding the regulation of ZBTB7A may also be useful. Here we show that Krüppel-like factor 1 (KLF1) directly drives expression of ZBTB7A in erythroid cells by binding to its proximal promoter. We have also uncovered an erythroid-specific regulation mechanism, leading to the upregulation of a novel ZBTB7A transcript in the erythroid compartment. The demonstration that ZBTB7A, like BCL11A, is a KLF1 target gene also fits with the observation that reduced KLF1 expression or activity is associated with HbF derepression.