scholarly journals Regulation of Fetal Hemoglobin Expression By the VHL-HIF1α Oxygen Sensing System

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 574-574
Author(s):  
Ruopeng Feng ◽  
Thiyagaraj Mayuranathan ◽  
Peng Huang ◽  
Phillip A Doerfler ◽  
Yichao Li ◽  
...  
Keyword(s):  
Noncoding Rna ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Protein Accumulation ◽  
Globin Mrna ◽  
Chromosome Conformation ◽  
Hematopoietic Stem ◽  
Base Editing ◽  
Stress Erythropoiesis

Abstract Defining the mechanisms that control the perinatal switch from γ-globin (HBG1 and HBG2) to β-globin (HBB) gene expression in human red blood cells (RBCs) has informed novel approaches to reactivate fetal hemoglobin (HbF, α2γ2) therapeutically for sickle cell disease and β-thalassemia. However, one longstanding unsolved problem is to explain how HbF becomes elevated in conditions such as blood loss, hypoxia and hemolysis. These conditions are associated with accelerated RBC production, also referred to as stress erythropoiesis, driven by activation of hypoxia-inducible factor (HIF) via a canonical O 2 sensing pathway. At high O 2 levels ("normoxia"), O 2-dependent prolyl hydroxylase domain (PHD) enzymes hydroxylate HIFα, thereby targeting it for ubiquitination by the von Hippel-Lindau (VHL) E3 ubiquitin ligase complex, followed by proteasomal degradation. At low O 2 tension (hypoxia), PHD activity is reduced, causing HIF1α to accumulate, dimerize with constitutively expressed HIF1β, and bind hypoxia response elements (HREs) to activate a broad array of genes that facilitate hypoxic adaptation. We identified VHL and HIF1α, as negative and positive regulators of HbF expression, respectively. Disruption of the VHL gene in CD34 + hematopoietic stem and progenitor cells (HSPCs) by transfection with ribonucleoprotein (RNP) consisting of Cas9 and VHL-targeting guide RNA increased HbF expression from 7.5% ±1.2% in control cells to 30.9% ± 4.8% (mean ± SD, P<0.0001) in RBC progeny generated by in vitro differentiation. Similarly, γ-globin mRNA was induced by 5 -fold after disruption of VHL in HUDEP-2 cells, an immortalized erythroid line that expresses mainly adult hemoglobin (HbA, α2/β2). Mass spectrometry and transcriptome analysis of VHL-disrupted CD34 + HSPCs revealed increased HIF1α protein expression with no change in the corresponding mRNA. Inhibition of HIF1A mRNA by RNA interference suppressed γ-globin induction in VHL-/- HUDEP-2 clones and in RBCs generated from VHL RNP-treated CD34 + cells, indicating VHL knockout induced HbF through HIF1α protein accumulation. CUT&RUN analysis of VHL-depleted erythroblasts revealed HIF1α/HIF1β heterodimer occupancy at BGLT3, a long-noncoding RNA locus approximately 2.7kb 3' of HBG1. The HIF1α-bound BGLT3 locus contains two canonical HREs (ACGTG) separated by 13 bp. Disruption of each HRE motif in VHL-/- HUDEP-2 cells by base editing caused additive reductions in BGLT3 HIF1α occupancy and γ-globin expression. Mechanistically, VHL depletion caused the accumulation of HIFα/β heterodimers at BGLT3, recruitment of the transcriptional activators GATA1 and P300, and targeted chromatin accessibility to establish the active enhancer mark H3K27ac. These changes were accompanied by altered chromosome conformation to favor long-range interactions between the γ-globin loci (HBG1 and HBG2) and the locus control region, a powerful upstream enhancer. Treatment of healthy donor CD34 + HSPCs-derived erythroblasts with the clinically approved PHD inhibitor FG-4592 (Roxadustat) caused HbF to increase from 4.76%±1.22% at baseline to 12.86 ± 2.40% (mean ± SD in 3 biological replicates, P<0.01). Treatment of the same erythroblasts with FG-4592 and hydroxyurea, a widely used SCD drug that acts partly by inducing HbF, caused HbF to increase from 4.76% ± 1.22% at baseline to 24.1% ± 5.3% (mean ± SD in 3 biological replicates, P<0.01), indicating an additive effect. Our findings link developmental globin gene regulation with O 2 sensing, provide a mechanism for HbF induction during stress erythropoiesis, and identify a novel therapeutic approach for β-hemoglobinopathies. Disclosures Blobel: Pfizer: Consultancy; Fulcrum Therapeutics, Inc.: Consultancy. Weiss: Beam Therapeutics: Current holder of stock options in a privately-held company; Forma Therapeutics: Consultancy; Cellarity Inc.: Consultancy; Novartis: Consultancy.

The Human Ankyrin Insulator Supports Production of Therapeutic Levels of Adult Hemoglobin Following β-Globin Gene Transfer in Hematopoietic Cells Derived From Thalassemic and Sickle Cell Patients

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2055-2055
Author(s):  
Laura Breda ◽  
Carla Casu ◽  
Nicoletta Bianchi ◽  
Luca Cartegni ◽  
Karina Yazdanbakhsh ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Gene Transfer ◽  
Globin Gene ◽  
Marrow Transplant ◽  
Globin Mrna ◽  
Hematopoietic Stem ◽  
Globin Chains ◽  
Adult Hemoglobin

Abstract Abstract 2055 β-thalassemia and sickle cell disease (SCD) are two of the most common genetic red cell blood disorders, affecting millions. Although both conditions originate from genetic defects that reside within the β-globin gene, β-thalassemia is characterized by limited or absent synthesis of β-globin chains, whereas SCD by production of an aberrant β-globin molecule. The only definitive cure for these disorders requires allogeneic bone-marrow (BM) transplant, a procedure whose success is limited by the availability of suitable donors and the occurrence of graft versus host disease. Therefore, the modification of a patient's own BM cells by insertion of the correct β-globin gene might offer a relatively safe alternative therapy. Recently, a patient affected by βE/β0-thalassemia received an autologous bone marrow transplant of hematopoietic stem cells treated with a lentiviral vector carrying the β-globin gene (Cavazzano-Calvo, Nature, 2010). This patient no longer requires transfusion therapy raising great hope that this disease can be cured in this way. However, only one-third of the total hemoglobin content in the patient is derived from the vector, the remainder being the endogenous hemoglobin, half adult and half fetal. To date, no study has focused on the correlation between gene transfer and increased hemoglobin levels in patients carrying different β-globin mutations and exhibiting phenotypic differences. Therefore, it would be extremely helpful if one could anticipate a patient response to gene transfer before undergoing myeloablation. For this purpose we devised a novel method to analyze patient derived erythroid cells in vitro following gene transfer. We generated lentiviral vectors carrying the human β-globin gene, large elements of the locus control region (LCR) with (AnkT9W) and without (T9W) an ankyrin insulator inserted in the 3' self-inactivating long terminal repeat. Analysis of Murine Erythroleukemia (MEL) cells single-integrant-clones indicated that the presence of the ankyrin insulator increased the synthesis of chimeric α-mouse/β-human hemoglobin by 47% (p=0.0023). This was further validated by comparing the amelioration of hematological parameters of thalassemic animals (Hbbth3/+) transplanted with thalassemic hematopoietic stem cells transduced with T9W or AnkT9W. To better understand the mechanism for increased globin expression in the AnkT9W-bearing MEL cells, we performed a time-course real-time PCR analysis on the human β-globin messenger, chromatin immunoprecipitation (ChIP) and polysomal analyses. Our results suggest a novel mechanism triggered by the presence of the ankyrin element, which increases the rate of transcription and confers temporal advantage of the transgenic β-globin mRNA during erythroid differentiation, facilitating ribosomal loading and efficient translation. We also established a preclinical assay to assess in vitro the response to gene transfer with AnkT9W of hematopoietic cells, isolated from twentytwo patients with β-thalassemia and SCD. Among β-thalassemic individuals, we found that in specimens carrying one or two β+ alleles the integration of 0.6 copies of the vector achieved hemoglobin production comparable to specimens from healthy individuals and 35% higher compared to erythroid cells from patients harboring two β0 mutations (p<0.0001). Our preliminary results in three SCD specimens treated with AnkT9W show that sickle cells are able to produce therapeutic levels of adult hemoglobin in a dose-response manner, whereas the amount of sickle hemoglobin decreases proportionally, suggesting that the transgenic β-globin mRNA competes with the sickle transcript to synthesize β-globin chains and form normal hemoglobin tetramers. From our results we conclude that the ankyrin element is particularly effective for the purpose of expressing the β-globin gene not only in a quantitative but also in a qualitative fashion. Furthermore, this approach could provide vital information to select the best gene therapy tools for patients before undergoing myeloablation and bone marrow transplant. Further experiments are in progress to increase the number of SCD specimens and to analyze whether the integration pattern is different in cells infected with T9W versus AnkT9W. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Complementary Base Editing Approaches for the Treatment of Sickle Cell Disease and Beta Thalassemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3352-3352 ◽  
Author(s):  
Ling Lin ◽  
Adrian P. Rybak ◽  
Conrad Rinaldi ◽  
Jonathan Yen ◽  
Yanfang Fu ◽  
...  
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Cell Disease ◽  
Hematopoietic Stem ◽  
Base Editing ◽  
Gamma Globin

Sickle cell disease (SCD) and Beta thalassemia are disorders of beta globin production and function that lead to severe anemia and significant disease complications across a multitude of organ systems. Autologous transplantation of hematopoietic stem cells engineered through the upregulation of fetal hemoglobin (HbF) or correction of the beta globin gene have the potential to reduce disease burden in patients with beta hemoglobinopathies. Base editing is a recently developed technology that enables precise modification of the genome without the introduction of double strand DNA breaks. Gamma globin gene promoters were comprehensively screened with cytosine and adenine base editors (ABE) for the identification of alterations that would derepress HbF. Three regions were identified that significantly upregulated HbF, and the most effective nucleotide residue conversions are supported by natural variation seen in patients with hereditary persistence of fetal hemoglobin (HPFH). ABEs have been developed that significantly increase the level of HbF following nucleotide conversion at key regulatory motifs within the HBG1 and HBG2 promoters. CD34+ hematopoietic stem and progenitor cells (HSPC) were purified at clinical scale and edited using a process designed to preserve self-renewal capacity. Editing at two independent sites with different ABEs reached 94 percent and resulted in up to 63 percent gamma globin by UPLC. The levels of HbF observed should afford protection to the majority of SCD and Beta thalassemia patients based on clinical observations of HPFH and non-interventional therapy that links higher HbF dosage with milder disease (Ngo et al, 2011 Brit J Hem; Musallam et al, 2012 Blood). Directly correcting the Glu6Val mutation of SCD has been a recent goal of genetic therapies designed for the SCD population. Current base editing technology cannot yet convert mutations like those that result from the A-T transversion in sickle beta globin; however, ABE variants have been designed to recognize and edit the opposite stranded adenine residue of valine. This results in the conversion of valine to alanine and the production of a naturally occurring variant known as Hb G-Makassar. Beta globin with alanine at this position does not contribute to polymer formation, and patients with Hb G-Makassar present with normal hematological parameters and red blood cell morphology. SCD patient fibroblasts edited with these ABE variants achieve up to 70 percent conversion of the target adenine. CD34 cells from healthy donors were then edited with a lead ABE variant, targeting a synonymous mutation in an adjacent proline that resides within the editing window and serves as a proxy for editing the SCD mutation. The average editing frequency was 40 percent. Donor myeloid chimerism documented at these levels in the allogeneic transplant setting exceeds the 20 percent that is required for reversing the sickle phenotype (Fitzhugh et al, 2017 Blood). These next generation editing approaches provide a promising new modality for treating patients with Beta thalassemia and SCD. Disclosures No relevant conflicts of interest to declare.

scholarly journals Expression of γ-globin genes in β-thalassemia patients treated with sirolimus: results from a pilot clinical trial (Sirthalaclin)

2021 ◽  
Author(s):  
Cristina Zuccato ◽  
Lucia Carmela Cosenza ◽  
Matteo Zurlo ◽  
Jessica Gasparello ◽  
Chiara Papi ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Clinical Results ◽  
Globin Genes ◽  
Globin Mrna ◽  
Important Conclusion ◽  
Erythroid Precursor

Introduction: The β-thalassemias are due to autosomal mutations of the β-globin gene, inducing absence or low-level synthesis of β-globin in erythroid cells. It is widely accepted that high production of fetal hemoglobin (HbF) is beneficial for β-thalassemia patients. Sirolimus, also known as rapamycin, is a lipophilic macrolide isolated from a strain of Streptomyces hygroscopicus found to be a strong HbF inducer in vitro and in vivo. In this study, we report biochemical, molecular and clinical results of the sirolimus-based NCT03877809 clinical trial (A Personalized Medicine Approach for β-thalassemia Transfusion Dependent Patients: Testing sirolimus in a First Pilot Clinical Trial: Sirthalaclin). Methods: Accumulation of γ-globin mRNA was analyzed by reverse-transcription-quantitative PCR and the hemoglobin pattern by HPLC. The immunophenotype was analyzed by FACS using antibodies against CD3, CD4, CD8, CD14, CD19, CD25. Results: The results were obtained in 8 patients with β+/β+ and β+/β0 genotypes, treated with a starting dosage of 1 mg/day sirolimus for 24-48 weeks. The first finding of the study was that expression of γ-globin mRNA was increased in blood and erythroid precursor cells isolated from β-thalassemia patients treated with low-dose sirolimus. A second important conclusion of our trial was that sirolimus influences erythropoiesis and reduces biochemical markers associated to ineffective erythropoiesis (I.E.) (excess of free α-globin chains, bilirubin, soluble transferrin receptor and ferritin). In most (7/8) of the patients a decrease of the transfusion index was observed. The drug was well tolerated with minor effects on immunophenotype, the only side effect being frequently occurring stomatitis. Conclusions: The data obtained indicate that sirolimus given at low doses modifies hematopoiesis and induces increased expression of γ-globin genes in a sub-set of β-thalassemia patients. Further clinical trials are warranted, considering the possibility to test the drug in patients with less severe forms of the disease and exploring combination therapies.

Targeting BCL11A and KLF1 For The Treatment Of Sickle Cell Disease and β-Thalassemia In Vitro using Antisense Oligonucleotides

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1022-1022 ◽  
Author(s):  
Raechel Peralta ◽  
Audrey Low ◽  
Aneeza Kim ◽  
Sue Murray ◽  
Shuling Guo ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mrna Expression ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Antisense Oligonucleotides ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Globin Mrna ◽  
Dose Dependent

Abstract Sickle cell anemia (SCD) is a hereditary blood disorder in which red blood cells (RBC) become sickle-shaped and block blood vessels, leading to painful vaso-occlusive episodes. Sickling occurs because of a point-mutation in the β-globin gene of hemoglobin. Fetal hemoglobin (HbF, α2γ2) is the main oxygen transport protein with greater oxygen binding affinity in the fetus during the last months of embryonic development and the first few months of life after birth. HbF inhibits sickling by interfering with the polymerization of hemoglobin S. Higher HbF levels in SCD correlate with better survival and because HbF production can be reactivated pharmacologically in adults, it can be used for the treatment of SCD as well as β-thalassemia. In β-thalassemia, there is reduced or absent synthesis of the β-globin gene, causing ineffective erythropoiesis. B-cell lymphoma/leukemia 11A (BCL11A) is a transcription factor in the zinc-finger protein family and is expressed in B cells and erythroid cells. BCL11A represses fetal hemoglobin expression by binding to the GGCCCGG motif in the β-globin promoter region. Erythroid Kruppel-like factor (KLF1) is an erythroid-specific transcription factor that regulates β-globin expression through direct interaction with its promoter and indirectly regulates γ-globin expression through the regulation of BCL11A. By reducing the expression of BCL11A and KLF1, we can promote production of HbF through the upregulation of γ-globin expression. To demonstrate upregulation of γ-globin mRNA expression in vitro, we used MEL-h-b-BAC line#7 cells, a murine erythroleukemic cell line harboring the entire human beta globin locus and expressing mouse BCL11A and KLF1 (Tim Townes, Univ. of Alabama at Birmingham). Antisense oligonucleotides (ASOs) targeting mouse BCL11A or mouse KLF1 were added to the cells in a dose-dependent manner. Seven days later, with free uptake of the ASOs into the cells, we observed dose-dependent reduction of mouse BCL11A mRNA (IC50 = 0.7 μM) and mouse KLF1 mRNA (IC50 = 3 μM). Consequently, we observed a 300 +/- 8% upregulation of human γ-globin mRNA expression after achieving ∼90% reduction in BCL11A mRNA expression after ASO treatment compared to the untreated control cells. Similarly, KLF1 ASO treatment caused a 500 +/- 58% up regulation of human γ-globin mRNA expression after achieving ∼80% mRNA reduction in KLF expression. These data indicate that targeting BCL11A and/or KLF1 with ASO treatment can cause an increase in γ-globin expression that is necessary for the upregulation of fetal hemoglobin and may be used for the treatment of sickle-cell anemia and β-thalassemia. Disclosures: Peralta: Isis Pharmaceuticals, Inc.: Employment. Low: Isis Pharmaceuticals, Inc.: Employment. Kim: Isis Pharmaceuticals, Inc.: Employment. Murray: Isis Pharmaceuticals, Inc.: Employment. Guo: Isis Pharmaceuticals, Inc.: Employment. Freier: Isis Pharmaceuticals, Inc.: Employment. Townes: University of Alabama at Birmingham: Employment. Hung: Isis Pharmaceuticals, Inc.: Employment.

scholarly journals 3'HS1 CTCF binding site in human β-globin locus regulates fetal hemoglobin expression

2021 ◽  
Author(s):  
Pamela Himadewi ◽  
Xue Qing David Wang ◽  
Fan Feng ◽  
Haley Gore ◽  
Yushuai Liu ◽  
...  
Keyword(s):  
Binding Site ◽  
Progenitor Cells ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Ctcf Binding ◽  
Ctcf Binding Site ◽  
Distal Enhancer ◽  
Erythroid Progenitor ◽  
Hematopoietic Stem ◽  
Ctcf Site

Mutations in the adult β-globin gene can lead to a variety of hemoglobinopathies, including sickle cell disease and β-thalassemia. An increase in fetal hemoglobin expression throughout adulthood, a condition named Hereditary Persistence of Fetal Hemoglobin (HPFH), has been found to ameliorate hemoglobinopathies. Deletional HPFH occurs through the excision of a significant portion of the 3 prime end of the β-globin locus, including a CTCF binding site termed 3'HS1. Here, we show that the deletion of this CTCF site alone induces fetal hemoglobin expression in both adult CD34+ hematopoietic stem and progenitor cells and HUDEP-2 erythroid progenitor cells. This induction is driven by the ectopic access of a previously postulated distal enhancer located in the OR52A1 gene downstream of the locus, which can also be insulated by the inversion of the 3'HS1 CTCF site. This suggests that genetic editing of this binding site can have therapeutic implications to treat hemoglobinopathies.

scholarly journals Genome editing using CRISPR-Cas9 to create the HPFH genotype in HSPCs: An approach for treating sickle cell disease and β-thalassemia

2016 ◽  
Vol 113 (38) ◽  
pp. 10661-10665 ◽  
Author(s):  
Lin Ye ◽  
Jiaming Wang ◽  
Yuting Tan ◽  
Ashley I. Beyer ◽  
Fei Xie ◽  
...  
Keyword(s):  
Sickle Cell Disease ◽  
Genome Editing ◽  
Sickle Cell ◽  
Globin Gene ◽  
Autologous Transplantation ◽  
Clinical Manifestations ◽  
Fetal Hemoglobin ◽  
Compound Heterozygous ◽  
Cell Disease ◽  
Hematopoietic Stem

Hereditary persistence of fetal hemoglobin (HPFH) is a condition in some individuals who have a high level of fetal hemoglobin throughout life. Individuals with compound heterozygous β-thalassemia or sickle cell disease (SCD) and HPFH have milder clinical manifestations. Using RNA-guided clustered regularly interspaced short palindromic repeats-associated Cas9 (CRISPR-Cas9) genome-editing technology, we deleted, in normal hematopoietic stem and progenitor cells (HSPCs), 13 kb of the β-globin locus to mimic the naturally occurring Sicilian HPFH mutation. The efficiency of targeting deletion reached 31% in cells with the delivery of both upstream and downstream breakpoint guide RNA (gRNA)-guided Staphylococcus aureus Cas9 nuclease (SaCas9). The erythroid colonies differentiated from HSPCs with HPFH deletion showed significantly higher γ-globin gene expression compared with the colonies without deletion. By T7 endonuclease 1 assay, we did not detect any off-target effects in the colonies with deletion. We propose that this strategy of using nonhomologous end joining (NHEJ) to modify the genome may provide an efficient approach toward the development of a safe autologous transplantation for patients with homozygous β-thalassemia and SCD.

scholarly journals AUF-1 and YB-1 are critical determinants of β-globin mRNA expression in erythroid cells

Blood ◽  
2012 ◽  
Vol 119 (4) ◽  
pp. 1045-1053 ◽  
Author(s):  
Sebastiaan van Zalen ◽  
Grace R. Jeschke ◽  
Elizabeth O. Hexner ◽  
J. Eric Russell
Keyword(s):  
Posttranscriptional Regulation ◽  
Rna Binding ◽  
Globin Gene ◽  
K562 Cells ◽  
Erythroid Cells ◽  
Erythroid Progenitors ◽  
Globin Mrna ◽  
Affinity Enrichment

Abstract The normal accumulation of β-globin protein in terminally differentiating erythroid cells is critically dependent on the high stability of its encoding mRNA. The molecular basis for this property, though, is incompletely understood. Factors that regulate β-globin mRNA within the nucleus of early erythroid progenitors are unlikely to account for the constitutively high half-life of β-globin mRNA in the cytoplasm of their anucleate erythroid progeny. We conducted in vitro protein-RNA binding analyses that identified a cytoplasm-restricted β-globin messenger ribonucleoprotein (mRNP) complex in both cultured K562 cells and erythroid-differentiated human CD34+ cells. This novel mRNP targets a specific guanine-rich pentanucleotide in a region of the β-globin 3′untranslated region that has recently been implicated as a determinant of β-globin mRNA stability. Subsequent affinity-enrichment analyses identified AUF-1 and YB-1, 2 cytoplasmic proteins with well-established roles in RNA biology, as trans-acting components of the mRNP. Factor-depletion studies conducted in vivo demonstrated the importance of the mRNP to normal steady-state levels of β-globin mRNA in erythroid precursors. These data define a previously unrecognized mechanism for the posttranscriptional regulation of β-globin mRNA during normal erythropoiesis, providing new therapeutic targets for disorders of β-globin gene expression.

Point mutation associated with hereditary persistence of fetal hemoglobin decreases RNA polymerase III transcription upstream of the affected gamma-globin gene

1986 ◽  
Vol 6 (9) ◽  
pp. 3278-3282
Author(s):  
D P Carlson ◽  
J Ross
Keyword(s):  
Rna Polymerase ◽  
Globin Gene ◽  
Rna Polymerase Iii ◽  
Fetal Hemoglobin ◽  
In Vitro Transcription ◽  
Base Substitution ◽  
Gamma Globin ◽  
Polymerase Iii ◽  
Hemoglobin Production

A base substitution in the 5'-flanking region of a human fetal globin gene is associated with abnormal fetal hemoglobin production. It also reduces by 5- to 10-fold in vitro transcription of the gene by RNA polymerase III. We discuss potential links between polymerase III transcription and abnormal hemoglobin production.

scholarly journals A novel deletion of approximately 27 kb including the beta-globin gene and the locus control region 3'HS-1 regulatory sequence: beta zero- thalassemia or hereditary persistence of fetal hemoglobin?

Blood ◽  
1994 ◽  
Vol 83 (3) ◽  
pp. 822-827 ◽  
Author(s):  
AJ Dimovski ◽  
V Divoky ◽  
AD Adekile ◽  
E Baysal ◽  
JB Wilson ◽  
...  
Keyword(s):  
Control Region ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Locus Control Region ◽  
Regulatory Sequence ◽  
Beta Globin ◽  
Gamma Chain ◽  
Beta Globin Gene ◽  
Gamma Globin

Abstract A novel deletion of approximately 27 kb with the 5′ breakpoint 1.5 to 2.2 kb upstream of the beta-globin gene, and the 3′ breakpoint approximately 24 kb downstream of the beta-globin gene, has been found in five members of two families from Southeast Asia (Vietnam and Cambodia). Six members of another family from China, previously reported from our laboratory, have also been shown to carry this deletion. The patients presented with mild hypochromia and microcytosis, a hemoglobin (Hb) A2 level of approximately 4.0%, and a markedly increased, heterocellularly distributed, Hb F level (14.0 to 26.0%). In vitro globin-chain synthesis showed a mild imbalance with appreciable gamma-chain compensation (alpha/beta + gamma ratio of 1.46). The 3′ end of this deletion includes the 3′HS-1, and we hypothesize that removal of this region results in the loss of its gamma-globin gene-silencing effect, which causes a markedly elevated Hb F level with a modest increase in Hb A2 levels, unlike the situation in other deletional beta zero-thalassemias. The possible influence of particular sequence variations in the locus control region 5′HS-2 and the G gamma promoter, present on the chromosome with this deletion, on the overall gamma-globin gene should also be considered.

scholarly journals Genome editing of HBG1 and HBG2 to induce fetal hemoglobin

2019 ◽  
Vol 3 (21) ◽  
pp. 3379-3392 ◽  
Author(s):  
Jean-Yves Métais ◽  
Phillip A. Doerfler ◽  
Thiyagaraj Mayuranathan ◽  
Daniel E. Bauer ◽  
Stephanie C. Fowler ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Genome Editing ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Gene Promoters ◽  
Red Cell ◽  
Hematopoietic Stem ◽  
Key Points

Key Points Cas9 editing of the γ-globin gene promoters in hematopoietic stem cells (HSCs) increases red cell HbF by ≤40%. No deleterious effects on hematopoiesis or off-target mutations were detected 16 weeks after xenotransplantation of edited HSCs.

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