Genetic modifiers of β-thalassemia and clinical severity as assessed by age at first transfusion

Anemia and iron overload as prognostic markers of outcomes in β-thalassemia

INTRODUCTION

Ineffective erythropoiesis and subsequent anemia as well as primary and secondary (transfusional) iron overload are key drivers for morbidity and mortality outcomes in patients with β-thalassemia.

AREAS COVERED

In this review, we highlight evidence from observational studies evaluating the association between measures of anemia and iron overload versus outcomes in both non-transfusion-dependent and transfusion-dependent forms of β-thalassemia.

EXPERT OPINION

Several prognostic thresholds have been identified with implications for patient management. These have also formed the basis for the design of novel therapy clinical trials by informing eligibility and target endpoints. Still, several data gaps persist in view of the challenge of assessing prospective long-term outcomes in a chronic disease. Pooling insights on the prognostic value of different measures of disease mechanism will be key to design future scoring systems that can help optimize patient management.

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.

Responses of β-thalassemia and compound heterozygote of Sickle/βthalassemia of BCL11A Gene Polymorphism in Pakistani Patients

Background and Objective

Beta-thalassemia major (β-Thal) and compound heterozygote of Sickle β-thalassemia (S-β Thal) are hereditary autosomal recessive disorders resulting from mutations or deletion in β-globin gene cluster. Patients with increased HbF levels having polymorphism at BCL11A site loci have shown clinical significance. The present study aimed to assess the frequency of BCL11A gene polymorphism in a study population of β-Thal, S-β Thal & Controls using Sanger sequencing leading to plot the HbF response of polymorphism with reference to wild type.

Methods

The sample size of the study is n=180, groups were divided in Controls, β-thal & S-β thal. One ml blood was drawn from patients and controls to extract DNA for PCR amplification and BCL11A locus genotyping using Sanger sequencing. This study was carried out at Dow Research Institute of Biotechnology and Biomedical Sciences, for one year from March 2021 to February 2022.

Results

The HbF response of three groups is hyperbolic with 83 for β-Thal, 16 for S-β Thal and close to zero for controls. The frequency of heterozygous variant GA of BCL11A gene polymorphism is 51%. The frequency of homozygous variant GG is 49%. Complete absence of wild type AA in patient group. The frequency of BCL11A polymorphism in control group was 43% (with male 18% and female 21%) showing wild type status of 57%.

Conclusions

The patient groups of SCD and Beta thalassemia are devoid of wild type status. The wild type status of BCL11A is 57% even in control population. Higher level of HbF in B-thalassemia and SCD and B Thalassemia is a cost-effective screening marker before switching to an expensive genotyping testing.

The Long Scientific Journey of Sirolimus (Rapamycin): From the Soil of Easter Island (Rapa Nui) to Applied Research and Clinical Trials on β-Thalassemia and Other Hemoglobinopathies

In this review article, we present the fascinating story of rapamycin (sirolimus), a drug able to induce γ-globin gene expression and increased production of fetal hemoglobin (HbF) in erythroid cells, including primary erythroid precursor cells (ErPCs) isolated from β-thalassemia patients. For this reason, rapamycin is considered of great interest for the treatment of β-thalassemia. In fact, high levels of HbF are known to be highly beneficial for β-thalassemia patients. The story of rapamycin discovery began in 1964, with METEI, the Medical Expedition to Easter Island (Rapa Nui). During this expedition, samples of the soil from different parts of the island were collected and, from this material, an antibiotic-producing microorganism (Streptomyces hygroscopicus) was identified. Rapamycin was extracted from the mycelium with organic solvents, isolated, and demonstrated to be very active as an anti-bacterial and anti-fungal agent. Later, rapamycin was demonstrated to inhibit the in vitro cell growth of tumor cell lines. More importantly, rapamycin was found to be an immunosuppressive agent applicable to prevent kidney rejection after transplantation. More recently, rapamycin was found to be a potent inducer of HbF both in vitro using ErPCs isolated from β-thalassemia patients, in vivo using experimental mice, and in patients treated with this compound. These studies were the basis for proposing clinical trials on β-thalassemia patients.

Frequency of secondary modifiers in Beta Thalassemia intermedia in patients from Northern Punjab

Objective

The aim of this study was to determine frequency of secondary modifiers in non-transfusion dependent thalassemia.

Methods

This descriptive cross sectional study was done at Fauji Foundation Hospital Islamabad. Seventy diagnosed patients of thalassemia intermedia were included. Deoxyribonucleic acid (DNA) was extracted using Chelex method. The Xmn-1 and BCL11A polymorphisms were analyzed by Amplification Refractory Mutation System (ARMS) and Restriction Fragment Length Polymorphism (RFLP) PCR. The PCR amplified products were run on Polyacrylamide Gel Electrophoresis (PAGE).

Results

The Xmn-l polymorphism was seen in 26/70 (37.1%) and BCL11A polymorphism was seem in 50/70 (71.4%) of the patients.

Conclusion

BCL11A and Xmn-l polymorphisms are important secondary modifiers in patients with thalassaemia intermedia in Northern Punjab.

Combined approaches for increasing fetal hemoglobin (HbF) and de novo production of adult hemoglobin (HbA) in erythroid cells from β-thalassemia patients: treatment with HbF inducers and CRISPR-Cas9 based genome editing

Genome editing (GE) is one of the most efficient and useful molecular approaches to correct the effects of gene mutations in hereditary monogenetic diseases, including β-thalassemia. CRISPR-Cas9 gene editing has been proposed for effective correction of the β-thalassemia mutation, obtaining high-level "de novo" production of adult hemoglobin (HbA). In addition to the correction of the primary gene mutations causing β-thalassemia, several reports demonstrate that gene editing can be employed to increase fetal hemoglobin (HbF), obtaining important clinical benefits in treated β-thalassemia patients. This important objective can be achieved through CRISPR-Cas9 disruption of genes encoding transcriptional repressors of γ-globin gene expression (such as BCL11A, SOX6, KLF-1) or their binding sites in the HBG promoter, mimicking non-deletional and deletional HPFH mutations. These two approaches (β-globin gene correction and genome editing of the genes encoding repressors of γ-globin gene transcription) can be, at least in theory, combined. However, since multiplex CRISPR-Cas9 gene editing is associated with documented evidence concerning possible genotoxicity, this review is focused on the possibility to combine pharmacologically-mediated HbF induction protocols with the "de novo" production of HbA using CRISPR-Cas9 gene editing.

Genetic basis of ß-thalassemia in families of pashtun ethnicity in Dera Ismail Khan district of Khyber Pakhtun-Khwa province, Pakistan

OBJECTIVES

The objective of current genetic research was to verify the genetic basis of ß-thalassemia and its pattern of inheritance in families of Pashtun ethnicity in District Dera Ismail Khan, Pakistan.

METHODOLOGY

Blood samples from clinically diagnosed five unrelated ß-thalassemia families were collected and target Sanger Sequencing of HBB gene was done. Moreover, in silico analysis including protein modeling and Protein-Protein docking was aslo performed.

RESULTS AND DISCUSSION

Clinical analysis of patients from family 1,2, 4, and 5 revealed Thalassemia Intermedia, while patient from family 3 was suffering from thalassemia major. The average Hb concentrations between the cases that were severe were found to be a little lower (6.3 mg/dl) than the patients with milder clinical manifestations (7.6 ± 1.4). Genetic analysis in family 1 identified compound heterozygous mutation of HBB (NM_000518) i.e. c.20A>T +c.92 G>A, in family 2 and 4 compound heterozygous mutations c.20A>T + c.27_28insG, in family 3 homozygous mutation c.27_28insG, while in family 5 we identified homozygous mutation c.92 + 5 G>C (IVS-1 + 5 G>C).

CONCLUSION

This study offers an effective incentive to establish a mutation detection as well as prenatal diagnosis (PND) centers at a larger scale in the Pashtun ethnicity residing in District Dera Ismail Khan, Pakistan.

Genotype-Phenotype Study of β-Thalassemia Patients in Sabah

β-thalassemia is a serious public health problem in Sabah due to its high prevalence. This study aimed to investigate the effects of different types of β-globin gene mutations, coinheritance with α-globin gene mutations, XmnI-^Gγ, and rs368698783 polymorphisms on the β-thalassemia phenotypes in Sabahan patients. A total of 111 patients were included in this study. The sociodemographic profile of the patients was collected using a semi-structured questionnaire, while clinical data were obtained from their medical records. Gap-PCR, ARMS-PCR, RFLP-PCR, and multiplex PCR were performed to detect β- and α-globin gene mutations, as well as XmnI-^Gγ and rs368698783 polymorphisms. Our data show that the high prevalence of β-thalassemia in Sabah is not due to consanguineous marriages (5.4%). A total of six different β-globin gene mutations were detected, with Filipino β°-deletion being the most dominant (87.4%). There were 77.5% homozygous β-thalassemia patients, 16.2% compound heterozygous β-thalassemia patients, and 6.3% β-thalassemia/Hb E patients. Further evaluation on compound heterozygous β-thalassemia and β-thalassemia/Hb E patients found no concomitant α-globin gene mutations and the rs368698783 polymorphism. Furthermore, the XmnI-^Gγ (-/+) genotype did not demonstrate a strong impact on the disease phenotype, as only two of five patients in the compound heterozygous β-thalassemia group and two of three patients in the β-thalassemia/Hb E group had a moderate phenotype. Our findings indicate that the severity of the β-thalassemia phenotypes is closely related to the type of β-globin gene mutations but not to the XmnI-^Gγ and rs368698783 polymorphisms.

Expression of γ-globin genes in β-thalassemia patients treated with sirolimus: results from a pilot clinical trial (Sirthalaclin)

Introduction

β-thalassemia is caused by autosomal mutations in the β-globin gene, which induce the absence or low-level synthesis of β-globin in erythroid cells. It is widely accepted that a high production of fetal hemoglobin (HbF) is beneficial for patients with β-thalassemia. Sirolimus, also known as rapamycin, is a lipophilic macrolide isolated from a strain of Streptomyces hygroscopicus that serves as a strong HbF inducer in vitro and in vivo. In this study, we report biochemical, molecular, and clinical results of a sirolimus-based NCT03877809 clinical trial (a personalized medicine approach for β-thalassemia transfusion-dependent patients: testing sirolimus in a first pilot clinical trial, Sirthalaclin).

Methods

Accumulation of γ-globin mRNA was analyzed using reverse-transcription quantitative polymerase chain reaction (PCR), while the hemoglobin pattern was analyzed using high-performance liquid chromatography (HPLC). The immunophenotype was analyzed using a fluorescence-activated cell sorter (FACS), with antibodies against CD3, CD4, CD8, CD14, CD19, CD25 (for analysis of peripheral blood mononuclear cells), or CD71 and CD235a (for analysis of in vitro cultured erythroid precursors).

Results

The results were obtained in eight patients with the β+/β+ and β+/β0 genotypes, who were treated with a starting dosage of 1 mg/day sirolimus for 24-48 weeks. The first finding of this study was that the expression of γ-globin mRNA increased in the blood and erythroid precursor cells isolated from β-thalassemia patients treated with low-dose sirolimus. This trial also led to the important finding that sirolimus influences erythropoiesis and reduces biochemical markers associated with ineffective erythropoiesis (excess free α-globin chains, bilirubin, soluble transferrin receptor, and ferritin). A decrease in the transfusion demand index was observed in most (7/8) of the patients. The drug was well tolerated, with minor effects on the immunophenotype, and an only side effect of frequently occurring stomatitis.

Conclusion

The data obtained indicate that low doses of sirolimus modify hematopoiesis and induce increased expression of γ-globin genes in a subset of patients with β-thalassemia. Further clinical trials are warranted, possibly including testing of the drug in patients with less severe forms of the disease and exploring combination therapies.

Plasma proteome profiling combined with clinical and genetic features reveals the pathophysiological characteristics of β-thalassemia

The phenotype of β-thalassemia underlies multigene interactions, making clinical stratification complicated. An increasing number of genetic modifiers affecting the disease severity have been identified, but are still unable to meet the demand of precision diagnosis. Here, we systematically conducted a comparative plasma proteomic profiling on patients with β-thalassemia and healthy controls. Among 246 dysregulated proteins, 13 core protein signatures with excellent biomarker potential are proposed. The combination of proteome and patients' clinical data revealed patients with codons 41/42 -TTCT mutations have an elevated risk of higher iron burden, dysplasia, and osteoporosis than patients with other genotypes. Notably, 85 proteins correlating to fetal hemoglobin (Hb F) were identified, among which the abundance of 27 proteins may affect the transfusion burden in patients with β-thalassemia. The current study thus provides protein signatures as potential diagnostic biomarkers or therapeutic clues for β-thalassemia.

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246 dysregulated proteins are detected in plasma of patients with β-thalassemia

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13 potential biomarkers and 27 proteins related to disease progression are found

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Variations in plasma proteome reveal the disease pathophysiological characteristics

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Codons 41/42 -TTCT carriers have higher ferritin levels compared to non-carriers

Treatment of Erythroid Precursor Cells from β-Thalassemia Patients with Cinchona Alkaloids: Induction of Fetal Hemoglobin Production

β-thalassemias are among the most common inherited hemoglobinopathies worldwide and are the result of autosomal mutations in the gene encoding β-globin, causing an absence or low-level production of adult hemoglobin (HbA). Induction of fetal hemoglobin (HbF) is considered to be of key importance for the development of therapeutic protocols for β-thalassemia and novel HbF inducers need to be proposed for pre-clinical development. The main purpose on this study was to analyze Cinchona alkaloids (cinchonidine, quinidine and cinchonine) as natural HbF-inducing agents in human erythroid cells. The analytical methods employed were Reverse Transcription quantitative real-time PCR (RT-qPCR) (for quantification of γ-globin mRNA) and High Performance Liquid Chromatography (HPLC) (for analysis of the hemoglobin pattern). After an initial analysis using the K562 cell line as an experimental model system, showing induction of hemoglobin and γ-globin mRNA, we verified whether the two more active compounds, cinchonidine and quinidine, were able to induce HbF in erythroid progenitor cells isolated from β-thalassemia patients. The data obtained demonstrate that cinchonidine and quinidine are potent inducers of γ-globin mRNA and HbF in erythroid progenitor cells isolated from nine β-thalassemia patients. In addition, both compounds were found to synergize with the HbF inducer sirolimus for maximal production of HbF. The data obtained strongly indicate that these compounds deserve consideration in the development of pre-clinical approaches for therapeutic protocols of β-thalassemia.

Primary HBB gene mutation severity and long-term outcomes in a global cohort of β-thalassaemia

In β-thalassaemia, the severity of inherited β-globin gene mutations determines the severity of the clinical phenotype at presentation and subsequent transfusion requirements. However, data on associated long-term outcomes remain limited. We analysed data from 2109 β-thalassaemia patients with available genotypes in a global database. Genotype severity was grouped as β⁰ /β⁰ , β⁰ /β⁺ , β⁺ /β⁺ , β⁰ /β⁺⁺ , β⁺ /β⁺⁺ , and β⁺⁺ /β⁺⁺ . Patients were followed from birth until death or loss to follow-up. The median follow-up time was 34·1 years. Mortality and multiple morbidity outcomes were analyzed through five different stratification models of genotype severity groups. Interestingly, β⁰ and β⁺ mutations showed similar risk profiles. Upon adjustment for demographics and receipt of conventional therapy, patients with β⁰ /β⁰ , β⁰ /β⁺ , or β⁺ /β⁺ had a 2·104-increased risk of death [95% confidence interval (CI): 1·176-3·763, P = 0·011] and 2·956-increased odds of multiple morbidity (95% CI: 2·310-3·784, P < 0·001) compared to patients in lower genotype severity groups. Cumulative survival estimates by age 65 years were 36·8% for this subgroup compared with 90·2% for patients in lower genotype severity groups (P < 0·001). Our study identified mortality and morbidity risk estimates across various genotype severity groups in patients with β-thalassaemia and suggests inclusion of both β⁺ and β⁰ mutations in strata of greatest severity.

Significance of genetic modifiers of hemoglobinopathies leading towards precision medicine

Hemoglobinopathies though a monogenic disorder, show phenotypic variability. Hence, understanding the genetics underlying the heritable sub-phenotypes of hemoglobinopathies, specific to each population, would be prognostically useful and could inform personalized therapeutics. This study aimed to evaluate the role of genetic modifiers leading to higher HbF production with cumulative impact of the modifiers on disease severity. 200 patients (100 β-thalassemia homozygotes, 100 Sickle Cell Anemia), and 50 healthy controls were recruited. Primary screening followed with molecular analysis for confirming the β-hemoglobinopathy was performed. Co-existing α-thalassemia and the polymorphisms located in 3 genetic loci linked to HbF regulation were screened. The most remarkable result was the association of SNPs with clinically relevant phenotypic groups. The γ-globin gene promoter polymorphisms [- 158 C → T, + 25 G → A],BCL11A rs1427407 G → T, - 3 bp HBS1L-MYB rs66650371 and rs9399137 T → C polymorphisms were correlated with higher HbF, in group that has lower disease severity score (P < 0.00001), milder clinical presentation, and a significant delay in the age of the first transfusion. Our study emphasizes the complex genetic interactions underlying the disease phenotype that may be a prognostic marker for predicting the clinical severity and assist in disease management.

Effect of HBB genotype on survival in a cohort of transfusion-dependent thalassemia patients in Cyprus

Initiation of regular transfusion in transfusion-dependent thalassemia (TDT) is based on the assessment of clinical phenotype. Pathogenic HBB variants causing β-thalassemia are important determinants of phenotype and could be used to aid decision-making. We investigated the association of HBB genotype with survival in a cohort study in the four thalassemia centers in Cyprus. HBB genotype was classified as severe (β0/β0 or β+/β0), moderate (β+/β+), or mild (β0/β++ or β+/β++). Risk factors for mortality were evaluated using multivariate Cox proportional- hazards regression. Of the 537 subjects who were followed for a total of 20,963 person-years, 80.4% (95% confidence interval [95% CI]: 76.4-84.7) survived to 50 years of age with increasing rates of liver-, infectionand malignancy-related deaths observed during recent follow-up. We evaluated non-modifiable risk factors and found worse outcomes associated with male sex (hazard ratio 1.9, 95% CI: 1.1-3.0, P=0.01) and milder genotype (hazard ratio 1.6, 95% CI: 1.1-2.3, P=0.02). The effect of genotype was confirmed in a second model, which included treatment effects. Patients with a milder genotype initiated transfusion significantly later and had reduced blood requirements compared to those with moderate or severe genotypes, although pre-transfusion hemoglobin levels did not differ between genotypes. Our results suggest that early treatment decisions to delay transfusion and different long-term treatment strategies in individuals with milder genotypes have led to adverse longterm effects of under-treated thalassemia and worse survival. We propose that HBB genotype determination and use of this information to aid in decision-making can improve long-term outcomes of thalassemia patients.

The Prevalence of HBB Mutations among the Transfusion-Dependent and Non Transfusion-Dependent Hb E/β-Thalassemia Children in a Tertiary Center of West Bengal, India

Hb E (HBB: c.79G>A)/β-thalassemia (Hb E/β-thal) is responsible for nearly half of all the different kinds of severe β-thal. This disorder is characterized by a wide range of clinical variability ranging from mild, asymptomatic non transfusion-dependent thalassemia (NTDT) to severe transfusion-dependent thalassemia (TDT). The aim of the present study was to determine the prevalence of different β-globin gene (HBB) mutations in Hb E/β-thal subjects and their potential role in transfusion dependence. One hundred and ten consecutive children with Hb E/β-thal attending the Pediatric Department of Burdwan Medical College, Burdwan, West Bengal, India were enrolled. Based on hemoglobin (Hb) electrophoresis or high-performance liquid chromatography (HPLC), patients were recruited and later β-globin gene sequencing was done to find out the prevalence of different HBB mutations. Transfusion-dependent thalassemia was seen in 42 children (38.2%), while NTDT was seen in 68 children (61.8%). A total of 10 different β-globin mutant alleles were characterized. The most frequent mutation on the β-globin gene was IVS-I-5 (G>C) (HBB: c0.92+5G>C) in both groups. The β-globin gene mutations alone cannot determine transfusion dependence among the Hb E/β-thal patients.

BCL11A Polymorphism in Egyptian Children with β-Thalassemia: Relation to Phenotypic Heterogeneity

Fetal hemoglobin (HbF) is a potent genetic modifier of β-thalassemia phenotype. B-cell lymphoma 11A ( BCL11A ) gene results in significant silencing of HbF. The aim of this study was to assess the prevalence of different BCL11A genotypes among a cohort of Egyptian children with β-thalassemia and to correlate them to HbF and clinical severity score. Eighty-two children with β-thalassemia (aged 12.95 ± 3.63 years) were recruited from the Pediatric Hematology Clinic, Ain Shams University. They were divided based on the clinical severity of β-thalassemia into three subgroups: 20 mild (24.4%), 24 moderate (29.3%), and 38 severe (46.3%). Age, gender, age of diagnosis, initial HbF level, transfusion history, and history of splenectomy were assessed. Anthropometric measures, signs of anemia and hemosiderosis, and the severity score were determined. Laboratory investigations such as complete blood picture, ferritin, and single gene polymorphism genotyping of the rs11886868 were also performed. Our findings showed that 16 children had CC genotype (19.5%), 38 had TC genotype (46.3%), and 28 had TT genotype (34.1%) of the rs#. β-thalassemia children with TT genotype had significantly higher severity scoring than the other two groups ( p  < 0.001). Moreover, mean initial HbF was found to be lower in children with TT genotype followed by TC and CC genotypes ( p  < 0.001). Increased γ-globin expression associated with BCL11A gene polymorphism is associated with better clinical severity of β-thalassemia.

Thalassemia Major and Intermedia Patients in East Java do not Show Fetal Hemoglobin Level Difference in Relation to XMNI Polymorphism

Introduction

Thalassemia is a genetic disorder, which shows, varies phenotype due to genetic modifier. XmnI is one of the genetic modifiers which affect clinical severity in thalassemia. XmnI polymorphism may increase HbF production beyond fetal life, thus ameliorating the clinical phenotype.

Aim

this study aimed to investigate the difference in HbF level and the relation of HbF level and XmnI polymorphism in Thalassemia Major (TM) and Thalassemia Intermedia (TI) patients.

Methods

forty-eight beta thalassemia patients (28 males and 20 females), consists of 16 TM and 32 TI; mean age, 25.30 year old. Hemoglobin Fetal and HbA₂ level were determined using High performance Liquid Chromatography (HPLC), and XmnI polymorphism was confirmed by PCR-RFLP. Statistical analysis was done using T-test, Mann-Whitney and Pearson Chi-square.

Results

The frequency of heterozygote (+/-) XmnI polymorphism in TM and TI patients was 56.25% vs 71.87%, while the frequency of homozygote (-/-) in TM and TI was 43.75% vs 28.13% with p value >0.05. The insignificant difference also found in HbF level between XmnI +/- and -/- in TM and TI patients.

Conclusion

This study revealed that thalassemia major and thalassemia intermedia patients in East Java showed similar XmnI polymorphism. These phenomena also showed by HbF level in relation to XmnI polymorphism in the phenotype groups (TM and TI).

HBB mutations and HbA2 level: Escaping the carrier screening programs

HbA2 level alone for beta thalassemia trait may not be accurate and reliable even without iron deficiency so molecular genetic testing is important and should be considered for some individuals.

Detection of BCL11A and HBS1L-MYB Genotypes in Sickle Cell Anemia

Sickle Cell Anemia (SCA) is one of the most common monogenic disorders worldwide. Molecular modifiers of clinical symptoms play an essential role in the amelioration of the effects of the disease. Single Nucleotide Polymorphisms (SNPs) of the BCL11A gene and within the HBS1L-MYB intergenic region, which are located outside the β-globin locus on chromosome 11, are considered to be genetic modifiers that are associated with elevated levels of foetal haemoglobin HbF, and thus they reduce the clinical impact of sickle haemoglobin, HbS. The work reported here aimed to detect the most common SNPs of BCL11A and HBS1L-MYB related to HbF in SCA patients and to estimate the frequency of occurrence of these genotypes. A total of 132 SCA patients whose condition was stable were recruited from Jeddah city, Saudi Arabia. SNPs at site locus rs4671393 on BCL11A, and at loci rs28384513 and rs9399137 on HBS1L-MYB were identified using TaqMan genotyping assay. Haematological parameters were analysed based on complete blood count and haemoglobin separation using the capillary electrophoresis technique. Highly significant differences in the diagnostic haematological parameters, including all blood-cell types and HbF, were observed between the study cohort and control groups. We also found that BCL11A rs4671393 genotypes of GG and AG were more likely to show increases in HbF levels than other genotypes. In addition, a strong relationship was found between HBS1L-MYB rs9399137 and rs28384513 genotypes in the cohort, whereas no significant association was observed between BCL11A rs4671393 variant and other variants. Our study highlights the importance of investigating genetic determinants that play roles in the amelioration of the severity of clinical symptoms and complications of SCA.

Red blood cell consumption in a large cohort of patients with thalassaemia: a retrospective analysis of main predictors

The phenotype/genotype relationship of patients with transfusion-dependent thalassaemia (TDT) is particularly complex and variable, thus generating different levels of severity and of annual transfusion volume (ATV). In this study, we explored the role and the contribution of several factors potentially involved in determining mean ATV in a cohort of TDT patients which have been followed since long time. We collected data on one-hundred and twenty-seven patients with transfusion-dependent β-thalassaemia followed at Rare Blood Cell Disease Unit, AORN Cardarelli Hospital. Age at first transfusion, genotype, spleen status (splenectomy or not), and mean soluble transferrin receptor (sTfR) were the parameters included in the analysis. At stepwise regression analysis which included all the parameters, only splenectomy and mean sTfR significantly predicted the mean ATV (F = 70.94, P < 0.0001, R² = 0.540). Overall, our data may suggest that in patients with TDT, the measurement of sTfR level together with the spleen status could contribute, more accurately than genotype, to provide a basal evaluation of residual erythropoietic activity and mean ATV.

HBG2 -158 (C>T) polymorphism and its contribution to fetal hemoglobin variability in Iraqi Kurds with beta-thalassemia minor

PURPOSE

Hemoglobin (Hb) F% is increased in up to half of beta-thalassemia (β-thal) carriers. Several polymorphisms have been linked to such variability in different populations, including HBG2 - 158(C>T) (Xmn I polymorphism) on chromosome 11. To determine the role of this polymorphism in such variability among Iraqi Kurds, the current study was initiated.

MATERIALS AND METHODS

A total of 102 consecutive patients diagnosed as β-thal minor were enrolled. The enrollees had their diagnosis based on peripheral blood counts and high-performance liquid chromatography to determine HbA2 and HbF. All enrollees had their DNA extracted by phenol-chloroform method and Xmn I polymorphism detected by restriction fragment length polymorphism-polymerase chain reaction.

RESULTS

The mean age (standard deviation [SD]) of the 102 enrollees was 25.4 (14.0) years, and the enrollees included 48 males and 54 females. Xmn I polymorphism was identified in heterozygous state in 46 (45.1%) patients and in homozygous state in one patient (0.98%). Thus, the minor allele frequency of this polymorphism was 0.235 in the studied group. There were no significant differences in red cell indices and HbA2% in carriers of the minor allele compared to noncarriers, while HbF% and absolute HbF concentrations were significantly higher in the former subgroup (P = 0.032 and 0.014, respectively). This polymorphism's contribution to HbF variability was found to be 5.8% in the studied sample. Furthermore, those with HbF ≥2% were 3.2 folds more likely to carry the minor allele.

CONCLUSIONS

Xmn I polymorphism is frequently encountered in Iraqi Kurds with β-thal minor, and it is significantly associated with higher fetal hemoglobin in these patients.

Long non-coding RNAs MALAT1, MIAT and ANRIL gene expression profiles in beta-thalassemia patients: a cross-sectional analysis

OBJECTIVES

Beta-thalassemia (β-thal) is one of the most common genetic disorders worldwide. Multiple genetic and epigenetic mechanisms could be implicated in the pathogenesis and/or phenotype variations. We sought to explore the serum expression profile of three disease-related long non-coding RNAs (lncRNAs) in a sample of Egyptian β-thal patients with correlation to the patients' clinicolaboratory data.

METHODS

Fifty consecutive β-thal patients and 50 unrelated controls were enrolled in the study. Quantification of circulating lncRNAs; MALAT1 (metastasis-associated lung adenocarcinoma transcript 1), MIAT (myocardial infarction associated transcript), and ANRIL (antisense non-coding RNA in the INK4 locus) was done by Real-time qRT-PCR.

RESULTS

Significant higher expression levels of the studied lncRNAs in β-thal patients compared to the controls (all P values < 0.001) were identified. There was no significant difference between β-thal-major and intermedia patients at the level of any of the studied lncRNAs. Higher MALAT1 expression profile was associated with early age at onset, early age at first blood transfusion, and a higher frequency of splenomegaly. Whereas, up-regulated MIAT levels were associated with early age at first blood transfusion.

CONCLUSIONS

Taken together, the studied lncRNAs MALAT1, MIAT, and ANRIL might be implicated in β-thal pathogenesis and could provide new molecular biomarkers for β-thalassemia after validation in large-scale future studies.

Common fetal hemoglobin variants in Lebanese patients bearing the codon 29 beta gene mutation associated with different thalassemia phenotypes

Beta-thalassemia can present with a wide spectrum of phenotypes determined by the coinheritance of α-thalassemia, hereditary persistence of fetal hemoglobin, and polymorphic variants in the BCL11A, HMIP, and HBB clusters. The codon 29 (cd29) mutation in the beta gene has been associated with a broad diversity of thalassemia phenotypes, possibly through genetic modifiers determining the genotype-phenotype relationship. In this study, we evaluated the effect of 10 single nucleotide polymorphisms (SNPs) on β-thalassemia severity in a group of 21 Lebanese patients bearing the cd29 mutation. Hematological parameters and clinical characteristics were evaluated according to transfusion dependence. The proportions and absolute concentrations of HbF were found to be higher in non-transfusion-dependent (NTD) patients than in transfusion-dependent (TD) ones. Iron parameters were found to be higher in TD patients. The SNPs that were evaluated included the XmnI-158 polymorphism in the HBG gene and SNPs in the BCL11A and HMIP loci. It was noted that individuals homozygous or heterozygous for the effect allele in the BCL11A and HMIP SNPs had higher HbF levels, lower ferritin concentrations, and lower liver iron content and were less likely to be transfusion dependent. Our results showed that HbF production variants may have an important impact on the severity of β-thalassemia, which might provide a severity prediction tool that can help in the anticipation of patients' phenotypes and therefore in future therapeutic decision making.

Inducing indel mutation in the SOX6 gene by zinc finger nuclease for gamma reactivation: An approach towards gene therapy of beta thalassemia

β-thalassemia is a common autosomal recessive disorder characterized by a deficiency in the synthesis of β-chains. Evidences show that increased HbF levels improve the symptoms in patients with β-thalassemia or sickle cell anemia. In this study, ZFN technology was applied to induce a mutation in the binding domain region of SOX6 to reactivate γ-globin expression. The sequences coding for ZFP arrays were designed and sub cloned in TDH plus as a transfer vector. The ZFN expression was confirmed using Western blot analysis. In the next step, using the site-directed mutagenesis strategy through the overlap PCR, a missense mutation (D64V) was induced in the catalytic domain of the integrase gene in the packaging plasmid and verified using DNA sequencing. Then, the integrase minus lentivirus containing ZFN cassette was packaged. Transduction of K562 cells with this virus was performed. Mutation detection assay was performed. The indel percentage of the cells transducted with lenti virus containing ZFN was 31%. After 5 days of erythroid differentiation with 15 μg/mL cisplatin, the levels of γ-globin mRNA were sixfold in the cells treated with ZFN compared to untreated cells. In the meantime, the measurement of HbF expression levels was carried out using hemoglobin electrophoresis and showed the same results. Integrase minus lentivirus can provide a useful tool for efficient transient gene expression and helps avoid disadvantages of gene targeting using the native virus. The ZFN strategy applied here to induce indel on SOX6 gene in adult erythroid progenitors may provide a method to activate fetal hemoglobin expression in individuals with β-thalassemia.

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.

Genetic Variants at BCL11A and HBS1L-MYB loci Influence Hb F Levels in Chinese Zhuang β-Thalassemia Intermedia Patients

Increased Hb F levels can ameliorate the symptoms of β-thalassemia (β-thal). Due to the genetic heterogenicity of β-thal, the relationship between genetic variants in modifier genes and Hb F level has been studied in different populations. The Chinese Zhuang has the second largest population in China and has 6.78% prevalence of β-thal. However, the effects of these single nucleotide polymorphism (SNP) variants on the Hb F levels of β-thal intermedia (β-TI) patients in this population have not been reported. To explore the association between modifier loci (β-globin gene cluster, HBS1L-MYB intergenic region and BCL11A) and Hb F levels in Chinese Zhuang β-TI patients, 96 unrelated β-TI patients (50 males and 46 females) with different Hb F levels were recruited and genotyped by mass spectrometry. A total of 13 SNPs were confirmed to be in a significant relationship with Hb F levels in this population. Of these, high-risk genotypes of six Hb F-associated SNPs, rs9376090, rs7776054, rs9399137, rs9389268, rs9402685 in the HBS1L-MYB intergenic region and rs189984760 in the BCL11A locus, showed association with high Hb F levels, especially for SNPs in linkage disequilibrium. One novel Hb F-associated SNP, rs189984760, was identified in our study. Our findings will be of valuable reference for correlation between modifier genes and Hb F in Chinese Zhuang populations and may lead to better understand the modifying mechanisms for β-thal.

Genetic Basis and Genetic Modifiers of β-Thalassemia and Sickle Cell Disease

β-thalassemia and sickle cell disease (SCD) are prototypical Mendelian single gene disorders, both caused by mutations affecting the adult β-globin gene. Despite the apparent genetic simplicity, both disorders display a remarkable spectrum of phenotypic severity and share two major genetic modifiers-α-globin genotype and innate ability to produce fetal hemoglobin (HbF, α₂γ₂).This article provides an overview of the genetic basis for SCD and β-thalassemia, and genetic modifiers identified through phenotype correlation studies. Identification of the genetic variants modifying HbF production in combination with α-globin genotype provide some prediction of disease severity for β-thalassemia and SCD 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 some of the key variants and pathways involved in HbF regulation, providing new therapeutic targets for HbF reactivation.

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.

Thalassemia Intermedia Caused by 16p13.3 Sectional Duplication in a β-Thalassemia Heterozygous Child

Thalassemia intermedia is an inherited hemoglobin disorder characterized by a significant genetic and clinical heterogeneity. A wide spectrum of different genotypes-homozygous, heterozygous, and compound heterozygous-have been found to be responsible for it. The authors describe a Chinese child of β-thalassemia heterozygote with the mutation IVS2-654 (C→T) (HBB:c.316-197C→T) presenting with severe thalassemia intermedia. Multiplex ligation-dependent probe amplification (MLPA) and array comparative genomic hybridization (CGH) analyses of the α gene cluster revealed an approximate 146-kb duplication at 16p13.3 including the complete α gene cluster. The duplicated allele and the normal allele in trans result in a total of 6 active α genes. The severe clinical phenotype seemed to be related to the considerable excess of the α-globin and the β-globin deficit caused by the presence of the β-thalassemia. The α gene duplication should be considered in patients heterozygous for β-thalassemia who show a more severe phenotype than β-thalassemia trait.

Modifying effect of XmnI, BCL11A, and HBS1L-MYB on clinical appearances: A study on β-thalassemia and hemoglobin E/β-thalassemia patients in Indonesia

OBJECTIVE/BACKGROUND

Thalassemia is a monogenic hematologic disease that has the highest prevalence globally. In addition, there is complexity of the genetic background associated with a variety of phenotypes presented among patients. Genetic heterogeneity related to fetal hemoglobin (HbF) production has been reported as an influencing phenotypic factor of β-thalassemia (β-thal). Therefore, this study aimed to find the effect of these genetic modifiers, especially in the XmnI locus, rs11886868, rs766432 (BCL11A), and rs9399137 (HBS1L-MYB), among β-thal and HbE/β-thal patients in Indonesia, according to laboratory and clinical outcomes, including HbF levels and clinical scores. This study was also designed to compare these modifying effects among β-thal and HbE/β-thal patients in Indonesia.

METHODS

A total of 189 patients with genotyping of β-thal and HbE/β-thal were included in this study. The erythrocytes index and Hb electrophoresis measurements were calculated using appropriate methods. The severity of β-thal and HbE/β-thal was classified based on the Mahidol score. Polymorphism of the XmnI locus, rs11886868, rs766432 (BCL11A), and rs9399137 (HBS1L-MYB) was determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and amplification refractory mutation system (ARMS) methods.

RESULTS

The distributions of minor allele in the XmnI locus, rs11886868, rs766432, and rs9399137 were 14%, 22%, 19% and 18% respectively. The variation allele in the XmnI locus, rs11886868, and rs766432 showed a significant value for modifying HbF and clinical score in HbE/β-thal patients, but rs9399137 did not demonstrate such features. In β-thal patients, however, no correlation was found for any single-nucleotide polymorphisms and clinical appearance.

CONCLUSION

The XmnI locus, rs11886868, and rs766432 have a modifying effect on HbF and clinical score in HbE/β-thal patients in Indonesia, but not in β-thal patients.

Regulation of the fetal hemoglobin silencing factor BCL11A

The clinical severity of sickle cell disease and β-thalassemia, the major disorders of β-globin, can be ameliorated by increased production of fetal hemoglobin (HbF). Here, we provide a brief overview of the fetal-to-adult hemoglobin switch that occurs in humans shortly after birth and review our current understanding of one of the most potent known regulators of this switching process, the multiple zinc finger-containing transcription factor BCL11A. Originally identified in genome-wide association studies, multiple orthogonal lines of evidence have validated BCL11A as a key regulator of hemoglobin switching and as a promising therapeutic target for HbF induction. We discuss recent studies that have highlighted its importance in silencing the HbF-encoding genes and discuss opportunities that exist to further understand the regulation of BCL11A and its mechanism of action, which could provide new insight into opportunities to induce HbF for therapeutic purposes.

Extramedullary hematopoiesis is associated with lower cardiac iron loading in chronically transfused thalassemia patients

The aim of this study was to evaluate, in a large cohort of chronically transfused patients, whether the presence of extramedullary hematopoiesis (EMH) accounts for the typical patterns of cardiac iron distribution and/or cardiac function parameters. We retrospectively selected 1,266 thalassemia major patients who had undergone regular transfusions (611 men and 655 women; mean age: 31.3 ± 8.9 years, range: 4.2-66.6 years) and were consecutively enrolled within the Myocardial Iron Overload in Thalassemia network. The presence of EMH was evaluated based on steady-state free precession sequences; cardiac and liver iron overloads were quantified using a multiecho T2* approach; cardiac function parameters and pulmonary diameter were quantified using the steady-state free precession sequences; and myocardial fibrosis was evaluated using the late gadolinium enhancement technique. EMH was detected in 167 (13.2%) patients. The EMH+ patients had significantly lower cardiac iron overload than that of the EMH- patients (P = 0.003). The patterns of cardiac iron distribution were significantly different in the EMH+ and EMH- patients (P < 0.0001), with a higher prevalence of patients with no myocardial iron overload and heterogeneous myocardial iron overload and no significant global heart iron in the EMH+ group EMH+ patients had a significantly higher left ventricle mass index (P = 0.001) and a significantly higher pulmonary artery diameter (P = 0.002). In conclusion, in regularly transfused thalassemia patients, EMH was common and was associated with a thalassemia intermedia-like pattern of cardiac iron deposition despite regular transfusion therapy.

Genome-wide association analyses based on whole-genome sequencing in Sardinia provide insights into regulation of hemoglobin levels

We report genome-wide association study results for the levels of A1, A2 and fetal hemoglobins, analyzed for the first time concurrently. Integrating high-density array genotyping and whole-genome sequencing in a large general population cohort from Sardinia, we detected 23 associations at 10 loci. Five signals are due to variants at previously undetected loci: MPHOSPH9, PLTP-PCIF1, ZFPM1 (FOG1), NFIX and CCND3. Among the signals at known loci, ten are new lead variants and four are new independent signals. Half of all variants also showed pleiotropic associations with different hemoglobins, which further corroborated some of the detected associations and identified features of coordinated hemoglobin species production.

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 determinants of β-thalassemia intermedia in Pakistan

This study covers the molecular characterization of clinically diagnosed β-thalassemia intermedia (β-TI) patients in Pakistan. Blood samples of β-TI patients were collected from all four provinces of Pakistan throughout the period of 2011-2013. The study was carried out using allele-specific primers through polymerase chain reaction or sequencing to determine both α- and β-thalassemia (α- and β-thal) mutations, and restriction enzymes for the characterization of β-globin gene arrangements. In a total of 63 patients, the IVS-I-5 (G > C) was the most frequent mutation (33.88%). The codon 30 (G > A) and IVS-II-1 (T > C) mutations were found only in the Punjabi ethnic group, while the codon 30 (G > C) and Hb S (HBB: c.20A > T) mutations were found only in the Pashtoon and Sindhi ethnic groups, respectively. In case of α-globin genotypes, 44 patients were normal (αα/αα), six patients carried the αα/-α(3.7) genotype, 12 patients carried the -α(3.7)/-α(3.7) genotype, while one patient had the αα/ααα(anti 3.7) genotype. We found that haplotype I was the most frequent, mostly associated with the codons 8/9 (+G) mutation, while the Saudi haplotype was found only with Hb S.

A genetic score for the prediction of beta-thalassemia severity

Clinical and hematologic characteristics of beta(β)-thalassemia are determined by several factors resulting in a wide spectrum of severity. Phenotype modulators are: HBB mutations, HBA defects and fetal hemoglobin production modulators (HBG2:g.-158C>T polymorphism, HBS1L-MYB intergenic region and the BCL11A). We characterized 54 genetic variants at these five loci robustly associated with the amelioration of beta-thalassemia phenotype, to build a predictive score of severity using a representative cohort of 890 β-thalassemic patients. Using Cox proportional hazard analysis on a training set, we assessed the effect of these loci on the age at which patient started regular transfusions, built a Thalassemia Severity Score, and validated it on a testing set. Discriminatory power of the model was high (C-index=0.705; R(2)=0.343) and the validation conducted on the testing set confirmed its predictive accuracy with transfusion-free survival probability (P<0.001) and with transfusion dependency status (Area Under the Receiver Operating Characteristic Curve=0.774; P<0.001). Finally, an automatized on-line calculation of the score was made available at http://tss.unica.it. Besides the accurate assessment of genetic predictors effect, the present results could be helpful in the management of patients, both as a predictive score for screening and a standardized scale of severity to overcome the major-intermedia dichotomy and support clinical decisions.

A new β(0) frameshift mutation, HBB: c.44delT (p.Leu14ArgfsX5), identified in an Argentinean family associated with secondary genetic modifiers of β-thalassemia

β-Thalassemia intermedia (β-TI) patients present with a wide spectrum of phenotypes depending on the presence of primary, secondary, and tertiary genetic modifiers which modulate, by different mechanisms, the degree of imbalance between α and β chains. Here we describe a new β(0) frameshift mutation, HBB: c.44delT (p.Leu14ArgfsX5), identified in four members of a family, associated with secondary genetic modifiers in three of them. The different genotype present in this family was suspected after hematological analysis and thorough observation of blood smears highlighting their importance in the identification of β-TI patients among members of the same family.

Development and Recent Progresses of Gene Therapy for β-Thalassemia

β-thalassemias are among the most common inherited monogenic disorders worldwide due to mutations in the β-globin gene that reduce or abolish the production of the β-globin chain resulting in transfusion-dependent chronic anemia. Currently, the only curative treatment is allogeneic hematopoietic stem cells (HSCs) transplantation, but this option is limited by the a vailability of HLA-matched donor. Gene therapy, based on autologous transplantation of genetically corrected HSCs, holds the promise to treat patients lacking a compati ble bone marrow donor. I nit ial attempts of gene transfer have been unsuccessful due to limitations of available vectors to stably transfer a globin gene in HSCs and reach high and regulated expression in the erythroid progeny. With the advent of lentiviral vectors (LVs), based on human immunodeficiency virus, many of the initial limitations have been overcome. Since 2000 when Sadelain and co-workers first demonstrated successful globin gene transfer in murine thalassemia models with improvement of the phenotype using a recombinant β globin/LV, several other groups have developed different vectors encoding either β, γ or mutated globin genes and confirmed these results in both murine models and erythroid progeny derived from patient’s HSCs. In light of these encouraging results, research has recently moved into clinical trials that are ongoing or soon to begin. One participant in an ongoing gene transfer trial for β-thalassemia has achieved clinical benefit with elimination of his transfusi on re quirement. Here , dev elopmen t and recent progress of gene therapy for β-thalassemia is reviewed.

Changes in hematological parameters in α-thalassemia individuals co-inherited with erythroid Krüppel-like factor mutations

Phenotypic variations in α-thalassemia mainly depend on the defective α-globin gene number. Genetic modifiers of the phenotype of Hemoglobin H (HbH) disease were poorly reported, apart from β-thalassemia allele that was identified ameliorating the severity of α-thalassemia. Because erythroid Krüppel-like factor (KLF1) mutations can modulate the red blood phenotype, we evaluated its effect on the α-thalassemia phenotype. Overall, we identified 72 subjects with five different KLF1 heterozygous mutations in 1468 individuals, including 65 out of 432 α-thalassemia carriers with fetal hemoglobin (HbF) levels ≥1%, 0 out of 310 carriers with HbF levels <1% and 7 out of 726 HbH disease patients. We firstly established the link between KLF1 mutations and relatively elevated hemoglobin A2 (HbA2 ) and HbF levels, along with lower mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) values in a group of α-thalassemia carriers. However, we concluded that KLF1 mutations were not significantly linked to HbH disease severity. On the basis of HBA or HBB genotype and gender, clinical severity of patients with HbH disease was correctly predicted in 73.3% cases. It may improve the screening and diagnostic assessment of α-thalassemia.

IthaGenes: an interactive database for haemoglobin variations and epidemiology

Inherited haemoglobinopathies are the most common monogenic diseases, with millions of carriers and patients worldwide. At present, we know several hundred disease-causing mutations on the globin gene clusters, in addition to numerous clinically important trans-acting disease modifiers encoded elsewhere and a multitude of polymorphisms with relevance for advanced diagnostic approaches. Moreover, new disease-linked variations are discovered every year that are not included in traditional and often functionally limited locus-specific databases. This paper presents IthaGenes, a new interactive database of haemoglobin variations, which stores information about genes and variations affecting haemoglobin disorders. In addition, IthaGenes organises phenotype, relevant publications and external links, while embedding the NCBI Sequence Viewer for graphical representation of each variation. Finally, IthaGenes is integrated with the companion tool IthaMaps for the display of corresponding epidemiological data on distribution maps. IthaGenes is incorporated in the ITHANET community portal and is free and publicly available at http://www.ithanet.eu/db/ithagenes.

Advances in technologies for screening and diagnosis of hemoglobinopathies

Hemoglobinopathies constitute the most common monogenic disorders worldwide, caused by mutations in the globin genes that synthesize the globin chains of hemoglobin. Synthesis may be reduced (thalassemia) or underlie abnormal hemoglobins. Mutation interactions produce a wide range of disorders. For neonatal and antenatal screening, identification of affected newborns or carriers is achieved by hematological tests. DNA analysis supports definitive diagnosis, and additionally facilitates prenatal diagnosis procedures. Most methods used today have been developed over several decades, with few recent advances in hematology methods. However, DNA methods evolve continuously. With global migration and multiethnic societies the trend is from targeted, population-specific methods towards generic methods, such as Sanger sequencing (point mutations) and multiplex ligation probe amplification (deletions). DNA microarrays constitute an advanced DNA method for some mutation categories. The newest DNA technology is next-generation sequencing. Although not completely ready for routine use currently, next-generation sequencing may soon become a reality for some hemoglobin diagnostic laboratories.

Genotyping of BCL11A and HBS1L-MYB SNPs associated with fetal haemoglobin levels: a SNaPshot minisequencing approach

BACKGROUND

B-thalassaemia and sickle cell disease (SCD) are two of the most common monogenic diseases that are found in many populations worldwide. In both disorders the clinical severity is highly variable, with the persistence of fetal haemoglobin (HbF) being one of the major ameliorating factors. HbF levels are affected by, amongst other factors, single nucleotide polymorphisms (SNPs) at the BCL11A gene and the HBS1L-MYB intergenic region, which are located outside the β-globin locus. For this reason, we developed two multiplex assays that allow the genotyping of SNPs at these two genomic regions which have been shown to be associated with variable HbF levels in different populations.

RESULTS

Two multiplex assays based on the SNaPshot minisequencing approach were developed. The two assays can be used to simultaneous genotype twelve SNPs at the BCL11A gene and sixteen SNPs at HBS1L-MYB intergenic region which were shown to modify HbF levels. The different genotypes can be determined based on the position and the fluorescent colour of the peaks in a single electropherogram. DNA sequencing and restriction fragment length polymorphism (PCR-RFLP) assays were used to verify genotyping results obtained by SNaPshot minisequencing.

CONCLUSIONS

In summary, we propose two multiplex assays based on the SNaPshot minisequencing approach for the simultaneous identification of SNPs located at the BCL11A gene and HBS1L-MYB intergenic region which have an effect on HbF levels. The assays can be easily applied for accurate, time and cost efficient genotyping of the selected SNPs in various populations.

Non-transfusion-dependent thalassemias

Non-transfusion-dependent thalassemias include a variety of phenotypes that, unlike patients with beta (β)-thalassemia major, do not require regular transfusion therapy for survival. The most commonly investigated forms are β-thalassemia intermedia, hemoglobin E/β-thalassemia, and α-thalassemia intermedia (hemoglobin H disease). However, transfusion-independence in such patients is not without side effects. Ineffective erythropoiesis and peripheral hemolysis, the hallmarks of disease process, lead to a variety of subsequent pathophysiologies including iron overload and hypercoagulability that ultimately lead to a number of serious clinical morbidities. Thus, prompt and accurate diagnosis of non-transfusion-dependent thalassemia is essential to ensure early intervention. Although several management options are currently available, the need to develop more novel therapeutics is justified by recent advances in our understanding of the mechanisms of disease. Such efforts require wide international collaboration, especially since non-transfusion-dependent thalassemias are no longer bound to low- and middle-income countries but have spread to large multiethnic cities in Europe and the Americas due to continued migration.