Project description:The reactivation of developmental silenced g-globin genes (HBG1/2) has shown promise as a therapeutic strategy for improving symptoms of b-hemoglobinopathies. Currently, the focus of therapeutic targets is primarily on the major fetal hemoglobin suppressors, such as BCL11A and ZBTB7A and of their binding sites on the proximal HBG promoter. However, the role of the distal HBG promoter in regulating gene expression remains to be explored. Here, we discovered an insertion of nucleotide A (insA) between -1368 and -1369 bp upstream of the TSS in HBG2 resulting in remarkable increase in γ-globin expression in HUDEP-2 cells. We also observed elevated γ-globin expression in human CD34+ erythroid progenitor cells from healthy individuals and those with b-thalassemia when introducing insA mutation. Similarly, engrafted NCG-Kit-V831M mice showed increased γ-globin expression. Importantly, neither did insA have any off-target effects nor did it affect the maturation of erythroid cells. Furthermore, we found that the insA mutation created a binding site for the transcription activator FOXO3, which can reactivate g-globin. Additionally, introducing insA specifically and significantly demethylated the -162 CpG site on HBG promoter by reducing the enrichment of DNA methyltransferase 3A (DNMT3A). At the same time, it activated histone modifications and RNA polymerase II (Pol II) in both distal and proximal HBG promoter and inhibited the binding of BCL11A and ZBTB7A on -115 and -200 sites on the HBG promoter respectively. Overall, our study suggests that introducing insA mutation leads to significantly boosted fetal globin levels and uncovers new safe therapeutic target or strategy for β-hemoglobinopathies.
Project description:The reactivation of developmental silenced g-globin genes (HBG1/2) has shown promise as a therapeutic strategy for improving symptoms of b-hemoglobinopathies. Currently, the focus of therapeutic targets is primarily on the major fetal hemoglobin suppressors, such as BCL11A and ZBTB7A and of their binding sites on the proximal HBG promoter. However, the role of the distal HBG promoter in regulating gene expression remains to be explored. Here, we discovered an insertion of nucleotide A (insA) between -1368 and -1369 bp upstream of the TSS in HBG2 resulting in remarkable increase in γ-globin expression in HUDEP-2 cells. We also observed elevated γ-globin expression in human CD34+ erythroid progenitor cells from healthy individuals and those with b-thalassemia when introducing insA mutation. Similarly, engrafted NCG-Kit-V831M mice showed increased γ-globin expression. Importantly, neither did insA have any off-target effects nor did it affect the maturation of erythroid cells. Furthermore, we found that the insA mutation created a binding site for the transcription activator FOXO3, which can reactivate g-globin. Additionally, introducing insA specifically and significantly demethylated the -162 CpG site on HBG promoter by reducing the enrichment of DNA methyltransferase 3A (DNMT3A). At the same time, it activated histone modifications and RNA polymerase II (Pol II) in both distal and proximal HBG promoter and inhibited the binding of BCL11A and ZBTB7A on -115 and -200 sites on the HBG promoter respectively. Overall, our study suggests that introducing insA mutation leads to significantly boosted fetal globin levels and uncovers new safe therapeutic target or strategy for β-hemoglobinopathies.
Project description:The reactivation of developmental silenced g-globin genes (HBG1/2) has shown promise as a therapeutic strategy for improving symptoms of b-hemoglobinopathies. Currently, the focus of therapeutic targets is primarily on the major fetal hemoglobin suppressors, such as BCL11A and ZBTB7A and of their binding sites on the proximal HBG promoter. However, the role of the distal HBG promoter in regulating gene expression remains to be explored. Here, we discovered an insertion of nucleotide A (insA) between -1368 and -1369 bp upstream of the TSS in HBG2 resulting in remarkable increase in γ-globin expression in HUDEP-2 cells. We also observed elevated γ-globin expression in human CD34+ erythroid progenitor cells from healthy individuals and those with b-thalassemia when introducing insA mutation. Similarly, engrafted NCG-Kit-V831M mice showed increased γ-globin expression. Importantly, neither did insA have any off-target effects nor did it affect the maturation of erythroid cells. Furthermore, we found that the insA mutation created a binding site for the transcription activator FOXO3, which can reactivate g-globin. Additionally, introducing insA specifically and significantly demethylated the -162 CpG site on HBG promoter by reducing the enrichment of DNA methyltransferase 3A (DNMT3A). At the same time, it activated histone modifications and RNA polymerase II (Pol II) in both distal and proximal HBG promoter and inhibited the binding of BCL11A and ZBTB7A on -115 and -200 sites on the HBG promoter respectively. Overall, our study suggests that introducing insA mutation leads to significantly boosted fetal globin levels and uncovers new safe therapeutic target or strategy for β-hemoglobinopathies.
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.
Project description:Beta-hemoglobinopathies caused by mutations in adult-expressed HBB can be treated by re-activating the adjacent paralogous genes HBG1 and HBG2 (HBG), which are normally silenced perinatally. Although HBG expression is induced by global demethylating drugs, their mechanism is poorly understood and toxicity limits their use. We identified the DNMT1-associated maintenance methylation protein UHRF1 as a mediator of HBG repression in a genome-wide screen. Loss of UHRF1 in the adult-type erythroid cell line HUDEP2 caused global demethylation and HBG activation that was reversed upon localized promoter re-methylation. Conversely, targeted demethylation of the HBG promoters activated their genes in HUDEP2 or primary CD34+ cell-derived erythroblasts. Mutation of MBD2, a CpG-methylation reading component of the NuRD complex, to impair methylation sensitivity recapitulated the effects of promoter demethylation. Our studies demonstrate that localized CpG-methylation at the HBG promoters facilitates developmental silencing and identify a targeted therapeutic approach for b-hemoglobinopathies via epigenomic editing.
Project description:Beta-hemoglobinopathies caused by mutations in adult-expressed HBB can be treated by re-activating the adjacent paralogous genes HBG1 and HBG2 (HBG), which are normally silenced perinatally. Although HBG expression is induced by global demethylating drugs, their mechanism is poorly understood and toxicity limits their use. We identified the DNMT1-associated maintenance methylation protein UHRF1 as a mediator of HBG repression in a genome-wide screen. Loss of UHRF1 in the adult-type erythroid cell line HUDEP2 caused global demethylation and HBG activation that was reversed upon localized promoter re-methylation. Conversely, targeted demethylation of the HBG promoters activated their genes in HUDEP2 or primary CD34+ cell-derived erythroblasts. Mutation of MBD2, a CpG-methylation reading component of the NuRD complex, to impair methylation sensitivity recapitulated the effects of promoter demethylation. Our studies demonstrate that localized CpG-methylation at the HBG promoters facilitates developmental silencing and identify a targeted therapeutic approach for b-hemoglobinopathies via epigenomic editing.
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 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.
Project description:Beta-hemoglobinopathies caused by mutations in adult-expressed HBB can be treated by re-activating the adjacent paralogous genes HBG1 and HBG2 (HBG), which are normally silenced perinatally. Although HBG expression is induced by global demethylating drugs, their mechanism is poorly understood and toxicity limits their use. We identified the DNMT1-associated maintenance methylation protein UHRF1 as a mediator of HBG repression in a genome-wide screen. Loss of UHRF1 in the adult-type erythroid cell line HUDEP2 caused global demethylation and HBG activation that was reversed upon localized promoter re-methylation. Conversely, targeted demethylation of the HBG promoters activated their genes in HUDEP2 or primary CD34+ cell-derived erythroblasts. Mutation of MBD2, a CpG-methylation reading component of the NuRD complex, to impair methylation sensitivity recapitulated the effects of promoter demethylation. Our studies demonstrate that localized CpG-methylation at the HBG promoters facilitates developmental silencing and identify a targeted therapeutic approach for b-hemoglobinopathies via epigenomic editing.
Project description:Background: Beta-thalassemia is among the commonest monogenic disorders, posing a major global health challenge. Editing of genetic modifiers of β-thalassemia, such as BCL11A erythroid enhancer and HBG promoters, enhances fetal hemoglobin (HbF) expression and confers major therapeutic potential. Double-strand-break (DSB)-independent genome editing tools, such as base editors, are potentially safer and better suited for multiplexed application than traditional DSB-dependent CRISPR/Cas technology. However, harmful inadvertent on- and off-target events remain a concern and must be excluded before clinical application, including chromosomal rearrangements, which are invisible to standard detection technologies. Results: Using primary patient-derived CD34+ cells from three donors, we investigated simplex and duplex BE-based disruption of the BCL11A erythroid enhancer and the BCL11A binding site (-115bp) on the HBG promoter for DNA-level events and functional studies at the RNA, protein, and morphological level. Analyses included direct comparison to DSB-based editing, as the current clinically applied standard, and analysis of DNA recombination events by CAST-seq to allow wider inferences for relative safety of DSB-, BE- and duplex BE-based editing. Our study reveals the effectiveness of duplex base editing, with robust γ-globin and HbF induction and significantly improved functional correction over simplex editing. Moreover, duplex editing resulted in low incidence of simple and complex genomic alterations in both therapeutically relevant target loci. Conclusions: Here we display simultaneous duplex base editing by targeting both BCL11A erythroid enhancer and HBG promoter for functional correction and genome integrity. Our study highlights the efficacy, safety, and therapeutic potential of the present duplex BE approach