The XmnI Gγ polymorphism influences hemoglobin F synthesis contrary to BCL11A and HBS1L-MYB SNPs in a cohort of 57 β-thalassemia intermedia patients

Genetic polymorphism of novel SNP rs5006884 in OR51B6 and SNP rs4499252 in AHSP among transfusion-dependent and non-transfusion-dependent β-thalassemia/Hb E patients in Thailand: a multivariate analysis of clinical and genetic polymorphism

Compound heterozygous β-thalassemia and Hb E, a prevalent and severe form of thalassemia in Southeast Asia, manifests in two major clinical forms: transfusion-dependent thalassemia (TDT) and non-transfusion-dependent thalassemia (NTDT). This study investigates the association of genetic polymorphisms rs5006884 in OR51B6, rs4499252 in AHSP, rs9399137 in HBS1L-MYB, and rs4671393 in BCL11A with clinical severity and transfusion dependency in β-thalassemia/Hb E patients in Thailand. A total of 189 samples, including 58 TDT, 58 NTDT, 33 homozygous Hb E, and 40 wild-type individuals, were analyzed. Genotyping of the four single nucleotide polymorphisms (SNPs) was conducted using the rhAmp SNP Genotyping assay. Multivariate regression models were developed to evaluate the combined effects of genetic and clinical factors on transfusion dependency. The results showed that OR51B6 SNP rs5006884 TT genotype was significantly more frequent in the NTDT group (P < 0.05), suggesting a strong association with reduced transfusion dependency. Conversely, the AHSP SNP rs4499252 GG genotype was significantly less frequent in the homozygous Hb E group (P < 0.05) compared to other groups. Multivariate analyses highlighted hemoglobin (Hb) levels as a robust predictor of transfusion dependency, with specific HBB mutations including HBB:c.59 A > G, HBB:c.-78 A > G, HBB:c.316-197 C > T, and NC_000011.10:g.5224302_5227791del being significantly associated with NTDT (P < 0.05). Furthermore, rs5006884 in OR51B6 also played a significant role in NTDT in multivariate analyses. In contrast, SNPs in BCL11A (rs4671393), HBS1L-MYB (rs9399137), and AHSP (rs4499252) showed no significant independent associations with transfusion dependency or disease severity in this cohort. This study explores rs5006884 in OR51B6 and rs4499252 in AHSP in TDT and NTDT patients for the first time. These findings elucidate the interplay of genetic and clinical factors influencing β-thalassemia severity, paving the way for personalized management strategies to mitigate transfusion requirements.

Gene-environmental influence of space and microgravity on red blood cells with sickle cell disease

A fundamental question in human biology and for hematological disease is how do complex gene-environment interactions lead to individual disease outcome? This is no less the case for sickle cell disease (SCD), a monogenic disorder of Mendelian inheritance, both clinical course, severity, and treatment response, is variable amongst affected individuals. New insight and discovery often lie between the intersection of seemingly disparate disciplines. Recently, opportunities for space medicine have flourished and have offered a new paradigm for study. Two recent Nature papers have shown that hemolysis and oxidative stress play key mechanistic roles in erythrocyte pathogenesis during spaceflight. This paper reviews existing genetic and environmental modifiers of the sickle cell disease phenotype. It reviews evidence for erythrocyte pathology in microgravity environments and demonstrates why this may be relevant for the unique gene-environment interaction of the SCD phenotype. It also introduces the hematology and scientific community to methodological tools for evaluation in space and microgravity research. The increasing understanding of space biology may yield insight into gene-environment influences and new treatment paradigms in SCD and other hematological disease phenotypes.

Pharmacogenomics of Drugs Used in β-Thalassemia and Sickle-Cell Disease: From Basic Research to Clinical Applications

In this short review we have presented and discussed studies on pharmacogenomics (also termed pharmacogenetics) of the drugs employed in the treatment of β-thalassemia or Sickle-cell disease (SCD). This field of investigation is relevant, since it is expected to help clinicians select the appropriate drug and the correct dosage for each patient. We first discussed the search for DNA polymorphisms associated with a high expression of γ-globin genes and identified this using GWAS studies and CRISPR-based gene editing approaches. We then presented validated DNA polymorphisms associated with a high HbF production (including, but not limited to the HBG2 XmnI polymorphism and those related to the BCL11A, MYB, KLF-1, and LYAR genes). The expression of microRNAs involved in the regulation of γ-globin genes was also presented in the context of pharmacomiRNomics. Then, the pharmacogenomics of validated fetal hemoglobin inducers (hydroxyurea, butyrate and butyrate analogues, thalidomide, and sirolimus), of iron chelators, and of analgesics in the pain management of SCD patients were considered. Finally, we discuss current clinical trials, as well as international research networks focusing on clinical issues related to pharmacogenomics in hematological diseases.

A Population-Oriented Genetic Scoring System to Predict Phenotype: A Pathway to Personalized Medicine in Iraqis With β-Thalassemia

To assess the roles of genetic modifiers in Iraqi β-thalassemia patients, and determine whether a genotype-based scoring system could be used to predict phenotype, a total of 224 Iraqi patients with molecularly characterized homozygous or compound heterozygous β-thalassemia were further investigated for α-thalassemia deletions as well as five polymorphisms namely: rs7482144 C > T at HBG2, rs1427407 G > T and rs10189857 A > G at BCL11A, and rs28384513 A > C and rs9399137 T > C at HMIP. The enrolled patients had a median age of 14 years, with 96 males and 128 females. They included 144 thalassemia major, and 80 thalassemia intermedia patients. Multivariate logistic regression analysis revealed that a model including sex and four of these genetic modifiers, namely: β+ alleles, HBG2 rs7482144, α-thalassemia deletions, and BCL11A rs1427407 could significantly predict phenotype (major versus intermedia) with an overall accuracy of 83.9%. Furthermore, a log odds genetic score based on these significant predictors had a highly significant area under curve of 0.917 (95% CI 0.882-0.953). This study underscores the notion that genetic scoring systems should be tailored to populations in question, since genetic modifiers (and/or their relative weight) vary between populations. The population-oriented genetic scoring system created by the current study to predict β-thalassemia phenotype among Iraqis may pave the way to personalized medicine in this patient's group.

Impact of Genetic Polymorphisms in Modifier Genes in Determining Fetal Hemoglobin Levels in Beta-Thalassemia

Genetic polymorphisms in Quantitative Trait Loci (QTL) genes such as BCL11A, HBS1L-MYB and KLF1 have been reported to influence fetal hemoglobin (HbF) levels. This prospective study was planned to evaluate the role of genetic polymorphisms in QTL genes as determinant of HbF levels in beta thalassemia major patients. The study was carried out on 100 thalassemia major patients. Blood samples were collected in EDTA and plain vials for biochemical and molecular evaluation. The BCL11A, HBS1L-MYB and KLF1 genotypes were determined using a polymerase chain reaction (PCR)-based method. Red Blood Cell (RBC) indices and HbF levels were assessed. In silico analysis was assessed using loss-of-function tool (Lof Tool). Statistical difference and genetic comparisons between groups were evaluated by using SPSS for Windows, version 16.0 (SPSS Inc., Chicago, IL, USA). Comparisons between quantitative variables were carried out after data explored for normality using Kolmogorov–Smirnov test of normality. Logistic regression was used for computation of ORs and 95% CIs (Confidence Interval). We observed association of HbF levels in thalassemia major patients with the polymorphisms in BCL11A (rs11886868 rs7557939; rs1427407 and rs766432) and HBS1L-MYB (rs9399137) gene. The results of this study indicated that the presence of polymorphisms on modifier genes are strongly associated with an increase in HbF levels in thalassemia major patients. Further research with a larger sample size and with other genes of modifier genes is required.

The rs368698783 (G>A) Polymorphism Affecting LYAR Binding to the Aγ-Globin Gene Is Associated with High Fetal Hemoglobin (HbF) in β-Thalassemia Erythroid Precursor Cells Treated with HbF Inducers

The human homologue of mouse Ly-1 antibody reactive clone protein (LYAR) is a putative novel regulator of γ-globin gene transcription. The LYAR DNA-binding motif (5′-GGTTAT-3′) is located within the 5′-UTR of the Aγ-globin gene. The LYAR rs368698783 (G>A) polymorphism is present in β-thalassemia patients and decreases the LYAR binding efficiency to the Aγ-globin gene. The objective of this study was to stratify β-thalassemia patients with respect to the rs368698783 (G>A) polymorphism and to verify whether their erythroid precursor cells (ErPCs) differentially respond in vitro to selected fetal hemoglobin (HbF) inducers. The rs368698783 (G>A) polymorphism was detected by DNA sequencing, hemoglobin production by HPLC, and accumulation of globin mRNAs by RT-qPCR. We found that the LYAR rs368698783 (G>A) polymorphism is associated with high basal and induced production of fetal hemoglobin in β-thalassemia patients. The most striking association was found using rapamycin as an HbF inducer. The results presented here could be considered important not only for basic biomedicine but also in applied translational research for precision medicine in personalized therapy of β-thalassemia. Accordingly, our data suggest that the rs368698783 polymorphism might be considered among the parameters useful to recruit patients with the highest probability of responding to in vivo hydroxyurea (HU) treatment.

Risk Association, Linkage Disequilibrium, and Haplotype Analyses of β-Like Globin Gene Polymorphisms with Malaria Risk in the Sabah Population of Malaysian Borneo

Single nucleotide polymorphisms (SNPs) in the β-like globin gene of the human hosts to the risk of malaria are unclear. Therefore, this study investigates these associations in the Sabah population, with a high incidence of malaria cases. In brief, DNA was extracted from 188 post-diagnostic blood samples infected with Plasmodium parasites and 170 healthy controls without a history of malaria. Genotyping of the β-like globin C-158T, G79A, C16G, and C-551T SNPs was performed using a polymerase chain reaction-restriction fragment length polymorphism approach. Risk association, linkage disequilibrium (LD), and haplotype analyses of these SNPs were assessed. This study found that the variant allele in the C-158T and C16G SNPs were protective against malaria infections by 0.5-fold, while the variant allele in the G79A SNP had a 6-fold increased risk of malaria infection. No SNP combination was in perfect LD, but several haplotypes (CGCC, CGCT, and CGGC) were identified to link with different correlation levels of malaria risk in the population. In conclusion, the C-158T, G79A, and C16G SNPs in the β-like globin gene are associated with the risk of malaria. The haplotypes (CGCC, CGCT, and CGGC) identified in this study could serve as biomarkers to estimate malaria risk in the population. This study provides essential data for the design of malaria control and management strategies.

EF Bart's Disease with Coinheritance of Gγ-XmnI and Aγ-Globin Polymorphisms: A Case of Nontransfusion-Dependant Thalassemia

EF Bart's disease is a rare form of nontransfusion-dependant thalassemia (NTDT) due to the coinheritance of homozygous hemoglobin E (β^E/β^E) genotype with hemoglobin H disease. These individuals are routinely found to have thalassemia intermedia with moderate anemia, increased hemoglobin Bart's and hemoglobin F on electrophoresis. The contribution of hemoglobin F-inducing polymorphisms in this disease has not been described previously. Here, we describe the hematological profile in a young child with coinheritance of Gγ-XmnI and Aγ-globin gene polymorphisms in EF Bart's disease. Interestingly, in this rare form of NTDT, normal HbF and elevated HbA2 were noted.

Fifteen Cases of Hb J-Meerut: The Rare Association with Hb E and/or HBA1: c.-24C>G (or HBA2) Variants

Hb J-Meerut [HBA2: c.362C>A (or HBA1)] is a rare, stable, nonpathogenic α-globin gene variant that peaks in the area between the P3 and A₀ windows on high performance liquid chromatography (HPLC). Few cases from different ethnic origins have been published but the majority were Asian Indians. Coinheritance with other hemoglobin (Hb) variants are rarer and can change the Hb J-Meerut phenotype making a diagnostic dilemma. In this study, we have reported 15 cases of Hb J-Meerut, discovered during a wide spectrum study of α-globin chain variants in the UK. The diagnosis was confirmed by forward and reverse DNA sequencing of the α1- and α2-globin genes. The average of the Hb J-Meerut expression was 20.9% of total Hb and characterized by a retention time (RT) of 1.9 min. (on average) on HPLC. The median of isoelectric focusing (IEF) was 5.6 mm above Hb A. Among the 15 cases studied, one case coinherited the Hb E (HBB: c.79G>A) mutation in heterozygosity and another case was associated with the Cap +14 (C>G) [HBA1: c.-24C>G (or HBA2)] variant. We noticed that the coinheritance of the Hb E mutation reduced the Hb J-Meerut expression with the formation of a hybrid peak missed on the HPLC chromatograph. We also noticed an increased expression of Hb J-Meerut in the case showing the coinheritance of the HBA2: c.-24C>G (or HBA1) variant.

The Effect of Five Single Nucleotide Polymorphisms on Hb F Variation of β-Thalassemia Traits and Hematologically Normal Individuals in Southeast Turkey

β-Thalassemia (β-thal) is caused by deficiency of β-globin chain synthesis and leads to the accumulation of unstable globin chain production. This results in a higher Hb F level in order to neutralize the excess α chains. In addition, γ-globin gene expression, due to genetic factors after birth, leads to increased Hb F levels in adulthood [hereditary persistence of fetal hemoglobin (Hb) (HPFH)]. In this study, the relationship between β-thal trait and individuals with suspected HPFH and a control group was investigated in Adıyaman, Turkey. Single nucleotide polymorphism (SNP) analyses were performed in five different polymorphic regions using real-time polymerase chain reaction (qPCR) methods [rs4671393 (G>A), rs766432 (A>C), rs9402686 (G>A), rs28384513 (T>G), rs1609812 (A>G)]. No significant difference was found between the control and β-thal group in the codominant inheritance model in the rs1609812 (A>G) polymorphism region only, while all the other polymorphic regions were found to be statistically significant. It was found that different genotype models increased Hb F levels between 1.6- and 3.06-fold in four studied polymorphic regions [rs4671393 (G>A), rs766432 (A>C), rs9402686 (G>A), rs28384513 (T>G)]. All of the polymorphic regions increased the Hb F levels from 1.86- to 24.76-fold, except rs9402686 (G>A) and rs28384513 (T>G) over dominant and rs1609812 (A>G) codominant inheritance models. The AC and AA genotypes increased Hb F levels in the B-cell CLL/lymphoma 11 A haplotype studies. It was determined that both haplotypes 2 and 4 increased Hb F levels. As a result, SNPs strongly affect the Hb F levels in both healthy individuals and β-thal trait.

Functional polymorphisms of BCL11A and HBS1L-MYB genes affect both fetal hemoglobin level and clinical outcomes in a cohort of children with sickle cell anemia

Fetal hemoglobin (HbF) ameliorates clinical severity of sickle cell anemia (SCA). The major loci regulating HbF levels are HBB cluster, BCL11A, and HMIP-2 (HBS1L-MYB). However, the impact of noncoding single-nucleotide polymorphisms (SNPs) in these loci on clinical outcomes and their functional role on regulating HbF levels should be better elucidated. Therefore, we performed comprehensive association analyses of 14 noncoding SNPs in five loci with HbF levels and with clinical outcomes in a cohort of 250 children with SCA from Southeastern Brazil, and further performed functional annotation of these SNPs. We found SNPs independently associated with HbF levels: rs4671393 in BCL11A (β-coefficient = 0.28), rs9399137 in HMIP-2A (β-coefficient = 0.16), and rs4895441 in HMIP-2B (β-coefficient = 0.15). Patients carrying minor (HbF-boosting) alleles for rs1427407, rs93979137, rs4895441, rs9402686, and rs9494145 showed reduced count of reticulocytes (p < 0.01), while those carrying the T allele of rs9494145 showed lower white blood cell count (p = 0.002). Carriers of the minor allele for rs9402686 showed higher peripheral saturation of oxygen (p = 0.002). Patients carrying minor alleles in BCL11A showed lower risk of transfusion incidence rate ratio (IRR ≥ 1.3; p < 0.0001). This effect was independent of HbF effect (p = 0.005). Carriers of minor alleles for rs9399137 and rs9402686 showed lower risk of acute chest syndrome (IRR > 1.3; p ≤ 0.01). Carriers of the reference allele for rs4671393 showed lower risk of infections (IRR = 1.16; p = 0.01). In conclusion, patients carrying HbF-boosting alleles of BCL11A and HMIP-2 were associated with milder clinical phenotypes. Higher HbF concentration may underlie this effect.

Association between Different Polymorphic Markers and β-Thalassemia Intermedia in Central Iran

β-Thalassemia intermedia (β-TI) is a clinical condition characterized by moderate, non transfusional anemia and hepatosplenomegaly. The main objective of this study was to determine the molecular basis of the clinical phenotype of β-TI in Iran. To elucidate the mild phenotype of many patients with β-TI, we screened for three prevalent β-globin gene mutations [IVS-II-1 (G>A) HBB: c.315+1G>A, IVS-I-110 (G>A) HBB: c.93-21G>A and IVS-I-5 (G>C) [HBB: c.92+5G>C], deletions on the α-globin genes, XmnI polymorphisms and restriction fragment length polymorphism (RFLP) haplotypes on the β-globin gene cluster in 50 β-TI patients. Fifty-eight percent of the patients (29 cases) were associated with the mentioned mutations. We showed that the HBB: c.315+1G>A mutation is linked to haplotype [+ - + +] (57.69%). This haplotype is in linkage disequilibrium with the XmnI polymorphism (NG_000007.3: g.42677C>T) and has been associated with increased expression of Hb F in β-TI patients. The XmnI polymorphism is defined in association with this prevalent mutation. Two patients had a single α-globin gene deletion [-α^3.7 (rightward) deletion]. The main genetic factor in mild phenotype β-TI patients is the linkage of an XmnI polymorphism (NG_000007.3: g.42677C>T) with the HBB: c.315+1G>A (80.76%), which is associated with increased production of Hb F and coinheritance of haplotype [+ - + +] with β-TI, especially with the homozygous HBB: c.315+1G>A mutation. Molecular basis of β-TI could be explained by the involvement of different factors that tend to develop the disease phenotype.

Surface plasmon resonance based analysis of the binding of LYAR protein to the rs368698783 (G>A) polymorphic Aγ-globin gene sequences mutated in β-thalassemia

Recent studies have identified and characterized a novel putative transcriptional repressor site in a 5' untranslated region of the Aγ-globin gene that interacts with the Ly-1 antibody reactive clone (LYAR) protein. LYAR binds the 5'-GGTTAT-3' site of the Aγ-globin gene, and this molecular interaction causes repression of gene transcription. In β-thalassemia patients, a polymorphism has been demonstrated (the rs368698783 G>A polymorphism) within the 5'-GGTTAT-3' LYAR-binding site of the Aγ-globin gene. The major results gathered from surface plasmon resonance based biospecific interaction analysis (SPR-BIA) studies (using crude nuclear extracts, LYAR-enriched lysates, and recombinant LYAR) support the concept that the rs368698783 G>A polymorphism of the Aγ-globin gene attenuates the efficiency of LYAR binding to the LYAR-binding site. This conclusion was fully confirmed by a molecular docking analysis. This might lead to a very important difference in erythroid cells from β-thalassemia patients in respect to basal and induced levels of production of fetal hemoglobin. The novelty of the reported SPR-BIA method is that it allows the characterization and validation of the altered binding of a key nuclear factor (LYAR) to mutated LYAR-binding sites. These results, in addition to theoretical implications, should be considered of interest in applied pharmacology studies as a basis for the screening of drugs able to inhibit LYAR-DNA interactions. This might lead to the identification of molecules facilitating induced increase of γ-globin gene expression and fetal hemoglobin production in erythroid cells, which is associated with possible reduction of the clinical severity of the β-thalassemia phenotype. Graphical abstract.

Molecular Analysis of Non-Transfusion Dependent Thalassemia Associated with Hemoglobin E-β-Thalassemia Disease without α-Thalassemia

Background

The finding of many Thai Hb E-β⁰-thalassemia patients with non-transfusion dependent thalassemia (NTDT) phenotype without co-inheritance of α-thalassemia has prompted us to investigate the existence of other genetic modifying factors.

Methods

Study was done on 122 adult Thai patients with NTDT Hb E-β-thalassemia patients without co-inheritance of α-thalassemia. Multiple single-nucleotide polymorphisms (SNPs) associated with γ-globin gene expression including the ^Gγ-XmnI of HBG2 gene, rs2297339, rs4895441, and rs9399137 of the HBS1L-MYB gene, rs4671393 in the BCL11A gene, and G176AfsX179, T334R, R238H and −154 (C-T) in the KLF1 gene were investigated using PCR and related techniques.

Results

Heterozygous and homozygous for ^Gγ-XmnI of HBG2 gene were detected at 70.5% and 7.4%, respectively. Further DNA analysis identified the rs2297339 (C-T), rs4895441 (A-G), and rs9399137 (T-C) of HBS1L-MYB gene in 86.9%, 25.4%, and 23.0%, respectively. The rs4671393 (G-A) of the BCL11A gene was found at 31.2%. For the KLF1 gene, only T334R was detected at 9.0%.

Conclusions

It was found that these SNPs, when analyzed in combination, could explain the mild phenotypic expression of all cases. These results underline the importance of these informative SNPs on phenotypic expression of Hb E-β-thalassemia patients.

Molecular characterization of β-thalassemia intermedia in the West Bank, Palestine

BACKGROUND

We aimed to investigate the molecular basis of β-Thalassemia intermedia (TI) in the West Bank region and its management practices.

METHODS

This was a case series multi-center study and included 51 cases of TI. DNA sequencing was used to analyze β-globin gene mutations. Common α-globin gene mutations were screened by Gap-PCR (-α3.7, -α4.2, --MED, αααanti3.7) or DNA sequencing (α2-IVS II 5 nt del). XmnI -158 C > T polymorphisms of Gγ-globin gene was determined by RFLP-PCR.

RESULTS

Seven β-globin gene mutations were observed, namely IVS-I -6 C > T, IVS-I-110 G > A, IVS-II-1 G > A, IVS-I-1 G > A, Codon 37 Trp > Stop, beta - 101 and IVS-II-848 C > A. Ten genotypes were observed. Homozygosity for IVS-I-6 accounted for the majority of TI cases with a frequency of 74.5%. The second common β-globin gene genotype was homozygote IVS-I-110 G > A (5.8%) and homozygote IVS-II-1 G > A (5.8%). The remaining seven genotypes were each detected in about 2% of patients. α-Thalassemia mutations were seen in five patients (9.8%), and included (-α3.7, αααanti3.7 and α2-IVSII-5 nt del). XmnI polymorphism was observed in four patients (7.8%), three homozygotes and one heterozygote.

CONCLUSIONS

Homozygosity for the mild β-globin gene IVS-I-6 allele was the major contributing factor for the TI phenotype among the study subjects. The role of XmnI SNP and α-thalassemia mutations in ameliorating the TI phenotype was observed in few patients for each factor. The beta - 101 C > T mutation was diagnosed in one patient in homozygote state for the first time in Palestine.

Study on the Role of Polymorphisms of the SOX-6 and MYB Genes and Fetal Hemoglobin Levels in Sicilian Patients with β-Thalassemia and Sickle Cell Disease

The hemoglobinopathies, as β-thalassemia (β-thal) and sickle cell disease, are the most common hereditary hemolytic anemias. The increase of fetal hemoglobin (Hb F) levels can ameliorate the symptoms of hemoglobinopathies. There are several transcription factors such as MYB and SOX-6, which are involved in the regulation of Hb F. There are not enough studies investigating the association between single nucleotide polymorphisms (SNPs) of the SOX-6 and MYB genes and the variation of Hb F levels in patients affected by sickle cell disease and β-thal. We therefore decided to analyze the role of four missense variants of MYB and SOX-6 genes in the regulation of Hb F levels. In order to do so, we examinated 30 Sicilian patients affected by sickle cell disease and β-thal, to understand if these variants could also have an influence in our populations. Comparing two groups of patients with low and high levels of Hb F, we found no significant differences in the genetic distribution and allelic frequency of MYB and SOX-6 gene polymorphisms. We also created and compared a 'high producer' and 'low producer' genotype with different genes achieving the same result of no significant difference. Our results may be due either to the fact that the association between these genes and the regulation of Hb F levels are influenced by environmental history and population genetics, or to the small number of samples being analyzed.

Genetic determinants related to pharmacological induction of foetal haemoglobin in transfusion-dependent HbE-β thalassaemia

Thalassaemia are the most common inherited autosomal recessive single gene disorders characterized by chronic hereditary haemolytic anaemia due to the absence or reduced synthesis of one or more of the globin chains. Haemoglobin E-β thalassaemia is the genotype responsible for approximately one half of all severe beta-thalassaemia worldwide. This study proposes to evaluate the effect of various molecular parameters on the response of hydroxyurea. Hydroxyurea was started at an initial dose of 10 mg/kg of body weight/day on 110 transfusion-dependent HbE-β thalassaemia patients. HbF level was measured by HPLC analysis. β-Thalassaemia mutations, XmnI and five other SNPs, and α-globin gene deletions and triplications were detected by ARMS-PCR, RFLP-PCR and Gap-PCR, respectively. Based on the factors for evaluating hydroxyurea-response, 42 patients were responders as they showed an increment of Hb from a mean baseline value of 6.45 g/dl (± 0.70) to 7.78 g/dl (± 0.72) post-therapy. Based on increase in HbF above the median value (14.72%) post-therapy, 78 patients were found to be responders. All the 78 responders showed mean decrease in transfusion of 74.26% (± 8.32) with a maximum decrease of 98.43%. There was a significant correlation between decrease in transfusion and increase in HbF level for all 78 responders. XmnI polymorphism showed the strongest association (p < 0.0001) with increase in HbF levels and Hb levels. Patients with α-globin gene deletions were better responders. It was concluded that hydroxyurea treatment is effective in transfusion-dependent HbE-β thalassaemia patients and the response is best in patients having both XmnI polymorphism and α-deletion.

An Aγ-globin G->A gene polymorphism associated with β039 thalassemia globin gene and high fetal hemoglobin production

BACKGROUND

Increase of the expression of γ-globin gene and high production of fetal hemoglobin (HbF) in β-thalassemia patients is widely accepted as associated with a milder or even asymptomatic disease. The search for HbF-associated polymorphisms (such as the XmnI, BCL11A and MYB polymorphisms) has recently gained great attention, in order to stratify β-thalassemia patients with respect to expectancy of the first transfusion, need for annual intake of blood, response to HbF inducers (the most studied of which is hydroxyurea).

METHODS

Aγ-globin gene sequencing was performed on genomic DNA isolated from a total of 75 β-thalassemia patients, including 31 β⁰39/β⁰39, 33 β⁰39/β⁺IVSI-110, 9 β⁺IVSI-110/β⁺IVSI-110, one β⁰IVSI-1/β⁺IVSI-6 and one β⁰39/β⁺IVSI-6.

RESULTS

The results show that the rs368698783 polymorphism is present in β-thalassemia patients in the 5'UTR sequence (+25) of the Aγ-globin gene, known to affect the LYAR (human homologue of mouse Ly-1 antibody reactive clone) binding site 5'-GGTTAT-3'. This Aγ(+25 G->A) polymorphism is associated with the Gγ-globin-XmnI polymorphism and both are linked with the β⁰39-globin gene, but not with the β⁺IVSI-110-globin gene. In agreement with the expectation that this mutation alters the LYAR binding activity, we found that the Aγ(+25 G->A) and Gγ-globin-XmnI polymorphisms are associated with high HbF in erythroid precursor cells isolated from β⁰39/β⁰39 thalassemia patients.

CONCLUSIONS

As a potential explanation of our findings, we hypothesize that in β-thalassemia the Gγ-globin-XmnI/Aγ-globin-(G->A) genotype is frequently under genetic linkage with β⁰-thalassemia mutations, but not with the β⁺-thalassemia mutation here studied (i.e. β⁺IVSI-110) and that this genetic combination has been selected within the population of β⁰-thalassemia patients, due to functional association with high HbF. Here we describe the characterization of the rs368698783 (+25 G->A) polymorphism of the Aγ-globin gene associated in β⁰39 thalassemia patients with high HbF in erythroid precursor cells.

Existence of HbF Enhancer Haplotypes at HBS1L-MYB Intergenic Region in Transfusion-Dependent Saudi β-Thalassemia Patients

Background and Objectives. β-Thalassemia and sickle cell disease are genetic disorders characterized by reduced and abnormal β-globin chain production, respectively. The elevation of fetal hemoglobin (HbF) can ameliorate the severity of these disorders. In sickle cell disease patients, the HbF level elevation is associated with three quantitative trait loci (QTLs), BCL11A, HBG2 promoter, and HBS1L-MYB intergenic region. This study elucidates the existence of the variants in these three QTLs to determine their association with HbF levels of transfusion-dependent Saudi β-thalassemia patients. Materials and Methods. A total of 174 transfusion-dependent β-thalassemia patients and 164 healthy controls from Eastern Province of Saudi Arabia were genotyped for fourteen single nucleotide polymorphisms (SNPs) from the three QTL regions using TaqMan assay on real-time PCR. Results. Genotype analysis revealed that six alleles of HBS1L-MYB QTL (rs9376090C p = 0.0009, rs9399137C p = 0.008, rs4895441G p = 0.004, rs9389269C p = 0.008, rs9402686A p = 0.008, and rs9494142C p = 0.002) were predominantly associated with β-thalassemia. In addition, haplotype analysis revealed that haplotypes of HBS1L-MYB (GCCGCAC p = 0.022) and HBG2 (GTT p = 0.009) were also predominantly associated with β-thalassemia. Furthermore, the HBS1L-MYB region also exhibited association with the high HbF cohort. Conclusion. The stimulation of HbF gene expression may provide alternative therapies for the amelioration of the disease severity of β-thalassemia.

Structural and Functional Insights on an Uncharacterized Aγ-Globin-Gene Polymorphism Present in Four β0-Thalassemia Families with High Fetal Hemoglobin Levels

INTRODUCTION

Several DNA polymorphisms have been associated with high production of fetal hemoglobin (HbF), although the molecular basis is not completely understood. In order to identify and characterize novel HbF-associated elements, we focused on five probands and their four families (from Egypt, Iraq and Iran) with thalassemia major (either β(0)-IVSII-1 or β(0)-IVSI-1) and unusual HbF elevation (>98 %), congenital or acquired after rejection of bone marrow transplantation, suggesting an anticipated favorable genetic background to high HbF expression.

METHODS

Patient recruitment, genomic DNA sequencing, western blotting, electrophoretic mobility shift assays, surface plasmon resonance (SPR) biospecific interaction analysis, bioinformatics analyses based on docking experiments.

RESULTS

A polymorphism of the Aγ-globin gene is here studied in four families with β(0)-thalassemia (β(0)-IVSII-1 and β(0)-IVSI-1) and expressing unusual high HbF levels, congenital or acquired after rejection of bone marrow transplantation. This (G→A) polymorphism is present at position +25 of the Aγ-globin genes, corresponding to a 5'-UTR region of the Aγ-globin mRNA and, when present, is physically linked in chromosomes 11 of all the familiar members studied to the XmnI polymorphism and to the β(0)-thalassemia mutations. The region corresponding to the +25(G→A) polymorphism of the Aγ-globin gene belongs to a sequence recognized by DNA-binding protein complexes, including LYAR (Ly-1 antibody reactive clone), a zinc-finger transcription factor previously proposed to be involved in down-regulation of the expression of γ-globin genes in erythroid cells.

CONCLUSION

We found a novel polymorphism of the Aγ-globin gene in four families with β(0)-thalassemia and high levels of HbF expression. Additionally, we report evidence suggesting that the Aγ-globin gene +25(G→A) polymorphism decreases the efficiency of the interaction between this sequence and specific DNA binding protein complexes.

Molecular Understanding of Non-Transfusion-Dependent Thalassemia Associated with Hemoglobin E-β-Thalassemia in Northeast Thailand

Non-transfusion-dependent thalassemia (NTDT) is associated with various forms of thalassemia and genetic modifiers. We report the molecular basis of NTDT in hemoglobin (Hb) E-β-thalassemia disease. This study was done in 73 adult patients encountered at the prenatal diagnosis center of Khon Kaen University, Northeast Thailand. Hematological parameters and Hb patterns were collected, and α- and β-globin gene mutations were determined. Multiple single-nucleotide polymorphisms (SNPs) including the rs7482144/Gγ-XmnI polymorphism, rs2297339, rs2838513, rs4895441, and rs9399137 in the HBS1L-MYB gene, rs4671393 and rs11886868 in the BCL11A gene, and G176AfsX179 in the KLF1 gene were examined. Five β0-thalassemia mutations and a severe β+-thalassemia mutation in trans to the βE gene were identified. No significant difference in hematological parameters was observed among β-thalassemia genotypes. Coinheritance of α-thalassemia was observed in 31 of the 73 subjects (42.5%). Four SNPs including Gγ-XmnI, rs2297339, rs4895441, and rs9399137 of HBS1L-MYB were found to be associated with high Hb F levels in 39 (53.4%) subjects. The molecular basis of NTDT in the remaining 3 (4.1%) cases could not be defined. These results indicate multiple genetic factors in NTDT patients and underline the importance of complete genotyping to provide proper management, make clinical predictions, and improve genetic counseling.

The Impact of XmnI-HBG2, BCL11A and HBS1L-MYB Single Nucleotide Polymorphisms on Hb F Variation of Hematologically Normal Iranian Individuals

The impact of Hb F on severity of sickle cell disease and β-thalassemia (β-thal) is well documented. The XmnI-HBG2, BCL11A and HBS1L-MYB single nucleotide polymorphisms (SNPs) have been introduced as the most important factors causing variation in fetal hemoglobin (Hb F) levels in different population studies. However, the extent of their effect could be population-specific. In this study, multivariate linear regression analysis was used to evaluate the association of Hb F with age, sex, and eight SNPs, including XmnI-HBG2, four BCL11A, two HBS1L-MYB SNPs and the polymorphic palindromic 5' hypersensitive 4-locus control region (5'HS4-LCR). One hundred and twenty-two hematologically normal individuals, from a previous study cohort, constituted our study population. In multivariate regression analyses, no association of Hb F was observed with age or sex of the individuals and SNPs in this study. We conducted a univariate regression analysis to further investigate the results, which among all the factors only detected XmnI-HBG2 and 5'HS4 SNPs as significant modifiers of Hb F. The significance of these two factors disappeared in a bivariate analysis. These results suggest that either XmnI-HBG2 or 5'HS4-LCR have a stronger contribution in Hb F variations of the Iranian population than BCL11A and HBS1L-MYB SNPs. Furthermore, the effect of low population size and technical limitations on obtained results could not be ruled out.

Current and future alternative therapies for beta-thalassemia major

Beta-thalassemia is a group of frequent genetic disorders resulting in the synthesis of little or no β-globin chains. Novel approaches are being developed to correct the resulting α/β-globin chain imbalance, in an effort to move beyond the palliative management of this disease and the complications of its treatment (e.g. life-long red blood cell transfusion, iron chelation, splenectomy), which impose high costs on healthcare systems. Three approaches are envisaged: fetal globin gene reactivation by pharmacological compounds injected into patients throughout their lives, allogeneic hematopoietic stem cell transplantation (HSCT), and gene therapy. HSCT is currently the only treatment shown to provide an effective, definitive cure for β-thalassemia. However, this procedure remains risky and histocompatible donors are identified for only a small fraction of patients. New pharmacological compounds are being tested, but none has yet made it into common clinical practice for the treatment of beta-thalassemia major. Gene therapy is in the experimental phase. It is emerging as a powerful approach without the immunological complications of HSCT, but with other possible drawbacks. Rapid progress is being made in this field, and long-term efficacy and safety studies are underway.

Clinical, Hematological and Molecular Analysis of Homozygous Hb E (HBB: c.79G > A) in the Indian Population

Homozygous Hb E [β26(B8)Glu→Lys; HBB: c.79G > A] is a clinically mild disease with no significant symptoms. Very few studies are available on clinical variability in Hb E disorders. We report the profile of a series of homozygous Hb E patients in the Indian population. We analyzed various genetic factors that contribute to the heterogeneity in the phenotype of homozygous Hb E patients. Analysis of these parameters further enhances our understanding of the Hb E syndrome.

Recent patents and technology transfer for molecular diagnosis of β-thalassemia and other hemoglobinopathies

INTRODUCTION

Biological tests and genetic analyses for diagnosis and characterization of hematological diseases in health laboratories are designed with the aim of meeting the major medical needs of hospitals and pharmaceutical companies involved in this field of applied biomedicine. Genetic testing approaches to perform diagnosis consist of molecular techniques, which should be absolutely reproducible, fast, sensitive, cheap, and portable.

AREAS COVERED

Biological tests analyzed involve adult/newborn subjects, whereas genetic analyses involve adult thalassemia patients, newborns, embryos/fetuses (including non-invasive prenatal diagnosis), pre-implantation embryos, and pre-fertilization oocytes.

EXPERT OPINION

The most recent findings in the diagnostic approach for β-thalassemias are related to three major fields of investigation: moving towards ultrasensitive methodologies for effective detection of the primary causative mutation of β-thalassemia, including the development of polymerase chain reaction-free approaches and non-invasive prenatal diagnosis; comparing analyses of the genotype of β-thalassemia patients to high-HbF-associated polymorphisms; introducing whole genome association assays and next-generation sequencing. All these issues should be considered and discussed in the context of several aspects, including regulatory, ethical and social issues. DNA sequence data aligned with the identification of genes central to the induction, development, progression, and outcome of β-thalassemia will be a key point for directing personalized therapy.

Genetics of fetal hemoglobin in tribal Indian patients with sickle cell anemia

India tops the list of countries with sickle cell disease (SCD) with an estimated 44,000 live births in 2010 and a prevalence of 10%-33%. In the present study, the first from India, we have investigated the effect of genetic variants in the BCL11A, the HMIP (HBS1L-MYB intergenic polymorphism) locus, in addition to the HBB locus, which are known to be associated with fetal hemoglobin (HbF) levels, a major modulator of the disease phenotype. The present study was conducted on 240 individuals with SCD and 60 with sickle cell trait. Genotyping was performed for the BCL11A rs11886868 and rs34211119; HMIP rs9399137, rs189600565, rs7776196, rs34778774, and rs53293029; HBG2 Xmn1 polymorphism rs7482144; and -68C > T HBD promoter polymorphism. All the 3 quantitative trait loci were associated with HbF levels in Indian patients with SCD. The highest difference was seen in the Xmn1 single-nucleotide polymorphism, which accounted for 11% of the trait variance, the BCL11A rs11886868 for 3.65%, whereas the HMIP rs9399137 for 3.8%. The present study indicates the BCL11A, HMIP, and β-globin region to be associated with increased HbF levels in Indian patient. Further interrogation of these genotypes with respect to pain crisis is warranted in this population, which may help in prognostication, as also a genome-wide association study, which may help uncover new loci controlling HbF levels.

Role of XmnIgG Polymorphism in Hydroxyurea Treatment and Fetal Hemoglobin Level at Isfahanian Intermediate β-Thalassemia Patients

BACKGROUND

β-thalassemia is the most common monogenic disorder in human. The (C-->T) polymorphism at -158 upstream region of the γG-globin gene and pharmacological factors such as hydroxyurea have been reported to influence γ-globin gene expression and the severity of clinical symptoms of β-thalassemia.

METHODS

In the present study, 51 β-thalassemia intermediate patients were studied. Xmn1γG polymorphism genotype was determined using Tetra-Primer ARMS-PCR technique. Hemoglobin (Hb) and fetal hemoglobin (HbF) levels were determined by gel electrophoresis.

RESULTS

Of 51 patients, 35 (68.6%) patients were heterozygous (CT) and 16 (31.4%) patients were homozygous (CC). Of 30 patients under treatment by hydroxyurea, 20 (66.7%) patients were heterozygous (CT) and 10 (33.3%) patients were homozygous (CC). Our results demonstrated that in the heterozygous (CT) genotype, the Hb (9.58 ± 1.25 gm/dl) and HbF (89.30 ± 21.87) levels were significantly higher in comparison with homozygous (CC) genotype (7.94 ± 1.34 gm/dl and 70.32 ± 40.56, respectively). Furthermore, we observed that after drug usage, the Hb and HbF levels in patients with heterozygous (CT) genotype (0.7 ± 1.26 gm/dl and 5.95 ± 14.8, respectively) raised more in comparison with homozygous (CC) genotype (0.26 ± 1.43 gm/dl and 0.8 ± 1.31, respectively).

CONCLUSION

Hb and HbF levels in the patients carrying T allele are increased significantly, and they also response to hydroxyurea treatment.

Genetic Modifiers in β-Thalassemia Intermedia: A Study on 102 Iraqi Arab Patients

To determine the molecular basis of β-thalassemia intermedia (TI) and the contribution of the three hemoglobin F (HbF) quantitative trait loci (QTLs) on chromosomes 11, 2, and 6 to the milder phenotype, a total of 102 Iraqi Arab patients with TI were studied. The β and α genotypes as well as HBG2 g. 158 C>T (rs7482144), BCL11A (rs1427407 and rs10189857), and HBS1L-MYB (rs28384513 and rs9399137) by multiplex polymerase chain reaction and reverse hybridization were studied. A total of 21 different β-thalassemia mutations arranged in 35 different genotypes were identified. The genotypes encompassed β(+)/β(+) mutations in 33 cases, β(+)/β(0) in 17 cases, β(0)/β(0) in 47 cases, β(0)/wild type in 3 and β(0)/Hb E in 2 cases. The most common was IVS-II-1 (G>A)/IVS-II-1 (G>A), followed by IVS-I-6 (T>C)/IVS-I-6 (T>C) and IVS-I-110 (G>A)/IVS-I-110 (G>A), in 31.4%, 17.6%, and 6.9%, respectively. Alpha-thalassemia mutations were found in 15.2% of those homozygous for the β-mutations, while α gene triplication was identified in all three heterozygotes. Of the five QTLs tested, only rs7482144 and rs10189857 were significantly associated with β(0)/β(0) when compared to β(+)/β(+), with odds ratios of 6.4 (95% confidence interval [CI] 2.9-14.0) and 3.2 (95% CI 1.2-8.6), respectively. In conclusion, this study has demonstrated that among Iraqi patients with thal intermedia, the main contributors to the milder phenotype were β(+) alleles, XmnI polymorphism, and BCL11A (rs10189857), while other QTLs on chromosomes 2 and 6, as well as alpha-thalassemia, were not significantly relevant.

Genetic variant in the BCL11A (rs1427407), but not HBS1-MYB (rs6934903) loci associate with fetal hemoglobin levels in Indian sickle cell disease patients

India along with Nigeria and DRC contribute to 57% of the world sickle cell anemia population. The annual number of newborns in India with SCA was estimated at 44,000 in 2010. Even with this high prevalence there is minimal information about genetic factors that influence the disease course in Indian patients. The current study was conducted on 240 patients with SCD and 60 with sickle cell trait, to determine the association of genetic variants at the BCL11A (rs1427407) and HBS1-MYB (rs6934903) loci with fetal hemoglobin levels (HbF). Both these loci have been implicated with influencing HbF levels, a powerful modulator of the clinical and hematologic features of SCD. Our results indicate the BCL11A rs1427407 G>T variant to be significantly associated with HbF levels {19.12±6.61 (GG), 20.27±6.92 (GT) and 24.83±2.92 (TT) respectively} contributing to ~23% of the trait variance. Interestingly no association of the HBS1L-MYB rs6934903 with the HbF levels was seen. The present study indicates the BCL11A (rs1427407) but not HMIP (rs6934903) to be associated with elevated HbF levels in Indian patient. Further interrogation of additional variants at both the loci; as also a GWAS which may help uncover new loci controlling HbF levels.

Combining gene therapy and fetal hemoglobin induction for treatment of β-thalassemia

β-thalassemias are caused by nearly 300 mutations of the β-globin gene, leading to a low or absent production of adult hemoglobin (HbA). Two major therapeutic approaches have recently been proposed: gene therapy and induction of fetal hemoglobin (HbF) with the objective of achieving clinically relevant levels of Hbs. The objective of this article is to describe the development of therapeutic strategies based on a combination of gene therapy and induction of HbFs. An increase of β-globin gene expression in β-thalassemia cells can be achieved by gene therapy, although de novo production of clinically relevant levels of adult Hb may be difficult to obtain. On the other hand, an increased production of HbF is beneficial in β-thalassemia. The combination of gene therapy and HbF induction appears to be a pertinent strategy to achieve clinically relevant results.

Utility of the multivariate approach in predicting β-thalassemia intermedia or β-thalassemia major types In Iranian patients

Recently, five genetic modifiers [β-globin mutations, coinheritance of α-thalassemia (α-thal), XmnI polymorphism and single nucleotide polymorphisms (SNPs) in the BCL11A and HBS1L-MYB loci] were used to predict the β-thal major (β-TM) or β-thal intermedia (β-TI) types in 106 French patients with 83.2% accuracy. The dichotomous grouping was based on the age when the patient received his/her first transfusion (4 years). Here, a similar study was conducted in a cohort of 306 Iranian β-thal patients having distinct β-globin mutations and minor allele frequencies of key SNPs in these loci. Multivariate regression analyses and a simple scoring system were used to predict the β-TM/β-TI types using three scenarios: 1) when considering only the severe β-TM and the mild β-TI cases, 2) using clinical parameters for β-thal typing, and 3) using age at first transfusion as the basis for classification. Using these scenarios, the β-thal types could be correctly predicted in 77.6, 75.5 and 68.0% of cases, respectively.

Hydroxyurea treatment in β-thalassemia patients: to respond or not to respond?

Hydroxyurea (HU) is a drug that induces fetal hemoglobin production. As a result, HU is widely used to treat β-thalassemia (β-thal) patients. However, the response of these patients to HU varies. Some β-thal patients respond favorably to treatment while others do not respond at all. HU has a number of side-effects and therefore its targeted prescription is beneficial. Hence, identifying the genetic determinants which lead to the differential HU response is important. This review summarizes recent findings which have shed light on this topic. Special emphasis is given to the mechanisms and genetic loci which may govern these differences. These findings have helped identify several single nucleotide polymorphisms which associate with the response to HU in both β-thal and sickle cell disease patients.

Effect of a group of genetic markers around the 5' regulatory regions of the β globin gene cluster linked to high HbF on the clinical severity of β thalassemia

The clinical and hematological course of β thalassemia intermedia is influenced by a number of genetic factors which play a role in increasing fetal haemoglobin levels. Several polymorphisms located in the promoters of β and γ globin gene are involved in influencing the disease severity. Our objective was to study the effect of cis-DNA haplotypes, motifs, or polymorphisms (Pre G γ globin gene haplotypes, Aγ-δ intergenic region haplotypes XmnI and (AT)(x)(T)(y) polymorphisms, β-LCR HS2 and HS3 site motifs) that may contribute to higher HbF levels and a milder clinical course. We found that a combination of T haplotype of the Aγ-δ intergenic region, TAG Pre-Gγ haplotype, presence of the XmnI polymorphism along with the (AT)(9)(T)(5) motif constitutes a topography that co-relates with raised HbF levels which may contribute in ameliorating the disease severity.

Influence of BCL11A, HBS1L-MYB, HBBP1 single nucleotide polymorphisms and the HBG2 XmnI polymorphism On Hb F levels

In search of genetic alterations responsible for high fetal hemoglobin (Hb F) phenotypes in the population of eastern India, 91 probands were screened for four polymorphisms by sequencing and/or restriction fragment length polymorphism (RFLP) analysis. These are the A>G allele on the rs4895441 locus in the intergenic region between HBS1L and MYB on chromosome 6, the G>A allele on the rs4671393 locus on chromosome 2 (BCL11A gene), the A>C allele on the rs2071348 (HBBP1 gene) and the XmnI polymorphism (rs7482144, -158 position of HBG2) on chromosome 11. We found a significant association (p = 0.002 and 0.0013) of Hb F levels with rs2071348 and rs4895441, respectively. However, the polymorphism rs4671393 gene did not show significant association with Hb F levels (p = 0.0655). As is well known, the XmnI polymorphism (p <0.0001) showed the strongest association.

What influences Hb fetal production in adulthood?

Human hemoglobin genes are located in α and β globin gene clusters in chromosomes 16 and 11, respectively. Different types of hemoglobin are synthesized according to the stage of development with fetal hemoglobin (α(2)γ(2)) (Hb F) being the main hemoglobin in the fetal period. After birth, there is a reduction (to about 1%) in Hb F levels and adult hemoglobin, Hb A (2α(2)β(2)), increases to more than 96% of total hemoglobin. However, some genetic conditions whether linked to the β-globin gene cluster or not are associated with high Hb F levels in adults. Among those linked to β-globin are hereditary persistence of fetal hemoglobin, delta-beta thalassemia (δβ-Thalassemia) and the XmnI polymorphism (-158 C = T). Other polymorphisms not related to β-globin gene cluster are known to influence the γ-globin gene expression in adulthood. The most relevant polymorphisms that increase concentrations of Hb F are the HMIP locus on chromosome 6, the BCL11A locus on chromosome 2, the Xp22.2 region of the X chromosome and the 8q region on chromosome 8. Findings from our research group studying genetic factors involved in γ-globin gene regulation in adults without anemia in the northwestern region of São Paulo State showed that high Hb F levels are influenced by the presence of hereditary persistence of fetal hemoglobin mutations and the XmnI polymorphism, suggesting that both genetic alterations characterize the molecular basis of the evaluated population.

Alternative options for DNA-based experimental therapy of β-thalassemia

INTRODUCTION

Beta-thalassemias are caused by more than 200 mutations of the β-globin gene, leading to low or absent production of adult hemoglobin. Achievements have been made with innovative therapeutic strategies for β-thalassemias, based on research conducted at the levels of gene structure, transcription, mRNA processing and protein synthesis.

AREAS COVERED

The objective of this review is to describe the development of therapeutic strategies employing viral and non-viral DNA-based approaches for treatment of β-thalassemia.

EXPERT OPINION

Modification of β-globin gene expression in β-thalassemia cells has been achieved by gene therapy, correction of the mutated β-globin gene and RNA repair. In addition, cellular therapy has been proposed for β-thalassemia, including reprogramming of somatic cells to generate induced pluripotent stem cells to be genetically corrected. Based on the concept that increased production of fetal hemoglobin (HbF) is beneficial in β-thalassemia, DNA-based approaches to increase HbF production have been optimized, including treatment of target cells with lentiviral vectors carrying γ-globin genes. Finally, DNA-based targeting of α-globin gene expression has been applied to reduce the excess of α-globin production by β-thalassemia cells, one of the major causes of the clinical phenotype.

Identification of candidate genes involved in clinical variability among Tunisian patients with β-thalassemia

The short tandem repeats (STR) are undoubtedly the most used molecular markers in genetic diversity studies. β-thalassemia is a hereditary hemolytic anemia which is a common health problem all over the world. The disease has two main clinical forms: the severe form or β-thalassemia major (TM) and the moderate form or β-thalassemia intermedia (TI). To help understand this inconsistency, five STR have been studied in a group of 27 β-thalassemic patients divided into 15 (TM) and 12 (TI). For each STR, the distribution of alleles, has been compared among patients with β-thalassemia major (TM) and those with β-thalassemia intermedia (TI).The comparison has shown, for the STR D14S72, one specific allele to (TM) and for the STR D14S990 and D14S68, two specific alleles to TI patients. The combination of these alleles with severe beta-thalassemia genotypes leads to the phenotype of beta-thalassemia intermedia even though there are no any attenuating factors such as XmnI Gg polymorphism at position -158 of the HBG2 promotor or the alpha-globin defects. This suggests that these alleles are associated with factors reducing β-thalassemia clinical effects. One of this STR is located in the 5'UTR of the CEBPε gene which incodes a transcription factor expressed in the myeloid lineage. Thus, the involvement of the transcription factor CEBPε in the myeloid cells suggests that CEBPε is a candidate gene involved in the modulation of the β-thalassemia expression through immune system reactions.

The XmnI and BCL11A single nucleotide polymorphisms may help predict hydroxyurea response in Iranian β-thalassemia patients

Hydroxyurea (HU), a drug which can reactivate fetal hemoglobin (Hb F) production, is frequently prescribed to β-thalassemia (β-thal) patients. However, transfusion requirements of only a subset of patients are reduced upon HU treatment. Because of its potential side-effects, targeted prescription of HU is imperative. To identify genetic markers that correlate with drug response, we have carried out a retrospective association study of single nucleotide polymorphisms (SNPs) in three Hb F quantitative trait loci (QTLs): the XmnI polymorphism, BCL11A, and the HBS1L-MYB intergenic region, with the response to HU in a cohort of 81 transfusion-dependent Iranian β-thal patients. An increase in blood transfusion intervals post-therapy was used to measure drug response. Our results suggest that presence of the XmnI T/T genotype or the BCL11A rs766432 C allele correlates strongly with response to HU (p <0.001). Accordingly, these markers may be used to accurately predict the HU response of Iranian β-thal patients.

Genetic origin and interaction of the Filipino β⁰-thalassemia with Hb E and α-thalassemia in a Thai family

We describe hematologic and molecular characteristics of a hitherto undescribed interaction between the Filipino deletional β⁰-thalassemia with Hb E and α-thalassemia in a Thai family. This study was conducted during the prenatal screening of a pregnant Thai woman and her family members. A prenatal diagnosis was performed at her second pregnancy by amniocentesis. Laboratory investigations identified that the pregnant woman was Hb E heterozygote with α⁺-thalassemia, whereas her husband was a double heterozygote for the Filipino deletional β⁰-thalassemia and α⁺-thalassemia. Their affected son was a patient with a previously undescribed condition of Hb E-β⁰-thalassemia with α⁺-thalassemia. Both a combined gap-polymerase chain reaction (PCR) and allele-specific PCR were used successfully in the prenatal diagnosis, which identified an affected fetus with Hb E-β⁰-thalassemia without α⁺-thalassemia. Beta globin gene haplotype analysis indicated the same origin of this Filipino β⁰-thalassemia in Asian populations.