Β-globin Gene Promoter Research Articles

Examining the Role of Individual Baf Chromatin Remodeling Complex Components in Globin Gene Regulation

Regulation of the switch from fetal (HbF, α2γ2) to adult (HbA,α2β2) hemoglobin production is an important area of study as reversal of the switch is a key therapeutic approach for treatment of sickle cell disease and β-thalassemia. While multiple specific repressors of γ-globin gene transcription have been identified, there has not been a parallel finding of a γ-globin specific transcriptional activator. The mammalian BAF (BRG1/BRM-associated factor) complex is a multi-subunit, ATP-dependent, chromatin remodeling complex of the SWI/SNF family, with diverse composition and roles in regulation of gene expression. BRG1/SMARCA4 is a core component of the complex with ATPase catalytic activity. Prior studies showed that BRG1 is essential for proper β-globin expression and regulates long-range chromatin interactions between the locus control region (LCR) and the β-globin gene promoter. Studies in K562 cells, where γ-globin expression is predominant, have similarly shown the requirement for BRG1 for transcriptional activation. To date, the role of the BAF complex in regulation of γ-globin versus β-globin gene expression has not been well characterized. Moreover, the considerable diversity in the subtypes of this complex (such as polybromo-associated BAF or PBAF and non-canonical BAF), with subunit composition and functions that differ across cell types and developmental stages, suggests the hypothesis that specific subtypes or subunits of the BAF complex have specific roles in γ-globin gene regulation. We recently identified BRG1 as a potential activator of γ-globin production in a HUDEP2 CRISPR screen targeting ATPase and helicase domains. In validation experiments in HUDEP2 and primary human erythroid cultures, loss of BRG1 led to a marked decrease in γ-globin containing F-cells by flow cytometry and γ-globin protein by western blot, along with a smaller decrease in β-globin production. Because the BAF subunits have significant heterogeneity in expression and function, we asked whether any components may have specificity for γ-globin versus β-globin gene transcription in adult erythroid cells. Using CRISPR-Cas9 targeting in a HUDEP2 sub-clone with elevated fetal hemoglobin levels, we systematically ablated 12 individual BAF/PBAF complex components and assayed fetal hemoglobin by flow cytometry, HPLC, and quantitative western blots. We identified 5 components whose loss of function led to a reduction in γ-globin relative to β-globin: BAF53A, BAF155, BAF60A, BAF60B, and BAF57. We subsequently depleted these five components in primary human erythroid cultures from three independent donors using CRISPR-Cas9 targeting. While loss of BAF53A impaired cell proliferation, loss of remaining components was well tolerated. Loss of BAF155 and BAF60B had minimal effect on globin chain production. Loss of BAF60A had the most potent effect on γ-globin, with up to 80% reduction in γ-globin with no decrease in β-globin production. BAF57 knockdown led to a more modest decrease in γ-globin, but with some decrease in total globin production. Together these data suggest that the requirements for some specific components of the BAF complex differ for activation of fetal or adult globin gene transcription. Additional studies are under way to characterize chromatin accessibility changes at the β-globin locus in response to alterations in the BAF complex, as well as the response to loss of additional BAF complex components.

Hemoglobin F (HbF) Inducers; History, Structure and Efficacies.

Inherited beta-thalassemia is caused by irregular production of hemoglobin through reducing beta-globin chains. It has been observed that increasing fetal hemoglobin (HbF) production improves symptoms in the patients; thus, it has been an operative approach to treat patients with betathalassemia. This review represents compounds with biological activities and pharmacological properties that can be useful in promoting the HBF level in β-thalassemia patients. Various natural products with different mechanisms of action can be helpful in this medication cure. Clinical trials were efficient in improving the signs of patients. Association of in vivo, and in vitro studies of HbF induction and γ-globin mRNA growth displays that in vitro experiments could be an indicator of the in vivo response. The current study resulted that; (a) HbF inducers can be grouped into several classes based on their chemical structures and mechanism of actions; (b) According to several clinical trials, wellknown drugs such as hydroxyurea and decitabine are useful HbF inducers. (c) The cellular biosensor K562 carrying genes under the control of the human γ-globin and β-globin gene promoters were applied during the researches. (d) New natural products and lead compounds were found based on various studies as HbF inducers.

The Hematopoietic Reconstitution through Intra-Bone-Marrow Injection Using Murine Fetal Liver Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) were considered an effective treatment option for many blood diseases and autoimmune diseases. HSCs can currently be isolated from bone marrow and umbilical cord blood. Due to the shortage of these resources, an alternative source of HSCs preparation were sorted out in this study and the ability of hematopoietic reconstruction were examined using such HSCs obtained from fetal liver.Fetal liver hematopoietic stem cells (FL-HSCs) were isolated from embryos of transgenic mice with an erythoid-specific GFP expression that was driven by a human β-globin gene promoter (HS23-GFP mice). Thus, GFP expression could be used as tracer of marker genes of red blood cells derived from the donor FL-HSCs visually. Single-cell suspension of E13.5 HS23-GFP murine liver was used for Ficoll density gradient separation, and the FL-HSC enriched portion was collected for intra-bone-marrow injection (IBMI) into 6-8 week-old recipient mice post 137Cs γ irradiation treatment. Three doses were tested for injection, i.e. 1×105, 1×106 and 1×107 cells, respectively.Hematopoietic reconstruction ability was observed every week after injection using blood smear and routine blood panel such as RBC, HGB and HCT. Bone marrow smear and pathological sections of liver and spleen of recipient mice were analyzed 8 weeks post FL-HSC transplantation. GFP expressed erythrocyte was captured in the peripheral blood starting one week after HL-HSC transplantation. The ability of hematopoietic reconstruction continued to rise until week 7, and became stable thereafter. Among the three treatment groups, the highest cell number group (1×107 ) had the best hematopoietic restoration, according to the RBC, HGB and HCT data. No abnormality such as lymphocytic infiltration in pathological sections of liver and spleen of recipients were noted. Bone marrow smear of recipient mice showed no difference when comparing to that of the wide type mice. This demonstrated HSC obtained from fetal liver, are capable of reconstructing hematopoietic function after transplantation using IBMI. This could provide an alternative source of HSC for future study of hematopoietic function and for future therapeutic treatment for blood diseases. DisclosuresNo relevant conflicts of interest to declare.

A “Shot in the Arm” for Sickle Cell Disease

A “Shot in the Arm” for Sickle Cell Disease

Gene Editing of KLF1 to Cure Sickle Cell Disease

Sickle cell disease (SCD) affects millions of people worldwide and represents the most common monogenic disease of mankind (1). It is due to a homozygous T to A transversion in the β-globin gene that results in an amino acid variant - G6V - and production of HbS, which polymerises in red blood cells (RBCs) under hypoxic conditions. This generates irreversibly sickled cells that fail to traverse the microcirculation, resulting in micro-infarcts, hypoxia and pain, or 'sickle cell crises'. During gestation RBCs utilise different sets of globin genes to produce embryonic and fetal hemoglobins (HbF), so it is not until after birth when adult hemoglobin (HbA) is first produced that the first signs of SCD become apparent. This process termed 'hemoglobin switching' has been the focus of research efforts for decades because it offers an opportunity to reactivate HbF in adult cells of patients with hemoglobinopathies. A number of transcription factors, including Krüppel-like factor 1 (KLF1), play critical roles in hemoglobin switching. KLF1 is an essential erythroid transcription factor that co-ordinates the expression of more than a thousand genes critical to the formation of adult RBCs. KLF1 directly binds the β-globin gene promoter to up regulate its expression, whilst regulating the expression of additional factors like BCL11A and LRF that directly repress γ-globin expression (HbF). Heterozygosity for loss of function mutations in KLF1 leads to a significant increase in HbF that is beneficial to patients with β-thalassemia. We propose this can be recreated by advanced gene editing techniques to provide an effective therapy for SCD. We have employed CRISPR-based gene editing to knockout the expression of KLF1 in human cells. We designed two separate sgRNAs with corresponding HDR templates to target the second exon of KLF1 and ablate its function. We optimised transfection protocols and tested the on-target specificity of our sgRNAs achieving >90% efficacy in all cell types assayed. Using HUDEP-2 cells (2), a conditionally immortalised erythroid cell line which harbors three copies of KLF1 (3), we have demonstrated that these cells require at least one copy (>1/3) for survival; heterozygous cells (+/-/- or +/+/-) proliferate at a reduced rate, but are able to differentiate normally. Using RNA-seq, we identified some genes, including ICAM-4 and BCAM, which are down-regulated accordingly in a KLF1 gene dosage-dependent manner. ICAM-4 and BCAM are cellular adhesion molecules implicated in triggering vaso-occlusive episodes (4; 5), so it is anticipated their reduced expression may provide additional benefit in treating SCD. Gamma-globin is upregulated 10-fold, BCL11A down-regulated 3-fold, and HbF+ RBCs generated at ~20% of total RBCs in KLF1 +/-/- HUDEP-2 cell lines. We also engineered the ablation of KLF1 in CD34+ cells harvested from the peripheral blood of SCD patients undergoing exchange transfusions. Following transfection of the two guides, we performed directed differentiation using an erythroid differentiation medium and analysed the levels of HbF. We observed HbF at levels of between 40-60% of total Hb by HPLC, and HbF+ cells of ~50% by FACS. There was no measurable block in erythroid differentiation by FACS. We documented the types of gene editing using a high throughout NGS assay (6). We compared efficiencies of CRISPR repair of the HbS mutation with CRIPSR damage of the KLF1 gene. Lastly, we transplanted gene-edited CD34 cells into NSGW41 mice (where human erythropoiesis is established) to determine the efficiency and safety of editing long term HSCs from SCD patients. We will report on the results of these xenotransplantation assays. Taken together these results reveal the potential utility in targeting KLF1 to cure SCD.

Discovery of Novel Fetal Hemoglobin Inducers through Small Chemical Library Screening.

The screening of chemical libraries based on cellular biosensors is a useful approach to identify new hits for novel therapeutic targets involved in rare genetic pathologies, such as β-thalassemia and sickle cell disease. In particular, pharmacologically mediated stimulation of human γ-globin gene expression, and increase of fetal hemoglobin (HbF) production, have been suggested as potential therapeutic strategies for these hemoglobinopathies. In this article, we screened a small chemical library, constituted of 150 compounds, using the cellular biosensor K562.GR, carrying enhanced green fluorescence protein (EGFP) and red fluorescence protein (RFP) genes under the control of the human γ-globin and β-globin gene promoters, respectively. Then the identified compounds were analyzed as HbF inducers on primary cell cultures, obtained from β-thalassemia patients, confirming their activity as HbF inducers, and suggesting these molecules as lead compounds for further chemical and biological investigations.

High level of fetal-globin reactivation by designed transcriptional activator-like effector

AbstractThe fetal-to-adult hemoglobin switch has been a focus of a long-standing effort to potentially treat sickle cell disease and β thalassemia by induction of fetal hemoglobin. In a continuation of this effort, we designed specific transcriptional activator-like effectors (TALEs) to target both the Gγ and Aγ-globin promoters. We fused the TALEs to a LIM domain binding protein (Ldb1) dimerization domain, followed by a T2A green fluorescent protein (GFP) cassette, which were assembled into a lentiviral vector. To prevent deletions caused by the repeats of TALEs during the lentivirus packing process, we changed the TALE encoding DNA by codon optimization. Intriguingly, 5 of 14 TALEs showed forced reactivation of fetal-globin expression in human umbilical cord blood-derived erythroid progenitor (HUDEP-2) cells, with a significant increase in the γ-globin mRNA level by more than 70-fold. We also observed a more than 50% reduction of β-globin mRNA. High-performance liquid chromatography analysis revealed more than 30% fetal globin in TALE-induced cells compared with the control of 2%. Among several promoters studied, the β-globin gene promoter with the locus control region (LCR) enhancer showed the highest TALE expression during CD34 erythroid differentiation. At day 19 of differentiation, 2 TALEs increased fetal-globin expression more than 40-fold in the mRNA level and up to 70% of the total globin protein. These TALEs have potential for clinical translation.

Development and characterization of cellular biosensors for HTS of erythroid differentiation inducers targeting the transcriptional activity of γ-globin and β-globin gene promoters.

There is a general agreement that pharmacologically mediated stimulation of human γ-globin gene expression and increase of production of fetal hemoglobin (HbF) is a potential therapeutic approach in the experimental therapy of β-thalassemia and sickle cell anemia. Here, we report the development and characterization of cellular biosensors carrying enhanced green fluorescence protein (EGFP) and red fluorescence protein (RFP) genes under the control of the human γ-globin and β-globin gene promoters, respectively; these dual-reporter cell lines are suitable to identify the induction ability of screened compounds on the transcription in erythroid cells of γ-globin and β-globin genes by FACSwith efficiency and reproducibility. Our experimental system allows to identify (a) HbF inducers stimulating to different extent the activity of the γ-globin gene promoter and (b) molecules that stimulate also the activity of the β-globin gene promoter. A good correlation does exist between the results obtained by using the EGFP/RFP clones and experiments performed on erythroid precursor cells from β-thalassemic patients, confirming that this experimental system can be employed for high-throughput screening (HTS) analysis. Finally, we have demonstrated that this dual-reporter cell line can be used for HTS in 384-well plate, in order to identify novel HbF inducers for the therapy of β-thalassemia and sickle cell anemia. Graphical abstract.

First Identification of the 3.5 kb Deletion (NC_000011.10: g.5224302-5227791del3490bp) on the β-Globin Gene Cluster in a Chinese Family

β-Thalassemia (β-thal) is one of the most common autosomal recessive disorders worldwide. It is caused mainly by point mutations or, more rarely, deletions on the β-globin gene, leading to reduced (β+) or absent (β0) synthesis of the β chains of hemoglobin (Hb). Molecular characterization of β-thal is essential for the prevention of this disease in the population. In China, more than 46 different mutations have been found, while approximately five large deletional types of β-thal have been reported. Here we described a large deletional mutation of the β-globin gene cluster previously unreported in the Chinese population, the 3.5 kb deletion (NC_000011.10: g.5224302-5227791del3490bp) removing the β-globin gene promoter and the whole β-globin gene leading to a β0-thal phenotype.

Characterization of Two Novel Deletions Involving the 5′ Region of the β-Globin Gene

We report two novel β-thalassemia (β-thal) deletions involving the 5′ region of the β-globin gene (HBB). The first deletion spans 538 bp and removes the β-globin promoter, 5′ untranslated region (5′UTR) and most of exon 1. This deletion was identified in a 3-year-old Vietnamese boy with non transfusion dependent Hb E (HBB: c.79G>A)/β0-thal. The second deletion spans 1517 bp and removes the β-globin gene promoter, 5′UTR, and exons 1 and 2. This deletion was identified in two unrelated adults of European descent who had β-thal trait with unusually high Hb A2 levels. Deletions such as these are generally associated with higher levels of Hb A2 and Hb F than typical β-thal alleles, which may ameliorate the severity of the disease.

A Novel -72 (T→A) β-Promoter Mutation Causing Slightly Elevated HbA2 in a Vietnamese Heterozygote.

We report a novel β+-thalassemia mutation found in a Vietnamese family. The molecular defect T→A lies at -72 of the β-globin gene promoter, within the conserved CCAAT box. The index case was a 5-year-old child having red blood cells indices close to normal and slightly increased level of HbA2 (3.96%). The expression of the mutated β allele was inferred by luciferase reporter assay in K562 cells. The β -72 determinant is the eighth β-thalassemic mutation identified in Vietnam and it was not previously reported in any population. The absence of homozygous or compound heterozygous states did not allow us to precisely predict either its clinical impact or its relevance in management programs. Our results further underline the importance of identifying and characterizing new or rare β+-thalassemic alleles in carrier screening and prenatal diagnosis.

A Novel Mutation in the Promoter Region of the β-Globin Gene: HBB: c.-127G > C

Novel β-globin gene mutations are still occasionally being reported, especially when evaluating milder phenotypes. We report here a novel putative mutation in the promoter region of the β-globin gene and assess its clinical implications. A family, parents and four siblings, with hematological and clinical features suspected of being β-globin gene mutation(s), were involved in this study. In addition to hematological and clinical evaluations of the whole family, molecular analyses of the β-globin gene were performed by direct sequencing. Sequencing of the β-globin gene revealed a novel genomic alteration in the regulatory region of the gene. This novel genomic alteration was defined as HBB: c.-127G > C according to the Human Genome Variation Society (HGVS) nomenclature. Two siblings were found to be carriers of the HBB: c.-127G > C mutation, while the other two siblings were carriers of the codon 8 (−AA) (HBB: c.25_26delAA) deletion of the β-globin gene. The mother was a compound heterozygote for the codon 8 and HBB: c.-127G > C mutations. Based on hematological and clinical evaluations, we conclude that this novel β-globin gene promoter region change would be associated with a mild phenotype of β-thalassemia (β-thal).

High Fractional Occupancy of a Tandem Maf Recognition Element and Its Role in Long-Range β-Globin Gene Regulation.

Enhancers and promoters assemble protein complexes that ultimately regulate the recruitment and activity of RNA polymerases. Previous work has shown that at least some enhancers form stable protein complexes, leading to the formation of enhanceosomes. We analyzed protein-DNA interactions in the murine β-globin gene locus using the methyltransferase accessibility protocol for individual templates (MAPit). The data show that a tandem Maf recognition element (MARE) in locus control region (LCR) hypersensitive site 2 (HS2) reveals a remarkably high degree of occupancy during differentiation of mouse erythroleukemia cells. Most of the other transcription factor binding sites in LCR HS2 or in the adult β-globin gene promoter regions exhibit low fractional occupancy, suggesting highly dynamic protein-DNA interactions. Targeting of an artificial zinc finger DNA-binding domain (ZF-DBD) to the HS2 tandem MARE caused a reduction in the association of MARE-binding proteins and transcription complexes at LCR HS2 and the adult βmajor-globin gene promoter but did not affect expression of the βminor-globin gene. The data demonstrate that a stable MARE-associated footprint in LCR HS2 is important for the recruitment of transcription complexes to the adult βmajor-globin gene promoter during erythroid cell differentiation.

A Luciferase Reporter Gene System for High-Throughput Screening of γ-Globin Gene Activators.

Luciferase reporter gene assays have long been used for drug discovery due to their high sensitivity and robust signal. A dual reporter gene system contains a gene of interest and a control gene to monitor non-specific effects on gene expression. In our dual luciferase reporter gene system, a synthetic promoter of γ-globin gene was constructed immediately upstream of the firefly luciferase gene, followed downstream by a synthetic β-globin gene promoter in front of the Renilla luciferase gene. A stable cell line with the dual reporter gene was cloned and used for all assay development and HTS work. Due to the low activity of the control Renilla luciferase, only the firefly luciferase activity was further optimized for HTS. Several critical factors, such as cell density, serum concentration, and miniaturization, were optimized using tool compounds to achieve maximum robustness and sensitivity. Using the optimized reporter assay, the HTS campaign was successfully completed and approximately 1000 hits were identified. In this chapter, we also describe strategies to triage hits that non-specifically interfere with firefly luciferase.

Hb Lansing (HBA2: c.264C > G) and a New β Promoter Transversion [−52 (G > T)]: An Attempt to Define the Phenotype of Two Mutations Found in the Omani Population

We report two examples showing how problematic it can be to define the phenotype of new or rare globin genes mutations. We describe two mutations observed for the first time in the Omani population: the first was found in the consanguineous parents of a deceased newborn with hepatomegaly, cardiomegaly and severe hemolytic anemia, putatively homozygous for the rare Hb Lansing (HBA2: c.264C > G) variant. The second is a novel β-globin gene promoter mutation [−52 (G > T)] observed in four independent patients. Two with borderline/elevated Hb A2, α-thalassemia (α-thal) and hypochromic red cell indices, and two heterozygotes for Hb S (HBB: c.20A > T), α-thal and with Hb A/Hb S ratios possibly indicating a very mild β+-thalassemia (β+-thal) mutation.

A Novel Promoter Mutation (HBB: c.-75G>T) Was Identified as a Cause of β+-Thalassemia

We report a novel β-globin gene promoter mutation in a Chinese family identified using fluorescence resolution melting curve analysis and gene sequencing. The proband, who showed the phenotype of β-thalassemia intermedia (β-TI), was found to be a compound heterozygote for the novel mutation −25 (G>T) (HBB: c.-75G>T) and a codon 17 (HBB: c.52A>T) mutation. Moreover, conservation analysis using phyloP and phastCons indicated that the mutated base in the proband was conserved. This novel point mutation on the β-globin gene is in close proximity to the conserved ATAA sequence located at position −25 relative to the mRNA Cap site. We performed a further comparative analysis of the clinical phenotypes and hematological parameters in this pedigree and found that the father was a carrier of the novel point mutation and showed low levels of hemoglobin (Hb), mean corpuscular volume (MCV) and mean corpuscular Hb (MCH). Thus, the available evidence suggests that this novel mutation, −25, results in β+-thalassemia (β+-thal).

Non-Thalassemic Phenotype Associated With the -83 (G > A) Mutation of the β-Globin Gene Promoter (HBB: c.-133G > A)

The -83 (G > A) mutation of the β-globin gene promoter (HBB: c.-133G > A) was first reported in an adult male patient with mild thalassemic indices, suggesting that this may be a mild β+-thalassemia (β+-thal) allele. In this report, we present data from several patients who are simple heterozygotes for the -83 mutation, or compound heterozygotes for -83 and Hb S (HBB: c.20A > T) or β-thal. These cases illustrate that the -83 sequence variant is not associated with a thalassemic phenotype. This has important implications for carrier screening and genetic counseling, particularly since the -83 mutation is relatively common in African and Hispanic populations.

Molecular Characterization of a β-Thalassemia Intermedia Patient Presenting Inferior Vena Cava Thrombosis: Interaction of the β-Globin Erythroid Krüppel-Like Factor Binding Site Mutation with Hb E and α+-Thalassemia

The molecular basis and hematological phenotype of adult Thai β-thalassemia intermedia (β-TI) patients encountered with inferior vena cava (IVC) thrombosis were investigated. Hematological and molecular analysis revealed a trait previously not described. The disease was caused by interaction of the β+-thalassemia (β+-thal) gene with the −90 (C > T) (HBB: c.-140C > T) transition within the erythroid Krüppel-like factor (EKLF) binding site of the β-globin gene promoter with Hb E (HBB: c.79G > A) and α+-thalassemia (α+-thal). Hematological data of the patient were compared with those of heterozygous forms of these defects found in his family members and different genotype-phenotype interactions are illustrated. Globin gene haplotype analysis indicates an independent origin of this Thai β+-thal gene. Accurate diagnoses as well as knowledge of genotype-phenotype relationships were required for providing appropriate management of such cases.

Using Forced Chromatin Looping To Overcome Developmental Silencing Of Embryonic and Fetal β-Type Globin Genes In Adult Erythroid Cells

The β-genes undergo developmental activation and silencing in part by competing for their upstream enhancer, the locus control region (LCR). In adult erythroid cells, the LCR contacts the β-globin gene promoter by forming a loop that precludes interaction with the embryonic and fetal β-type globin genes. Reversing this developmental gene expression switch in favor of embryonic/fetal genes has therapeutic implications for patients with hemoglobinopathies. Here we employed a forced chromatin looping approach to activate the silenced murine embryonic βh1-globin gene and the human fetal γ-globin gene in adult erythroid cells. We have previously shown that forced recruitment via artificial zinc finger proteins of Ldb1, a protein necessary for long-range chromatin interactions at the β-globin locus, can trigger chromatin loop formation and transcription initiation. Here, we designed a zinc finger protein targeting the βh1 promoter, fused it to the self-association domain of Ldb1 (βh1-Ldb1), and introduced it into an adult murine erythroid cell line that normally produces nearly 100% adult β-globin. βh1-Ldb1 expression activated βh1-globin transcription up to 3000-fold accounting for ∼20% of total β-globin expression. βh1-Ldb1 similarly increased expression of βh1-globin in fetal liver derived primary erythroid cells. These results are striking given the degree to which murine embryonic globin genes are normally repressed. To test whether the activity βh1-Ldb1 was due to a looped interaction of the βh1 promoter with the LCR, we introduced βh1-Ldb1 into fetal liver derived erythroblasts from mice in which the LCR had been deleted. βh1-Ldb1 was virtually inactive in the absence of the LCR, demonstrating the dependence on the LCR and, by inference, long range looping of βh1-Ldb1 function. We next extended this approach to the human β-globin locus in an effort to activate expression of the fetal γ-globin gene in adult erythroid cells. Ldb1 was fused to a previously described γ-globin promoter binding zinc finger protein, GG1, to generate GG1-Ldb1. Introduction of GG1-Ldb1 into adult primary human erythroid cells strongly activated γ-globin expression with a concomitant reduction in β-globin transcription. Strikingly, γ-globin accounted for nearly 90% of total β-type globin transcription. Furthermore, fetal hemoglobin expression was nearly pan-cellular as determined by flow cytometry. These results demonstrate the power of forced chromatin looping to reprogram developmental regulation of gene expression, and provide a novel proof of concept for activating the γ-globin gene for the benefit of patients with hemoglobinopathies. Disclosures:Gregory: Sangamo BioSciences: Employment. Reik:Sangamo BioSciences: Employment.

Beta-globin gene mutations in children with beta-thalassemia major from Şanlıurfa province, Turkey.

The prevalence of β-thalassemia in Şanlıurfa province, Turkey is reported to be 2.6%-3.7%, whereas nation-wide the frequency of β-thalassemia is 2%. This study aimed to identify the most frequent β-thalassemia mutations in Şanlıurfa province. In total, 22 mutations were investigated in 115 pediatric patients with β-thalassemia using a commercially available reverse dot blot platform. The study included 60 male and 55 female patients with a mean age of 7.3±4.6 years (range: 1-17 years). In total, 76% of the patients had consanguineous parents. In all, 16 different mutations were observed in the 115 patients. IVS-1-110 (G-A) (29.1%), IVS-1-1 (G-A) (13.9%), codon 39 (C>T) (10.4%), and codon 8 (-AA) (9.1%) accounted for 62.5% of all the β-thalassemia mutations, and 6% of the patients had 2 different thalassemia mutations. According to the present results, IVS-1-110 (G>A) was the most frequent mutation observed in the patients from Şanlıurfa province, as in other geographical regions of Turkey. In addition, the following 34 compound heterozygote mutant alleles were observed; IVS-1-1 (G>A)/IVS 2.848 (n=4), codon 39 (C>T)/codon 8 (-AA) (n=2), codon 6 (-A)/IVS 1.5 (G>C) (n=2), IVS-1-110 (G>A)/IVS-1-1 (G>A) (n=2), IVS-1-110 (G>A)/codon 8 (-AA) (n=1), IVS-1-110 (G>A)/codon 39 (C>T) (n=1), IVS-1-110 (G>A)/IVS-1-6 (T>C) (n=1), IVS-1-110 (G>A)/IVS-1-5 (G>C) (n=1), IVS-1-110 (G>A]/codon 8/9 (+G) (n=1), IVS-1-1 (G>A)/codon 39 (C>T) (n=1), and codon 8 (-AA)/IVS-1-5 (G>C) (n=1). The following β-globin gene promoter mutations were not observed; -101 (C>T), -87(C>T), -30 (T>A), codon 15 (TTG>TGA), codon 27 (G>T) Knossos, and IVS-1-116 (G>C). In all, 5 of the 115 patients (4.3%) had an unidentified mutation. The present results illustrate the heterogeneity of β-thalassemia mutations in Şanlıurfa Province. The present findings may be of value for genetic counseling, and premarital and prenatal diagnosis in Şanlıurfa province.