Human Fetal Hemoglobin Expression Is Regulated by the Developmental Stage-Specific Repressor BCL11A

Science ◽  
2008 ◽  
Vol 322 (5909) ◽  
pp. 1839-1842 ◽  
Author(s):  
Vijay G. Sankaran ◽  
Tobias F. Menne ◽  
Jian Xu ◽  
Thomas E. Akie ◽  
Guillaume Lettre ◽  
...  
Keyword(s):  
Association Studies ◽  
Globin Gene ◽  
Genetic Association Studies ◽  
Fetal Hemoglobin ◽  
Sequence Variants ◽  
Erythroid Cells ◽  
Cell Disease ◽  
Direct Role ◽  
Globin Gene Regulation

Differences in the amount of fetal hemoglobin (HbF) that persists into adulthood affect the severity of sickle cell disease and the β-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 β-globin gene cluster. BCL11A emerges as a therapeutic target for reactivation of HbF in β-hemoglobin disorders.

Genetic association studies in β-hemoglobinopathies

Hematology ◽  
2013 ◽  
Vol 2013 (1) ◽  
pp. 354-361 ◽  
Author(s):  
Swee Lay Thein
Keyword(s):  
Association Studies ◽  
Globin Gene ◽  
Genetic Association Studies ◽  
Fetal Hemoglobin ◽  
Clinical Severity ◽  
Genetic Modifiers ◽  
Genetic Studies ◽  
Globin Gene Regulation ◽  
Innate Ability

Abstract Characterization of the molecular basis of the β-thalassemias and sickle cell disease (SCD) clearly showed that individuals with the same β-globin genotypes can have extremely diverse clinical severity. Two key modifiers, an innate ability to produce fetal hemoglobin and coinheritance of α-thalassemia, both derived from family and population studies, affect the pathophysiology of both disorders at the primary level. In the past 2 decades, scientific research had applied genetic approaches to identify additional genetic modifiers. The review summarizes recent genetic studies and key genetic modifiers identified and traces the story of fetal hemoglobin genetics, which has led to an emerging network of globin gene regulation. The discoveries have provided insights on new targets for therapeutic intervention and raise possibilities of developing fetal hemoglobin predictive diagnostics for predicting disease severity in the newborn and for integration into prenatal diagnosis to better inform genetic counseling.

scholarly journals Exploring epigenetic and microRNA approaches for γ-globin gene regulation

2021 ◽  
pp. 153537022110281
Author(s):  
Athena Starlard-Davenport ◽  
Ashley Fitzgerald ◽  
Betty S Pace
Keyword(s):  
Gene Regulation ◽  
Globin Gene ◽  
Single Agent ◽  
Unmet Need ◽  
Fetal Hemoglobin ◽  
Therapeutic Interventions ◽  
Globin Genes ◽  
Chromosome 11 ◽  
Globin Gene Regulation

Therapeutic interventions aimed at inducing fetal hemoglobin and reducing the concentration of sickle hemoglobin is an effective approach to ameliorating acute and chronic complications of sickle cell disease, exemplified by the long-term use of hydroxyurea. However, there remains an unmet need for the development of additional safe and effective drugs for single agent or combination therapy for individuals with β-hemoglobinopathies. Regulation of the γ-globin to β-globin switch is achieved by chromatin remodeling at the HBB locus on chromosome 11 and interactions of major DNA binding proteins, such as KLF1 and BCL11A in the proximal promoters of the globin genes. Experimental evidence also supports a role of epigenetic modifications including DNA methylation, histone acetylation/methylation, and microRNA expression in γ-globin gene silencing during development. In this review, we will critically evaluate the role of epigenetic mechanisms in γ-globin gene regulation and discuss data generated in tissue culture, pre-clinical animal models, and clinical trials to support drug development to date. The question remains whether modulation of epigenetic pathways will produce sufficient efficacy and specificity for fetal hemoglobin induction and to what extent targeting these pathways form the basis of prospects for clinical therapy.

Additive Effect of Butyrate and Hemin on Fetal Hemoglobin Induction in Erythroid Cells from Sickle Cell Disease and Beta-Thalassemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1224-1224
Author(s):  
Hassana Fathallah ◽  
Ali Taher ◽  
Ali Bazarbachi ◽  
George F. Atweh
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Histone Deacetylases ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Beta Thalassemia ◽  
Erythroid Cells ◽  
Cell Disease ◽  
Globin Mrna ◽  
In Erythroid Cells

Abstract High levels of fetal hemoglobin (HbF) are known to ameliorate the pathophysiology of β-globin disorders. The objective of this study is twofold: the first is to evaluate the efficacy of hemin as an inducer of HbF in erythroid cells from patients with sickle cell disease (SCD) and β-thalassemia (β-thal); the second is to determine if the combination of butyrate and hemin can induce higher levels of expression of HbF than either agent alone. BFU-E derived cells from the peripheral blood of two patients with homozygous SCD, three patients with β-thal, one patient with sickle β-thalassemia (S/β-thal) and one normal individual (AA) were cultured in the absence (control) or presence of butyrate (B), hemin (H) or butyrate and hemin (B+H). As expected, the levels of γ-globin mRNA [expressed as % γ/(β+γ)] increased upon butyrate exposure in progenitor-derived erythroid cells from SS and S/β-thal patients, and to a lesser extent in patients with β-thal (P = 0.01). In contrast, butyrate did not increase γ-globin expression in BFU-E derived colonies from the AA individual. Moreover, hemin exposure increased the γ/(β+γ) ratio in all subjects (P = 0.02). These findings confirm that hemin can be an effective HbF inducing agent in SCD and β-thal. Although the mechanism of induction of HbF by hemin is not known, unlike butyrate, hemin is clearly not a direct inhibitor of histone deacetylases and is likely to induce HbF by a different mechanism of action. Thus, we investigated the effect of the combination of hemin and butyrate on γ-globin gene expression. Interestingly, the combination of butyrate and hemin resulted in additive increases in the γ/(β+γ) ratios in all patients compared to butyrate alone (P = 0.03) or hemin alone (P = 0.01) (Table I). Just as importantly, exposure to both drugs resulted in a decrease in the α/(β+γ) mRNA imbalance in β-thal, which is the predominant pathophysiological feature of this disorder. In conclusion, combination therapy consisting of butyrate and hemin, which are two agents with different mechanisms of action and different toxicity profiles, may provide a more effective way of inducing HbF in patients with SCD and β-thal. Table I mRNA SCD β-Thal S/β-Thal AA n 2 3 1 1 %γ/(β+γ) Control 36 42 26 7.1 B 45 50 41 6.9 H 55 55 52 15 B+H 60 61 59 13 α/(β+γ) Control 3.1 8.9 1.8 1.9 B 2.0 7.7 2.9 1.7 H 3.0 7.5 1.7 1.0 B+H 2.9 6.4 2.2 1.3

scholarly journals Loss of NRF2 Function Worsens the Pathophysiology of Sickle Cell Disease in a Transgenic Mouse Model

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. 960-960
Author(s):  
Xingguo Zhu ◽  
Betty S. Pace
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Globin Gene ◽  
Critical Role ◽  
Fetal Hemoglobin ◽  
Oxygen Species ◽  
Cell Disease ◽  
Nrf2 Knockout ◽  
Globin Gene Expression

The basic leucine zipper transcription factor, nuclear factor (erythroid-derived 2)-like 2 (NRF2) plays a critical role in the cellular antioxidant response to control oxidative stress. We and others previously demonstrated that NRF2 activation enhances γ-globin gene transcription and fetal hemoglobin expression in human primary erythroid progenitors through changes in chromatin structure (Zhu et al., Haematologica 2017). In this study, we investigated the protective role of NRF2 in reversing the pathophysiology of sickle cell disease (SCD) in a SCD/NRF2 knockout (SCD/NRF2KO) transgenic model created in our lab by crossbreeding Townes SCD mice (Ryan et al., Science 1997) and NRF2 knockout mice (Kuroha et al., J Biochem 1998). The NRF2 gene is transmitted through autosomal recessive Mendelian genetics for wild-type, heterozygote and NRF2KO pups. By contrast, the SCD/NRF2KO genotype was present in <2% of pups. In addition, the fertility and litter size of SCD/NRF2KO females were lower than SCDWT mice, suggesting a critical role of NRF2 in the survival of pups during gestation. To determine the hematopoietic effect of NRF2KO in SCD, we monitored the complete blood count with differential and reticulocyte count. There was no significant change in any parameters except higher total white blood cell counts in the SS/NRF2KO mouse suggesting increased inflammation. Examination of globin gene expression patterns in SS/NRF2KO mice showed reduced γ-globin gene expression during erythroid differentiation in the E13.5 and E18.5 fetal liver, adult spleen and bone marrow. In addition, peripheral blood red cells had a 33% increase (p<0.05) in reactive oxygen species and a significant 38% increase in sickling under in vitro hypoxic conditions. We next characterized the effects of NRF2 loss on organ pathology. The SCD/NRF2KO mice displayed greater splenomegaly indicating exaggerated hemolysis most likely due to high levels of reactive oxygen species. By 8-10 weeks of age, the SCD/NRF2KO mouse showed significant inflammation by hematoxylin-eosin staining of the spleen, lung and liver when compared to SCD/NRF2WT mice. Protein expression profiling by western blotting using adult spleen demonstrated downregulation of the antioxidant proteins heme oxygenase 1 (HMOX1), NADPH: quinone oxidoreductase 1 (NQO1) and catalase by 31%, 60%, and 48% respectively (p<0.05). To further support a severe disease phenotype, the expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) were increased by 1.7-fold and 2.3-fold (p<0.05) while vascular endothelial growth factor (VEGF) levels were not changed. Lastly, the expression of interleukin 1β (IL-1β), IL-6, tumor necrosis factor α (TNF-α), monocyte chemoattractant protein (MCP-1) and macrophage migration inhibitory factor (MIF-1) was elevated in SCD/NRF2KO mice compared to SCDWT mice. These data validate a critical role of NRF2 in ameliorating the phenotypic severity of SCD by protecting against red blood cell sickling, oxidative stress and tissue inflammation. Furthermore, the ability of NRF2 to mediate fetal hemoglobin induction provides a rationale for the development of therapeutic agents that activate NRF2 expression. Disclosures No relevant conflicts of interest to declare.

scholarly journals The HRI-regulated transcription factor ATF4 activates BCL11A transcription to silence fetal hemoglobin expression

Blood ◽  
2020 ◽  
Vol 135 (24) ◽  
pp. 2121-2132 ◽  
Author(s):  
Peng Huang ◽  
Scott A. Peslak ◽  
Xianjiang Lan ◽  
Eugene Khandros ◽  
Jennifer A. Yano ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Murine Models ◽  
Loss Of Function ◽  
Cell Disease ◽  
Identify Transcription Factor ◽  
Eif2α Kinase ◽  
Globin Gene Regulation ◽  
Deficient Mice

Abstract Reactivation of fetal hemoglobin remains a critical goal in the treatment of patients with sickle cell disease and β-thalassemia. Previously, we discovered that silencing of the fetal γ-globin gene requires the erythroid-specific eIF2α kinase heme-regulated inhibitor (HRI), suggesting that HRI might present a pharmacologic target for raising fetal hemoglobin levels. Here, via a CRISPR-Cas9–guided loss-of-function screen in human erythroblasts, we identify transcription factor ATF4, a known HRI-regulated protein, as a novel γ-globin regulator. ATF4 directly stimulates transcription of BCL11A, a repressor of γ-globin transcription, by binding to its enhancer and fostering enhancer-promoter contacts. Notably, HRI-deficient mice display normal Bcl11a levels, suggesting species-selective regulation, which we explain here by demonstrating that the analogous ATF4 motif at the murine Bcl11a enhancer is largely dispensable. Our studies uncover a linear signaling pathway from HRI to ATF4 to BCL11A to γ-globin and illustrate potential limits of murine models of globin gene regulation.

scholarly journals NRF2 mediates γ-globin gene regulation through epigenetic modifications in a β-YAC transgenic mouse model

2020 ◽  
Vol 245 (15) ◽  
pp. 1308-1318
Author(s):  
Xingguo Zhu ◽  
Caixia Xi ◽  
Alexander Ward ◽  
Mayuko Takezaki ◽  
Huidong Shi ◽  
...  
Keyword(s):  
Sickle Cell Disease ◽  
Mouse Model ◽  
Sickle Cell ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Dimethyl Fumarate ◽  
Cell Disease ◽  
Nrf2 Activator ◽  
Globin Gene Regulation ◽  
Globin Gene Expression

NRF2 is the master regulator for the cellular oxidative stress response and regulates γ-globin gene expression in human erythroid progenitors and sickle cell disease mice. To explore NRF2 function, we established a human β-globin locus yeast artificial chromosome transgenic/NRF2 knockout (β-YAC/NRF2−/−) mouse model. NRF2 loss reduced γ-globin gene expression during erythropoiesis and abolished the ability of dimethyl fumarate, an NRF2 activator, to enhance γ-globin transcription. We observed decreased H3K4Me1 and H3K4Me3 chromatin marks and association of TATA-binding protein and RNA polymerase II at the β-locus control region (LCR) and γ-globin gene promoters in β-YAC/NRF2−/− mice. As a result, long-range chromatin interaction between the LCR DNase I hypersensitive sites and γ-globin gene was decreased, while interaction with the β-globin was not affected. Further, NRF2 loss silenced the expression of DNA methylcytosine dioxygenases TET1, TET2, and TET3 and inhibited γ-globin gene DNA hydroxymethylation. Subsequently, protein-protein interaction between NRF2 and TET3 was demonstrated. These data support the ability of NRF2 to mediate γ-globin gene regulation through epigenetic DNA and histone modifications. Impact statement Sickle cell disease is an inherited hemoglobin disorder that affects over 100,000 people in the United States causing high morbidity and early mortality. Although new treatments were recently approved by the FDA, only one drug Hydroxyurea induces fetal hemoglobin expression to inhibit sickle hemoglobin polymerization in red blood cells. Our laboratory previously demonstrated the ability of the NRF2 activator, dimethyl fumarate to induce fetal hemoglobin in the sickle cell mouse model. In this study, we investigated molecular mechanisms of γ-globin gene activation by NRF2. We observed the ability of NRF2 to modulate chromatin structure in the human β-like globin gene locus of β-YAC transgenic mice during development. Furthermore, an NRF2/TET3 interaction regulates γ-globin gene DNA methylation. These findings provide potential new molecular targets for small molecule drug developed for treating sickle cell disease.

Hemoglobinopathies

Hematology ◽  
2003 ◽  
Vol 2003 (1) ◽  
pp. 14-39 ◽  
Author(s):  
George F. Atweh ◽  
Joseph DeSimone ◽  
Yogen Saunthararajah ◽  
Hassana Fathallah ◽  
Rona S. Weinberg ◽  
...  
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Experimental Models ◽  
Adult Patients ◽  
Main Theme ◽  
Cell Disease ◽  
Hematopoietic Stem

Abstract The outlook for patients with sickle cell disease has improved steadily during the last two decades. In spite of these improvements, curative therapies are currently available only to a small minority of patients. The main theme of this chapter is to describe new therapeutic options that are at different stages of development that might result in further improvements in the outlook for patients with these disorders. Dr. Joseph DeSimone and his colleagues had previously made the important observation that the hypomethylating agent 5-azacytidine can reverse the switch from adult to fetal hemoglobin in adult baboons. Although similar activity was demonstrated in patients with sickle cell disease and β-thalassemia, concern about the toxicity of 5-azacytidine prevented its widespread use in these disorders. In Section I, Dr. DeSimone discusses the role of DNA methylation in globin gene regulation and describe recent clinical experience with decitabine (an analogue of 5-azacytidine) in patients with sickle cell disease. These encouraging studies demonstrate significant fetal hemoglobin inducing activity of decitabine in patients who fail to respond to hydroxyurea. In Section II, Dr. George Atweh continues the same theme by describing recent progress in the study of butyrate, another inducer of fetal hemoglobin, in patients with sickle cell disease and β-thalassemia. The main focus of his section is on the use of a combination of butyrate and hydroxyurea to achieve higher levels of fetal hemoglobin that might be necessary for complete amelioration of the clinical manifestations of these disorders. Dr. Atweh also describes novel laboratory studies that shed new light on the mechanisms of fetal hemoglobin induction by butyrate. In Section III, Dr. Ronald Nagel discusses the different available transgenic sickle mice as experimental models for human sickle cell disease. These experimental models have already had a significant impact on our understanding of the pathophysiology of sickle cell disease. Dr. Nagel describes more recent studies in which transgenic sickle mice provide the first proof of principle that globin gene transfer into hematopoietic stem cells inhibits in vivo sickling and ameliorates the severity of the disease. Although stroke in adult patients with sickle cell disease is not as common as in children, adult hematologists, like their pediatric colleagues, need to make management decisions in adult patients with a stroke or a history of stroke. Dr. Robert Adams has led several large clinical studies that investigated the role of transfusions in the prevention of stroke in children with sickle cell disease. Much less is known, however, about the prevention of first or subsequent strokes in adult patients with sickle cell disease. In Section IV, Dr. Adams provides some general guidelines for the management of adult patients with stroke while carefully distinguishing between recommendations that are evidence-based and those that are anecdotal in nature.

scholarly journals 3,3′,5-Triiodothyroacetic acid (TRIAC) induces embryonic ζ-globin expression via thyroid hormone receptor α

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Huiqiao Chen ◽  
Zixuan Wang ◽  
Shanhe Yu ◽  
Xiao Han ◽  
Yun Deng ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Globin Gene ◽  
Erythroid Cells ◽  
Cell Disease ◽  
Potent Inducer ◽  
Thyroid Hormone Receptor Α

AbstractThe human ζ-globin gene (HBZ) is transcribed in primitive erythroid cells only during the embryonic stages of development. Reactivation of this embryonic globin synthesis would likely alleviate symptoms both in α-thalassemia and sickle-cell disease. However, the molecular mechanisms controlling ζ-globin expression have remained largely undefined. Moreover, the pharmacologic agent capable of inducing ζ-globin production is currently unavailable. Here, we show that TRIAC, a bioactive thyroid hormone metabolite, significantly induced ζ-globin gene expression during zebrafish embryogenesis. The induction of ζ-globin expression by TRIAC was also observed in human K562 erythroleukemia cell line and primary erythroid cells. Thyroid hormone receptor α (THRA) deficiency abolished the ζ-globin-inducing effect of TRIAC. Furthermore, THRA could directly bind to the distal enhancer regulatory element to regulate ζ-globin expression. Our study provides the first evidence that TRIAC acts as a potent inducer of ζ-globin expression, which might serve as a new potential therapeutic option for patients with severe α-thalassemia or sickle-cell disease.

scholarly journals Sickle Cell Disease: Role of Oxidative Stress and Antioxidant Therapy

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 296
Author(s):  
Rosa Vona ◽  
Nadia Maria Sposi ◽  
Lorenza Mattia ◽  
Lucrezia Gambardella ◽  
Elisabetta Straface ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Globin Gene ◽  
Organ Damage ◽  
Cell Disease ◽  
Vessel Occlusion ◽  
Antioxidant Agents ◽  
Oxidant Status

Sickle cell disease (SCD) is the most common hereditary disorder of hemoglobin (Hb), which affects approximately a million people worldwide. It is characterized by a single nucleotide substitution in the β-globin gene, leading to the production of abnormal sickle hemoglobin (HbS) with multi-system consequences. HbS polymerization is the primary event in SCD. Repeated polymerization and depolymerization of Hb causes oxidative stress that plays a key role in the pathophysiology of hemolysis, vessel occlusion and the following organ damage in sickle cell patients. For this reason, reactive oxidizing species and the (end)-products of their oxidative reactions have been proposed as markers of both tissue pro-oxidant status and disease severity. Although more studies are needed to clarify their role, antioxidant agents have been shown to be effective in reducing pathological consequences of the disease by preventing oxidative damage in SCD, i.e., by decreasing the oxidant formation or repairing the induced damage. An improved understanding of oxidative stress will lead to targeted antioxidant therapies that should prevent or delay the development of organ complications in this patient population.

Vaso-occlusion in sickle cell disease: pathophysiology and novel targeted therapies

Hematology ◽  
2013 ◽  
Vol 2013 (1) ◽  
pp. 362-369 ◽  
Author(s):  
Deepa Manwani ◽  
Paul S. Frenette
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Targeted Therapies ◽  
Therapeutic Intervention ◽  
Fetal Hemoglobin ◽  
Cell Disease ◽  
The Past ◽  
Symptomatic Management

Abstract Recurrent and unpredictable episodes of vaso-occlusion are the hallmark of sickle cell disease. Symptomatic management and prevention of these events using the fetal hemoglobin–reactivating agent hydroxyurea are currently the mainstay of treatment. Discoveries over the past 2 decades have highlighted the important contributions of various cellular and soluble participants in the vaso-occlusive cascade. The role of these elements and the opportunities for therapeutic intervention are summarized in this review.

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