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: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.