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Chromatin Accessibility Mapping of Primary Erythroid Cell Populations Leads to Identification and Validation of NFIX As a Novel Fetal Hemoglobin Repressor

ABSTRACT: Human genetics has validated de-repression of fetal gamma globin (HBG) in adult erythroblasts as a powerful therapeutic paradigm in diseases involving defective adult beta globin (HBB)1. To identify factors involved in the switch from HBG to HBB expression, we performed Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq)2 on sorted erythroid lineage cells derived from bone marrow (BM) or cord blood (CB), representing adult and fetal states, respectively. BM to CB cell ATAC-seq profile comparisons revealed genome-wide enrichment of NFI DNA binding motifs and increased NFIX promoter chromatin accessibility, suggesting that NFIX may repress HBG. NFIX knockdown in BM cells increased HBG mRNA and fetal hemoglobin (HbF) protein levels, coincident with increased chromatin accessibility and decreased DNA methylation at the HBG promoter. Conversely, overexpression of NFIX in CB cells reduced HbF levels. Identification and validation of NFIX as a new target for HbF activation has implications in the development of therapeutics for hemoglobinopathies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE234155 | GEO | 2023/06/07

REPOSITORIES: GEO

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Chromatin Accessibility Mapping of Primary Erythroid Cell Populations Leads to Identification and Validation of NFIX As a Novel Fetal Hemoglobin Repressor

Project description:Human genetics has validated de-repression of fetal gamma globin (HBG) in adult erythroblasts as a powerful therapeutic paradigm in diseases involving defective adult beta globin (HBB)1. To identify novel factors involved in the switch from HBG to HBB expression, we performed Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq)2 on discrete sorted erythroblast populations derived from bone marrow (BM) or cord blood (CB) progenitors, representing adult and fetal states, respectively. Comparison of the ATAC-seq profiles revealed enrichment of NFI DNA binding motifs and increased chromatin accessibility at the NFIX promoter in BM populations relative to CB populations, suggesting that NFIX may repress HBG. NFIX knockdown in BM cells increased HBG mRNA and fetal hemoglobin (HbF) protein levels, coincident with increased chromatin accessibility and decreased DNA methylation at the HBG promoter. Conversely, overexpression of NFIX in CB cells reduced HbF levels. Identification of NFIX as a novel target for HbF activation has potential implications in the development of therapeutics for hemoglobinopathies.

2023-05-31 | GSE196731 | GEO

Editing the core region in HPFH deletions alters fetal and adult globin expression for treatment of β-hemoglobinopathies

Project description:We have identified putative repressor region (PRR) to exon-1 of β-globin (βE1) in the β-globin cluster as a core region in alll the HPFH deletions that activates fetal hemoglobin and silences adult hemoglobin. Here we charactised the transcriptome of the erythroblasts derived from PRR-βE1 gene edited HSPCs. Transcriptome analysis showed an increased expression of HBG, HBBP1 and decreased expression of HBB transcripts compared to control.

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Forced enhancer-promoter rewiring to alter gene expression in animal models

Project description:Transcriptional enhancers can be in physical proximity with their target genes via chromatin looping. The enhancer at the beta-globin locus (LCR) contacts the fetal (HBG) and adult (HBB) type beta-globin genes during corresponding developmental stages. We previously demonstrated that forcing proximity between the LCR and HBG genes in cultured adult-stage erythroid cells can activate HBG transcription. Activation of HBG expression in erythroid cells is of benefit to patients with sickle cell disease. Here, using the beta-globin locus as a model we provide proof-of-concept at the organismal level that forced enhancer re-wiring might present a strategy to alter gene expression for therapeutic purposes. Hematopoietic stem and progenitor cells (HSPC) from mice bearing human beta-globin genes were transduced with lentiviral vectors expressing a synthetic transcription factor (ZF-Ldb1) that fosters LCR-HBG contacts. When engrafted into host animals, HSPCs gave rise to adult-type erythroid cells with elevated HBG expression. Vectors containing ZF-Ldb1 were optimized for activity in cultured human and rhesus erythroid cells. Upon transplantation into rhesus macaques, erythroid cells from HSPCs expressing ZF-Ldb1 displayed elevated HBG production. These findings in two animal models suggest that forced redirection of gene regulatory elements may be used to alter gene expression to treat disease.

2023-02-08 | GSE221182 | GEO

Epigenetic inactivation of ERF reactivates γ-globin expression in β-thalassemia [ChIP-seq]

Project description:The fetal-to-adult hemoglobin switch is regulated in a developmental stage-specific manner and reactivation of fetal hemoglobin (HbF) has therapeutic potential for β-hemoglobinopathies. Although BCL11A and ZBTB7A interact with their coregulators, reportedly mediating most γ-globin transcriptional silencing in erythroid in trans, and in cis, the molecular mechanism underlying the epigenetic dysregulation of the switch remains largely unclear. Here we showed that epigenetic inactivation of an ETS2 repressor factor (ERF) reactivates γ-globin expression during stress erythropoiesis, and ERF depletion elevates γ-globin in erythroid cells and in erythroid progenies from the edited HSPCs engrafted into immunodeficient mice. ERF represses γ-globin by directly binding to two motifs regulating HBG expression, independently of the major HbF repressors BCL11A and ZBTB7A. We further uncovered that an lncRNA, RP11-196G18.23 mediates ERF promoter hypermethylation resulting in reactivation of g-globin. Herein, the epigenetic alterations were identified as novel modulators ameliorating the severity of b-thalassemia, thus providing novel therapeutic targets for β-hemoglobinopathies.

2020-12-27 | GSE160602 | GEO

Epigenetic inactivation of ERF reactivates γ-globin expression in β-thalassemia [RNA-seq]

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The LRF/ZBTB7A transcription factor is a BCL11A-independent repressor of fetal hemoglobin

Project description:Hemoglobinopathies, including sickle cell disease and _-thalassemia, are global public health concerns. Induction of fetal-type hemoglobin (HbF) is a promising means to treat these disorders; however, precisely how HbF expression is silenced in adult erythroid cells is not fully understood. Here, we show that the LRF/ZBTB7A transcription factor is a potent repressor of HbF production. LRF inactivation derepresses embryonic/fetal _-globin expression in mouse and human adult erythroid cells. We employed genome-wide analysis of the transcriptome, chromatin accessibility and LRF occupancy sites, and demonstrate that LRF occupies the _-globin loci and maintains nucleosome density necessary for _-globin silencing. LRF confers its repressive activity through a unique NuRD repressor complex independent of BCL11A. Strikingly, human erythroid lines lacking both LRF and BCL11A exhibited almost a complete switch in expression from adult- to fetal-type globin, suggesting that these two factors cumulatively represent the near entirety of _-globin repressive activity in adult erythroid cells. RNA-seq, LRF ChIP-seq and ATAC-seq assays were used to investigtae LRF binding, effect of LRF depletion on transcription and chromatin landscape in mouse and human cells.

2016-01-15 | E-GEOD-74977 | biostudies-arrayexpress

The LRF/ZBTB7A transcription factor is a BCL11A-independent repressor of fetal hemoglobin

2016-01-15 | GSE74977 | GEO

Targeted disruption of BCL11A-XL specific zinc finger motif for de-repression of fetal globin expression

Project description:BCL11A is a major gamma globin repressor widely used target for the clinical amelioration of beta-hemoglobinopathies. The longer BCL11A-XL isoform has three distinct ZnF domains at the C-terminal which has been implicated in DNA interactions with the HBG region. These unique ZnF domains harbor missense mutations in neurodevelopmental disorder patients and have been shown to elevate HbF levels with normal hematological parameters. However, the therapeutic potential of targeting the BCL11A-XL-specific ZnF domains without affecting other isoforms remains unexplored. Hence, wedisrupted the BCL11A-XL specific ZnF domains usingCRISPR/Cas9 and observed high HbF induction albeit with defects in Hematopoietic Stem and Progenitor Cells(HSPC) engraftment and erythroid maturation. Subsequently, we observed that base substitutions at the key residues of ZnF-domainsinvolved in DNA recognition effectively upregulated HbF with minor defects. A ZnF4 mutation resulted in minimal changes to erythroid gene expression, no impact on erythroid maturation in vitro, but a reduction in HSPC engraftment in vivo. A modification of ZnF6showeda potential elevation of HbF levels, which was unexpected as this region does not directly interact with DNA at the HBG promoter.Our strategy of specifically altering ZnF domains of BCL11A-XL will potentially identify residues critical for fetal globin repression but less important in the other biological functions of BCL11A-XL for the treatment of beta-hemoglobinopathies.

2024-08-01 | GSE229989 | GEO

Transcription profiling of mouse erythroleukemia (MEL) cells expressing tagged versions of BCL11A

Project description:Differences in the amount of fetal hemoglobin (HbF) that persists into adulthood affect the severity of sickle cell disease and the beta-thalassemia syndromes. Genetic association studies have identified sequence variants in the gene BCL11A that influence HbF levels. Here we examine BCL11A as a potential regulator of HbF expression. The high HbF BCL11A genotype is associated with reduced BCL11A expression. Moreover, abundant expression of full-length forms of BCL11A is developmentally restricted to adult erythroid cells. Down-regulation of BCL11A expression in primary adult erythroid cells leads to robust HbF expression. Consistent with a direct role of BCL11A in globin gene regulation, we find that BCL11A occupies several discrete sites in the beta-globin gene cluster. BCL11A emerges as a therapeutic target for reactivation of HbF in beta-hemoglobin disorders. Expression clone label: FBB (4 different subclones, with 2 arrays each), Control label: MelBirA Experiment Overall Design: Microarray expression analysis from parental control mouse erythroleukemia (MEL) cells containing the BirA enzyme (MelBirA cells) and cells containing tagged versions (FLAG-Biotag) of BCL11A. Two control datasets and eight datasets from four subclones containing tagged BCL11A are included.

2009-01-13 | E-GEOD-13283 | biostudies-arrayexpress

Dimethyl fumarate increases fetal hemoglobin, provides heme detoxification, and corrects anemia in sickle cell disease

Project description:Sickle cell disease (SCD) results from a point mutation in the β-globin gene forming hemoglobin S (HbS), which polymerizes in deoxygenated erythrocytes, triggering recurrent painful vaso-occlusive crises and chronic hemolytic anemia. Reactivation of fetal Hb (HbF) expression ameliorates these symptoms of SCD. Nuclear factor (erythroid derived-2)–like 2 (Nrf2) is a transcription factor that triggers cytoprotective and antioxidant pathways to limit oxidative damage and inflammation and increases HbF synthesis in CD34+ stem cell–derived erythroid progenitors. We investigated the ability of dimethyl fumarate (DMF), a small-molecule Nrf2 agonist, to activate γ-globin transcription and enhance HbF in tissue culture, murine and primate models. DMF recruited Nrf2 to the γ-globin promoters and the locus control region of the β-globin locus in erythroleukemia cells, elevated HbF in SCD donor–derived erythroid progenitors, and reduced hypoxia-induced sickling. Chronic DMF administration in SCD mice induced HbF and increased Nrf2-dependent genes to detoxify heme and limit inflammation. This improved hematological parameters, reduced plasma-free Hb, and attenuated inflammatory markers. Chronic DMF administration to nonanemic primates increased γ-globin mRNA in BM and HbF protein in red cells. DMF represents a potential therapy for SCD to induce HbF and augment vasoprotection and heme detoxification

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