A PCR-based strategy to detect the common severe determinants of alpha thalassaemia

Development of a Quantitative Multiplex PCR to Detect Three Common Alpha Thalassemia Deletions

Alpha thalassemia is an autosomal recessive genetic disorder with a high prevalence in the Middle East. The severe form of alpha-thalassemia is incompatible with life and can cause significant obstetric complications in the mother. Therefore, it is important to determine the genotype in parents who have a chance of having a fetus with one of the severe forms of this disease. A total of 112 samples that were previously analyzed for common alpha thalassemia mutations in Iran were used in this study. A new multiplex PCR including quantitative polymerase chain reaction to amplify the homologous regions of the alpha-globin gene cluster and fluorescent gap PCR was designed to identify -α3.7, -α4.2, --MED deletions. The ROC curve was used to determine the optimum cutoff points. Statistical analysis showed that there is a significant difference between the peak height ratios for different genotypes. The peak corresponding to the 297 bp fragment resulting from the amplification of the allele with MED-I deletion was detected in all the samples with this deletion. Different cutoffs for a range of sensitivities and specificities were determined by the ROC curve. The suggested method can identify three common large deletions in the alpha-globin gene cluster. A study with a larger sample size can provide more accurate information about the sensitivity and specificity of this test.

Genotype-phenotype correlation in patients with deletional and nondeletional mutations of Hb H disease in Southwest of Iran

We studied the alpha-globin gene genotypes, hematologic values, and transfusion-dependence of patients with Hb H disease. Molecular characterization of alpha-thalassemia was performed. We identified 120 patients with Hb H disease. Of these patients, 35 (29.16%) had deletional form of Hb H disease, and 85 (70.83%) had different form of non-deletional Hb H disease. The most frequently observed Hb H genotypes were --^Med/-α^3.7 in 33 patients (27.5%), α^CD19(-G) α^/αCD19(-G) α in 25 cases (20.83%), α^polyA2α/α^polyA2α in 15 (12.5%), and α^polyA1α/α^polyA1α in 13 (10.83%) respectively. The probability of receiving at least one transfusion blood in deletional form was observed in 3 of 35 (8.57%) patients which just seen in 3 of 33 (9%) patients with --^Med/-α^3.7 genotype. This form was also observed in 8 of 85 (9.4%) patients in non-deletional Hb H diseases which five of them had Med deletion in compound with alpha globin point mutations. Nondeletional Hb H disease was more severe than deletional Hb H disease requiring more blood transfusions. We can recommend that Med deletion in compound with alpha-globin point mutations, polyA1 and constant spring in homozygous form needs to be taken into consideration when offering counseling to high-risk couples.

Droplet-based digital PCR for non-invasive prenatal genetic diagnosis of α and β-thalassemia

Non-invasive prenatal diagnosis (NIPD) of isolated cell-free DNA from maternal plasma has been applied to detect monogenic diseases in the fetus. Droplet digital PCR (ddPCR) is a sensitive and quantitative technique for NIPD. In the present study, the development and evaluation of ddPCR-based assays for common α and β-thalassemia variants amongst the Asian population was described; specifically, Southeast Asian (SEA) deletion, HbE, and 41/42 (-CTTT). SEA is caused by deletion of a 20 kb region surrounding the α-globin gene, whilst HbE and 41/42 (-CTTT) are caused by point mutations on the β-globin gene. Cell-free DNA samples from 46 singleton pregnant women who were carriers of these mutations were isolated and quantified using ddPCR with specially designed probes for each target allele. Allelic copy number calculation and likelihood ratio tests were used to classify fetal genotypes. Classification performances were evaluated against ground truth fetal genotypes obtained from conventional amniocentesis. Copy number variation analysis of SEA deletion accurately classified fetal genotypes in 20 out of 22 cases with an area under the receiver operating characteristic curve of 0.98 for detecting Hb Bart's hydrops fetalis. For HbE cases, 10 out of 16 samples were correctly classified, and three were inconclusive. For 41/42 (-CTTT) cases, 2 out of 8 were correctly classified, and four were inconclusive. The correct genotype was not rejected in any inconclusive case and may be resolved with additional ddPCR experiments. These results indicate that ddPCR-based analysis of maternal plasma can become an accurate and effective NIPD for SEA deletion α-(0) thalassemia. Although the performance of ddPCR on HbE and 41/42 (-CTTT) mutations were not sufficient for clinical application, these results may serve as a foundation for future works in this field.

Alpha‐globin gene triplication and its effect in beta‐thalassemia carrier, sickle cell trait, and healthy individual

The genotype and phenotype correlation between coinheritance of heterozygous beta‐thalassemia with the alpha‐globin triplication is unclear. In this study we have investigated and reviewed alpha triplication frequency in beta‐thalassemia carriers, sickle cell trait, and healthy individuals and its effect on hematological and phenotypical changes. In this study, 4005 beta‐thalassemia carriers, 455 sickle cell trait, and 2000 healthy individuals were included. Molecular characterization of beta and alpha‐thalassemia was performed. The frequencies of alpha‐globin triplication in beta‐thalassemia carriers, sickle cell trait, and healthy individuals were 67 (1.67%), 4 (0.88%), and 18 (0.9%), respectively. In total, the frequency of alpha‐triplications is approximately 89 (1.39%) in Khuzestan province, South of Iran population. We have compared the average hematological parameters of beta‐thalassemia carriers, sickle cell trait, and healthy individuals with and without alpha gene triplication.

This mutation did not show any significant effect on the change of blood indices, neither in healthy individuals nor in sickle cell trait and beta‐thalassemia carriers. Therefore, there is no need to take more notice of anti 3.7 mutation in beta‐thalassemia carriers is opposed with some studies reported that the presence of excess alpha‐globin genes in beta‐thalassemia carriers can lead to the phenotype of beta‐thalassemia intermedia. Therefore, not every individual with triplicated alpha globin coinherited with beta‐thalassemia trait will have a significantly lower Hb than normal, and it is highly likely that none of them will need transfusion.

Prevalence and Genetic Analysis of α- and β-Thalassemia and Sickle Cell Anemia in Southwest Iran

This prospective study assessed the prevalence and genetic analysis of α- and β-thalassemia and sickle cell anemia (SCA) in Southwest Iran. Hematological indices were measured in 17,581 couples living in Khuzestan Province, Southwest Iran. Individuals with mean corpuscular volume <80, mean corpuscular hemoglobin <27, hemoglobin A2 ≥3/5 were considered as β-thalassemia traits. Prevalence of minor β-thalassemia, α-thalassemia, SCA, iron deficiency anemia, and silent thalassemia were respectively identified in 995 (5.6%), 1169 (6.65%), 1240 (7.05%), 911 (5.18%), and 1134 (6.45%) individuals using a multiplex amplification refractory mutation system, and direct DNA sequencing of globin genes. Three codons IVS-II-1 (G → A; 26%; n = 13), IVS-I-1 (G → T; 16%; n = 8), and IVS-I-110 (G → A; 14%; n = 7) were the most frequent mutants and IVS-II-1 was the most common β-thalassemia mutation. Also, based on a gap-polymerase chain reaction assay, genotype frequencies of α-globin mutations were -α^{3.7 kb} (50%; n = 25), Med/αα^thal (12%; n = 6), and -α4.2/αα (10%; n = 5), which were the most frequent deletion mutants (72% in total). The most common deletion (50%) was -α^{3.7 kb}. Our data suggest that the population of Southwest Iran is at high risk of α- and β-thalassemia caused by these deletion mutants and SCA. Our findings will be useful for developing an efficient control program and genetic counseling.

Double Heterozygosity for Hb Durham-N.C. (HBB: c.344T>C) [β114(G16)Leu→Pro] and the IVS-I-110 (HBB: c.93-21G>A) Causing a Severe β-Thalassemia Phenotype

The evaluation of a 10-month-old girl of Sicilian origin with a clinical phenotype of severe thalassemia led to the identification of two β-globin gene defects, a β-thalassemia (β-thal), mutation at IVS-I-110 (HBB: c.93-21G>A) and a variant hemoglobin (Hb) mutation at codon 114 (HBB: c.344T>C) on the other allele, reported as Hb Durham-N.C. (also known as Hb Brescia) [β114(G16)Leu→Pro] in the HbVar database. A very low Hb level (Hb 3.5 g/dL), microcytosis [mean corpuscular volume (MCV) 63.2 fL] and hypocromia [mean corpuscular Hb (MCH) 19.6 pg], increased red blood cell (RBC) distribution width (RDW) (36.0%), higher reticulocytes (6.2%), anisocytosis, poikilocytosis, hypocromia, basophilic stippling and inclusion body formation, were present in the affected subject. Analysis of other family components showed the presence of HBB: c.93-21G>A defect in the mother and in her brother, while Hb Durham-N.C. was absent in all other relatives, thus, this mutation has arisen as a de novo defect. This is the first case described as a severe thalassemic phenotype in a compound heterozygote carrier of this unstable Hb and a common β-thalassemic allele. The important information gained from this case is that a rare dominant or recessive mutation may arise in every individual, even if this is a very rare event.

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.

Molecular Characterization of β-Thalassemia Intermedia in Southeast Iran

Inheritance of mild mutations within the β-globin gene and coinheritance of α-thalassemia (α-thal) are known as two important genetic modifiers in β-thalassemia (β-thal) intermedia (β-TI). We aimed to evaluate the spectrum of β- and α-thal mutations in β-TI patients in Southeast Iran. Common β- and α-globin gene mutations were detected by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and multiplex gap-PCR, respectively. There were 26 male (57.8%) and 19 female (42.2%) patients. HBB: c.92 + 5T > C [IVS-I-5 (G > C)] and HBB: c.-138C + 1G > A [IVS-II-I (G > A)] represented the prevalent alleles with respective frequencies of 60.0 and 10.0%. Other β-globin mutations included HBB: c.-138C > T [-88 (C > T)], HBB: c.27_28insG [frameshift codons (FSC) 8/9 (+G)], HBB: c.46delT [codon 15 (-T)], HBB: c.93-22_95del (IVS-I, 25 del), and the 619 bp deletion (NG_000007.3: g.71609_72227del619). The predominant genotypic combinations were β(0)/β(0) (68.9%), β(0)/β(+ )(8.9%) and β(+)/β(+ )(2.2%). Coinheritance of α-thal was observed in 33.0% of the patients, with the -α(3.7) (rightward) (NG_000006.1: g.34164_37967del3804) as the most common deletion (86.0%). One patient was diagnosed with the -α(4.2) (leftward) (AF221717) and one with the - -(MED) (g.24664_41064del16401) deletions, while no patients carried the -(α)(20.5) (g.15164_37864del22701), α(-5 nt) (HBA2: c.95 + 2_95_6delTGAGG) or codon 19 (-G) (HBA2: c.56delG) mutations. The alleviating molecular mechanism was not explainable by β(+ )or concurrent α-thal in more than half of our β-TI patients. This encourages conducting more studies to identify other contributing factors, especially Hb F-inducing genetic modifiers.

Incidence of haemoglobinopathies in Sicily: the impact of screening and prenatal diagnosis

BACKGROUND

Haemoglobinopathies are a major public health problem in Sicily: it was estimated a frequency of 1/245 couples are at risk of haemoglobinopathies. This paper reviews legislative actions, prevention activities, carrier screening, genetic counselling, foetal sampling and laboratory methodology analysis evolution reporting the results of 30 years of prevention actions to assess the efficiency of our preventative programme in the control of haemoglobinopathies in Sicily.

METHODS

This programme consisted principally of five phases: legislative actions, public awareness campaign, carrier screening, genetic counselling and prenatal diagnosis.

RESULTS

These programmes have been very effective, which we can see from a greater public awareness of thalassaemia and its prevention in the target population furthermore by a marked decline in the incidence of thalassaemia major and sickle cell anaemia from 1 in 245 live births in the absence of prevention to 1 in 2000, with a reduction in about 85%. The residual cases were because of a conscious choice by expecting parents in relation to improved life expectancy as well as improved quality of life of the affected patients.

CONCLUSION

The study suggests that public health authorities should act and invest in a similar programme for prevention of thalassaemia, as well as in relation to the increased survival of patients and the consequent organ complications.

The Hematological and Molecular Spectrum of α-Thalassemias in Turkey: The Hacettepe Experience

OBJECTIVE

The spectrum of α-thalassemias correlates well with the number of affected α-globin genes. Additionally, combinations of the several non-deletional types of mutations with a large trans deletion comprising the 2 α-globin genes have an impact on the clinical severity. The objective of this study was to analyze the hematological and molecular data of 35 patients with Hb H disease from a single center in order to identify the genotypes of Hb H disease and genotype-phenotype correlations.

MATERIALS AND METHODS

Herein, we report the hematological and mutational spectrum of patients with Hb H disease (n=35). Additionally, genotypes of α-gene mutations of 78 individuals, who were referred to our institution for α-gene screening, were analyzed.

RESULTS

Supporting the previous data from Turkey, -α3.7 was the most common mutation among patients with Hb H disease (62.8%) and in the other 78 subjects (39.7%). Of the patients with Hb H disease, the most common genotypes were -α3.7/--20.5, -α3.7/--26.5, and -α3.7/--17.5 in 10 (28.6%), 6 (17.1%), and 6 (17.1%) patients, respectively. Another small deletion, -4.2 alpha, and several non-deletional types of α-gene mutations, namely α (-5nt): IVS-I donor site (GAG.GTG.AGG->GAG.G-----); α (PA-2): AATAAA>AATGGA, and α (cd59): GGC->GAC, were found to be associated with Hb H disease when present at trans loci of one of the large deletions given above. The combinations consisting of 1 non-deletional and 1 of the large deletional types of mutations (αTα/--) at trans loci were found to result in a more severe phenotype compared to the genotypes composed of 1 small trans deletion of a large deletion (-α/--). The combination of α (Cd59) and -- in trans was associated with severe phenotype and the disease was associated with an increase in Hb Bart's level with null Hb H. In spite of the presence of 2 intact α-globin genes, homozygosity for PA-2 mutation resulted in severe Hb H disease.

CONCLUSION

This study indicated that Hb H disease is not rare in Turkey and its genotype is quite heterogeneous.

The Spectrum of α-Thalassemia Mutations in Kermanshah Province, West Iran

Thalassemia is a hereditary blood disorder that results from genetic defects causing deficient synthesis of hemoglobin (Hb) polypeptide chains. Although thalassemia mostly affects developing countries, there is limited knowledge of its accurate frequency and distribution in these regions. Knowing the prevalence of thalassemia and the frequency of responsible mutations is therefore an important step in the prevention and control program as well as treatment strategies. α-Thalassemia (α-thal) is prevalent in Middle East Asian populations, including Iran. In this study, 678 unrelated α-thal carriers, attending the Kermanshah Medical Genetics Laboratory, Kermanshah, Iran, were investigated for α-globin gene mutations by multiplex polymerase chain reaction (PCR) and direct sequencing. The most common mutation among our patients was -α(3.7) (rightward) (60.9%) deletion, which is also known to occur in high frequencies in other parts of Iran, in Southeast Asia and Mediterranean countries. Other prevalent α-thal mutations were α(-5 nt) (10.6%), α(polyA4) (9.9%), α(polyA6) (3.7%), - -(MED) (3.2%), -α(4.2) (leftward) (3.1%) deletion and codon 59 (Hb Adana; HBA1: c.179 G > A) (2.5%). These comprehensive new data are useful for establishing a screening strategy for the effective control of α-thal in Kermanshah Province.

Investigating alpha-globin structural variants: a retrospective review of 135,000 Brazilian individuals

Background

Brazil has a multiethnic population with a high diversity of hemoglobinopathies. While screenings for beta-globin mutations are far more common, alterations affecting alpha-globin genes are usually more silent and less well known. The aim of this study was to describe the results of a screening program for alpha-globin gene mutations in a representative sample of the Southeastern Brazilian population.

Methods

A total of 135,000 individuals, including patients with clinical suspicion of hemoglobinopathies and their family members, randomly chosen individuals submitted to blood tests and blood donors who were abnormal hemoglobin carriers were analyzed. The variants were screened by alkaline and acid electrophoreses, isoelectric focusing and cation-exchange high performance liquid chromatography (HPLC) and the abnormal chains were investigated by reverse-phase high performance liquid chromatography (RP-HPLC). Mutations were identified by molecular analyses, and the oxygen affinity, heme–heme cooperativity and Bohr effect of the variants were evaluated by functional tests.

Results

Four new and 22 rare variants were detected in 98 families. Some of these variants were found in co-inheritance with other hemoglobinopathies. Of the rare hemoglobins, Hasharon, Stanleyville II and J-Rovigo were the most common, the first two being S-like and associated with alpha-thalassemia.

Conclusion

The variability of alpha-globin alterations reflects the high degree of racial miscegenation and an intense internal migratory flow between different Brazilian regions. This diversity highlights the importance of programs for diagnosing hemoglobinopathies and preventing combinations that may lead to important clinical manifestations in multiethnic populations.

Prenatal Diagnosis of Hemoglobinopathies: From Fetoscopy to Coelocentesis

Prenatal diagnosis of hemoglobinopathies involves the study of fetal material from blood, amniocytes, trophoblast coelomatic cells and fetal DNA in maternal circulation. Its first application dates back to the 70s and it involves globin chain synthesis analysis on fetal blood. In the 1980s molecular analysis was introduced as well as amniocentesis and chorionic villi sampling under high-resolution ultrasound imaging. The application of direct sequencing and polymerase chain reactionbased methodologies improved the DNA analysis procedures and reduced the sampling age for invasive prenatal diagnosis from 18 to 16–11 weeks allowing fetal genotyping within the first trimester of pregnancy. In the last years, fetal material obtained at 7–8 weeks of gestation by coelocentesis and isolation of fetal cells has provided new platforms on which to develop diagnostic capabilities while non-invasive technologies using fetal DNA in maternal circulation are starting to develop.

Hb AHVAZ [α83(F4)Leu→Arg, CTG>CGG (α2); HBA2: c.251T>G],a new hemoglobin variant of the α2-globin gene

We report a novel mutation on the α2-globin gene, codon 83 (T>G), which was detected in two members of two unrelated families from Khuzestan Province, South Iran, that we named Hb Ahvaz. This mutation was detected by cellulose acetate electrophoresis and characterized by molecular studies. Hb Ahvaz does not seem to be responsible for hematological abnormalities in the carriers, but with α(0)-thalassemia (α(0)-thal) defects, might induce severe clinical symptoms.

Identification of two rare β-globin gene mutations in a patient with β-thalassemia intermedia from Azerbaijan

β-Thalassemias are an inherited group of disorders of hemoglobin (Hb) and comprise the most common monogenic disorders in Azerbaijan. They are extremely heterogeneous at the molecular level. Here we report the first identification of a patient who is a compound heterozygote for two rare β-thalassemia (β-thal) mutations, IVS-I-130 (G>C) and codon 37 (TGG>TGA).

Molecular mechanisms of a novel β-thalassaemia mutation due to the duplication of tetranucleotide 'AGCT' at the junction IVS-II/exon 3

We report a new β-thalassaemia allele detected in a young Italian woman, suffering with mild non-haemolytic anaemia (Hb < 10 g/dL) and not showing Hb variant or Heinz bodies. The allele is characterised by duplication of tetranucleotide 'AG/CT' (+1344/+1347) including the invariant dinucleotide 'AG' of IVS-II acceptor splicing site and the first two nucleotides of codon 105. β-Globin complementary DNA (cDNA) sequencing did not reveal any mutation and qualitative analysis of the reverse transcription PCR reaction showed that only the proximal 3' splice site present in the duplicated gene is used giving race to an anomalous messenger RNA (mRNA) present in trace (1.5 %) because, most probably, rapidly degraded. In the anomalous mRNA, the insertion causes a frameshift and synthesis of an abnormal truncated β-chain (139 residues), unable to form Hb variant because of the severe conformational changes. The duplication might have arisen from secondary structures generated by quasi-palindromic sequence 5'-CCCA(C)AG/CT(CC)TGGG-3'. Restriction fragment length polymorphism analysis for the β-globin haplotype and familiar segregation analysis indicated that the mutant β-globin gene was associated with the haplotype V.

Genotype-phenotype relationship of the δ-thalassemia and Hb A(2) variants: observation of 52 genotypes

The increase of Hb A(2) (α2δ2) beyond the upper limit [2.0-2.2/3.3-3.4% of the total hemoglobin (Hb)] is an invaluable tool in the hematological screening of β-thalassemia (β-thal) carriers. Factors decreasing Hb A(2) percentages can hinder correct diagnosis. In order to analyze the genotype-phenotype relationship, we characterized δ-, β- and α-globin genotypes in 190 families where the probands had Hb A(2) values of ≤2.0% or were β-thal heterozygotes with normal Hb A(2) levels. Hb A(2) was measured with cation exchange high performance liquid chromatography (HPLC). Mutations were detected with allele-specific methods or DNA sequencing; two multiplex-ARMS (amplification refractory mutation system) assays were set up. The molecular basis underlying the decrease in Hb A(2) was extremely heterogeneous. Nineteen δ-globin alleles (Hb A(2)-S.N. Garganico was new) were detected; their interaction with α- or β-globin alleles (10 and eight, respectively) led us to observe 52 genotypes in 261 carriers. The type of δ-globin mutations, the relative genotypes, the interaction with α(0)-thal traits, are the most important factors in decreasing the Hb A(2) percentage. These results are extremely useful in addressing the molecular diagnosis of hemoglobinopathies and thalassemias.

Molecular characterization of β-thalassemia intermedia: a report from Iran

Thalassemia intermedia is a clinical definition applied to patients whose clinical phenotype is milder than thalassemia major. To characterize different common mechanisms involving in pathogenesis of moderate to severe β-thalassemia intermedia, we have studied four factors in 38 Iranian patients with thalassemia intermedia: β-globin gene mutation, deletion in α-globin genes, presence of XmnI polymprphism and RFLP haplotype at β-globin gene cluster. The results showed that 84.4% of patients were associated with severe mutations in β-globin gene, mainly IVSII-1(G to A) (56.4%). The positive XmnI polymorphism was seen in 76.9% of the studied alleles which showed strong linkage to β° mutations and high level of fetal hemoglobin. Co-existence of α-globin gene deletions, β(+) mutation and the most frequent of RFLP haplotype (-/-, +/+, -/+, +/+, +/+, +/+, -/-) were seen in 7.7, 12.8 and 17.9%, respectively. In this group of our study it seems the main ameliorating factor in the patients was co-inheritance of a positive XmnI polymorphism with β° mutation especially IVSII-1, which were associated with increased production of fetal hemoglobin. However, the other probable genetic factors should be investigated to describe genotype-phenotype correlation in thalassemia intermedia patients.

The epidemiology of abnormal hemoglobins in Mediterranean high-level athletes

The aim of this study was to determine the prevalence and nature of hemoglobin (Hb) defects in a Mediterranean high-level (HL) athlete population. Five hundred and ninety-four HL male and female athletes were recruited during the annual follow-up of the members of Tunisian national teams. Hematological data, Hb electrophoresis, and DNA analysis were assessed using conventional techniques. Sporting discipline, type of sport, and performance levels were assessed using a questionnaire. The results showed that 32 HL athletes had abnormal Hb (5.4%): beta-thalassemia (2.2%), alpha-thalassemia (0.5%), HbAS (1.5%), HbAC (0.5%), and rare Hb variants (0.7%). Of the 32 defect carriers, all but one (a alpha-thalassemia) were heterozygous. All the detected hemoglobinopathies but one (an Hb Hope) had already been reported in the country. The prevalence of Hb defect in the HL athletes was similar to that described in the general Tunisian population (P > 0.05). The percentage of Hb defect in the athletes was not dependent on gender, or performance level (P > 0.05). Within each type of sport the percentages of athletes with normal and abnormal Hb were similar (P > 0.05). The hematological data revealed the diversity of anemia, microcytosis, and hypochromia in thalassemic HL athletes. We concluded that HL athletes in Tunisia were a representative sample of the general Tunisian population regarding the prevalence and nature of benign abnormal Hb. The hematological data of the thalassemia carriers exhibited high variability and raised the question of genetic and sporting counseling, as well as biological follow-up for these carriers.

A Novel α‐Thalassemia Nonsense Mutation in Codon 23 of the α2‐Globin Gene (GAG→TAG) in a Tunisian Family

Herein we describe a novel alpha-thalassemia (thal) point mutation in the alpha2-globin gene, found in a 3-year-old Tunisian girl who had Hb Bart's (gamma4) at birth, later on presenting with moderate anemia, microcytosis and hypochromia. She had a normal Hb A2 level and no abnormal hemoglobin (Hb) fraction. After excluding most of the common Mediterranean mutations, the alpha2-globin gene was sequenced and found to have a point mutation in the heterozygous state that creates a premature stop signal for translation (GAG-->TAG or Glu-->Term) at codon 23. The same mutation was also found in the mother in the heterozygous state, while the father had a normal sequence. The presence of the mutation was also confirmed by nucleotide sequencing of the opposite strand. Since the mutation creates a restriction site for the BfaI enzyme, a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based assay was established for screening purposes.

First Description in Tunisia of a Point Mutation at Codon 119 (CCT→TCT) in the α1-Globin Gene: Hb Groene Hart in Association with the − α3.7Deletion

Herein we describe the case of a Tunisian girl who presented with 3% Hb Bart's (gamma4) at birth. At the age of 3 years, she showed microcytosis and hypochromia in the absence of iron deficiency. The first step of molecular analysis was to test for the common Mediterranean mutations and the classical -alpha3.7 deletion was found in the heterozygous state. Since this finding could not explain the level of Hb Bart's at birth, or the hypochromia and microcytosis, all the alpha-globin genes were sequenced. This revealed a rare point mutation at codon 119 (CCT-->TCT) in the alpha1-globin gene, identified for the first time in Tunisia, and which has previously been described as an unstable hemoglobin (Hb) variant named Hb Groene Hart [alpha119(H2)Pro-->Ser (alpha1)]. Here the -alpha3.7/alpha(alpha)119(CCT-->TCT) genotype is responsible for the alpha-thalassemia (thal) trait phenotype.

Hb H (β4) Disease in Çukurova, Southern Turkey

In this study, 32 patients with Hb H (beta(4)) disease have been identified. Three different alpha-thalassemia-1 (thal) determinants; nine with the -17.4 kb (MED I) type, 12 with the -20.5 kb type and 10 with the -26.5 kb (MED II) type were characterized. Of the 32 patients, 19 had the 3.7 kb deletion and one had the 4.2 kb deletion in trans to alpha-thal-1 determinants. Only one patient, homozygous for the polyadenylation signal (poly A) site (PA 1) mutation, was identified to be associated with Hb H disease. The other patient had the poly A (PA 1) mutation in trans to the MED I (-17.4 kb) determinant. The 5 nt (nucleotide) deletion was present in three patients, two of them in the same family; this mutation was found in association with the MED II (26.5 kb deletion). The other patient had the -5 nt mutation in trans to the MED I (-17.4 kb) determinant. An unstable hemoglobin (Hb) variant [Hb Adana, codon 59 (CA)] was present in association with the alpha-thal-1 deletion (20.5 kb) in two adults and caused a severe type of Hb H disease. Five patients with Hb H disease had the genotype - -(MED II)/alpha(PA 2)alpha one had a Hb S heterozygosity (- -(MED II)/alpha(PA 2)alpha + Hb AS). A patient with Hb H disease (- -(MED I)/-alpha(3.7)) also had Hb S trait.

A Newly Identified Deletion of 970 bp at the α-Globin Locus That Removes the Promoter Region of the α1 Gene

The most common causes of alpha-thalassemia (thal) are deletions that remove a part, or one or both of the functional alpha-globin genes. These deletions cause diminished expression of the alpha-globin protein, which may result in relatively low hemoglobin (Hb) and/or mean corpuscular volume (MCV) values. We here report the identification of a 970 bp deletion in the alpha1-globin gene that encompasses the entire promoter region of the alpha1-globin gene and 26 bp encoding the 5' end of the mRNA. Thus, the affected alpha1-globin gene is prone to be nonfunctional. We therefore nominated the newly identified deletion allele alpha-alphaDelta970. The MCV values of four related carriers of the alpha-alphaDelta970 allele were slightly lowered, consistent with the presence of three functional alpha-globin genes.

Two new unstable haemoglobins leading to chronic haemolytic anaemia: Hb Caruaru [beta122 (GH5) Phe-->Ser], a probable case of germ line mutation, and Hb Olinda [beta22 (B4) - 25 (B7)], a deletion of a 12 base-pair sequence

We describe here two new unstable beta-globin variants, Hb Caruaru and Hb Olinda, found in northeastern Brazil, both associated with chronic haemolytic anaemia. Haemoglobin Caruaru is caused by a single base substitution at codon 122 (TTC-->TCC), possibly originating from the germ line cells of the patient's grandmother. Haemoglobin Olinda is also a de novo mutation, caused by a 12 bp deletion leading to the removal of the 22nd to the 25th residues of the normal beta-globin chain.

Perinatal zidovudine prophylaxis in HIV type-1-infected pregnant women with thalassaemia carriage in Thailand

Background

To investigate a possible interaction between α-thalassaemia, β-thalassaemia and haemoglobin-E trait and the haematological parameters of HIV type-1 (HIV-1)-infected pregnant women receiving zidovudine prophylaxis for the prevention of mother-to-child HIV-1 transmission in Thailand.

Methods

The study sample was composed of HIV-1-infected pregnant women receiving zidovudine (300 mg twice daily) from 28 weeks of gestational age to delivery as part of the Perinatal HIV Prevention Trial (PHPT-1), a large trial investigating zidovudine use in pregnancy. These women were randomly selected and screened for haemoglobin abnormalities. Haemoglobin levels, haematocrit and erythrocyte, leukocyte, absolute neutrophil and absolute lymphocyte counts were measured at 26, 32 and 35 weeks of gestation and at delivery. PCR genotyping techniques were used to screen for haemoglobin abnormalities, which included α-thalassaemia-1 Southeast Asian type deletion, β-thalassaemia mutation (codons 41/42 [-TCTT], codon 17 [A→T], intervening sequence-I nucleotide 1 [G→T], codons 71/72 [+A]) and haemoglobin-E trait. The evolution of haematological parameters between 26 weeks and delivery was compared according to thalassaemia carriage using linear mixed models adjusted for baseline sociodemographic characteristics, HIV clinical stage, CD4+ T-cell count and viral load.

Results

At baseline, women with thalassaemia or haemoglobin-E trait had significantly lower haemoglobin level and red blood cell counts than women with no haemoglobin abnormalities, whereas absolute neutrophil and leukocyte counts were significantly higher. Exposure to zidovudine until delivery did not increase this difference.

Conclusions

Zidovudine exposure did not appear to have increased haematological toxicity in HIV-1-infected pregnant women with thalassaemia.

A family with multiple mutations and sequence variations in the alpha- and beta-globin gene clusters

BACKGROUND

Usually, laboratory diagnostics of hereditary hemoglobin disorders is fairly straightforward. Sometimes, however, correct diagnosis can be difficult. In this study, we describe a family with multiple mutations and sequence variations in the alpha- and beta-globin gene clusters.

METHODS

Hemocytometry results were obtained using an automated cell counter. Hemoglobin variant analysis was performed by cation-exchange HPLC. PCR and DNA sequence analyses were used to identify mutations in the globin genes.

RESULTS

The proposita was referred to our laboratory for hematological evaluation [hemoglobin 145 g/L (119-155 g/L) mean corpuscular volume 72 fl (80-97 fl), mean corpuscular hemoglobin 26 pg (28-36 pg), erythrocytes 5.6 x 10(12)/L (3.7-5.0 10(12)/L)]. Characterization and quantification of hemoglobin variants showed 11.3% HbA1, 4.4% HbA2, 58.9% HbC and 23.0% HbF. Subsequent analysis revealed, in addition to a heterozygous HbC mutation, the presence of a beta-thalassemia causing mutation (-90C>T), a heterozygous alpha-thalassemia (-alpha(-3.7)/alpha alpha) and three different gamma-globin sequence variations. Additional molecular analysis was performed in all family members.

CONCLUSIONS

In the family presented in this study, 10 different mutations were found in the globin genes. Molecular analysis was necessary to clarify hemoglobin variant analysis, in particular the low amount of HbA1 in the proposita. Knowledge of the molecular background facilitates in the understanding of the hematological parameters and proper counseling of the patient.

Experience in preimplantation genetic diagnosis for exclusion of homozygous alpha degrees thalassemia

OBJECTIVE

To report our experience in preimplantation genetic diagnosis (PGD) for the exclusion of homozygous alpha degrees thalassemia.

PATIENTS AND METHODS

PGD was performed on nine couples with alpha degrees thalassemia genotype undergoing assisted reproduction. Oocytes were aspirated after ovarian stimulation and fertilized by intracytoplasmic sperm injection. One or two blastomeres were biopsied from the six- to eight-cell embryo. Single cell multiplex PCR of the normal and alpha degrees thalassemia alleles was performed for first round, followed by semi-nested PCR of the respective alleles using 5'-end labelled fluorescent primers. Only those embryos with a blastomere diagnosed as having at least one normal allele were selected for transfer.

RESULTS

One hundred and twenty-six blastomeres from 82 embryos were analyzed. The rates of allele dropout was 10.2% and PCR failure 12.7%. Fifty-eight embryos (70.7%) had at least one normal allele, of which 31 were transferred to 13 prepared cycles and one triplet pregnancy achieved. The triplets showed no ultrasound features of homozygous alpha degrees thalassemia at 18 weeks and were delivered in healthy condition by caesarean section at 34 weeks. Their genotypes were confirmed by cord blood analysis.

CONCLUSIONS

PGD for alpha degrees thalassemia is possible by single cell PCR. The transfer and successful implantation of unaffected embryos ensure birth of disease-free babies.

Microsatellite Markers within —SEA Breakpoints for Prenatal Diagnosis of HbBarts Hydrops Fetalis

Background: We sought to develop a rapid prenatal diagnostic test for simultaneous detection of HbBarts hydrops fetalis and exclusion of maternal contamination.

Methods: We developed a multiplex quantitative fluorescent PCR (QF-PCR) test that detects the presence/ absence of 2 microsatellite markers (16PTEL05/16PTEL06) located within breakpoints of the Southeast Asia (—SEA) deletion. HbBarts hydrops fetalis (—SEA/—SEA) is diagnosed by absence of both markers, and maternal contamination of fetal DNA is excluded by absence of noninherited maternal alleles. Fetal and parental DNA samples from 50 families were analyzed in a blinded clinical validation study, and QF-PCR results were compared with their respective molecular genotypes.

Results: The multiplex QF-PCR results included correct diagnoses of HbBarts hydrops fetalis in 11 of the fetuses tested, correct verification as unaffected in 20 fetuses, and correct identification as either carriers (αα/—SEA) or unaffected homozygotes in 18. Misidentification as unaffected occurred for 1 carrier. Sensitivity for diagnosis of HbBarts hydrops fetalis was 100% [lower 95% confidence interval, 76.2%], and specificity was 100% (lower 95% confidence interval, 92.6%). None of the samples tested showed any traces of noninherited maternal alleles; thus false-positives because of maternal contamination were eliminated.

Conclusions: In this QF-PCR method, detection of maternally and paternally inherited fetal alleles allowed diagnosis of the double-deletion syndrome, and the ability to differentiate between these alleles allowed simultaneous exclusion of maternal contamination of the fetal genetic material. This novel strategy using cell-free fetal DNA in maternal plasma could form the basis for noninvasive testing for HbBarts hydrops fetalis.

Human alpha2-globin nonsense-mediated mRNA decay induced by a novel alpha-thalassaemia frameshift mutation at codon 22

We describe a novel alpha-thalassaemia determinant in a 3-year-old girl presenting a mild microcytic and hypochromic anaemia, and normal haemoglobin A2 level. Molecular studies revealed heterozygosity for a novel microdeletion (-C) at codon 22 of the alpha2-globin gene. As the frameshift mutation generates a premature translation termination codon at position 48/49, we investigated the effect of the nonsense codon on the alpha2-globin gene expression. Although it does not affect RNA splicing, the premature nonsense codon induces accelerated mRNA degradation. To our knowledge, this is the first time the nonsense-mediated mRNA decay has been reported to occur in human alpha-globin mRNA.

Hemoglobin Loves Park [beta68 (E12) Leu-->Phe]: report of five cases including one originating from a de novo mutation

Hemoglobin (Hb) Loves Park [beta68 (E12) Leu-->Phe] was identified in a 2-year-old Portuguese boy with anemia, microcytosis, and hypochromia. This Hb variant was detected by isoelectric focusing and quantified by reverse-phase high-performance liquid chromatography (HPLC) (48.4%), and the DNA mutation was identified by HBB (beta-globin gene) sequencing. Hematological and biochemical analyses performed on his parents revealed normal hematological parameters and normal hemoglobin and globin chain profiles. DNA sequence analysis of the HBB gene of both parents showed the absence of the Hb Loves Park mutation. Study of the haplotypes in the beta-globin gene cluster confirmed parenthood. Moreover, paternity was confirmed by the study of nine short tandem repeats (STRs) and four variable-number tandem repeat (VNTRs) loci. The most likely explanation for these results is that the Hb Loves Park mutation has occurred de novo in this family. The original American cases of Hb Loves Park, from a family of Italian origin, which were never published, as well as two additional cases, are also included in this report. Functional studies revealed that Hb Loves Park is stable and has a decreased oxygen affinity.

Two children with thalassemia identified during screening for anemia in junior high school

We present two Japanese students with thalassemia identified during screening for anemia in their junior high school. Blood test results revealed marked hypochromic and microcytic erythrocytosis in one patient and microcytic anemia in the other. Both cases showed a mean corpuscular volume/red blood cell (MCV/RBC) ratio less than 13. Their beta/alpha synthesis ratio was elevated. Deletion of psialpha2, psialpha1, alpha2, alpha1 and theta1 genes in the alpha-globin gene clusters were noted in the first case. This pattern of gene deletion was consistent with heterozygous alpha-thalassemia 1 of the Southeast Asian type. On the other hand, an increased hemoglobin A2 level and reduced beta/alpha synthesis ratio were found in the second case. Direct cloning and DNA sequencing identified a point mutation (guanine to adenine) at position 1 of intervening sequence II in the beta-globin gene (IVS II-1 G-->A). These results suggest that this patient had heterozygous beta0-thalassemia. Diagnosis of thalassemia should be confirmed by molecular analysis in cases with microcytic anemia or hypochromic microcytosis with a MCV/RBC ratio of 13 or less.

Sequence variations of the ?-globin genes: Scanning of high CG content genes with DHPLC and DG-DGGE

The alpha-globin chains are encoded by two duplicated genes (HBA2 and HBA1, 5'-3') showing overall sequence homology >96% and average CG content >60%. alpha-Thalassemia, the most prevalent worldwide autosomal recessive disorder, is a hereditary anemia caused by sequence variations of these genes in about 25% of carriers. We evaluated the overall sensitivity and suitability of DHPLC and DG-DGGE in scanning both the alpha-globin genes by carrying out a retrospective analysis of 19 variant alleles in 29 genotypes. The HBA2 alleles c.1A>G, c.79G>A, and c.281T>G, and the HBA1 allele c.475C>A were new. Three pathogenic sequence variations were associated in cis with nonpathogenic variations in all families studied; they were the HBA2 variation c.2T>C associated with c.-24C>G, and the HBA2 variations c.391G>C and c.427T>C, both associated with c.565G>A. We set up original experimental conditions for DHPLC and DG-DGGE and analyzed 10 normal subjects, 46 heterozygotes, seven homozygotes, seven compound heterozygotes, and six compound heterozygotes for a hybrid gene. Both the methodologies gave reproducible results and no false-positive was detected. DHPLC showed 100% sensitivity and DG-DGGE nearly 90%. About 100% of the sequence from the cap site to the polyA addition site could be scanned by DHPLC, about 87% by DG-DGGE. It is noteworthy that the three most common pathogenic sequence variations (HBA2 alleles c.2T>C, c.95+2_95+6del, and c.523A>G) were unambiguously detected by both the methodologies. Genotype diagnosis must be confirmed with PCR sequencing of single amplicons or with an allele-specific method. This study can be helpful for scanning genes with high CG content and offers a model suitable for duplicated genes with high homology.

Rapid detection of six common Mediterranean and three non-Mediterranean alpha-thalassemia point mutations by reverse dot blot analysis

We describe the implementation of reverse dot blot (RDB) hybridization as a rapid nonradioactive method for the identification of six frequent globin gene point mutations in the Mediterranean population: alpha(Hph)alpha: alpha2 IVS I donor site GGTGAGG --> GG-----; alpha(NcoI)alpha: alpha2 initiation codon ATG --> ACG; alpha(TSaudi)alpha: alpha2Poly A signal AATAA --> AATAAG; alpha(Icaria)alpha: alpha2 termination codon TAA --> AAA (Ter --> LYS); alpha(CS)alpha: alpha2 termination codon TAA --> CAA (Ter --> gly); alphaalpha(NcoI): alpha1 initiation codon ATG --> GTG; and three alpha2 globin gene point mutations found in immigrants in Italy: alpha(T-Quongsze)alpha: alpha2 codon 12 CTG --> CCG (Leu --> Pro); alpha(Seal Rock)alpha: alpha2 termination codon TAA --> GAA (TER --> GLU); and alpha(Koyadora)alpha: alpha2 termination codon TAA --> TCA (TER --> SER). The method uses the principle of allele-specific oligonucleotide (ASO) hybridization, but it is a nonradioactive method and permits rapid and simultaneous typing of point mutations and small deletions.

Molecular characterization of alpha-thalassemia in Pakistan

Common alpha-thalassemia (thal) rearrangements were studied in a normal random population and in six ethnic groups of Pakistan. Analyses of 204 individuals from the normal population revealed the presence of only the -alpha(3.7) allele with an overall frequency of 8.3%. Ethnic differences were statistically significant for Pashtoon vs. Balochi (p < 0.0005) and Pashtoon vs. Sindhi (p < 0.002). Two hundred and eighty-five thalassemia patients were also studied to identify rare alpha-thal alleles. In this group, 24.6% of the patients had one or two alpha genes deleted. Two rare alleles in the Pakistani population, -alpha(4.2) (0.2%) and alphaalphaalpha(anti3.7) (0.9%), were identified in these patients. The -alpha(4.2) allele was found only in Sindhis, while alphaalphaalpha(anti3.7) was present in Punjabis, Sindhis and Balochis. Five patients with triplicated alpha genes were homozygous for either the beta+ or the beta(0) genotype.

Molecular characterization of hereditary persistence of fetal hemoglobin in the Karen people of Thailand

Hereditary persistence of fetal hemoglobin (HPFH) is the condition whereby a continuously active gamma-globin gene expression leads to elevated fetal hemoglobin (Hb F) levels in adult life [Stamatoyannopoulos G, Grosveld F. Hemoglobin switching. In: Stamatoyannopoulos G, Majerus PW, Perlmutter RM, Varmus H, eds. The Molecular Basis of Blood Diseases. Philadelphia: W.B. Saunders, 2001:135-182; Wood WG. Hereditary persistence of fetal hemoglobin and delta(beta) thalassemia. In: Steinberg MH, Forget BG, Higgs DR, Nagel RL, eds. Disorders of Hemoglobin: Genetics, Pathophysiology, and Clinical Management. Cambridge: Cambridge University Press, 2001:356-388; and Weatherall DJ, Clegg JB. Hereditary persistence of fetal hemoglobin. In: Weatherall DJ, Clegg JB, eds. The Thalassaemia Syndromes. Oxford: Blackwell Scientific Publishers, 1981:450-507]. The condition is caused either by mutation of the beta- and gamma-globin genes, or the gamma-gene controlled region on other chromosomes. Several families with this condition have been reported from Vietnam, Cambodia and China, and the Southeast Asian mutation (or HPFH-6), a 27 kb deletion, was demonstrated. Here we report on a mother and her daughter of the Karen ethnic group with high levels of Hb F, living in the Suan Pueng District on the border of Thailand and Myanmar. Genotyping showed a heterozygosity for the 27 kb deletion of the beta-globin gene. Their conditions have been confirmed by gap polymerase chain reaction (PCR) with three oligonucleotide primers recently developed by Xu et al. [Xu X-M, Li Z-Q, Liu Z-Y, Zhong X-L, Zhao Y-Z, Mo Q-H. Molecular characterization and PCR detection of a deletional HPFH: application to rapid prenatal diagnosis for compound heterozygotes of this defect with beta-thalassemia in a Chinese family. Am J Hematol 2000; 65:183-188.], and a DNA sequencing method. Thus far there has been no official report of the HPFH-6 anomaly from Thailand. The compound heterozygosity of beta-thalassemia (thal) and hereditary persistence of Hb F causes the phenotype of thalassemia intermedia; in contrast, homozygotes for this anomaly show only mild microcytic anemia. Hence, genetic counseling for hereditary persistence of Hb F carriers is needed for family planning.

Screening and genetic diagnosis of haemoglobin disorders

The inherited haemoglobinopathies are large group of disorders that include the thalassaemias and sickle cell disease. Carrier detection methods must be able to detect alpha-, beta- and deltabeta-thalassaemias, HPFH disorders and haemoglobin variants. Carrier diagnosis involves the accurate measurement of MCH, MCV, Hb A(2) and Hb F values in combination with an understanding of the haematological characteristics of the different types of thalassaemia genes and their interactions. The majority of the common thalassaemia mutations and abnormal haemoglobins can be identified by PCR-based techniques. The main applications of molecular analysis for carrier diagnosis are: the analysis of alpha-thalassaemia mutations by gap-PCR to discriminate between heterozygous alpha-thalassaemia and homozygous alpha-thalassaemia; the identification of beta-thalassaemia mutations for patients requiring prenatal diagnosis and for the prediction of the severity of the clinical phenotype of homozygous beta-thalassaemia; to discriminate between deltabeta-thalassaemia and HPFH deletions by gap-PCR.

Epidemiology of the delta globin alleles in southern Italy shows complex molecular, genetic, and phenotypic features

We characterized mutations and haplotypes of the delta-globin gene (HBD, MIM# 142000) in two regions of southern Italy. Mutations were discovered by screening for individuals with Hb A2<2%. In Basilicata, about 10,000 students were screened and 53 carriers in 43 unrelated families were diagnosed; in Campania, cases were referred through a routine thalassemia counseling service. Twelve alleles were detected. Four were novel variants [Hb A2-Metaponto (g.238C>A), Hb A2-Campania (g.302C>A), Hb A2-Lucania (g.393C>G), and Hb A2-Capri (g.443G>T)]. Hb A2-Lucania was not inherited but had arisen in the propositus. Two were novel mutations in the noncoding regions: the substitutions IVS2+6T>A, presumably affecting the splicing, and g.-126A>T in the GATA motif presumably affecting transcription. All novel alleles were found associated with haplotypes common in the Mediterranean area. The remaining six were alleles already described. The Hb A2-Yialousa (g.82G>T) was the most prevalent (42/63 families). Recurrent homologous crossing-over events have, most likely, linked this allele to Haplotypes IX (24 families), IV (10 families), or III (seven families). The ratio of Haplotypes IX:IV:III was about the same in the two regions. The rare allele Hb A2-NYU (g.39T>A) was found in 11 families from Basilicata associated with Haplotype I. All the 11 families lived in a restricted area extending from the Ionian Coast for 15 km along the Angri and Sinni Rivers. A founder effect most probably gave origin to this isolated group. The remaining four alleles were rare: the 7.2-kb deletion Corfù type (HBD g.-5946_1262del), Hb A2-Mitsero (g.14C>T), Hb A2-Etolia (g.385T>C), Hb A2-Coburg (g.1376G>A). Correlation between genotype and phenotype was established in 103 carriers.