Epigenetic Insights and Potential Modifiers as Therapeutic Targets in β–Thalassemia

Thalassemia, an inherited quantitative globin disorder, consists of two types, α– and β–thalassemia. β–thalassemia is a heterogeneous disease that can be asymptomatic, mild, or even severe. Considerable research has focused on investigating its underlying etiology. These studies found that DNA hypomethylation in the β–globin gene cluster is significantly related to fetal hemoglobin (HbF) elevation. Histone modification reactivates γ-globin gene expression in adults and increases β–globin expression. Down-regulation of γ–globin suppressor genes, i.e., BCL11A, KLF1, HBG-XMN1, HBS1L-MYB, and SOX6, elevates the HbF level. β–thalassemia severity is predictable through FLT1, ARG2, NOS2A, and MAP3K5 gene expression. NOS2A and MAP3K5 may predict the β–thalassemia patient’s response to hydroxyurea, a HbF-inducing drug. The transcription factors NRF2 and BACH1 work with antioxidant enzymes, i.e., PRDX1, PRDX2, TRX1, and SOD1, to protect erythrocytes from oxidative damage, thus increasing their lifespan. A single β–thalassemia-causing mutation can result in different phenotypes, and these are predictable by IGSF4 and LARP2 methylation as well as long non-coding RNA expression levels. Finally, the coinheritance of β–thalassemia with α–thalassemia ameliorates the β–thalassemia clinical presentation. In conclusion, the management of β–thalassemia is currently limited to genetic and epigenetic approaches, and numerous factors should be further explored in the future.

Brain injury pathophysiology study by a multimodal approach in children with sickle cell anemia with no intra or extra cranial arteriopathy

Despite its high prevalence in children with sickle cell anemia (SCA), the pathophysiology of silent cerebral infarcts (SCIs) remains elusive. The main objective of this study was to explore the respective roles of major determinants of brain perfusion in SCA children with no past or current history of intracranial or extracranial vasculopathy. We used a multimodal approach based notably on perfusion imaging Arterial spin labelling (ASL) MRI and Near Infra-Red Spectroscopy (NIRS), as well as biomarkers reflecting blood rheology and endothelial activation. Out of 59 SCA patients (mean age 11.4} 3.9 yrs), 8 (13%) had a total of 12 SCIs. Children with SCIs had a distinctive profile characterized by decreased blood pressure, impaired blood rheology, increased P-selectin levels, and marked anemia. Although ASL perfusion and oximetry values did not differ between groups, comparison of biological and clinical parameters according to the level of perfusion categorized in terciles showed an independent association between high perfusion and increased sP-selectin, decreased RBC deformability, low HbF level, increased blood viscosity and no alpha-thalassemia deletion. NIRS measurements did not yield additional novel results. Altogether, these findings argue for early MRI detection of SCIs in children with no identified vasculopathy and suggest a potential role for ASL as an additional screening tool. Early treatment targeting hemolysis, anemia and endothelial dysfunction should reduce the risk of this under diagnosed and serious complication.

β-globin gene cluster mutations and large deletions among anaemic patients with elevated HbF level in a tertiary teaching hospital in Kelantan, Malaysia

Mutations in the β-globin gene cluster can lead to β-thalassaemia, δβ-thalassaemia, hereditary persistence of foetal haemoglobin (HPFH) and some of the haemoglobin variants. The clinical and haematological spectrum of thalassaemia range from benign to pathogenic conditions including severe transfusion dependent thalassaemia. Therefore, it is important to accurately diagnose β-globin gene cluster mutations to prevent thalassaemia major or intermedia offspring. The objective of this study is to detect β-globin gene cluster mutations and large deletions among anaemic patients with elevated HbF level in a tertiary teaching hospital in Kelantan, Malaysia. This study involved 144 anaemic patients with HbF level >1.0%. High-Performance Liquid Chromatography (HPLC) was used to determine the HbF and HbA2 levels. Multiplex-ARMS (ARMS)-PCR and gap-PCR were performed for those patients with high HbA2 level (>3.2%) and normal HbA2 level (≤3.2%) to detect β-globin gene cluster mutations and large deletions respectively. The majority of patients were Malays (99.3%) with mean age of 19.99 ± 1.64 years and female 61.1% predominance. Out of 87 samples tested using multiplex ARMS-PCR against eight targeted single mutation; Cd 41/42, IVS 1–5, Cd 26, Cd 17, Cd 71/72, IVS 1–1, Cd 8/9 and -28 mutations, 65 (74.7%) patients were detected which comprises of Cd 26 (56.3%), Cd 41/42 (11.5%), compound Cd 26 and Cd 41/42 (3.4%) and IVS 1–1 (3.4%). Meanwhile, for multiplex gap-PCR which detect four types of large deletions; Thai (δβ)o-thalassaemia, HPFH-6, Siriraj J and Hb Lepore, one out of 57 patients (1.8%) was found positive with Thai (δβ)o-thalassaemia. There was a significant difference between the mean of HbF level, MCV level as well as MCH level of patients with and without β-globin gene mutations and large deletions (P<0.05). This study highlighted the presence of various types of β-globin gene cluster mutations detection in establishing a definitive diagnosis among this selected group of patients for the large-scale screening of the thalassaemia gene.

Evaluation of Beta Globin Gene Mutations in Beta Thalassemia Carrier Children in Aydın Province and its Environment

INTRODUCTION: Beta thalassemia carriers (BTC) in Turkey is observed with a frequency of 2.1%, and it is the most common cause of anemia after iron deficiency. There are few studies showing the effect of genotype on phenotype in beta thalassemia carrying children. The aim of this study is to determine the mutation diversity of these children in and around Aydın and evaluate the effects of these mutations on complete blood count parameters and hemoglobin electrophoresis. METHODS: This study included mutation analysis of 65 patients who were diagnosed as BTC in Adnan Menderes University, Faculty of Medicine, Department of Child Health and Diseases, Pediatric Hematology Outpatient Clinic between 01.01.2014 and 01.08.2019. Complete blood count, hemoglobin electrophoresis and mutation analysis results were obtained from the computer data system and patient files. Research data were evaluated by using SPSS 21.0 statistics program. RESULTS: 39 (60.0%) of the sixty-five patients were male, 26 (40.0%) were female, and the mean age was 8.34±4.94 years. When full blood count parameters were analyzed, 87.7% had anemia, 100% microcytosis and high red cell distribution width (RDW) level, 49.2% hypochromia and 87.7% high red blood cell (RBC) count. RDW level was ≥16 in 66.2% of the cases. Seventeen different mutations were detected. The mutations most frequently occurred in “intron 1” gene region (66.1%). The most common ones were IVS I-110 (44.11%), IVS I-1 G>A Heterozygotes (8.8%,) IVS I-6 T>C Heterozygotes (7.5%) and IVS II-745 (7.5%). RDW level was ≥16 in 66.2% of the cases. Seventeen different mutations were detected. The mutations most frequently occurred in “intron 1” (66.1%) gene region. IVS I-110 (44.11%), IVS I-1 G>A Heterozygotes (8.8%,) IVS I-6 T>C Heterozygotes (7.5%) and IVS II-745 (7.5%) were observed most commonly. In patients with IVS I-110 mutation, mean Hb level was 10.55 gr/dL, MCV level was 58.44 fL, RDW level was 16.51, RBC level was 5680x10⁹/L, HbA2 level was 4.77%, HbF level was 2.34%. Mutations detected in 12 patients with HbF level above 5% were as IVS I-110 (5 people), IVS I-6 T>C Heterozygotes, Codon 39 C>T Heterozygotes, IVS I-116, c.25-26 del AA (plys9Valfs) Heterozygotes, c.27dupG (pSer10valfs*14), c316-373 (IVSII-478 C>A Heterozygotes), -87 C>T Heterozygotes. Mentzer index was calculated as >13 in six patients (9.2%). The mutations seen in these patients were IVS-I 110, c.27dupG (p.Ser10valfs*14), c316-373 (IVS II-478 C>A Heterozygotes), -87 C>T Heterozygotes. There were four patients (6.1%) with a RDW index >220. Two of these patients had c.27dupG (p.Ser10valfs*14) and others had c316-373 (IVS II-478 C>A Heterozygotes) and -87 C>T Heterozygotes mutations. Mutations detected in four patients with HbF levels in the range of 9.48-15.67 were IVS I-116 T>G Heterozygotes, IVS I-110 G>A Heterozygotes, c.25-26 del AA (p.lys59valfs) Heterozygotes, c27 dupG (pSer10 valfs*14) and three of these mutations carrying β° mutation type were located in exon 1 and one of them carrying β⁺ mutation type (IVS I-110) was in intron 1. DISCUSSION AND CONCLUSION: The same mutations detected in patients with beta thalassemia carriers have different effects on complete blood count parameters. HbA2 and HbF levels suggest that these mutations are not effective on the phenotype alone and there may be additional factors which should be clarified. We think that there may be BTC in cases with low RBC, Mentzer index ≥13 and RDW index ≥220, HbA2 <3.5 and studying the mutation analysis of these patients will contribute significantly to the literature.

DNA methylation patterns of β-globin cluster in β-thalassemia patients

Background Reactivation of fetal hemoglobin (HbF, α2γ2) holds a therapeutic target for β-thalassemia and sickle cell disease. Although many HbF regulators have been identified, the methylation patterns in β-globin cluster driving the fetal-to-adult hemoglobin switch remains to be determined. Results Here, we evaluated DNA methylation patterns of the β-globin cluster from peripheral bloods of 105 β0/β0 thalassemia patients and 44 normal controls. We also recruited 15 bone marrows and 4 cord blood samples for further evaluation. We identified that the CpG sites in the locus control region (LCR) DNase I hypersensitive site 4 and 3 (HS4-3) regions, and γ- and β-globin promoters displayed hypomethylation in β0/β0-thalassemia patients, especially for the patients with high HbF level, as compared with normal controls. Furthermore, hypomethylations in most of CpG sites of the HS4-3 core regions were also observed in bone marrows (BM) of β0/β0-patients compared with normal controls; and methylation level of γ-globin promoter -50 and + 17 CpG sites showed lower methylation level in patients with high HbF level compared with those with low HbF level and a negative correlation with HbF level among β0-thalassemia patients. Finally, γ-globin promoter + 17 and + 50 CpG sites also displayed significant hypomethylation in cord blood (CB) tissues compared with BM tissues from normal controls. Conclusions Our findings revealed methylation patterns in β-globin cluster associated with β0 thalassemia disease and γ-globin expression, contributed to understand the epigenetic modification in β0 thalassemia patients and provided candidate targets for the therapies of β-hemoglobinopathies.

Sickle Cell Disease and COVID-19: Susceptibility and Severity

Sickle cell disease (SCD) patients are immunocompromised with multiple comorbidities and a hypercoagulation state. On the other hand COVID-19 is associated with cytokine storm and hypercoagulability. To find the susceptibility and the clinical course of COVID-19 in SCD patients we surveyed related published papers from USA, Europe, Middle East, few African patients and international SCD registry. The COVID-19 presentation was mild in children and moderate in many SCD adults. To explain these findings, possible benefits of high HbF level, and hydroxyurea therapy could be considered. The obtained results should be interpreted considering low cases from sub-Saharan people, younger age of SCD patients compared to general population, a bias toward registry of more severe form of the disease, the influence of preexisting comorbidities with multisystem organ damage in exacerbation of the COVID-19 and the fatality rate in SCD patients and the role of health socio-economic determinants.

HbF-promoting polymorphisms may specifically reduce the residual risk of cerebral vasculopathy in SCA children with alpha-thalassemia

Sickle cell anemia (SCA) is a disease characterized by abnormal red blood cell rheology. Because of their effects on HbS polymerization and red blood cell deformability, alpha-thalassemia and the residual HbF level are known genetic modifiers of the disease. The aim of our study was to determine if the number of HbF quantitative trait loci (QTL) would also favor a specific sub-phenotype of SCA as it is the case for alpha-thalassemia. Our results confirmed that alpha-thalassemia protected from cerebral vasculopathy but increased the risk for frequent painful vaso-occlusive crises. We also showed that more HbF-QTL may provide an additional and specific protection against cerebral vasculopathy but only for children with alpha-thalassemia (-α/αα or -α/-α genotypes).

Shift of HbF to HbA under Influence of SKA2 Gene; A Possible Link between Cortisol and Hematopoietic Maturation in Term and Preterm Newborns

Background: We hypothesized that SKA2 gene can convert hemoglobin F to A leading to the maturity of the hematopoietic system by glucocorticoid hormone; so, the present study aimed to investigate the health outcome of newborns by using the effect of SKA2 gene on hematopoietic maturation. Methods: At first, 142 samples were divided into term and preterm. After sampling from the umbilical cord blood, the expression of SKA2 genes and HbA and F were evaluated by quantitative RT-PCR. The blood gases were measured by Campact 3 device. Finally, cortisol level was measured by ELISA method and HbA and F levels were investigated by capillary electrophoresis. Results: The blood gases and Apgar scores was more favorable in term newborns (P <0.001). Levels of protein/expression of HbF in newborns with Apgar score greater than 7 was lower than that of the newborns with Apgar score below 7 (P <0.001). Cortisol and HbA levels were considerably higher in term newborns compared to the preterm ones (P <0.001). In the preterm and term groups, SKA2 gene expression had a positive and significant relationship with cortisol and HbA levels as well as a negative relationship with HbF level. In the preterm group, a positive and significant relationship was observed between the expression of SKA2 and HbF genes. Conclusion: The results revealed that the SKA2 gene affected on hematopoietic maturation in preterm and term newborns and the health outcome of newborns improved by increasing HbA level.

Therapeutic Base Editing of Human Hematopoietic Stem Cells

Base editing with fusions of RNA-guided DNA-binding proteins and nucleotide deaminases represents a promising approach to permanently remedy genetic blood disorders without obligatory double strand breaks, however its application in engrafting hematopoietic stem cells (HSCs) remains unexplored. Here we purified A3A(N57Q)-BE3 protein for RNP electroporation of human peripheral blood (PB) mobilized CD34+ hematopoietic stem and progenitor cells (HSPCs). We found that sgRNAs targeting for cytidine base editing the core GATA1 binding motif of the BCL11A +58 erythroid enhancer resulted in efficient on-target base edits (81% allele frequency) with low indels. There was similar HbF induction in erythroid progeny as compared to Cas9:sgRNA RNP nuclease mediated modification of the same target sequence (36% median HbF in base edited cells with 81% allele modifications, 39% HbF in 3xNLS-SpCas9:sgRNA#1617 nuclease edited cells with 99% indels, and 5%HbF in unedited cells). A single therapeutic base edit of the BCL11A enhancer was sufficient to ameliorate the pathobiology of both sickle cell disease (SCD) and beta-thalassemia. Base editing of CD34+ HSPCs from plerixafor mobilized PB SCD patient donors resulted in potent HbF induction (24-31% HbF level in bulk cells with 87-90% on-target allele modifications) and reduced sodium metabisulfite induced sickling (from 84% to 29% of erythrocytes). Base editing of non-mobilized PB CD34+ HSPCs from 3 beta-thalassemia patient donors potently induced gamma-globin and improved ineffective erythropoiesis in vitro, with 59-75% on-target allele modifications. Moreover highly efficient multiplex editing could be achieved in HSPCs. Simultaneous disruption of the BCL11A +58 erythroid enhancer core GATA1 motif and correction of the HBB -28A&gt;G promoter mutation in HSPCs resulted in production of at least one therapeutic allele in 35 of 35 erythroid colonies analyzed, with each colony achieving improved alpha-to-non-alpha globin chain balance. Finally we found that base editing could be efficiently produced in engrafting HSCs. Using 3 donors, we observed 62-64% base edits at the BCL11A +58 enhancer GATA1 motif in input HSPCs with one round of electroporation and 73-85% base edits with two rounds of electroporation (separated by 24 hours), albeit with modest reduction of cell viability with tandem electroporation. We observed 70-94% human chimerism and 35-82% base edits in engrafting human cells in primary recipients and 11-61% base edits in secondary recipients as measured 16 weeks following cell infusion. Similar edit frequencies were observed across all assayed hematopoietic lineages including engrafting B-lymphocytes, erythroid precursors, and HSPCs. We observed that compared to non-engrafting progenitors, long-term engrafting HSCs favored C to T (as compared to C to G/A) editing. There was a strong correlation (Spearman r 0.86, P&lt;0.0001) between base edit frequency and HbF level of engrafting erythroid cells, with in vivo HbF level induced from median 1.8% in unedited recipients to 22% in recipients of tandem base edited cells. Together these results demonstrate, to our knowledge for the first time, the potential of RNP base editing of human HSPCs as an alternative to nuclease editing for HSC-targeted therapeutic genome modification. Disclosures No relevant conflicts of interest to declare.