Regulation of human fetal hemoglobin: new players, new complexities

The blood count as a compass to navigate in the ever-changing landscape of the carrier state of hemoglobinopathies: a single-center Italian experience

Introduction

Approximately 7% of the worldwide population exhibits variations in the globin genes. The recent migration of populations from countries where hemoglobin disorders are endemic has resulted in important epidemiological changes with the diffusion of newly discovered or poorly characterized genetic variants and new combinations and very heterogeneous clinical phenotypes. The aim of our study is to assess the parameters that are more significant in predicting a positive genetic testing outcome for hemoglobinopathies in a pediatric population of patients presenting with anemia or microcythemia, without a definite diagnosis.

Methods and materials

This study included patients evaluated in our hematological outpatient clinic for anemia and/or microcythemia despite normal ferritin levels. A screening of pathological hemoglobins using high-performance liquid chromatography (HPLC) was performed for the entire population of the study. Subsequently, patients with hemoglobin (Hb) S trait and patients with an HPLC profile compatible with beta thalassemia trait were excluded from the study. Genetic screening tests for hemoglobinopathies were performed on the remaining patients, which involved measuring the red blood cell (RBC) counts, red blood cells distribution width (RDW), reticulocyte count, and mean corpuscular volume of reticulocytes (MCVr).

Results

This study evaluated a total of 65 patients, consisting of nine patients with negative genetic analysis results and 56 patients with positive genetic analysis results. The Hb and RDW values in these two groups did not demonstrate statistical significance. On the other hand, there were statistically significant differences observed in the mean corpuscular volume (MCV), RBC count, reticulocyte count, and MCVr between the two groups. Furthermore, in the group of patients with positive genetic test results, specific genetic findings associated with different HPLC results were observed. In particular, 13 patients with positive genetic test results had normal HPLC findings.

Discussion

This study has demonstrated that HPLC, while serving as a valuable first-level test, has some limitations. Specifically, it has been observed that some patients may exhibit a negative HPLC result despite a positive genetic analysis. In addition to the presence of low levels of Hb and HPLC alterations, other parameters could potentially indicate the underlying mutations in the globin genes. Therefore, we propose that the complete blood cell count be utilized as a widely available parameter for conducting targeted genetic analyses to avoid the risk of overlooking rare hemoglobinopathies.

IKAROS: from chromatin organization to transcriptional elongation control

IKAROS is a master regulator of cell fate determination in lymphoid and other hematopoietic cells. This transcription factor orchestrates the association of epigenetic regulators with chromatin, ensuring the expression pattern of target genes in a developmental and lineage-specific manner. Disruption of IKAROS function has been associated with the development of acute lymphocytic leukemia, lymphoma, chronic myeloid leukemia and immune disorders. Paradoxically, while IKAROS has been shown to be a tumor suppressor, it has also been identified as a key therapeutic target in the treatment of various forms of hematological malignancies, including multiple myeloma. Indeed, targeted proteolysis of IKAROS is associated with decreased proliferation and increased death of malignant cells. Although the molecular mechanisms have not been elucidated, the expression levels of IKAROS are variable during hematopoiesis and could therefore be a key determinant in explaining how its absence can have seemingly opposite effects. Mechanistically, IKAROS collaborates with a variety of proteins and complexes controlling chromatin organization at gene regulatory regions, including the Nucleosome Remodeling and Deacetylase complex, and may facilitate transcriptional repression or activation of specific genes. Several transcriptional regulatory functions of IKAROS have been proposed. An emerging mechanism of action involves the ability of IKAROS to promote gene repression or activation through its interaction with the RNA polymerase II machinery, which influences pausing and productive transcription at specific genes. This control appears to be influenced by IKAROS expression levels and isoform production. In here, we summarize the current state of knowledge about the biological roles and mechanisms by which IKAROS regulates gene expression. We highlight the dynamic regulation of this factor by post-translational modifications. Finally, potential avenues to explain how IKAROS destruction may be favorable in the treatment of certain hematological malignancies are also explored.

εγ-Thalassemia, a New Hemoglobinopathy Category

BACKGROUND

Large β-globin gene cluster deletions (hereditary persistence of fetal hemoglobin [Hb] or β-, δβ-, γδβ-, and ϵγδβ-thalassemia), are associated with widely disparate phenotypes, including variable degrees of microcytic anemia and Hb F levels. When present, increased Hb A2 is used as a surrogate marker for β-thalassemia. Notably, ϵγδβ-thalassemias lack the essential regulatory locus control region (LCR) and cause severe transient perinatal anemia but normal newborn screen (NBS) results and Hb A2 levels. Herein, we report a novel deletion of the ϵ, Aγ, Gγ, and ψβ loci with intact LCR, δ-, and β-regions in 2 women and newborn twins.

METHODS

Capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), DNA sequencing, multiplex ligation-dependent probe amplification (MLPA), gap-polymerase chain reaction (gap-PCR), and long-read sequencing (LRS) were performed.

RESULTS

NBS showed an Hb A > Hb F pattern for both twins. At 20 months, Hb A2 was increased similarly to that in the mother and an unrelated woman. Unexplained microcytosis was absent and the twins lacked severe neonatal anemia. MLPA, LRS, and gap-PCR confirmed a 32 599 base pair deletion of ϵ (HBE1) through ψβ (HBBP1) loci.

CONCLUSIONS

This deletion represents a hemoglobinopathy category with a distinct phenotype that has not been previously described, an ϵγ-thalassemia. Both the NBS Hb A > F pattern and the subsequent increased Hb A2 without microcytosis are unusual. A similar deletion should be considered when this pattern is encountered and appropriate test methods selected for detection. Knowledge of the clinical impact of this new category will improve genetic counselling, with distinction from the severe transient anemia associated with ϵγδβ-thalassemia.

CRISPR Gene Therapy: A Promising One-Time Therapeutic Approach for Transfusion-Dependent β-Thalassemia—CRISPR-Cas9 Gene Editing for β-Thalassemia

β-Thalassemia is an inherited hematological disorder that results from genetic changes in the β-globin gene, leading to the reduced or absent synthesis of β-globin. For several decades, the only curative treatment option for β-thalassemia has been allogeneic hematopoietic cell transplantation (allo-HCT). Nonetheless, rapid progress in genome modification technologies holds great potential for treating this disease and will soon change the current standard of care for β-thalassemia. For instance, the emergence of the CRISPR/Cas9 genome editing platform has opened the door for precision gene editing and can serve as an effective molecular treatment for a multitude of genetic diseases. Investigational studies were carried out to treat β-thalassemia patients utilizing CRISPR-based CTX001 therapy targeting the fetal hemoglobin silencer BCL11A to restore γ-globin expression in place of deficient β-globin. The results of recently carried out clinical trials provide hope of CTX001 being a promising one-time therapeutic option to treat β-hemoglobinopathies. This review provides an insight into the key scientific steps that led to the development and application of novel CRISPR/Cas9–based gene therapies as a promising therapeutic platform for transfusion-dependent β-thalassemia (TDT). Despite the resulting ethical, moral, and social challenges, CRISPR provides an excellent treatment option against hemoglobin-associated genetic diseases.

Kruppel-like factor 1-GATA1 fusion protein improves the sickle cell disease phenotype in mice both in vitro and in vivo

Sickle cell disease (SCD) and β-thalassemia are among the most common genetic disorders worldwide, affecting global health and mortality. Hemoglobin A2 (HbA2, α2δ2) is expressed at a low level in adult blood due to the lack of the Kruppel-like factor 1 (KLF1) binding motif in the δ-globin promoter region. However, HbA2 is fully functional as an oxygen transporter, and could be a valid antisickling agent in SCD, as well as a substitute for hemoglobin A in β-thalassemia. We have previously demonstrated that KLF1-GATA1 fusion protein could interact with the δ-globin promoter and increase δ-globin expression in human primary CD34+ cells. We report the effects of 2 KLF1-GATA1 fusion proteins on hemoglobin expression, as well as SCD phenotypic correction in vitro and in vivo. Forced expression of KLF1-GATA1 fusion protein enhanced δ-globin gene and HbA2 expression, as well as reduced hypoxia-related sickling, in erythroid cells cultured from both human sickle CD34+ cells and SCD mouse hematopoietic stem cells (HSCs). The fusion proteins had no impact on erythroid cell differentiation, proliferation, and enucleation. Transplantation of highly purified SCD mouse HSCs expressing KLF1-GATA1 fusion protein into SCD mice lessened the severity of the anemia, reduced the sickling of red blood cells, improved SCD-related pathological alterations in spleen, kidney, and liver, and restored urine-concentrating ability in recipient mice. Taken together, these results indicate that the use of KLF1-GATA1 fusion constructs may represent a new gene therapy approach for hemoglobinopathies.

Krüppel-Like Factor 1: A Pivotal Gene Regulator in Erythropoiesis

Krüppel-like factor 1 (KLF1) plays a crucial role in erythropoiesis. In-depth studies conducted on mice and humans have highlighted its importance in erythroid lineage commitment, terminal erythropoiesis progression and the switching of globin genes from γ to β. The role of KLF1 in haemoglobin switching is exerted by the direct activation of β-globin gene and by the silencing of γ-globin through activation of BCL11A, an important γ-globin gene repressor. The link between KLF1 and γ-globin silencing identifies this transcription factor as a possible therapeutic target for β-hemoglobinopathies. Moreover, several mutations have been identified in the human genes that are responsible for various benign phenotypes and erythroid disorders. The study of the phenotype associated with each mutation has greatly contributed to the current understanding of the complex role of KLF1 in erythropoiesis. This review will focus on some of the principal functions of KLF1 on erythroid cell commitment and differentiation, spanning from primitive to definitive erythropoiesis. The fundamental role of KLF1 in haemoglobin switching will be also highlighted. Finally, an overview of the principal human mutations and relative phenotypes and disorders will be described.

High phosphate intake induces bone loss in nephrectomized thalassemic mice

Although patients with either β-thalassemia or chronic kidney disease (CKD) clinically correlate with severe osteoporosis, the mechanism by which CKD exposed to high phosphate affects bone turnover has not been characterized in β-thalassemia. We aimed to determine the effects of renal insufficiency on high phosphate intake induced changes in bone metabolism after 5/6th nephrectomy in hemizygous β-globin knockout (BKO) mice. Male BKO mice manifested severe anemia and osteopenia. Nephrectomy induced renal fibrosis and reduced renal function as assessed by increased serum urea nitrogen levels. Moreover, nephrectomy increased bone turnover leading to bone loss in wild type (WT) but not BKO mice. In nephrectomized BKO, PBS in drinking water induced hyperphosphatemia, and hypercalcemia along with osteopenia in both cancellous and cortical bone. Histomorphometric analysis confirmed reduced cancellous bone volume due to decreased bone formation rate, osteoblast number and osteoclast number. The mRNA levels for Alpl, Sp7, Kl, Tnfsf11, and Tnfsf11/Tnfrsf11b were decreased in nephrectomized BKO mice drinking PBS. Interestingly, Fgf23, a bone-derived hormone produced by osteocytes and osteoblasts in response to hyperphosphatemia, were remarkably increased in nephrectomized BKO mice following PBS intake. Serum FGF23 and erythropoietin levels were markedly elevated in BKO mice. Nephrectomy decreased serum erythropoietin but not FGF23 levels. Hyperphosphatemia in BKO mice increased serum erythropoietin, FGF23, and PTH levels, nominating these factors as candidate mediators of bone loss in thalassemic mice with CKD during phosphate retention.

Tenofovir disoproxil fumarate-mediated γ-globin induction is correlated with the suppression of trans-acting factors in CD34+ progenitor cells: A role in the reactivation of fetal hemoglobin

Sickle-cell disease (SCD) and β-thalassemia are public health issues that affect people all over the world. Fetal hemoglobin (HbF) induction is a molecular intervention, including hydroxyurea, which has made an effort to improve current treatment. Tenofovir disoproxil fumarate (TDF) is formerly reported with improving levels of hemoglobin, mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV). Hence, in this preclinical investigation, human peripheral whole blood-derived CD34⁺ progenitor cells were cultured to prove the efficacy of TDF on erythroid proliferation, differentiation, γ-globin gene expression regulation, and ultimately HbF production. We observed that TDF increased the proliferation of immature erythroid cells, delayed the terminal erythroid maturation without cytotoxicity as correlated with other HbF inducers. Here, the presented data show that TDF can induce HbF expression by up-regulating the γ-globin gene transcription up to 7.1 ± 0.46-fold and subsequently increased the F-cells (10.79 ± 1.9-fold) population in terminally differentiated erythroid cells. Furthermore, our findings demonstrated that TDF-mediated γ-globin gene induction and HbF production was associated with down-fold regulation of BCL11A and SOX6, and their corresponding trans-acting regulators, FOP, KLF1, and GATA1. Collectively, our findings suggest TDF as an effective inducer of HbF in CD34⁺ cells and pave the way to put forward the assessment of TDF as a new potential therapy in treating β-hemoglobinopathies.

Gel Electrophoresis Chip Using Joule Heat Self-Dissipation, Short Run Time, and Online Dynamic Imaging

Gel electrophoresis (GE) is one of the most general tools in biomedicine. However, it suffers from low resolution, and its mechanism has not been fully revealed yet. Herein, we presented the dispersion model of w² (t) ∝ Tt, showing the band dispersion (w) via temperature (T) and running time (t) control. Second, we designed an efficient GE chip via the time control and rapid Joule heat self-dissipation by thermal conductive plastic (TCP) and electrode buffer. Third, we conducted the simulations on TCP and polymethylmethacrylate (PMMA) chips, unveiling that (i) the temperature of TCP was lower than the PMMA one, (ii) the temperature uniformity of TCP was better than the PMMA one, and (iii) the resolution of TCP was superior to the PMMA one. Fourth, we designed both TCP and PMMA chips for experimentally validating the dispersion model, TCP chip, and simulations. Finally, we applied the TCP chip to thalassemia and model urine protein assays. The TCP chip has merits of high resolution, rapid run of 6-10 min, and low cost. This work paves the way for greatly improving electrophoretic techniques in gel, chip, and capillary via temperature and time control for biologic study, biopharma quality control, clinical diagnosis, and so on.

Differential sialic acid content in adult and neonatal fibrinogen mediates differences in clot polymerization dynamics

Increased sialic acid in neonatal fibrinogen influences fibrin knob-hole interactions during polymerization.

Neonatal fibrin polymerization involves more B knob– and fewer A knob–mediated interactions compared with adults.

Neonates possess a molecular variant of fibrinogen, known as fetal fibrinogen, characterized by increased sialic acid, a greater negative charge, and decreased activity compared with adults. Despite these differences, adult fibrinogen is used for the treatment of bleeding in neonates, with mixed efficacy. To determine safe and efficacious bleeding protocols for neonates, more information on neonatal fibrin clot formation and the influence of sialic acid on these processes is needed. Here, we examine the influence of sialic acid on neonatal fibrin polymerization. We hypothesized that the increased sialic acid content of neonatal fibrinogen promotes fibrin B:b knob-hole interactions and consequently influences the structure and function of the neonatal fibrin matrix. We explored this hypothesis through analysis of structural properties and knob:hole polymerization dynamics of normal and desialylated neonatal fibrin networks and compared them with those formed with adult fibrinogen. We then characterized normal neonatal fibrin knob:hole interactions by forming neonatal and adult clots with either thrombin or snake-venom thrombin-like enzymes that preferentially cleave fibrinopeptide A or B. Sialic acid content of neonatal fibrinogen was determined to be a key determinant of resulting clot properties. Experiments analyzing knob:hole dynamics indicated that typical neonatal fibrin clots are formed with the release of more fibrinopeptide B and less fibrinopeptide A than adults. After the removal of sialic acid, fibrinopeptide release was roughly equivalent between adults and neonates, indicating the influence of sialic acid on fibrin neonatal fibrin polymerization mechanisms. These results could inform future studies developing neonatal-specific treatments of bleeding.

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

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' 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.

Miniaturized Electrochemical Sensors to Monitor Fetal Hypoxia and Acidosis in a Pregnant Sheep Model

Perinatal asphyxia is a major cause of severe brain damage and death. For its prenatal identification, Doppler ultrasound has been used as a surrogate marker of fetal hypoxia. However, Doppler evaluation cannot be performed continuously. We have evaluated the performance of a miniaturized multiparametric sensor aiming to evaluate tissular oxygen and pH changes continuously in an umbilical cord occlusion (UCO) sheep model. The electrochemical sensors were inserted in fetal hindlimb skeletal muscle and electrochemical signals were recorded. Fetal hemodynamic changes and metabolic status were also monitored during the experiment. Additionally, histological assessment of the tissue surrounding the sensors was performed. Both electrochemical sensors detected the pO₂ and pH changes induced by the UCO and these changes were correlated with hemodynamic parameters as well as with pH and oxygen content in the blood. Finally, histological assessment revealed no signs of alteration on the same day of insertion. This study provides the first evidence showing the application of miniaturized multiparametric electrochemical sensors detecting changes in oxygen and pH in skeletal muscular tissue in a fetal sheep model.

Transcriptional silencing of fetal hemoglobin expression by NonO

Human fetal globin (γ-globin) genes are developmentally silenced after birth, and reactivation of γ-globin expression in adulthood ameliorates symptoms of hemoglobin disorders, such as sickle cell disease (SCD) and β-thalassemia. However, the mechanisms by which γ-globin expression is precisely regulated are still incompletely understood. Here, we found that NonO (non-POU domain-containing octamer-binding protein) interacted directly with SOX6, and repressed the expression of γ-globin gene in human erythroid cells. We showed that NonO bound to the octamer binding motif, ATGCAAAT, of the γ-globin proximal promoter, resulting in inhibition of γ-globin transcription. Depletion of NonO resulted in significant activation of γ-globin expression in K562, HUDEP-2, and primary human erythroid progenitor cells. To confirm the role of NonO in vivo, we further generated a conditional knockout of NonO by using IFN-inducible Mx1-Cre transgenic mice. We found that induced NonO deletion reactivated murine embryonic globin and human γ-globin gene expression in adult β-YAC mice, suggesting a conserved role for NonO during mammalian evolution. Thus, our data indicate that NonO acts as a novel transcriptional repressor of γ-globin gene expression through direct promoter binding, and is essential for γ-globin gene silencing.

Benserazide racemate and enantiomers induce fetal globin gene expression in vivo: Studies to guide clinical development for beta thalassemia and sickle cell disease

Increased expression of developmentally silenced fetal globin (HBG) reduces the clinical severity of β-hemoglobinopathies. Benserazide has a relatively benign safety profile having been approved for 50 years in Europe and Canada for Parkinson's disease treatment. Benserazide was shown to activate HBG gene transcription in a high throughput screen, and subsequent studies confirmed fetal hemoglobin (HbF) induction in erythroid progenitors from hemoglobinopathy patients, transgenic mice containing the entire human β-globin gene (β-YAC) and anemic baboons. The goal of this study is to evaluate efficacies and plasma exposure profiles of benserazide racemate and its enantiomers to select the chemical form for clinical development. Intermittent treatment with all forms of benserazide in β-YAC mice significantly increased proportions of red blood cells expressing HbF and HbF protein per cell with similar pharmacokinetic profiles and with no cytopenia. These data contribute to the regulatory justification for development of the benserazide racemate. Additionally, dose ranges and frequencies required for HbF induction using racemic benserazide were explored. Orally administered escalating doses of benserazide in an anemic baboon induced γ-globin mRNA up to 13-fold and establish an intermittent dose regimen for clinical studies as a therapeutic candidate for potential treatment of β-hemoglobinopathies.

IKAROS is required for the measured response of NOTCH target genes upon external NOTCH signaling

The tumor suppressor IKAROS binds and represses multiple NOTCH target genes. For their induction upon NOTCH signaling, IKAROS is removed and replaced by NOTCH Intracellular Domain (NICD)-associated proteins. However, IKAROS remains associated to other NOTCH activated genes upon signaling and induction. Whether IKAROS could participate to the induction of this second group of NOTCH activated genes is unknown. We analyzed the combined effect of IKAROS abrogation and NOTCH signaling on the expression of NOTCH activated genes in erythroid cells. In IKAROS-deleted cells, we observed that many of these genes were either overexpressed or no longer responsive to NOTCH signaling. IKAROS is then required for the organization of bivalent chromatin and poised transcription of NOTCH activated genes belonging to either of the aforementioned groups. Furthermore, we show that IKAROS-dependent poised organization of the NOTCH target Cdkn1a is also required for its adequate induction upon genotoxic insults. These results highlight the critical role played by IKAROS in establishing bivalent chromatin and transcriptional poised state at target genes for their activation by NOTCH or other stress signals.

NOTCH1 deregulation can favor hematological malignancies. In addition to RBP-Jκ/NICD/MAML1, other regulators are required for the measured activation of NOTCH target genes. IKAROS is a known repressor of many NOTCH targets. Since it can also favor transcriptional activation and control gene expression levels, we questioned whether IKAROS could participate to the activation of specific NOTCH target genes. We are reporting that upon NOTCH induction, the absence of IKAROS impairs the measured activation of two groups of NOTCH target genes: (i) those overexpressed and characterized by an additive effect imposed by the absence of IKAROS and NOTCH induction; and (ii) those ‘desensitized’ and no more activated by NOTCH. At genes of both groups, IKAROS controls the timely recruitment of the chromatin remodelers CHD4 and BRG1. IKAROS then influences the activation of these genes through the organization of chromatin and poised transcription or through transcriptional elongation control. The importance of the IKAROS controlled and measured activation of genes is not limited to NOTCH signaling as it also characterizes Cdkn1a expression upon genotoxic stress. Thus, these results provide a new perspective on the importance of IKAROS for the adequate cellular response to stress, whether imposed by NOTCH or genotoxic insults.

Insight of fetal to adult hemoglobin switch: Genetic modulators and therapeutic targets

The clinical heterogeneity of β-hemoglobinopathies is so variable that it prompted the researchers to identify the genetic modulators of these diseases. Though the primary modulator is the type of β-globin mutation which affects the degree of β-globin chain synthesis, the co-inheritance of α-thalassemia and the fetal hemoglobin (HbF) levels also act as potent secondary genetic modifiers. As elevated HbF levels ameliorate the severity of hemoglobinopathies, in this review, the genetic modulators lying within and outside the β-globin gene cluster with their plausible role in governing the HbF levels have been summarised, which in future may act as potential therapeutic targets.

The Interaction between Hb A1C and Selected Genetic Factors in the African American Population in the USA

BACKGROUND

The global prevalence of diabetes mellitus has been growing in recent decades and the complications of longstanding type 2 diabetes continue to place a burden on healthcare systems. The hemoglobin A1c (Hb A1c) content of the blood is used to assess an individual's degree of glycemic control averaged over 2 to 3 months. In the USA, diabetes is the seventh leading cause of death. Black, indigenous, people of color (BIPOC) are disproportionately affected by diabetes compared to non-Hispanic whites. There are many reports of interaction of Hb A1c and hematologic conditions that have a high prevalence in the Black population; some of these effects are contradictory and not easily explained. This review attempts to document and categorize these apparently disparate effects and to assess any clinical impact.

METHODS

Hb A1C can be determined by a variety of techniques including cation-exchange chromatography, electrophoresis, immunoassays, and affinity chromatography. The amount of Hb A1c present in a patient specimen depends not only on blood glucose but is strongly influenced by erythrocyte survival and by structural variations in the globin chains. Sickling hemoglobinopathies are well-represented in the USA in African Americans and the effects of these hemoglobin disorders as well as G6PD deficiency is examined.

CONCLUSION

Hb A1c measurement should always be performed with a cautious approach. The laboratory scientist should be aware of possible pitfalls in unquestioningly determining Hb A1c without a consideration of hematologic factors, both inherited and acquired. This presents a challenge as often times, the laboratory is not aware of the patient's race.

Significance of heme oxygenase-1(HMOX1) gene on fetal hemoglobin induction in sickle cell anemia patients

Though the patients with sickle cell anemia (SCA) inherit same genetic mutation, they show considerable phenotypic heterogeneity. It has been observed that patients with elevated fetal hemoglobin (HbF) levels have a relatively mild clinical course. There is sparse literature on the association of higher HbF levels leading to reduction in the oxidative stress in SCA patients. Hence in this study, the significance between the HMOX1 gene polymorphisms and the HbF levels has been studied. Preliminary screening was carried out. Genotyping of 3 variants in the HMOX1 gene was performed in 90 SCA patients and 50 healthy controls by PCR–RFLP, GeneScan and direct DNA sequencing. It was observed that SCA patients with higher HbF levels, showed improved hematological indices with an inverse effect on HbS levels. The TT genotype of rs2071746 (A→T) polymorphism was found to be associated with elevated HbF levels (P: 0.012). Also, the long form (> 25 GT repeats) of rs3074372 (GT)n repeats was found to be linked with increased HbF levels. We could not find any association of rs2071749 (A→G) polymorphism with the HbF levels. As, the sickle cell anemia patients show significant oxidative stress due to hemolysis, the study of polymorphisms in the HMOX1 gene may act as a potential independent marker for elevated HbF levels.

Ready for Repair? Gene Editing Enters the Clinic for the Treatment of Human Disease

We present an overview of clinical trials involving gene editing using clustered interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases (TALENs), or zinc finger nucleases (ZFNs) and discuss the underlying mechanisms. In cancer immunotherapy, gene editing is applied ex vivo in T cells, transgenic T cell receptor (tTCR)-T cells, or chimeric antigen receptor (CAR)-T cells to improve adoptive cell therapy for multiple cancer types. This involves knockouts of immune checkpoint regulators such as PD-1, components of the endogenous TCR and histocompatibility leukocyte antigen (HLA) complex to generate universal allogeneic CAR-T cells, and CD7 to prevent self-destruction in adoptive cell therapy. In cervix carcinoma caused by human papillomavirus (HPV), E6 and E7 genes are disrupted using topically applied gene editing machinery. In HIV infection, the CCR5 co-receptor is disrupted ex vivo to generate HIV-resistant T cells, CAR-T cells, or hematopoietic stem cells. In β-thalassemia and sickle cell disease, hematopoietic stem cells are engineered ex vivo to induce the production of fetal hemoglobin. AAV-mediated in vivo gene editing is applied to exploit the liver for systemic production of therapeutic proteins in hemophilia and mucopolysaccharidoses, and in the eye to restore splicing of the CEP920 gene in Leber's congenital amaurosis. Close consideration of safety aspects and education of stakeholders will be essential for a successful implementation of gene editing technology in the clinic.

Lessons from the post-genomic era: Globin diversity beyond oxygen binding and transport

Vertebrate hemoglobin (Hb) and myoglobin (Mb) were among the first proteins whose structures and sequences were determined over 50 years ago. In the subsequent pregenomic period, numerous related proteins came to light in plants, invertebrates and bacteria, that shared the myoglobin fold, a signature sequence motif characteristic of a 3-on-3 α-helical sandwich. Concomitantly, eukaryote and bacterial globins with a truncated 2-on-2 α-helical fold were discovered. Genomic information over the last 20 years has dramatically expanded the list of known globins, demonstrating their existence in a limited number of archaeal genomes, a majority of bacterial genomes and an overwhelming majority of eukaryote genomes. In vertebrates, 6 additional globin types were identified, namely neuroglobin (Ngb), cytoglobin (Cygb), globin E (GbE), globin X (GbX), globin Y (GbY) and androglobin (Adgb). Furthermore, functions beyond the familiar oxygen transport and storage have been discovered within the vertebrate globin family, including NO metabolism, peroxidase activity, scavenging of free radicals, and signaling functions. The extension of the knowledge on globin functions suggests that the original roles of bacterial globins must have been enzymatic, involved in defense against NO toxicity, and perhaps also as sensors of O₂, regulating taxis away or towards high O₂ concentrations. In this review, we aimed to discuss the evolution and remarkable functional diversity of vertebrate globins with particular focus on the variety of non-canonical expression sites of mammalian globins and their according impressive variability of atypical functions.

The association of HBG2, BCL11A, and HBS1L-MYB polymorphisms to thalidomide response in Chinese β-thalassemia patients

Thalidomide has been shown to reactivate fetal hemoglobin (HbF) production and reduce the need for blood transfusions in β-thalassemia patients. However, some patients show a minor response or no response to thalidomide. In view of its potential side effects, targeted prescription of thalidomide is imperative. We initially aimed to explore the relevance of HBG2 (rs7482144), BCL11A (rs11886868, rs4671393, rs766432 and rs1427407) and HBS1L-MYB (rs9399137, rs4895440 and rs4895441) single nucleotide polymorphisms (SNPs) in thalidomide response. Eight SNPs were investigated by PCR and DNA sequencing, and their roles in thalidomide response in Chinese β-thalassemia patients were assessed. Results demonstrated that minor alleles of four SNPs were associated with an increased main response risk (rs7482144: P = 0.015; rs9399137: OR = 4.911, P = 0.029; rs4895440: OR = 4.522, P = 0.040; and rs4895441: OR = 4.522, P = 0.040). For patients with non-transfusion-dependent thalassemia (NTDT), with an increase in the minor allele numbers of rs7482144 (P = 0.011), rs9399137 (P = 0.013), rs4895440 (P = 0.011) and rs4895441 (P = 0.011), Hb increments after treatment were increased significantly as well. The cumulative effects of patients carrying any combination of one or three significant minor alleles included a gradually increased main response risk compared to those without the significant minor alleles (P = 0.040-0.018, OR = 8.556-11.000). Furthermore, Hb increments after treatment correlated with cumulative numbers of minor alleles in the four significant SNPs among patients with NTDT (P = 0.001). It was demonstrated that SNPs in HBG2 and HBS1L-MYB contributed significantly to thalidomide response in Chinese patients with β-thalassemia and that the cumulative number of minor SNP alleles may serve as good predictors of treatment response in this population.

Genetic variants in the G gamma-globin promoter modulate fetal hemoglobin expression in the Colombian population

Fetal hemoglobin (HbF) is a determining factor for the development of sickle cell anemia. High HbF levels lower the intensity of symptoms of this disease. HbF levels can vary in patients with sickle cell anemia and individuals without the disease. The purpose of this study was to identify the genetic variants in the G gamma-globin gene promoter that can modulate HbF expression in patients with sickle cell anemia and healthy individuals from Colombia. In total, 413 bp of the G gamma-globin gene promoter were sequenced in 60 patients with sickle cell anemia and 113 healthy individuals. The allelic and genotype frequencies of the identified variants were compared between individuals with low and high HbF for both patients and healthy individuals. In total, we identified 15 variants in both groups, only three of which were shared between patients and healthy individuals. In healthy individuals, sites -16 and -309 (rs112479156) exhibited differences in allele frequencies. The mutant allele of -16 lowered the production of HbF, whereas the mutant allele of -309 increased its production. These results reveal the presence of different mechanisms of HbF regulation between patients with sickle cell and healthy individuals.

Oxidative Stress in β-Thalassemia

Cell oxidative status, which represents the balance between oxidants and antioxidants, is involved in normal functions. Under pathological conditions, there is a shift toward the oxidants, leading to oxidative stress, which is cytotoxic, causing oxidation of cellular components that result in cell death and organ damage. Thalassemia is a hereditary hemolytic anemia caused by mutations in globin genes that cause reduced or complete absence of specific globin chains (commonly, α or β). Although oxidative stress is not the primary etiology of thalassemia, it mediates several of its pathologies. The main causes of oxidative stress in thalassemia are the degradation of the unstable hemoglobin and iron overload-both stimulate the production of excess free radicals. The symptoms aggravated by oxidative stress include increased hemolysis, ineffective erythropoiesis and functional failure of vital organs such as the heart and liver. The oxidative status of each patient is affected by multiple internal and external factors, including genetic makeup, health conditions, nutrition, physical activity, age, and the environment (e.g., air pollution, radiation). In addition, oxidative stress is influenced by the clinical manifestations of the disease (unpaired globin chains, iron overload, anemia, etc.). Application of personalized (theranostics) medicine principles, including diagnostic tests for selecting targeted therapy, is therefore important for optimal treatment of the oxidative stress of these patients. We summarize the role of oxidative stress and the current and potential antioxidative therapeutics in β-thalassemia and describe some methodologies, mostly cellular, that might be helpful for application of a theranostics approach to therapy.

Inhibition of γ/β Globin Gene Switching in CD 34+ Derived Erythroid Cells by BCL11A RNA Silencing

The induction of fetal haemoglobin (Hb F), due to the sustained clinical effects, is one of the most promising methods for the treatment of β hemoglobinopathies, such as thalassemia major and sickle cell disease (SCD). Inhibition of γ-globin gene silencing, possibly is a suitable strategy to induce HbF expression in these patients. In this study, the possibility of increasing HbF in the CD34⁺ derived erythroid cells was investigated by BCL11A inhibition using specific small-interfering RNAs (siRNAs). Human peripheral blood-derived hematopoietic stem cells were isolated and differentiated to erythroid cells. Erythroid maturation was investigated using cell morphology parameters and flow cytometry analysis of CD235a expression On day 20, siRNA complementary to BCL11A was transfected to differentiating cells via electroporation. BCL11A expression was evaluated through real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and enzyme linked immunosorbant assay (ELISA). β actin was used as the reference gene to confirm the relative expression level of BCL11A gene mRNA. 48 hours after transfection, BCL11A siRNA significantly reduced BCL11A mRNA levels and consequently led to 2.0 fold decrease in corresponding protein. On the 28th day, haemoglobin electrophoresis results showed that Hb F levels in transfected erythroid cells increased 3.3-fold when compared with non transfected cells. In this study we showed that BCL11A inhibition in erythroid cells could increase fetal hemoglobin, and this strategy can be the basis for designing a γ globin expressing cellular system to increase Hb F in patients with thalassemia and SCD.

Synergistic Effect of Simvastatin and Romidepsin on Gamma-globin Gene Induction

OBJECTIVE

Hemoglobinopathies such as beta-thalassemia and sickle cell disease (SCD) are inherited disorders that are caused by mutations in beta-globin chain. Gamma-globin gene reactivation can ameliorate clinical manifestations of betathalassemia and SCD. Drugs that induce fetal hemoglobin (HbF) can be promising tools for treatment of beta-thalassemia and SCD patients. Recently, it has been shown that Simvastatin (SIM) and Romidepsin (ROM) induce HbF. SIM is a BCL11a inhibitor and ROM is a HDAC inhibitor and both of these drugs are Food and Drug Administration (FDA)-approved for hypercholesterolemia and cutaneous T-cell lymphoma respectively. Our aim was to evaluate the synergistic effects of these drugs in inducing HbF.

MATERIALS AND METHODS

In our experimental study, we isolated CD34+ cells from five cord blood samples that were cultured in erythroid differentiation medium containing ROM and Simvastatin. Then Gamma-globin, BCL11a and HDAC gene expression were evaluated on the 7th and 14th day of erythroid differentiation by real-time polymerase chain reaction (PCR) and immunocytochemistry.

RESULTS

Our results showed that combination of SIM and ROM significantly increased Gamma-globin gene expression and inhibit BCL11a and HDAC expression compared to results of using each of them alone. SIM and ROM lead to 3.09- fold increase in HbF production compared to the control group. Also, SIM inhibited BCL11a expression (0.065-fold) and ROM inhibited HDAC1 expression (0.47-fold) as two important inhibitors of HbF production after birth.

CONCLUSION

We propose combination therapy of these drugs may be ameliorate clinical manifestation in beta-thalassemia and SCD with at least side effects and reduce the need for blood transfusion.

Identification of a Novel Enhancer/Chromatin Opening Element Associated with High-Level γ-Globin Gene Expression

The organization of the five β-type globin genes on chromosome 11 reflects the timing of expression during erythroid cell development, with the embryonic ε-globin gene being located at the 5′ end, followed by the two fetal γ-globin genes, and with the adult β- and δ-globin genes being located at the 3′ end. Here, we functionally characterized a DNase I-hypersensitive site (HS) located 4 kb upstream of the Gγ-globin gene (HBG-4kb HS).

The organization of the five β-type globin genes on chromosome 11 reflects the timing of expression during erythroid cell development, with the embryonic ε-globin gene being located at the 5′ end, followed by the two fetal γ-globin genes, and with the adult β- and δ-globin genes being located at the 3′ end. Here, we functionally characterized a DNase I-hypersensitive site (HS) located 4 kb upstream of the Gγ-globin gene (HBG-4kb HS). This site is occupied by transcription factors USF1, USF2, EGR1, MafK, and NF-E2 in the human erythroleukemia cell line K562 and exhibits histone modifications typical for enhancers. We generated a synthetic zinc finger (ZF) DNA-binding domain targeting the HBG-4kb HS (HBG-4kb ZF). The HBG-4kb ZF interacted with the target site in vitro and in the context of cells with a high affinity and specificity. Direct delivery of the HBG-4kb ZF to K562 and primary human erythroid cells caused a reduction in γ-globin gene expression which was associated with decreased binding of transcription factors and active histone marks at and downstream of the HS. The data demonstrate that the HBG-4kb HS is important for fetal globin production and suggest that it may act by opening chromatin in a directional manner.

Genetic and Epigenetic Mechanisms of β-Globin Gene Switching

Vertebrates have multiple forms of hemoglobin that differ in the composition of their polypeptide chains. During ontogenesis, the composition of these subunits changes. Genes encoding different α- and β-polypeptide chains are located in two multigene clusters on different chromosomes. Each cluster contains several genes that are expressed at different stages of ontogenesis. The phenomenon of stage-specific transcription of globin genes is referred to as globin gene switching. Mechanisms of expression switching, stage-specific activation, and repression of transcription of α- and β-globin genes are of interest from both theoretical and practical points of view. Alteration of balanced expression of globin genes, which usually occurs due to damage to adult β-globin genes, leads to development of severe diseases - hemoglobinopathies. In most cases, reactivation of the fetal hemoglobin gene in patients with β-thalassemia and sickle cell disease can reduce negative consequences of irreversible alterations of expression of the β-globin genes. This review focuses on the current state of research on genetic and epigenetic mechanisms underlying stage-specific switching of β-globin genes.

Relationship of the Interaction Between Two Quantitative Trait Loci with γ-Globin Expression in β-Thalassemia Intermedia Patients

Globin switching is a significant factor on blood hemoglobin (Hb) level but its molecular mechanisms have not yet been identified, however, several quantitative trait loci (QTL) and polymorphisms involved regions on chromosomes 2p, 6q, 8q and X account for variation in the γ-globin expression level. We studied the effect of interaction between a region on intron six of the TOX gene, chromosome 8q (chr8q) and XmnI locus on the γ-globin promoter, chr11p on γ-globin expression in 150 β-thalassemia intermedia (β-TI) patients, evaluated by statistical interaction analysis. Our results showed a significant interaction between one QTL on intron six of the TOX gene (rs9693712) and XmnI locus that effect γ-globin expression. Interchromosomal interaction mediates through transcriptional machanisms to preserve true genome architectural features, chromosomes localization and DNA bending. This interaction can be a part of the unknown molecular mechanism of globin switching and regulation of gene expression.

Genome Editing of Erythroid Cell Culture Model Systems

Genome editing to introduce specific mutations or to knock out genes in model cell systems has become an efficient platform for research in the fields of molecular biology, genetics, and cell biology. With recent rapid improvements in genome editing techniques, bench-top manipulation of the genome in cell culture has become progressively easier. The application of this knowledge to erythroid cell culture systems now allows the rapid analysis of the downstream effects of virtually any engineered gene disruption or modification in cell systems. Here, we describe a CRISPR/Cas9-based approach to making genomic modifications in erythroid lineage cells which we have successfully used in both murine (MEL) and human (K562) erythroleukaemia immortalized cell lines.

Using newborn screening analytes to identify cases of neonatal sepsis

Neonatal sepsis is associated with high mortality and morbidity, yet challenges with available diagnostic approaches can lead to delays in therapy. Our study assessed whether newborn screening analytes could be utilized to identify associations with neonatal sepsis. We linked a newborn screening registry with health databases to identify cases of sepsis among infants born in Ontario from 2010-2015. Correlations between sepsis and screening analytes were examined within three gestational age groups (early preterm: <34 weeks; late preterm: 34-36 weeks; term: ≥37 weeks), using multivariable logistic regression models. We started with a model containing only clinical factors, then added groups of screening analytes. Among 793,128 infants, 4,794 were diagnosed with sepsis during the neonatal period. Clinical variables alone or in combination with hemoglobin values were not strongly predictive of neonatal sepsis among infants born at term or late preterm. However, model fit improved considerably after adding markers of thyroid and adrenal function, acyl-carnitines, and amino acids. Among infants born at early preterm gestation, neither clinical variables alone nor models incorporating screening analytes adequately predicted neonatal sepsis. The combination of clinical variables and newborn screening analytes may have utility in identifying term or late preterm infants at risk for neonatal sepsis.

Pathophysiology and treatment of patients with beta-thalassemia - an update

Thalassemia (thal) is an autosomal recessive, hereditary, chronic hemolytic anemia due to a partial or complete deficiency in the synthesis of α-globin chains (α-thal) or β-globin chains (β-thal) that compose the major adult hemoglobin (α ₂β _2). It is caused by one or more mutations in the corresponding genes. The unpaired globin chains are unstable; they precipitate intracellularly, resulting in hemolysis, premature destruction of red blood cell [RBC] precursors in the bone marrow, and a short life-span of mature RBCs in the circulation. The state of anemia is treated by frequent RBC transfusions. This therapy results in the accumulation of iron (iron overload), a condition that is exacerbated by the breakdown products of hemoglobin (heme and iron) and the increased iron uptake for the chronic accelerated, but ineffective, RBC production. Iron catalyzes the generation of reactive oxygen species, which in excess are toxic, causing damage to vital organs such as the heart and liver and the endocrine system. Herein, we review recent findings regarding the pathophysiology underlying the major symptoms of β-thal and potential therapeutic modalities for the amelioration of its complications, as well as new modalities that may provide a cure for the disease.

Comparison of MicroRNAs Mediated in Reactivation of the γ-Globin in β-Thalassemia Patients, Responders and Non-Responders to Hydroxyurea

Drug induction of Hb F seems to be an ideal therapy for patients with hemoglobin (Hb) disorders, and many efforts have been made to reveal the mechanism behind it. Thus, we examined in vivo expression of some microRNAs (miRNAs) that are thought to be involved in this process. Among β-thalassemia (β-thal) patients who were undergoing hydroxyurea (HU) therapy in the past 3 months and five healthy individuals, five responders and five non-responders, were also included in the study. Erythroid progenitors were isolated by magnetic activated cell sorting (MACS) and miRNA expression analyzed using reverse transcription-polymerase chain reaction (RT-PCR). We showed that γ-globin, miR-210 and miR-486-3p had higher levels in the responders than the non-responders group. Moreover, miR-150 and miR-320 had higher levels in the healthy group than both non-responders and responders groups, but the expression of miR-96 did not show any significant difference between the study groups. To the best of our knowledge, this is the first study proposing that 'induction of cellular hypoxic condition by Hb F inducing agents' could be the milestone of possible mechanisms that explain why responders are able to reactivate γ-globin genes and subsequently, more production of Hb F, in response to these agents in comparison to non-responders. However, further investigations need to be performed to verify this hypothesis.

Fetal haemoglobin induction in sickle cell disease

Fetal haemoglobin (HbF, α2γ2) induction has long been an area of investigation, as it is known to ameliorate the clinical complications of sickle cell disease (SCD). Progress in identifying novel HbF-inducing strategies has been stymied by limited understanding of gamma (γ)-globin regulation. Genome-wide association studies (GWAS) have identified variants in BCL11A and HBS1L-MYB that are associated with HbF levels. Functional studies have established the roles of BCL11A, MYB, and KLF1 in γ-globin regulation, but this information has not yielded new pharmacological agents. Several drugs are under investigation in clinical trials as HbF-inducing agents, but hydroxycarbamide remains the only widely used pharmacologic therapy for SCD. Autologous transplant of edited haematopoietic stem cells holds promise as a cure for SCD, either through HbF induction or correction of the causative mutation, but several technical and safety hurdles must be overcome before this therapy can be offered widely, and pharmacological therapies are still needed.

Epigenetic dysregulation of the erythropoietic transcription factor KLF1 and the β-like globin locus in juvenile myelomonocytic leukemia

Increased levels of fetal hemoglobin (HbF) are a hallmark of more than half of the children diagnosed with juvenile myelomonocytic leukemia (JMML). Elevated HbF levels in JMML are associated with DNA hypermethylation of distinct gene promoter regions in leukemic cells. Since the regulation of globin gene transcription is known to be under epigenetic control, we set out to study the relation of DNA methylation patterns at β-/γ-globin promoters, mRNA and protein expression of globins, and epigenetic modifications of genes encoding the globin-regulatory transcription factors BCL11A and KLF1 in nucleated erythropoietic precursor cells of patients with JMML. We describe several altered epigenetic components resulting in disordered globin synthesis in JMML. We identify a cis-regulatory upstream KLF1 enhancer sequence as highly sensitive to DNA methylation and frequently hypermethylated in JMML. The data indicate that the dysregulation of β-like globin genes is a genuine attribute of the leukemic cell clone in JMML and involves mechanisms not taking part in the normal fetal-to-adult hemoglobin switch.

Induced Pluripotent Stem Cell for the Study and Treatment of Sickle Cell Anemia

Sickle cell anemia (SCA) is a monogenic disease of high mortality, affecting millions of people worldwide. There is no broad, effective, and safe definitive treatment for SCA, so the palliative treatments are the most used. The establishment of an in vitro model allows better understanding of how the disease occurs, besides allowing the development of more effective tests and treatments. In this context, iPSC technology is a powerful tool for basic research and disease modeling, and a promise for finding and screening more effective and safe drugs, besides the possibility of use in regenerative medicine. This work obtained a model for study and treatment of SCA using iPSC. Then, episomal vectors were used for reprogramming peripheral blood mononuclear cells to obtain integration-free iPSC. Cells were collected from patients treated with hydroxyurea and without treatment. The iPSCP Bscd lines were characterized for pluripotent and differentiation potential. The iPSC lines were differentiated into HSC, so that we obtained a dynamic and efficient protocol of CD34+CD45+ cells production. We offer a valuable tool for a better understanding of how SCA occurs, in addition to making possible the development of more effective drugs and treatments and providing better understanding of widely used treatments, such as hydroxyurea.

Molecular basis of β thalassemia and potential therapeutic targets

The remarkable phenotypic diversity of β thalassemia that range from severe anemia and transfusion-dependency, to a clinically asymptomatic state exemplifies how a spectrum of disease severity can be generated in single gene disorders. While the genetic basis for β thalassemia, and how severity of the anemia could be modified at different levels of its pathophysiology have been well documented, therapy remains largely supportive with bone marrow transplant being the only cure. Identification of the genetic variants modifying fetal hemoglobin (HbF) production in combination with α globin genotype provide some prediction of disease severity for β thalassemia but generation of a personalized genetic risk score to inform prognosis and guide management requires a larger panel of genetic modifiers yet to be discovered. Nonetheless, genetic studies have been successful in characterizing the key variants and pathways involved in HbF regulation, providing new therapeutic targets for HbF reactivation. BCL11A has been established as a quantitative repressor, and progress has been made in manipulating its expression using genomic and gene-editing approaches for therapeutic benefits. Recent discoveries and understanding in the mechanisms associated with ineffective and abnormal erythropoiesis have also provided additional therapeutic targets, a couple of which are currently being tested in clinical trials.

Xmn1-158 γGVariant in B-Thalassemia Intermediate Patients in South-East of Iran

Background: Xmn-1 polymorphism of 𝜸^Gglobin gene (HBG2) is a prominent quantitative trait loci (QTL) in β-thalassemia intermediate (β-TI). In current study, we evaluated the frequency of Xmn-1 polymorphism and its association with β-globin gene (HBB) alleles and Hb F level in β-TI patients in Sistan and Balouchestan province, south-east of Iran. Subjects and Methods: 45 β-TI patients were enrolled. HBB gene mutations and Xmn-1 polymorphism were determined by amplification-refractory mutation system (ARMS) PCR method. Hemoglobin profile was determined using capillary electrophoresis. Results: The study participants consisted of 26 (58%) males and 19 (42%) females. Mean age of the patients was 10.7±3.1 years old. Overall, Xmn-1 polymorphism was observed in 28 (62%) patients. Homozygous (TT) and heterozygous (CT) genotypes of the polymorphism represented with frequencies of 12 (26%) and 16 (35%), respectively. Main recognized HBB gene mutation was IVSI-5(G>C) with homozygous frequency of 44%. Non-zero (β⁺) alleles of HBB gene constituted 11.1 % (4 patients with heterozygous β⁺ and one with homozygous β⁺ genotype). Hb F level was significantly higher in patients with at least one Xmn-1allele (67.9±[Formula: see text]17.9%) than those without the polymorphism (19.5±20.3%, P<0.0001). Also, patients with homozygous genotype demonstrated significantly higher Hb F compared to heterozygous (CT) cases (respective percentages of 85±[Formula: see text]6.8 and 54.7±[Formula: see text]10.5, p<0.0001). Conclusion: Our results highlighted the role of Xmn-1 polymorphism as the main phenotypic modifier in β-TI patients in Sistan and Balouchestan province.

Heterochromatin Protein 1γ Is a Novel Epigenetic Repressor of Human Embryonic ϵ-Globin Gene Expression

Production of hemoglobin during development is tightly regulated. For example, expression from the human β-globin gene locus, comprising β-, δ-, ϵ-, and γ-globin genes, switches from ϵ-globin to γ-globin during embryonic development and then from γ-globin to β-globin after birth. Expression of human ϵ-globin in mice has been shown to ameliorate anemia caused by β-globin mutations, including those causing β-thalassemia and sickle cell disease, raising the prospect that reactivation of ϵ-globin expression could be used in managing these conditions in humans. Although the human globin genes are known to be regulated by a variety of multiprotein complexes containing enzymes that catalyze epigenetic modifications, the exact mechanisms controlling ϵ-globin gene silencing remain elusive. Here we found that the heterochromatin protein HP1γ, a multifunctional chromatin- and DNA-binding protein with roles in transcriptional activation and elongation, represses ϵ-globin expression by interacting with a histone-modifying enzyme, lysine methyltransferase SUV4-20h2. Silencing of HP1γ expression markedly decreased repressive histone marks and the multimethylation of histone H3 lysine 9 and H4 lysine 20, leading to a significant decrease in DNA methylation at the proximal promoter of the ϵ-globin gene and greatly increased ϵ-globin expression. In addition, using chromatin immunoprecipitation, we showed that SUV4-20h2 facilitates the deposition of HP1γ on the ϵ-globin-proximal promoter. Thus, these data indicate that HP1γ is a novel epigenetic repressor of ϵ-globin gene expression and provide a potential strategy for targeted therapies for β-thalassemia and sickle cell disease.

Clinical Features of β-Thalassemia and Sickle Cell Disease

Sickle cell disease (SCD) and β-thalassemia are among the most common inherited diseases, affecting millions of persons globally. It is estimated that 5-7% of the world's population is a carrier of a significant hemoglobin variant. Without early diagnosis followed by initiation of preventative and therapeutic care, both SCD and β-thalassemia result in significant morbidity and early mortality. Despite great strides in the understanding of the molecular basis and pathophysiology of these conditions, the burden of disease remains high, particularly in limited resource settings. Current therapy relies heavily upon the availability and safety of erythrocyte transfusions to treat acute and chronic complications of these conditions, but frequent transfusions results in significant iron overload, as well as challenges from acquired infections and alloimmunization. Hydroxyurea is a highly effective treatment for SCD but less so for β-thalassemia, and does not represent curative therapy. As technology and use of cellular and gene therapies expand, SCD and thalassemia should be among the highest disease priorities.

Reactivation of Fetal Hemoglobin for Treating β-Thalassemia and Sickle Cell Disease

Reactivation of fetal hemoglobin (HbF) in adult hematopoietic cells has the potential for great clinical benefit in patients bearing deleterious mutations in the β-globin gene, such as β-thalassemia and sickle cell disease (SCD), since increasing the production of HbF can compensate for underproduction of β-globin chains (in β-thalassemia) and it can also disrupt sickle hemoglobin polymerization (in SCD). Thus for the past few decades, concerted efforts have been made to identify an effective way to induce the synthesis of HbF in adult erythroid cells for potential therapeutic relief from the effects of these β-globinopathies. Chemical inducers of HbF as well as a number of transcription factors that are able to reactivate HbF synthesis in vitro and in vivo in adult erythroid cells have been identified. However, there has been only limited success in attempts to manipulate either the drugs or regulatory proteins, and in only a fraction of patients, and there is wide variation in individual response to these drugs or transcription factors. These studies highlight the importance for understanding the molecular mechanisms underlying hemoglobin switching so that future studies can be designed to treat these disorders.

Postnatal Prediction of Gestational Age Using Newborn Fetal Hemoglobin Levels

Introduction

In many parts of the developing world procurement of antenatal gestational age estimates is not possible, challenging provision of appropriate perinatal care. This study aimed to develop a model for postnatal gestational age estimation utilizing measures of the newborn hemoglobin levels and other metabolic analyte data derived from newborn blood spot samples.

Methods

We conducted a retrospective cohort analysis of 159,215 infants born January 2012–December 2014 in Ontario, Canada. Multivariable linear and logistic regression analyses were used to evaluate the precision of developed models.

Results

Models derived from a combination of hemoglobin ratios and birthweight were more precise at predicting gestational age (RMSE1·23 weeks) than models limited to birthweight (RMSE1·34). Models including birthweight, hemoglobin, TSH and 17-OHP levels were able to accurately estimate gestational age to ± 2 weeks in 95·3% of the cohort and discriminate ≤ 34 versus > 34 (c-statistic, 0·98). This model also performed well in small for gestational age infants (c-statistic, 0·998).

Discussion

The development of a point-of-care mechanism to allow widespread implementation of postnatal gestational age prediction tools that make use of hemoglobin or non-mass spectromietry-derived metabolites could serve areas where antenatal gestational age dating is not routinely available.

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Mechanisms for postnatal gestational age estimation are required to guide care in low resource settings.

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Newborn fetal/adult hemoglobin ratio and other non-mass spectrometry derived data can be used to provide precise estimates of gestational age.

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Hemoglobin derived postnatal gestational age prediction models also performed comparatively well in small for gestational age infants.

Three research groups including our own have recently published on the development of postnatal gestational age prediction algorithms derived from newborn screening metabolic profiles. Expanded newborn screening practices relying on tandem mass spectrometry instrumentation are not common place in many low resource settings, thus limiting the utility of such prediction models. Newborn fetal and adult hemoglobin levels are known to vary by gestational age of birth, and may be derived by methods other than mass spectrometry. In this study we used a retrospective cohort study design to develop and validate the precision of postnatal gestational age prediction models derived from fetal and adult hemoglobin levels, and readily available perinatal characteristics obtained from the Better Outcomes Registry & Network and the Newborn Screening of Ontario program. Final models were able to accurately predict postnatal gestational age to within 2 weeks of true gestational age, with excellent precision to discriminate the gestational age of average and small for gestational age infants. We have built upon our existing postnatal gestational age prediction algorithm to demonstrate both the stand-alone and additive predictive potential of newborn hemoglobin levels to the model. Methods to predict gestational age based on newborn screening markers have the potential to provide accurate postnatal assessments of gestational age in settings where gold standard first trimester ultrasounds are limited.

Fetal hemoglobin regulation in β-thalassemia: heterogeneity, modifiers and therapeutic approaches

INTRODUCTION

Stress erythropoiesis induces fetal hemoglobin (HbF) expression in β-thalassemias, however the level of expression is highly variable. The last decade has seen dramatic advances in our understanding of the molecular regulators of HbF production and the genetic factors associated with HbF levels, leading to the promise of new methods of the clinical induction of HbF. Areas covered: This article will review the heterogeneity and genetic modifiers of HbF and HbF induction therapy in β-thalassemia. Expert commentary: One promising curative β-thalassemia therapy is to induce HbF synthesis in β-thalassemic erythrocytes to therapeutic levels before clinical symptom occurs. Further understanding of HbF level variation and regulation is needed in order to predict the response from HbF-inducing approaches.

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

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.

AK048794 maintains the mouse embryonic stem cell pluripotency by functioning as an miRNA sponge for miR-592

MiR-592 has been identified as a neural-enriched microRNA, plays an important role in mNPCs differentiation, could induce astrogliogenesis differentiation arrest or/and enhance neurogenesis in vitro Previous studies showed that long noncoding RNAs (lncRNAs) were involved in the neuronal development and activity. To investigate the role of miR-592 in neurogenesis, we described the expression profile of lncRNAs in miR-592 knockout mouse embryonic stem cells (mESCs) and the corresponding normal mESCs by microarray. By the microarray analysis and luciferase reporter assays, we demonstrated that lncRNA - AK048794, regulated by transcription factor GATA1, functioned as a competing endogenous RNA (ceRNA) for miR-592 and led to the de-repression of its endogenous target FAM91A1, which is involved in mESC pluripotency maintenance. Taken together, these observations imply that AK048794 modulated the expression of multiple genes involved in mESC pluripotency maintenance by acting as a ceRNA for miR-592, which may build up the link between the regulatory miRNA network and mESC pluripotency.