The alpha thalassaemias

Hemoglobin Balkh, a Novel Mutation in Codon 132 of α2-Globin Gene [α132(H15) (+T) or HBA2:C.396dup (p.Val134fs)]: A Case Report and Insight into the Pathophysiology

We report a novel mutation on α2-globin gene leading to an elongated α-chain. This novel frameshift mutation was detected in a 13-year-old boy from Balkh province, Afghanistan. DNA analysis identified an insertion of thymine (T) at codon 132 [HBA2:c.396dup (p.Val134fs)]. We named the novel hemoglobin variant 'Hemoglobin Balkh' after the geographic location from which the patient originated. This novel variant was found in association with α3.7 kb α-globin gene deletion, suggesting a compound heterozygous state that contributes to the patient's clinical presentation.

Use of HSC-targeted LNP to generate a mouse model of lethal α-thalassemia and treatment via lentiviral gene therapy

ABSTRACT

α-Thalassemia (AT) is one of the most commonly occurring inherited hematological diseases. However, few treatments are available, and allogeneic bone marrow transplantation is the only available therapeutic option for patients with severe AT. Research into AT has remained limited because of a lack of adult mouse models, with severe AT typically resulting in in utero lethality. By using a lipid nanoparticle (LNP) targeting the receptor CD117 and delivering a Cre messenger RNA (mRNACreLNPCD117), we were able to delete floxed α-globin genes at high efficiency in hematopoietic stem cells (HSC) ex vivo. These cells were then engrafted in the absence or presence of a novel α-globin-expressing lentiviral vector (ALS20αI). Myeloablated mice infused with mRNACreLNPCD117-treated HSC showed a complete knock out (KO) of α-globin genes. They showed a phenotype characterized by the synthesis of hemoglobin H (HbH; also known as β-tetramers or β4), aberrant erythropoiesis, and abnormal organ morphology, culminating in lethality ∼8 weeks after engraftment. Mice infused with mRNACreLNPCD117-treated HSC with at least 1 copy of ALS20αI survived long term with normalization of erythropoiesis, decreased production of HbH, and amelioration of the abnormal organ morphology. Furthermore, we tested ALS20αI in erythroid progenitors derived from α-globin-KO CD34+ cells and cells isolated from patients with both deletional and nondeletional HbH disease, demonstrating improvement in α-globin/β-globin mRNA ratio and reduction in the formation of HbH by high-performance liquid chromatography. Our results demonstrate the broad applicability of LNP for disease modeling, characterization of a novel mouse model of severe AT, and the efficacy of ALS20αI for treating AT.

Diagnosis and screening of abnormal hemoglobins

Hemoglobin (Hb) abnormalities, such as thalassemia and structural Hb variants, are among the most prevalent inherited diseases and are associated with significant mortality and morbidity worldwide. However, there were not comprehensive reviews focusing on different clinical analytical techniques, research methods and artificial intelligence (AI) used in clinical screening and research on hemoglobinopathies. Hence the review offers a comprehensive summary of recent advancements and breakthroughs in the detection of aberrant Hbs, research methods and AI uses as well as the present restrictions anddifficulties in hemoglobinopathies. Recent advances in cation exchange high performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), isoelectric focusing (IEF), flow cytometry, mass spectrometry (MS) and polymerase chain reaction (PCR) etc have allowed for the definitive detection by using advanced AIand portable point of care tests (POCT) integrating with smartphone microscopic classification, machine learning (ML) model, complete blood counts (CBC), imaging-based method, speedy immunoassay, and electrochemical-, microfluidic- and sensing-related platforms. In addition, to confirm and validate unidentified and novel Hbs, highly specialized genetic based techniques like PCR, reverse transcribed (RT)-PCR, DNA microarray, sequencing of genomic DNA, and sequencing of RT-PCR amplified globin cDNA of the gene of interest have been used. Hence, adequate utilization and improvement of available diagnostic and screening technologies are important for the control and management of hemoglobinopathies.

Novel Decision Tool for More Severe α-Thalassemia Genotypes Screening with Functional Loss of Two or More α-Globin Genes: A Diagnostic Test Study

After the exclusion of iron deficiency and β-thalassemia, molecular research for α-thalassemia is recommended to investigate microcytic anemia. Aiming to suggest more efficiently the molecular analysis for individuals with a greater chance of having a symptomatic form of the disease, we have developed and validated a new decision tool to predict the presence of two or more deletions of α-thalassemia, increasing considerably the pre-test probability. The model was created using the variables: the percentage of HbA₂, serum ferritin and mean corpuscular volume standardized by age. The model was trained in 134 patients and validated in 160 randomly selected patients from the total sample. We used Youden's index applied to the ROC curve methodology to establish the optimal odds ratio (OR) cut-off for the presence of two or more α-globin gene deletions. Using the OR cut-off of 0.4, the model's negative predictive value (NPV) was 96.8%; the cut-off point accuracy was 85.4%; and the molecular analysis pre-test probability increased from 25.9% to 65.4% after the use of the proposed model. This tool aims to assist the physician in deciding when to perform molecular studies for the diagnosis of α-thalassemia. The model is useful in places with few financial health resources.

Detection of maternal carriers of common α-thalassemia deletions from cell-free DNA

α-Thalassemia is a common inherited blood disorder manifested mainly by the deletions of α-globin genes. In geographical areas with high carrier frequencies, screening of α-thalassemia carrier state is therefore of vital importance. This study presents a novel method for identifying female carriers of common α-thalassemia deletions using samples routinely taken for non-invasive prenatal tests for screening of fetal chromosomal aneuploidies. A total of 68,885 Vietnamese pregnant women were recruited and α-thalassemia statuses were determined by gap-PCR, revealing 5344 women (7.76%) carried deletions including αα/--SEA (4.066%), αα/-α3.7 (2.934%), αα/-α4.2 (0.656%), and rare genotypes (0.102%). A two-stage model was built to predict these α-thalassemia deletions from targeted sequencing of the HBA gene cluster on maternal cfDNA. Our method achieved F1-scores of 97.14-99.55% for detecting the three common genotypes and 94.74% for detecting rare genotypes (-α3.7/-α4.2, αα/--THAI, -α3.7/--SEA, -α4.2/--SEA). Additionally, the positive predictive values were 100.00% for αα/αα, 99.29% for αα/--SEA, 94.87% for αα/-α3.7, and 96.51% for αα/-α4.2; and the negative predictive values were 97.63%, 99.99%, 99.99%, and 100.00%, respectively. As NIPT is increasingly adopted for pregnant women, utilizing cfDNA from NIPT to detect maternal carriers of common α-thalassemia deletions will be cost-effective and expand the benefits of NIPT.

Molecular Heterogeneity of Hb H Disease in India

Alpha thalassemia is an autosomal recessive disorder caused by large deletions and/or point mutations in the α- globin genes. Hemoglobin H (Hb H) disease is most frequently due to deletion of three of the four α globin genes associated with variable clinical severity depending on the genotype. There are few reports on Hb H disease in Indians where genotyping has been done and we have reviewed the molecular and clinical heterogeneity of these cases. An electronic search for relevant articles was conducted using two journal databases, i.e., PubMed and Science Direct using the key words “Hb H Disease”, “Hemoglobin H”, “α-thalassemia”, “mutations”, “molecular heterogeneity”, “case reports” and “India”. This review was performed based on preferred reporting items for the systematic review and meta-analysis protocols (PRISMA-P) guidelines. The molecular spectrum of Hb H disease in Indians includes the most common [-α3.7, -α4.2, --SA, Poly A (AATAAA→AATA--), Hb Sallanches], rare [--SEA, --MED, IVS 1nt 1 (G→A), Hb Koya Dora, Hb Sun Prairie], very rare [Hb Iberia, Hb Seal Rock, Hb Zürich-Albisrieden] and novel [Codon 76 (+T) and --Kol] α-globin gene mutations inherited largely as compound heterozygotes with considerable clinical variability. The molecular diagnosis of Hb H disease is important for genetic counseling and management.

Detection of Common Deletional of α-Thalassemia 3.7 Kb from Metropolitan Region of Manaus, Amazonas, Brazil

Background

Alpha Thalassemia (α-thal) is a heterogeneous group of hereditary alterations caused by deletions that affect alpha regulatory genes, and the 3.7Kb deletion is the most frequent worldwide. The prevalence ranges from 20% and 35% in Brazil, depending mainly on race, predominant in Afro-descendants.

Purpose

The aim was to determine α-thal -^α3.7Kb and -^α4.2Kb deletions, estimating their frequency in individuals from six regions of Amazonas State.

Methods

Volunteers age between 18-59 years old of both genders participated in the study. Blood was collected from March 2014 to September 2017 at the health centers of each participant city. α-thal^3.7Kb was performed by GAP-PCR, while α-thal^4.2Kb by Multiplex-PCR. The total samples collected from each city were: Manaus (capital), 356 (19.7%); Iranduba 232 (12.8%); Manacapuru, 287 (15.9%); Presidente Figueiredo, 370 (20.5%); Itacoatiara, 301 (16.6%); and Coari, 263 (14.5%).

Results

The average age among males was 35.3±14.8, while for females, it was 36.7±14.9 years old. Microcytosis (MCV <80fL) was found in 158 individuals (8,46%) and α-thal diagnosed in 143 individuals (7.9%), and all of these individuals carried the ^3.7Kb deletion 5.95% in heterozygous and 1.95% in homozygous. α-thal^4.2kb was not found in any volunteer. The association analyses to the α-thal^3.7kb genotypes were statistically significant for all hematological parameters (p<.001), except serum iron and serum ferritin analyses.

Conclusion

This study highlights α-thal 3.7kb deletion as an important public health problem, especially in a population not yet characterized about this disease. Thus, epidemiological studies using molecular tools become relevant in regions where the disease is underestimated, contributing to a better understanding of thalassemia incidence and iron deficiency anemias incidence of the participating cities. We reinforce that future molecular studies in North Region from Brazil can be utilized to describe other genetic anemias as structural hemoglobinopathies that have already proven to be highly prevalent in Brazil.

Challenges in chronic transfusion for patients with thalassemia

The introduction of regular red cell transfusions 60 years ago transformed β-thalassemia major from a fatal childhood illness into a chronic disorder. Further advances in the prevention of transfusion-transmitted infections and management of iron overload have allowed survival and quality of life to approach normal. However, transfusion therapy for some other thalassemia syndromes continues to challenge clinical decision-making. Nearly one-half of the patients with E ß thalassemia are transfusion-dependent, yet the criteria for initiating transfusions or hemoglobin targets are not well defined. Patients with thalassemia intermedia who begin transfusions as adults are at very high risk for developing red cell alloimmunization and serious hemolytic transfusion reactions. In the growing number of survivors of Bart hydrops fetalis, the approach to transfusion therapy and iron chelation is rapidly evolving. A collaboration between hematology and transfusion medicine specialists will be essential to improving patient care and developing evidence-based guidelines.

Alpha-Thalassemia Carrier due to -α3.7 Deletion: Not So Silent

BACKGROUND/OBJECTIVE

Alpha-thalassemia is one of the most prevalent genetic diseases, with the -α3.7 deletion being the most common mutation. Molecular studies have suggested mechanisms to explain the mild phenotype of "silent carrier" heterozygotes. However, the correlation between the clinical laboratory picture and the -α3.7 heterozygous state remains unclear, thus we chose to investigate.

METHODS

We analyzed the medical files of 192 children evaluated for microcytosis at our tertiary center between 2007 and 2017 and diagnosed as heterozygotes for the -α3.7 deletion. Additional α-thalassemia mutations, iron deficiency anemia, and β-thalassemia were ruled out. Laboratory parameters were compared to age- and sex-matched reference values.

RESULTS

The -α3.7 carriers had significantly lower Hb and mean corpuscular volume (MCV) than the reference population, and significantly higher red blood cell counts across all age groups. The greatest reduction in Hb level appeared among male adolescents, while MCV was consistently 2 SDs lower than normal in most patients older than 2 years.

CONCLUSION

Heterozygosity for the -α3.7 deletion was associated with clinically significant microcytosis and mild anemia in our pediatric population. In the absence of iron deficiency and β-thalassemia, this finding provides a diagnosis for mild microcytic anemia, making additional investigations of microcytosis unnecessary.

Recent progress in laboratory diagnosis of thalassemia and hemoglobinopathy: a study by the Korean Red Blood Cell Disorder Working Party of the Korean Society of Hematology

Genetic hemoglobin disorders are caused by mutations and/or deletions in the α-globin or β-globin genes. Thalassemia is caused by quantitative defects and hemoglobinopathies by structural defect of hemoglobin. The incidence of thalassemia and hemoglobinopathy is increased in Korea with rapid influx of people from endemic areas. Thus, the awareness of the disease is needed. α-thalassemias are caused by deletions in α-globin gene, while β-thalassemias are associated with decreased synthesis of β-globin due to β-globin gene mutations. Hemoglobinopathies involve structural defects in hemoglobin due to altered amino acid sequence in the α- or β-globin chains. When the patient is suspected with thalassemia/hemoglobinopathy from abnormal complete blood count findings and/or family history, the next step is detecting hemoglobin abnormality using electrophoresis methods including high performance liquid chromatography and mass spectrometry. The development of novel molecular genetic technologies, such as massively parallel sequencing, facilitates a more precise molecular diagnosis of thalassemia/hemoglobinopathy. Moreover, prenatal diagnosis using genetic testing enables the prevention of thalassemia birth and pregnancy complications. We aimed to review the spectrum and classification of thalassemia/hemoglobinopathy diseases and the diagnostic strategies including screening tests, molecular genetic tests, and prenatal diagnosis.

Invasive molecular prenatal diagnosis of alpha and beta thalassemia among Hakka pregnant women

This study is a retrospective analysis of the prenatal genetic diagnosis results of fetuses with high risk of major thalassemia to provide information for clinical genetic counseling and to better control the birth of major thalassemia child in Hakka population. Totally, 467 fetuses in at-risk pregnancies were collected from Meizhou people's hospital from January 2014 to December 2017. Genomic DNAs were extracted from peripheral blood of the couples and villus, amniotic fluid or cord blood of the fetuses. DNA-based diagnosis was performed using polymerase chain reaction (PCR) and flow-through hybridization technique. Follow-up visits were done half a year after the fetuses were born. Around 467 fetus at-risk pregnancies were performed prenatal diagnosis. We detected 88 CVS samples, 375 amniocentesis fluid samples and, 4 cord blood samples. The 356 fetuses in α-thalassemia families consisted of 69 (19.38%) with Bart's hydrops syndrome, 20 (5.62%) fetuses with Hb H disease, and 184 (51.68%) fetuses with heterozygote. And the 111 fetuses in β-thalassemia families consisted of 31 (27.93%) thalassemia major, 51 (45.95%) fetuses with heterozygote. There are 13 fetuses with α+β-thalassemia, including 2 cases with severe β-thalassemia. DNA-based testing prenatal diagnosis of thalassemia was found to be highly reliable. Our findings provide key information for clinical genetic counseling of prenatal diagnosis for major thalassemia in Hakka pregnant women. Our work plays an important role in the prevention and control of thalassemia in Hakka population. We will also combine other techniques to further improve our molecular prenatal diagnostic capabilities, including the next-generation sequencing (NGS), Sanger sequencing and MLPA.

Population Screening for Hemoglobinopathies

Hemoglobinopathies are the most common single-gene disorders in the world. Their prevalence is predicted to increase in the future, and low-income hemoglobinopathy-endemic regions need to manage most of the world's affected persons. International organizations, governments, and other stakeholders have initiated national or regional prevention programs in both endemic and nonendemic countries by performing population screening for α- and β-thalassemia, HbE disease, and sickle cell disease in neonates, adolescents, reproductive-age adults (preconceptionally or in the early antenatal period), and family members of diagnosed cases. The main aim of screening is to reduce the number of affected births and, in the case of sickle cell disease, reduce childhood morbidity and mortality. Screening strategies vary depending on the population group, but a few common screening test methods are universally used. We discuss the salient features of population-screening programs around the globe as well as current and proposed screening test methodologies.

A modified sandwich ELISA for accurate measurement of HbF in α-thalassemia carriers containing Hb Bart's and Hb Portland 1

Hemoglobin F (HbF) in blood lysate can be accurately measured by various methods, including immunoassay. In this study, we have produced polyclonal antibody (pAb) against HbF and established a modified sandwich-type ELISA for HbF quantification in blood lysates. The modified sandwich ELISA utilized anti-γ-globin monoclonal antibody clones Thal N/B as the capture antibody (Ab) coated on solid-phase, fluorescein isothiocyanate (FITC)-labeled pAb as the detecting Ab, and HPR-labeled anti-FITC Ab as the signal-generating Ab. By using an optimized blood lysate dilution, the HbF could be measured with no interference from hemoglobin Bart's (Hb Bart's) and hemoglobin Portland (Hb Portland 1) presented in α-thalassemia carriers. HbF levels measured by the modified sandwich ELISA were comparable to those quantified by the standard cation-exchange high performance liquid chromatography. We suggested that this modified sandwich ELISA was able to accurately measure HbF levels even in α-thalassemia carriers containing Hb Bart's and Hb Portland 1 and be an alternative method for HbF measurement.

Causes of microcytic anaemia and evaluation of conventional laboratory parameters in the differentiation of erythrocytic microcytosis in blood donors candidates

CONTEXT AND OBJECTIVE

Microcytic anaemia results from defective synthesis of haemoglobin in the erythroid precursors, causing a reduction in its mean corpuscular volume (MCV). The most common causes of microcytosis, without the increase in HbA₂ levels, are iron deficiency anaemia (IDA) and α-thalassemia. The aim of this study was to identify the causes of microcytic anaemia and evaluate the haematological parameters from blood donors deemed ineligible (due to the low haematocrit level) that would differentiate the IDA and α-thal, whether isolated or in association.

METHODS

Genomic DNA was submitted to the polymerase chain reaction multiplex for the diagnosis of the most common allele deletions of α-thal and erythrogram and in order to verify haematological parameters. Iron deficiency (ID) was determined through the measurement of serum ferritin.

RESULTS

Of the 204 samples, 82 (40.2%) were identified with ID, 24 (17.8%) with α-thal and 10 (4.9%) with ID associated with α-thal. In the α-thal with ID group haemoglobin (Hb), MCV, mean corpuscular Hb concentration (MCHC) and mean corpuscular Hb (MCH) values were significantly lower compared to the isolated α-thal. In the group with ID Hb, MCV, MCHC and MCH values were significantly lower compared to those with isolated α-thal. The α-thal with ID group, showed Hb, MCV, MCHC and MCH significantly reduced when compared to those with IDA.

CONCLUSIONS

This study showed that the values of haematological parameters, especially haematocrit, Hb, MCV, MCH, MCHC and red blood cell distribution width (RDW), are lower in patients with IDA, especially when associated with α-thal and therefore it may be useful to discriminate between the different types of microcytic anaemia.

Haemoglobin variants, iron status and anaemia in Sri Lankan adolescents with low red cell indices: A cross sectional survey

Iron deficiency complicates the use of red cell indices to screen for carriers of haemoglobin variants in many populations. In a cross sectional survey of 7526 secondary school students from 25 districts of Sri Lanka, 1963 (26.0%) students had low red cell indices. Iron deficiency, identified by low serum ferritin, was the major identifiable cause occurring in 550/1806 (30.5%) students. Low red cell indices occurred in iron-replete students with alpha-thalassaemia including those with single alpha-globin gene deletions. Anaemia and low red cell indices were also common in beta-thalassaemia trait. An unexpected finding was that low red cell indices occurred in 713 iron-replete students with a normal haemoglobin genotype. It is common practice to prescribe iron supplements to individuals with low red cell indices. Since low red cell indices were a feature of all forms of α thalassaemia and also of iron deficiency, in areas where both conditions are common, such as Sri Lanka, it is imperative to differentiate between the two, to allow targeted administration of iron supplements and avoid the possible deleterious effects of increased iron availability in iron replete individuals with low red cell indices due to other causes such as α thalassaemia.

Molecular Basis of α-Thalassemia in Iran

Alpha-thalassemia (α-thal) is probably the most prevalent monogenic condition in the world. Deletions are the most common types of mutations in α-thal, followed by point mutations and small insertion/deletion. In the context of national screening program for prevention of thalassemia and hemoglobinopathies in Iran, α-thal carriers have come to more attention. Therefore, the frequency and distribution of α-globin mutations in various regions of the country have been studied in recent years. A comprehensive search was performed in PubMed, Scopus, and national databases for finding reports on mutation detection in α-thal carriers and HbH disease with Iranian origin. The mutation data of 10849 α-thal carriers showed that -α^3.7 and α^-5NT were the most common deletional and nondeletional mutations, respectively. In HbH disease cases, the -α^3.7/--^MED was the most prevalent genotype. Overall, 42 different mutations have been identified in α-globin cluster reflecting the high heterogeneity of the mutations in Iranian populations.

Molecular basis of α-thalassemia

α-Thalassemia is an inherited, autosomal recessive, disorder characterized by a microcytic hypochromic anemia. It is one of the most common monogenic gene disorders in the world population. The clinical severity varies from almost asymptomatic, to mild microcytic hypochromic, and to a lethal hemolytic condition, called Hb Bart's Hydrops Foetalis Syndrome. The molecular basis are usually deletions and less frequently, point mutations affecting the expression of one or more of the duplicated α-genes. The clinical variation and increase in disease severity is directly related to the decreased expression of one, two, three or four copies of the α-globin genes. Deletions and point mutations in the α-globin genes and their regulatory elements have been studied extensively in carriers and patients and these studies have given insight into the α-globin genes are regulated. By looking at naturally occurring deletions and point mutations, our knowledge of globin-gene regulation and expression will continue to increase and will lead to new targets of therapy.

Diagnostic approaches for inherited hemolytic anemia in the genetic era

Inherited hemolytic anemias (IHAs) are genetic diseases that present with anemia due to the increased destruction of circulating abnormal RBCs. The RBC abnormalities are classified into the three major disorders of membranopathies, hemoglobinopathies, and enzymopathies. Traditional diagnosis of IHA has been performed via a step-wise process combining clinical and laboratory findings. Nowadays, the etiology of IHA accounts for germline mutations of the responsible genes coding for the structural components of RBCs. Recent advances in molecular technologies, including next-generation sequencing, inspire us to apply these technologies as a first-line approach for the identification of potential mutations and to determine the novel causative genes in patients with IHAs. We herein review the concept and strategy for the genetic diagnosis of IHAs and provide an overview of the preparations for clinical applications of the new molecular technologies.

Prevalence of α-thalassaemia genotypes in pregnant women in northern Thailand

BACKGROUND & OBJECTIVES

Alpha-thalassaemias are genetic disorders with high prevalence in northern Thailand. However, common genotypes and current data on the prevalence of α-thalassaemias have not been reported in this region. Therefore, the objective of the present study was to determine the prevalence of α-thalassaemia genotypes in pregnant women in northern Thailand.

METHODS

Genomic DNA was extracted from blood samples of pregnant women who came to Maharaj Nakorn Chiang Mai University Hospital during July 2009 to 2010. The common deletion and point mutation genotypes of α-thalassaemia were evaluated by gap- polymerase chain reaction (PCR) and PCR with restriction fragment length polymorphism (RFLP).

RESULTS

Genotypes of 638 pregnant women were: 409 samples (64.11%) being normal subjects (αα/αα) and 229 samples (35.89%) with α-thalassaemias. these 229 samples could be classified into deletional HbH disease (--SEA/-α3.7) for 18 samples (2.82%); heterozygous α0-thalassaemia --SEA type (--SEA/αα)) for 78 (12.23%); heterozygous α+-thalassaemia - α3.7 type (-α3.7/αα) for 99 (15.52%); homozygous α+-thalassaemia - α3.7 type (-α3.7/- α3.7) for five (0.78%); heterozygous α+-thalassaemia - α4.2 type (-α4.2/αα) for two (0.31%); and heterozygous HbCS (αCSα/αα) for 27 (4.23%) cases.

INTERPRETATION & CONCLUSIONS

The prevalence of α-thalassaemias in pregnant women in northern Thailand was high. This finding supports the implementation of the prevention and control of this common genetic disorder by screening for α-thalassaemia genotypes.

Pregnancy in women with thalassemia: challenges and solutions

Advances in treatment of thalassemia have led to the aging of thalassemic patients, and consequently concern about successful reproductive outcome is augmented. Although women with thalassemia intermedia only were considered competent of achieving pregnancy, case series reveal the willingness of both thalassemia major and thalassemia intermedia women to have a family. Pregnancy in general is characterized by dynamic multiple-system changes and increased susceptibility to oxidative stress, while homozygous, transfusion-dependent, β-thalassemia patients manifest cardiac, hepatic, endocrine, and metabolic disorders attributable to chronic anoxia and iron overload and thalassemia intermedia, usually nontransfused, is associated with augmented risk of thromboembolic events. Pregnancy in thalassemia should be considered a high risk for both mother and fetus, and favorable outcomes are the result of continuous preconception, antenatal, and postpartum assessment and management by a team of thalassemia experts.

Genetic modulators of sickle cell disease in French Guiana: Markers of the slave trade

OBJECTIVES

Sickle cell disease (SCD) is the leading genetic disease in French Guiana, reflecting the predominantly African ancestry of the Guianese population. Our purpose was to characterize the genetic modulators of SCD in order to retrace the origin of the population in light of the slave trade.

METHODS

We have studied the sickle cell genotype, the βS haplotypes, the alpha and beta thalassemia and the UGT1A1 promoter polymorphisms in 224 Guianese patients with SCD.

RESULTS

The genotypes of SCD were HbSS 65.6%, HbSC 24.5%, and HbS-beta thalassemia 9.4%. The most frequent βS haplotypes were the Benin haplotype (65.9% of the chromosomes) and the Bantu (20.5%). Alpha thalassemic deletions were present in 37% of the patients and homozygosity for the (TA)7 allele of the UGT1A1 promoter in 21.4%. When the patients' origins were considered, 3 groups, Noir Marron, Haitians and Creoles, displayed distinctive characteristics. The HbSC genotype, the Benin haplotype, and the homozygous UGT1A1 genotype TA7/TA7 were significantly more frequent in Noir Marron. The Haitian patients were characterized by the occurrence of alpha-thalassemia and beta-thalassemia and by a higher prevalence of the Bantu haplotype. In the group of Creole patients, the genotype HbSS was predominant but the other modulators of SCD were associated with intermediate risk.

CONCLUSIONS

The results highlight the genetic diversity of the Guianese population and are concordant with historical data on the slave trade showing a West African origin for Noir Marron and a Central African origin for Haitians, while Guianese Creoles are highly admixed. Am. J. Hum. Biol. 28:811-816, 2016. © 2016Wiley Periodicals, Inc.

Prevalence of α(+)-Thalassemia in the Scheduled Tribe and Scheduled Caste Populations of Damoh District in Madhya Pradesh, Central India

This study was carried out to ascertain the allelic frequency of α(+)-thalassemia (α(+)-thal) in Scheduled caste and scheduled tribe populations of the Damoh district of Madhya Pradesh, India. Random blood samples of Scheduled tribe (267) and Scheduled caste (168), considering the family as a sampling unit, were analyzed for the presence of the -α(3.7) (rightward) (NG_000006.1: g.34164_37967del3804) and -α(4.2) (leftward) (AF221717) deletions. α(+)-Thal was significantly higher in the Scheduled tribals (77.9%) as compared to the scheduled caste population (9.0%). About 58.0% scheduled tribals carried at least one chromosome with the -α(3.7) deletion and 20.0% scheduled tribals carried the -α(4.2) deletion. Frequency for the -α(3.7) allele was 0.487 in the scheduled tribal populations in comparison to 0.021 in scheduled castes. Allelic frequency for -α(4.2) was 0.103 and 0.024, respectively, in the above communities. No Hardy-Weinberg equilibrium for α-thal gene (p < 0.05) was detected in the tribal population, indicating the presence of selection pressures in favor of α-thal mutation and adaptation.

Development and validation of a high throughput, closed tube method for the determination of haemoglobin alpha gene (HBA1 and HBA2) numbers by gene ratio assay copy enumeration-PCR (GRACE-PCR)

BACKGROUND

Deletions of the α-globin genes are the most common genetic abnormalities in the world. Currently multiplex Gap-PCRs are frequently used to identify specific sets of common deletions. However, these assays require significant post-amplification hands on time and cannot be used to identify novel or unexpected deletions. The aim of the current study was to develop a rapid screening test for the detection of all deletions of the α-globin genes that can be integrated into a high volume clinical laboratory workflow.

METHODS

A gene ratio assay copy enumeration (GRACE) PCR method was developed by simultaneous amplification of targets in the α-globin genes (HBA1 and HBA2) and the chloride channel voltage sensitive 7 (CLCN7) reference gene. A novel application of High Resolution Melting (HRM) analysis then allowed rapid determination of α-globin gene copy numbers. The assay was validated using 105 samples with previously determined and 62 samples with unknown α-globin genotypes.

RESULTS

The GRACE-PCR assay detected abnormal α-globin gene copy numbers in 108 of the 167 samples evaluated. The results were consistent with those from a commercial reverse hybridization assay and no allele drop out was observed.

CONCLUSIONS

We have successfully developed and validated a GRACE-PCR screening test for the detection of deletions and duplications of the α-globin genes. The assay is based on copy number determination and has the ability to detect both known and novel deletions of the α-globin genes. It is a closed tube technique; consequently the risk of amplicon contamination is negligible. Amplification, detection and analysis can be completed within one hour, making it faster, cheaper and simpler than other existing tests and thus well suited as a rapid first step in a clinical laboratory workflow.

Detection of α-Thalassemia by Using Multiplex Ligation-Dependent Probe Amplification as an Additional Method for Rare Mutations in Southern Turkey

α-thalassemia is the most common single gene disorder in the Cukurova Region in Turkey. It is therefore routinely screened, including premaritally, in our region. The heterogeneous molecular basis of the disease makes α-thalassemia mutation detection difficult and complex. Besides well established methods, multiplex ligation dependent probe amplification (MLPA) is known as an effective, simple and specific method for the detection and characterization of deletions and duplications. We employed MLPA testing to 30 patients with hematological parameters suggestive of α-thalassemia carrier status but was negative for α-thalassemia with conventional reverse dot blot hybridization (RDB). We found α-globin gene deletions in 3 out of 30 (10 %) patients with MLPA. We propose that MLPA can be used as a second tier test in addition to other techniques such as RDB to identify α-thalassemia carriers in high prevalence regions such as ours, thereby allowing clinicians to provide accurate genetic counselling.

Molecular characterization of Hb Hamilton Hill (HBA2: c.388delC), a novel HBA2 variant generating a premature termination codon and truncated HBA2 chain

In recent years, the identification of α-thalassemias caused by nondeletional mutations has increased significantly due to the advancement of sensitive molecular genetics tools. We report clinical and experimental data for a novel frameshift mutation caused by a single base deletion at position 388 in exon 3 of the α2-globin gene (HBA2: c.388delC; Hb Hamilton Hill), resulting in the phenotype of α-thalassemia (α-thal). Hb Hamilton Hill was identified in an adult female of unknown ethnicity investigated for unexplained microcytosis. Direct DNA sequencing of the HBA2 gene revealed a heterozygous mutation, HBA2: c.388delC, and the molecular effect of this mutation was assessed experimentally using our previously described in vitro model. The experimental analysis involved transfection of a human bladder carcinoma (5637) cell line with expression vectors carrying either HBA2-wild type (HBA2-WT) or HBA2: c.388delC followed by total RNA purification and cDNA synthesis. Both wild type and mutant gene expression was studied and compared at the transcriptional and translational levels using quantitative real time polymerase chain reaction (qReTi-PCR) and immunofluorochemistry (IFC), respectively. Our experimental data showed a significant reduction by 25.0% (p = 0.04) in the transcriptional activity generated from HBA2: c.388delC compared to HBA2-WT. As a result of this base deletion, a frameshift in the open reading frame generates a premature termination codon (PTC) at codon 132 of exon 3 resulting in the formation of a truncated α-globin chain. The truncated α-globin chain, observed by the IFC technique, is most likely unstable and undergoes a rapid turnover resulting in the thalassemic phenotype.

A simple and highly sensitive ELISA for screening of the α-thalassemia-1 Southeast Asian-type deletion

Couples in which both partners carry the α-thalassemia-1 trait have a 25% risk of hemoglobin Bart's hydrops fetalis in each pregnancy. Identification of α-thalassemia-1 trait is, therefore, necessary in order to control this severe form of α-thalassemia. We have generated monoclonal antibodies specific to the ζ-globin chain without cross reaction with other globin chains. A simple and sensitive ELISA was developed by using poly-l-lysine to increase the protein binding to the ELISA plate. The developed poly-l-lysine pre-coated ELISA has a very high sensitivity (100%) and specificity (97%) for detection of carriers of α-thalassemia-1 with Southeast Asian-type deletion.

The α-thalassemias

More than 100 varieties of α-thalassemia have been identified. Their geographic distribution and the challenges associated with screening, diagnosis, and management suggest that α-thalassemias should have a higher priority on global public health agendas.

An Alu element-mediated 28.5 kb α-thalassemia deletion found in a Chinese family

Over 95.0% of the α-thalassemia (α-thal) cases in southern China are caused by large deletions involving the α-globin gene. Here, we describe the molecular characterization of a novel 28.5 kb deletion that eliminated one of the duplicated α-globin genes in a Chinese family. The deletion breakpoint fragment involved Alu repeat sequences, suggesting a homologous recombination event. Phenotypic analysis on the heterozygous carrier of this deletion revealed that it leads to a very mild phenotype. Because of a 25.0% risk of Hb H (β4) disease in the offspring when in combination with another α(0)-thal allele, we should not ignore screening the deletion in prenatal diagnosis in order to decrease reproductive risk.

Characterization of Hb Calvino (HBB: c.406G > A): a new silent β-globin gene variant found in coexistence with α-thalassemia in a family of African origin

We report a new silent β-globin gene variant found in a family from Angola living in the north eastern Italian city of Ferrara. The probands, two young sisters, presented with hematological parameters compatible with a β-thalassemia (β-thal) minor but with normal Hb A₂ levels and normal hemoglobin (Hb) separation on high performance liquid chromatography (HPLC). Molecular analyses revealed a homozygosity for the common -α(3.7) (rightward) deletion and heterozygosity for a novel transition (GCT > ACT) at codon 135 of the β-globin gene, leading to an Ala → Thr single amino acid substitution that was inherited from the healthy father.

Clinical features and molecular analysis of Hb H disease in Taiwan

Thalassemia is highly prevalent in Taiwan, but limited data are available about the association between genotypes and clinical manifestations in Taiwanese patients with Hb H disease. Here, we studied α-globin gene abnormalities and clinical features in Taiwanese patients with Hb H disease. Of the 90 patients, sixty-four (71.1%) were deletional and twenty-six (28.9%) were nondeletional Hb H disease. The (- -^SEA) type of α⁰-thalassemia mutation was detected in the majority of patients (>95%). The most common genotype was (- -^SEA/-α^3.7), followed by (- -^SEA/α^csα). After further investigation of the genotype-phenotype correlation in 68 patients, we found that patients with nondeletional Hb H disease had more severe clinical features than those with deletional Hb H disease, including younger age at diagnosis, more requirement of blood transfusions, and larger proportion of patients with splenomegaly, hepatomegaly or jaundice. This is probably a consequence of the lower hemoglobin levels and the higher Hb H levels. The clinical severity was highly variable even among patients with an identical genotype, and the diversity was much more profound among patients with (- -/α^csα) genotype. Therefore, predicting the phenotype directly from the genotype in Hb H disease remains relatively difficult in Taiwan.

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.

Detection of acquired hemoglobinopathy in children with hematological malignancies at disease onset: results form a national referral centre

Abnormal hemoglobin synthesis is usually inherited but may also arise as a secondary manifestation of a hematological neoplasia. The objective of this study is to identify the presence of acquired hemoglobinopathy in children diagnosed with hematological malignancies and compare these against healthy controls. Prospective matched case-control study held from 2010 to 2012. For each patient with hematological malignancy two healthy controls matched on gender, age and race were recruited. Patients with other co-morbidities were excluded. All samples underwent supravital staining and high-performance liquid chromatography (HPLC) electrophoresis. Following identification of abnormal results, molecular genetic testing for all α- and β-thalassemia mutations prevalent in the Greek population was performed. Other causes of anemia were ruled out based on specific testing. A total of 44 (32 males) patients with a mean age of 7.1 years were enrolled in the study. Hematological disorders included acute lymphocytic leukemia (24), acute myeloid leukemia (8), non-Hodgkin lymphoma (8), Hodgkin disease (3), and Langerhans cell histiocytosis (1). Following exclusion of congenital hemoglobinopathies, atypical HPLC electrophoretic findings persisted in 18.1 % of the patient group, compared to 0 % in the control group (p < 0.001). The patient group showed marked microcytic anemia (p < 0.01) and detection of small inclusions (p = 0.034) on supravital staining. Comparison of the HPLC findings between the groups demonstrated significantly lower percentages of HbA (p = 0.02), normal HbA2 and higher percentage of fast moving Hb bands (p = 0.04) in the patient group. Interestingly, the majority of these patients belonged to the high-risk group. Acquired hemoglobinopathy is recognized in adult patients. This is a novel study describing evidence of abnormal erythropoiesis in children with hematological malignancies and in particular those classified as high-risk cancer patients according to international criteria.

Identification of one or two α-globin gene deletions by isoelectric focusing electrophoresis

OBJECTIVES

To investigate the utility of isoelectric focusing electrophoresis (IEF) for identifying patients with α-thalassemia, which results from the deletion of 1 or more of the α-globin genes.

METHODS

Samples were selected based on their hemoglobin H (HbH) concentration observed using IEF. The samples were analyzed for the most common α-globin gene deletions using molecular analysis.

RESULTS

α-Globin gene deletions corresponding to α-thalassemia trait or silent carrier were observed in all samples with the HbH less than 2% phenotype. The genotypes of the specimens with HbH greater than 5% were consistent with HbH disease, while the wild-type phenotype control samples showed a wild-type genotype.

CONCLUSIONS

Low concentrations of HbH can be detected in a patient with 1 or 2 α-gene deletions using IEF.

Genetic epidemiology, hematological and clinical features of hemoglobinopathies in Iran

There is large variation in the molecular genetics and clinical features of hemoglobinopathies in Iran. Studying structural variants of hemoglobin demonstrated that the β-chain variants of hemoglobin S and D-Punjab are more prevalent in the Fars (southwestern Iran) and Kermanshah (western Iran) provinces, respectively. Also, α-chain variants of Hb Q-Iran and Hb Setif are prevalent in western Iran. The molecular basis and clinical severity of thalassemias are extremely heterogenous among Iranians due to the presence of multiethnic groups in the country. β-Thalassemia is more prevalent in northern and southern Iran. Among 52 different β-thalassemia mutations that have been identified among Iranian populations, IVSII-1 G:A is the most frequent mutation in most parts of the country. The presence of IVS I-5 G:C mutation with high frequency in southeastern Iran might reflect gene flow from neighboring countries. A wide spectrum of α-thalassemia alleles has been detected among Iranians with -α(3.7 kb) as the most prevalent α-thalassemia mutation. The prevention program of thalassemia birth in Iran has reduced the birth rate of homozygous β-thalassemia since the implementation of the program in 1997. In this review genetic epidemiology, clinical and hematological aspects of hemoglobinopathies, and the prevention programs of β-thalassemia in Iran will be discussed.

Identification of biologically relevant enhancers in human erythroid cells

Identification of cell type-specific enhancers is important for understanding the regulation of programs controlling cellular development and differentiation. Enhancers are typically marked by the co-transcriptional activator protein p300 or by groups of cell-expressed transcription factors. We hypothesized that a unique set of enhancers regulates gene expression in human erythroid cells, a highly specialized cell type evolved to provide adequate amounts of oxygen throughout the body. Using chromatin immunoprecipitation followed by massively parallel sequencing, genome-wide maps of candidate enhancers were constructed for p300 and four transcription factors, GATA1, NF-E2, KLF1, and SCL, using primary human erythroid cells. These data were combined with gene expression analyses, and candidate enhancers were identified. Consistent with their predicted function as candidate enhancers, there was statistically significant enrichment of p300 and combinations of co-localizing erythroid transcription factors within 1-50 kb of the transcriptional start site (TSS) of genes highly expressed in erythroid cells. Candidate enhancers were also enriched near genes with known erythroid cell function or phenotype. Candidate enhancers exhibited moderate conservation with mouse and minimal conservation with nonplacental vertebrates. Candidate enhancers were mapped to a set of erythroid-associated, biologically relevant, SNPs from the genome-wide association studies (GWAS) catalogue of NHGRI, National Institutes of Health. Fourteen candidate enhancers, representing 10 genetic loci, mapped to sites associated with biologically relevant erythroid traits. Fragments from these loci directed statistically significant expression in reporter gene assays. Identification of enhancers in human erythroid cells will allow a better understanding of erythroid cell development, differentiation, structure, and function and provide insights into inherited and acquired hematologic disease.

Alpha thalassaemia and extended alpha globin genes in Sri Lanka

The α-globin genes were studied in nine families with unexplained hypochromic anaemia and in 167 patients with HbE β thalassaemia in Sri Lanka. As well as the common deletion forms of α(+) thalassaemia three families from an ethnic minority were found to carry a novel form of α(0) thalassaemia, one family carried a previously reported form of α(0) thalassaemia, --(THAI), and five families had different forms of non-deletional thalassaemia. The patients with HbE β thalassaemia who had co-inherited α thalassaemia all showed an extremely mild phenotype and reduced levels of HbF and there was a highly significant paucity of α(+) thalassaemia in these patients compared with the normal population. Extended α gene arrangements, including ααα, αααα and ααααα, occurred at a low frequency and were commoner in the more severe phenotypes of HbE β thalassaemia. As well as emphasising the ameliorating effect of α thalassaemia on HbE β thalassaemia the finding of a novel form of α(0) thalassaemia in an ethnic minority, together with an unexpected diversity of forms of non-deletion α thalassaemia in Sri Lanka, further emphasises the critical importance of micro-mapping populations for determining the frequency of clinically important forms of the disease.

Inherited hemoglobin disorders in an Afro-Amazonian community: Saracura

The most common hemoglobinopathies, viz, hemoglobins S and C, and α- and β-thalassemias, were investigated through the molecular screening of 116 subjects from the community of Saracura, comprising fugitive African slaves from farms of the municipality of Santarém, in the west of Pará State, Brazilian Amazon. The observed frequency of the HBB*S gene (0.9%) was significantly lower than that encountered in other Afro-derived communities in the region. Concomitantly, the absence of the HBB*C allele has been reported for most of the Afro-Amazonian communities thus far studied. As remnant populations of quilombos are generally small, the heterogeneous distribution of HBB*S and HBB*C alleles among them is probably due to genetic drift and/or founder effect. The observed frequency of 3.7 kb deletion in Saracura (8.5%) was consistent with the African origin of the population, with a certain degree of local differentiation and admixture with individuals of Caucasian ancestry, placed in evidence by the occurrence of - -(MED) deletion (1.2%), a common mutation in Mediterranean regions. As regards β-thalassemia, among the seven different mutations found in Saracura, three β^o and two β⁺ mutations were of Mediterranean origin, and two β⁺ of African. Thus, only 28% of the local β-thalassemia mutations found in Saracura were of African origin.

Recent advances in the molecular understanding of non-transfusion-dependent thalassemia

Thalassemias are a group of inherited autosomal recessive hematologic disorders that occur because of defects in the alpha (α)- and beta (β)-globin genes of adult hemoglobin (Hb). An imbalance in the synthesis of one or more of the globin chains can result in a wide spectrum of phenotypes depending on the type and amount of globin synthesized and additional genetic modifiers. In patients with thalassemia intermedia, a condition known as non-transfusion-dependent thalassemia (NTDT), transfusion requirements are absent or episodic. Non-transfusion-dependent thalassemia includes β-thalassemia intermedia, HbE β-thalassemia, and α-thalassemia intermedia, also known as Hb H disease. This article focuses on the molecular features and genetic mutations specific to NTDT.

Prevalence of α-thalassemia 3.7 kb deletion in the adult population of Rio Grande do Norte, Brazil

α-Thalassemia, arising from a defect in α-globin chain synthesis, is often caused by deletions involving one or both of the α-genes on the same allele. With the aim of investigating the prevalence of α-thalassemia 3.7 kb deletion in the adult population of Rio Grande do Norte, 713 unrelated individuals, between 18 and 59 years-of-age, were analyzed. Red blood cell indices were electronically determined, and A₂ and F hemoglobins evaluated by HPLC. PCR was applied to the molecular investigation of α-thalassemia 3.7 kb deletion. Eighty (11.2%) of the 713 individuals investigated presented α-thalassemia, of which 79 (11.1%) were heterozygous (-α^3.7/αα) deletions and 1 (0.1%) homozygous (-α^3.7/-α^3.7). Ethnically, heterozygous deletions were higher (24.8%) in Afro-Brazilians. Comparison of hematological parameters between individuals with normal genotype and those with heterozygous α⁺-thalassemia showed a statistically significant difference in the number of erythrocytes (p < 0.001), MCV (p < 0.001), MCH (p < 0.001) and Hb A₂ (p = 0.007). This study is one of the first dedicated to investigating α-thalassemia 3.7 kb deletion in the population of the State Rio Grande do Norte state. Results obtained demonstrate the importance of investigating this condition in order to elucidate the causes of microcytosis and hypochromia.

The case for intrauterine stem cell transplantation

The clinical burden imposed by the collective group of monogenic disorders demands novel therapies that are effective at achieving phenotypic cure early in the disease process before the development of permanent organ damage. This is important for lethal diseases and also for non-perinatally lethal conditions that are characterised by severe disability with little prospect of postnatal cure. Where postnatal treatments are limited to palliative options, intrauterine stem-cell therapies may offer the potential to arrest pathogenesis in the early undamaged fetus. Intrauterine stem-cell transplantation has been attempted for a variety of diseases, but has only been successful in immune deficiency states in the presence of a competitive advantage for donor cells. This disappointing clinical record requires preclinical investigations into strategies that improve donor cell engraftment, including optimising the donor cell source and manipulating the microenvironment to facilitate homing. This chapter aims to outline the current challenges of intrauterine stem-cell therapy.