Molecular characterization of beta-thalassaemia in 174 Greek patients with thalassaemia major

Clinical significance of mutational variants in beta and alpha genes in patients with hemoglobinopathies from two large Greek centers: a complex interplay between genotype and phenotype

Hemoglobinopathies affect patients in the wider Mediterranean area consisting of 4 distinct subgroups: beta thalassemia major (TM), beta thalassemia intermedia (TI), sickle cell disease (SCD) and hemoglobin H disease (alpha thalassemia). The clinical spectrum varies from mild to severe. Complex interactions between genes and environmental factors form the clinical manifestations. There is an unmet need to clarify these multifactorial mechanisms. This is the first Greek study describing mutational alleles (HBB and HBA1/HBA2 gene variants) in 217 patients with hemoglobinopathies of two large centers in Greece (Larissa and Athens) and associating particular genotypes or gene variants with clinical manifestations (transfusion frequency, complications). Thus, the complex interplay between corresponding genotypes and phenotypes was investigated. Our results are in accordance with previous national studies with limited variations, due to regional prevalence of specific gene variants, as expected. It is also a description of the prevalence of hemoglobinopathies in the Greek population. The type and prevalence of beta and alpha globin gene variants differ significantly among countries. We also confirm the well-known observation of many studies that in our beta thalassemic or SCD patients, co-inheritance of variants in the alpha globin genes, leading to absence or reduction of alpha globin synthesis were associated with milder clinical course, whereas the inheritance of additional alpha genes (triplication) led to a more severe clinical phenotype. In cases in whom the genotype and phenotype did not correlate, factors like the function or modification of possible regulatory genes or additional nutritional-environmental effects should be investigated. KEY MESSAGES: • This is the first Greek study, fully molecularly defining the beta and alpha mutational alleles in 217 patients with hemoglobinopathies of two large centers in Greece and correlating particular genotypes or gene variants with clinical manifestations (transfusion frequency, complications). • In the beta thalassemic or SCD patients of our cohort, co-inheritance of variants in the alpha globin genes, leading to absence or reduction of alpha globin synthesis were associated with milder clinical course (confirmation of a well-known previous observation). • The inheritance of additional alpha genes (triplication) led to a more severe clinical phenotype (confirmation of a well known previous observation). • The function or modification of possible regulatory genes should be investigated in cases in whom the genotype and phenotype did not correlate.

Presence of the IVS-I-6-Mutated Allele in Beta-Thalassemia Major Patients Correlates with Extramedullary Hematopoiesis Incidence

Extramedullary hematopoiesis (EMH) results from the extension of hematopoietic tissue beyond the confines of the bones. Since the initiation of regular transfusion programs from an early age for all thalassemia major (ΤΜ) patients, EMH has not been considered a clinical issue anymore. The present study aims to record the prevalence of EMH in chronically transfused ΤΜ patients followed at our institution and to investigate possible risk factors associated with its occurrence. The project was designed as a retrospective, nonexperimental, descriptive, exploratory study. In total, the study enrolled 104 patients. EMH was revealed in 15/104 (14%) patients. The presence of intravening sequence (IVS)-I-6 was significantly related with the development of EMH (p < 0.05). No other demographic or biological factor studied was found to be related with the presence of EMH. The study stresses a profound incidence of asymptomatic EMH in a solid group of well-transfused ΤΜ patients. Given the high incidence of the IVS-I-6 allele in the Mediterranean and Middle Eastern region, high-quality, prospective, multicenter studies could confirm the association of EMH occurrence with the presence of the IVS-I-6 mutation and further evaluate the exact role of this mutation in the EMH process.

β-Thalassemia Distribution in the Old World: an Ancient Disease Seen from a Historical Standpoint

Background

Haemoglobinopathies constitute the commonest recessive monogenic disorders worldwide, and the treatment of affected individuals presents a substantial global disease burden. β-thalassaemia is characterised by the reduced synthesis (β⁺) or absence (β^o) of the β-globin chains in the HbA molecule, resulting in accumulation of excess unbound α-globin chains that precipitate in erythroid precursors in the bone marrow and in the mature erythrocytes, leading to ineffective erythropoiesis and peripheral haemolysis. Approximately 1.5% of the global population are heterozygotes (carriers) of the β-thalassemias; there is a high incidence in populations from the Mediterranean basin, throughout the Middle East, the Indian subcontinent, Southeast Asia, and Melanesia to the Pacific Islands.

Aim

The principal aim of this paper is to review, from a historical standpoint, our knowledge about an ancient disease, the β-thalassemias, and in particular, when, how and in what way β-thalassemia spread worldwide to reach such high incidences in certain populations.

Results

Mutations involving the β-globin gene are the most common cause of genetic disorders in humans. To date, more than 350 β-thalassaemia mutations have been reported. Considering the current distribution of β- thalassemia, the wide diversity of mutations and the small number of specific mutations in individual populations, it seems unlikely that β-thalassemia originated in a single place and time.

Conclusions

Various processes are known to determine the frequency of genetic disease in human populations. However, it is almost impossible to decide to what extent each process is responsible for the presence of a particular genetic disease. The wide spectrum of β-thalassemia mutations could well be explained by looking at their geographical distribution, the history of malaria, wars, invasions, mass migrations, consanguinity, and settlements. An analysis of the distribution of the molecular spectrum of haemoglobinopathies allows for the development and improvement of diagnostic tests and management of these disorders.

Epidemiological profile of common haemoglobinopathies in Arab countries

Haemoglobinopathies including the thalassemias and sickle cell disease are known to be prevalent inherited disorders in most Arab countries with varying prevalence rates and molecular characterisation. β-thalassemia is encountered in polymorphic frequencies in almost all Arab countries with carrier rates of 1-11 % and a varying number of mutations. The most widespread mutation in Lebanon, Egypt, Syria, Jordan, Tunisia and Algeria is the IVS-I-110 (G>A). In the Eastern Arabian Peninsula, the Asian Indian mutations (IVS-I-5 (G>C), codons 8/9 (+G) and IVS-I (-25 bp del)) are more common. The α-thalassemias are encountered in the majority of Arab countries in frequencies ranging from 1 to 58 % with the highest frequencies reported from Gulf countries. The (-α(3.7)) mutation is the most frequent followed by the non-deletional α2 polyadenylation signal mutation (AATAAA>AATAAG) and the α2 IVS1 5-bp deletion. The rates of sickle cell trait in Arab countries range from 0.3 to 30 %, with the Benin, the Arab-Indian and the Bantu haplotypes constituting the bulk of the haplotypes, leading to two major phenotypes; a mild one associated with the Arab-Indian and a severe one with the Benin and Bantu haplotypes. Public health approaches targeting prevention of haemoglobinopathies in Arab countries include newborn screening for sickle cell disease, and premarital screening for carriers of β-thalassemia and sickle cell disease. These services are still patchy and inadequate in many Arab countries recommending the upgrade of these services with strengthening of the education and training of health care providers and raising public awareness on the feasibility of prevention and care for haemoglobinopathies.

Novel and known microsatellite markers within the β-globin cluster to support robust preimplantation genetic diagnosis of β-thalassemia and sickle cell syndromes

Preimplantation genetic diagnosis (PGD) for β hemoglobinopathies has become the most common application among monogenic disorders. We present the identification of microsatellite markers [short tandem repeats (STRs)] closely linked to the β-globin gene for incorporation within PGD protocols, with the aim of increasing the number of transferable embryos. Nine candidate STRs were identified in-silico, of which three were selected based on rate-of-heterozygosity, polymerase chain reaction (PCR) efficiency and size. The multiplex reaction (β-globin gene and selected STRs, all within <0.4 Mb from the β gene) was optimized in single lymphocytes, and subsequently applied in 38 PGD cycles in couples at-risk for transmitting β hemoglobinopathies. In conclusion, incorporation of closely linked polymorphic microsatellite markers <0.4 Mb from the β-globin gene, facilitates robust assignment of β hemoglobinopathy genotypes, increasing the number of transferrable embryos otherwise rejected due to allele-drop-out (ADO), at the mutation-specific locus, compared to results based on disease-mutation genotyping alone (p < 0.001).

First Spanish Case Of Thalassemia Major Due to a Compound Heterozygosity for the IVS-II-848 (C→A) And Codon 39 (C→T) Mutations Of The β-Globin Gene

This report describes the first case in Spain of a severe form of beta-thalassemia (thal) due to a compound heterozygosity for the IVS-II-848 (C --> A) and the nonsense codon 39 (C --> T) mutations. Five members of a family from Cadiz (southern Spain) were studied. The proband was an 8-year-old girl diagnosed as anemic at the age of 13 months. Her father had the codon 39 (C --> T) mutation and her mother the C --> A change at nucleotide (nt) 848 of IVS-II. Haplotype analysis showed that the proband was a compound heterozygote for haplotypes I [+ --> + +] and VII [+ --> +]. This is the first description in Spain of the IVS-II-848 (C --> A) mutation. It appears, from restriction fragment length polymorphism (RFLP) analysis, that this mutation has a different origin in the various populations, where it was found. This observation shows that in this case the association of a beta(0)- and a beta(+)-thal mutation does not lead to a thalassemia intermedia but to a severe thalassemia with very low hemoglobin (Hb) levels. From a therapeutic point of view, early introduction of a transfusion regimen may improve the clinical picture of these children, allowing for better development and growth.

Molecular heterogeneity of beta-thalassemia in Algeria: how to face up to a major health problem

This study concerns the molecular characterization of beta-thalassemia (beta-thal) alleles in 210 chromosomes. In the studied population, mutations were detected in 98% of the beta-thalassemic chromosomes. Twenty-one molecular defects have been found, where the five dominant mutations, IVS-I-110 (G>A), nonsense mutation at codon 39 (C>T), the frameshift codon (FSC) 6 (-A), IVS-I-1 (G>A), and IVS-I-6 (T>C), account for 80% of the independent chromosomes. Among the remaining alleles, 16 different mutations were identified, half of them being described for the first time in Algeria. These include the -101 (C>T) and the -90 (C>T) mutations in the distal and proximal promoter elements, respectively, the FSC 8 (-AA), IVS-I-5 (G>T), IVS-I-128 (T>G), FSC 47 (+A), IVS-II-1 (G>A), and the substitution in the polyadenylation signal (poly A) site AATAAA>AATGAA. Haplotype analyses on rare variants were performed. The possible origin of these mutations either by founder effect or by migrations is discussed, and raises the question of an adequate strategy to be used adapted to socio-economical status.

Increased gamma-globin gene expression in beta-thalassemia intermedia patients correlates with a mutation in 3'HS1

We report a novel set of genetic markers in the DNaseI hypersensitive sites comprising the human beta-globin locus chromatin hub (CH), namely HS-111 and 3'HS1. The HS-111 (-21 G>A) and 3'HS1 (+179 C>T) transitions form CH haplotypes, which occur at different frequencies in beta-thalassemia intermedia and major patients and normal (nonthalassemic) individuals. We also show that the 3'HS1 (+179 C>T) variation results in a GATA-1 binding site and correlates with increased fetal hemoglobin production in beta-thalassemia intermedia patients. In contrast, the HS-111 (+126 G>A) transition, found in three normal chromosomes, is simply a rare polymorphism. We conclude that the CH haplotypes are useful genetic determinants for beta-thalassemia major and intermedia patients, while the 3'HS1 (+179 C>T) mutation may have functional consequences in gamma-globin genes expression.

PCR-SSCP: a method for the molecular analysis of genetic diseases

Single strand conformation polymorphism (SSCP) is a reproducible, rapid and quite simple method for the detection of deletions/insertions/rearrangements in polymerase chain reaction amplified DNA. All the details for the use of PCR-SSCP are presented in the direction of genetic diseases (beta-thalassaemia, cystic fibrosis), optimum gel conditions, sensitivity and the latest modifications of the method, which are applied in most laboratories. This non-radioactive PCR-SSCP method can be reliably used to identify mutations in patients (beta-globin, CFTR), provided suitable controls are available. Moreover, it is widely used for mutation identification in carriers (beta-thalassaemia, cystic fibrosis), making it particularly useful in population screening.

Identification of the four most common beta-globin gene mutations in Greek beta-thalassemic patients and carriers by PCR-SSCP: advantages and limitations of the method

In the present study we investigated whether the single-strand conformational polymorphism (SSCP) method could be employed to identify (rather than simply detect) the four most common beta-globin gene mutations in the Greek population: IVS-I-110, Cd39, IVS-I-1, and IVS-I-6. Using DNA from 50 beta-thalassemic patients and carriers, we amplified by PCR the appropriate 238-bp region of the human beta-globin gene, analyzed the reaction products by nondenaturing polyacrylamide gel electrophoresis, and visualized the bands by silver staining. Single-stranded DNA (ssDNA) fragments showed a reproducible pattern of bands that was characteristic of the mutations present. With the use of control samples containing six of the 10 possible combinations of the four most common beta-globin gene mutations, we were able to predict the mutations present in a quarter of the patients studied. Our predictions were confirmed independently by the amplification refractory mutation system (ARMS) method. We conclude that this non-radioactive PCR-SSCP method can be used to reliably identify mutations in patients, provided that suitable controls are available. Moreover, the method is easy to apply to the identification of mutations in carriers, which makes it particularly useful for population screening.

Longitudinal Study of Survival and Causes of Death in Patients with Thalassemia Major in Greece

Iron-induced organ degeneration is the main factor of mortality in patients with thalassemia major. Since chelation therapy is at a turning point, from the laborious parenteral route to the use of new promising oral agents, we investigated the current status of survival of these patients to present reliable data that will be useful in future comparative studies. Survival probabilities were estimated by the Kaplan-Meier method, and results were compared by the log-rank test in a total of 647 thalassemic patients (pts) (52% males) born between 1/1/58 and 1/2/04. Terminal follow-up was 1/12/04. All transfusion-dependent pts monitored in our center, or in frequent contact if they had moved elsewhere, were strictly selected, excluding all rarely transfused or intermediate cases. Pts born before 1/1/75 were classified in group A (n = 366), while pts born later were included in group B (n = 281). According to the last 5 years' mean serum ferritin level, pts were divided into three hemosiderosis groups: (1) mild (<2000 microg/L) 49%, (2) moderate (2000-4000 microg/L) 28%, and (3) severe (>4000 microg/L) 23%. Of the 647 pts, 115 died (mean age: 22.6 +/- 6.2 years), most frequently by heart failure (71.3%) followed by sepsis (7.8%). Life expectancy in the entire population was up to 59% at 46 years. Survival was higher for pts born after 1975 than those before (P < .001). Statistically significantly different survival probabilities were found between groups with mild, moderate, or severe hemosiderosis (P < .001). Effective management with improved chelation therapy could lead to better results.

Molecular basis of thalassemia syndromes in Serbia and Montenegro

This study reports the molecular characterization of thalassemia syndromes in Serbian and Montenegrin populations. We identified eight beta-thalassemia mutations [codon 39 (C-->T), IVS-I-110 (G-->A), IVS-II-745 (C-->G), codon 44 (-C), -87 (C-->G), IVS-II-1 (G-->A), IVS-I-6 (T-->C), IVS I-1 (G-->A)] in 70 members of 29 families using polymerase chain reaction, reverse dot blot, amplification refractory mutation system and direct sequencing analysis. Hemoglobin (Hb) Lepore was found to be the most common cause of the thalassemia phenotype. Hb Sabine and alpha-thalassemia were detected as well. We also studied beta-globin gene cluster haplotypes and their association with the most common mutations. A novel haplotype associated with the Hb Lepore gene was identified. The results presented herein allowed the implementation of a prenatal diagnosis program in Serbia and Montenegro.

Genetic Heterogeneity of Beta Thalassemia in Lebanon Reflects Historic and Recent Population Migration

Beta thalassemia is an autosomal recessive disorder characterized by reduced (beta(+)) or absent (beta(0)) beta-globin chain synthesis. In Lebanon it is the most predominant genetic defect. In this study we investigated the religious and geographic distribution of the beta-thalassemia mutations identified in Lebanon, and traced their precise origins. A total of 520 beta-globin chromosomes from patients of different religious and regional backgrounds was studied. Beta thalassemia mutations were identified using Amplification Refractory Mutation System (ARMS) PCR or direct gene sequencing. Six (IVS-I-110, IVS-I-1, IVS-I-6, IVS-II-1, cd 5 and the C > T substitution at cd 29) out of 20 beta-globin defects identified accounted for more than 86% of the total beta-thalassemia chromosomes. Sunni Muslims had the highest beta-thalassemia carrier rate and presented the greatest heterogeneity, with 16 different mutations. Shiite Muslims followed closely with 13 mutations, whereas Maronites represented 11.9% of all beta-thalassemic subjects and carried 7 different mutations. RFLP haplotype analysis showed that the observed genetic diversity originated from both new mutational events and gene flow from population migration. This study provides information about the types and distribution of beta-thalassemia mutations within each religious group and geographic region, which is essential for the implementation of screening and prevention programs.

beta-globin gene cluster haplotypes associated with beta-thalassemia on Corsica island

In the Corsican population, the incidence of beta-thalassemia traits is reported to be 3.1%. We have investigated the 2 more important beta-thalassemia mutations present in the Corsican population: beta0-39 and beta+IVS1-110. Seven polymorphic sites in the beta-globin gene cluster were analyzed from a sample of 43 non-related beta-thalassemia heterozygotes and of 47 nonrelated healthy individuals, from Central Corsica (Corte). Among the 43 Corsican patients analyzed, the nonsense codon is predominant (88.40%), whereas the beta+IVS1-110 mutation, the most common of beta-thalassemia in the eastern part of the Mediterranean basin, is underrepresented (2.33%). The other individuals did not show positive for the two tested mutations (9.27%). The beta0-39 mutation in the studied population shows a strong association with haplotype II (18.7%) and a weaker association with haplotypes I (2.3%) and VII (2.1%). The strong association of the beta0-39 mutation with haplotype II was also found in Sardinia, suggesting that the mutation on the two islands have the same origin. In the present study all the data concerning frequencies of the mutations and of sequence haplotypes, support the hypothesis of a western Mediterranean origin of the beta0-39 mutation. For the first time, this paper analyzes the association of beta-globin gene cluster haplotypes with the 2 more frequent beta-thalassemia mutations in an isolated population in the centre of Corsica (Corte), which presents certain genetic peculiarities. However, the analysis of beta-haplotypes will be very useful for the genetic epidemiological study in this region.

Rapid screening of multiple beta-globin gene mutations by real-time PCR on the LightCycler: application to carrier screening and prenatal diagnosis of thalassemia syndromes

BACKGROUND

Hemoglobinopathies are priority genetic diseases for prevention programs. Rapid genotype characterization is fundamental in the diagnostic laboratory, especially when offering prenatal diagnosis for carrier couples.

METHODS

As a model, we designed a protocol based on the LightCycler technology to screen for a spectrum of beta-globin gene mutations in the Greek population. Design was facilitated by dual fluorochrome detection and close proximity of many mutations. Three probe sets were capable of screening 95% of beta-globin gene mutations in the Greek population, including IVSII-745C-->G, HbS, Cd5-CT, Cd6-A, Cd8-AA, IVSI-1G-->A, IVSI-5G-->A, IVSI-6T-->C, IVSI-110G-->A, and Cd39 C-->T.

RESULTS

The protocol, standardized by analysis of 100 beta-thalassemia heterozygotes with known mutations, was 100% reliable in distinguishing wild-type from mutant alleles. Subsequent screening of 100 Greek beta-thalassemia heterozygotes with unknown mutations found 96 of 100 samples heterozygous for 1 of the 10 mutations, although melting curves were indistinguishable for mutations HbS/Cd6 and IVSI-5/IVSI-1, indicating a need of alternative methods for definitive diagnosis. One sample demonstrating a unique melting curve was characterized by sequencing as Cd8/9+G. Three samples carried mutations outside the gene region covered by the probes. The protocol was 100% accurate in 25 prenatal diagnosis samples, with 14 different genotype combinations diagnosed. The protocol was also flexible, detecting five beta-globin gene mutations from other population groups (IVSI-1G-->T, IVSI-5G-->C, IVSI-116T-->G, Cd37 TGG-->TGA, and Cd41/42 -TCTT).

CONCLUSIONS

The described LightCycler system protocol can rapidly screen for many beta-globin gene mutations. It is appropriate for use in many populations for directing definitive mutation diagnosis and is suited for rapid prenatal diagnosis with low cost per assay.

Distribution and frequency of beta-thalassemia mutations in northwestern and central Greece

OBJECTIVES

Beta-Thalassemia is a common autosomal recessive disorder resulting from over 200 different mutations of the beta-globin genes. The spectrum of beta-thalassemia mutations in Greece has been previously described in the population of the capital city of Athens, or in beta-thalassemia patients having transfusion therapy. The aim of the present study was to identify the distribution of the most common beta-thalassemia mutations in the population of northwestern and central Greece.

METHODS

The data for this study were derived from a total of 1,130 unrelated subjects including 46 beta-thalassemia major, three beta -thalassemia intermedia and 1,081 carriers identified in our antenatal screening program. beta-Thalassemia mutations were identified by ARMS, DGGE and Reverse Dot Blot.

RESULTS

The most common mutation, IVS-I-110, is followed, in order of frequency, by the mutations Cd-39, IVS-I-1, IVS-II-1, Cd-6, IVS-I-6, IVS-I-5, IVS-II-745, Cd-5 and 44 bp del. IVS-I-110 and Cd-39 frequencies are similar with those found in other Balkan countries. Significant differences in regional distribution were observed. The results showed a clear drift of the distribution of the most frequent IVS-I-110 mutation in the south-north (29.4, 40.0, 44.6 and 61.7%) and the east-west axis (31.8 and 44.6%).

CONCLUSIONS

Population screening and prenatal diagnosis are significantly facilitated by these data. Furthermore, the detailed distribution tables of beta-thalassemia mutations are essential for counseling and extraction of genetic diversity estimates for population genetic studies in other inherited disorders.

Molecular analysis of beta-thalassaemia patients in a high incidence area of southern Italy

The prevalence of eight mutations in 84 patients with beta-thalassaemia major and in 16 subjects with thalassaemia intermedia was investigated. All of the patients were Italian, originating from Eastern Sicily (Messina area) and some Calabrian regions. Genomic DNA was amplified by polymerase chain reaction (PCR). DNA molecular investigations were performed by allele-specific oligonucleotide (ASO) hybridization, to identify the following beta-thalassaemia mutations: CD39 (C-T), IVS1-110 (G-A), IVS1-6 (T-C), IVS1-1 (G-A), IVS2-745 (C-G), IVS2-1 (G-A), -87 (C-G), CD6 A (-A). Our data underline that in thalassemia intermedia two mutations were statistically prevalent: IVS1-6 T-->C (P < 0.001) and CD 6-A (P < 0.05). CD 39 was statistically prevalent in beta-thalassaemia major patients (P < 0.01). The difference between the two groups was not statistically significant for all the other mutations. Five different genotypes were recorded among thalassaemia intermedia and 15 among beta-thalassaemia major patients. Twenty-five percent of the intermedia patients and 4.5% of the major patients had homozygosity for mild mutations (group I); 62.5% of the intermedia patients and 26.2% of the major patients had combinations of mild/severe mutations (group II). In addition, homozygosity or double heterozygosity for severe mutations (group III) was found in 12.5% of the intermedia patients and 69% of the major patients. Some genotypes were restricted to thalassaemia intermedia, including heterozygosity -87/IVS1-6 and IVS1-6/CD 6-A. It is essential to understand the distribution and frequency of the relevant mutations in each population where beta-thalassaemias exist. This is of particular importance for genotype-phenotype correlation and for carrier detection, genetic counselling and prenatal diagnosis.

Spectrum of beta-thalassemia in Jordan: identification of two novel mutations

Two hundred and forty-four beta-thalassemia alleles were identified from 135 unrelated occasionally and periodically transfusion dependent beta- and S/beta-thalassemia patients from all regions of Jordan. Allele identification was achieved by PCR amplification of beta-globin genes, dot-blotting the amplified DNA, hybridization with allele specific synthetic probes, and direct sequencing of amplified genomic DNA. A total of 19 different mutations were detected, eight of them constituted about 86% of the Jordanian thalassemic chromosomes. These mutations were IVS1-110 (G>A) (25%), IVS2-1 (G>A) (15%), IVS2-745 (C>G) (14.2%), IVS1-1 (G>A) (10%), IVS1-6 (T>C) (8.3%), codon 37 (G>A) (6.3%), codon 39 (C>T) (4.6%), and codon 5 (-C) (3.8%). The remaining eleven mutations were rare, presented with frequencies ranging between 0.4% and 1.6%. These included two novel mutations and four others detected in Jordan for the first time. The novel mutations were the frame shift (-C) at codon 49 and the substitution (A>C) at position -29 in the TATA box. Four alleles (1.6%) remained unidentified; having no abnormalities in their beta-globin gene sequences and therefore, constituted additional defects causing beta-thalassemia in the Jordanian population. These unknown alleles are expected to be candidates for upstream or downstream mutations affecting the expression of beta-globin gene. The results provided the essential foundation for planning a national preventive program for thalassemia in Jordan and will help improving the medical services for the patients and their families by helping their clinicians and genetic counselors in evaluating their variants and designing their treatment regimens.

The thalassemia syndromes: molecular characterization in the Spanish population

This work compiles the results of our research on alpha- and beta-thalassemias, and includes a literature review of the molecular genetics of alpha- and beta-thalassemias in Spain. We studied 1,564 subjects with thalassemia (294 with beta-thalassemia and 1,264 with alpha-thalassemia) by molecular biology techniques. In relation to beta-thalassemia, a total of 15 different mutations were characterized in a study of 308 chromosomes belonging to 294 unrelated subjects. Eleven were homozygotes (22 alleles), three compound heterozygotes (6 alleles), and the remaining 280 were heterozygotes (280 alleles). A total of 86.6% of the alleles identified can be grouped into five different mutations [IVS-I-1 (G-->A), IVS-I-6 (T-->C), IVS-I-110 (G-->A), codon 39 (C-->T), codons 8/9 (+G)]. In 14 subjects (4.5%), all heterozygotes, it was not possible to identify the alteration responsible for the beta-thalassemia. For alpha-thalassemia, 911 subjects showed heterozygous alpha(+)-thalassemia (872 with -3.7 kb; 14 with -4.2 kb; two with the deletion of 3.5 kb of DNA, and 23 with nondeletional alpha-thalassemia). Two hundred and thirty-three subjects had homozygous alpha(+)-thalassemia (223 for -alpha(-3.7)/-alpha(-3.7)); one for -alpha(-4.2)/-alpha(-4.2); six for -alpha(-3.7)/-alpha(-4.2); one for -alpha(-3.5)/-alpha(-3.7); one for alphaalpha(Nco)/alphaalpha(Nco); one for alpha(HPh)/alpha(Hph)). One hundred patients presented with heterozygous alpha(0)-thalassemia (18 of whom were progenitors of patients with Hb H disease). The alpha(0) determinant was found in 20 patients with Hb H disease associated with -alpha(-3.7). From the DNA analysis were identified the - -(MED), - -(SEA), - -(SPAN) deletions and the - -(MA) mutations; in three cases, a break that affects the distal portion of the short arm of chromosome 16; one of these was associated with the ATR-16 (alpha-thal with mental retardation) syndrome. Triplication of the alpha genes (alphaalphaalpha(-3.7)/alphaalpha) was found in 25 subjects, 16 of whom were associated with a heterozygous beta-thalassemia. Only one patient was homozygous for the triplication of alpha genes (alphaalphaalpha(-3.7)/alphaalphaalpha(-3.7)) that was associated with a heterozygous beta-thalassemia. In the Mediterranean region preventive programs for thalassemia, based on the detection of heterozygote carriers and genetic advice, are not sufficient to reduce the incidence of newborns with major thalassemia. Prenatal diagnosis of thalassemias has given a new dimension to the prevention of these, but in order to implement this, a knowledge of the mutations and the incidence of these, is essential. This study, therefore, aims to give a general picture of the molecular genetics of thalassemia and its geographical distribution in our area.

Agamma-haplotypes: a new group of genetic markers for thalassemic mutations inside the 5' regulatory region of the human Agamma-globin gene

This study illustrates the relationship between a group of nucleotide variations within the 5' regulatory region of the Agamma-globin gene [Agamma-588 A-->G, Agamma-499 T-->A and the 4-bp deletion (Agamma-225 to -222 AGCA)] and the spectrum of delta- and beta-thalassemia mutations in the Hellenic population. These sequence variations, screened by means of denaturing gradient gel electrophoresis, form four separate frameworks (Agamma-haplotypes), each one of which was found to be linked in cis with certain delta- and beta-thalassemia mutations found in the Hellenic population. In addition, two novel base substitutions inside the 5' regulatory region of the Agamma-globin gene (Agamma-521 C-->A and Ay-500 C-->T) were identified during this study, which together with Agamma-haplotypes seem to be silent polymorphisms during adult life, as indicated by transient expression assays. Our data show that Agamma-haplotypes represent genetic markers for the spectrum of thalassemic mutations, found in the Hellenic population and can constitute an important genetic repository upon which mutations leading to thalassemia and hemoglobinopathies occurred.

Neutrophil elastase in patients with homozygous beta-thalassemia and pseudoxanthoma elasticum-like syndrome

In this study we investigated the possible role of neutrophil (PMN) elastase and its natural inhibitor, alpha1-proteinase inhibitor (alpha1-PI) in the pathogenesis of the pseudoxanthoma elasticum (PXE)-like syndrome which is found in patients with homozygous beta-thalassemia. We studied 30 beta-thalassemia homozygotes with the PXE-like syndrome [PXE(+) group], 20 beta-thalassemia homozygotes without this syndrome [PXE(-) group] and 15 healthy controls. Plasma PMN elastase concentration in the PXE(+) and in the PXE(-) group was 136.4 +/- 89 and 163.8 +/- 126 microg/L, respectively (P > 0.05). In the control group, the concentration was 42.9 +/- 16.8 microg/L (P < 0.01 for the comparison with both patients' groups). The plasma alpha1-PI concentration in the PXE(+) and in the PXE(-) group was 2.28 +/- 0.75 and 2.6 +/- 0.96 g/L, respectively (P > 0.05). Using logistic regression, we studied the prognostic value for PXE of the following independent variables: number of transfusions, chelation therapy, mean hemoglobin concentration, PMN elastase concentration, alpha1-PI concentration, chronic transaminase elevation, and positivity for anti-HCV. None of the above variables was found to have significant prognostic value for the PXE. Plasma PMN elastase concentration is elevated in all beta-thalassemia homozygotes; its role in the pathogenesis of the PXE-like syndrome in beta-thalassemia can not be established, but our findings suggest that neutrophils of beta-thalassemia patients are activated, since PMN elastase is a marker of neutrophil activation.

Molecular characterization of beta-thalassemia in Syria

This study concerns the determination of beta-thalassemia alleles and other hemoglobin variants in 82 patients from Syria. We have characterized 146 chromosomes and found 17 different beta-thalassemia mutations, and one beta-globin chain variant that gives rise to the abnormal Hb S. The eight most common beta-thalassemia mutations were the IVS-I-110 (G-->A), IVS-I-1 (G-->A), codon 5 (-CT), -30 (T-->A), codon 39 (C-->T), IVS-I-6 (T-->C), IVS-II-1 (G-->A), and codon 15 (TGG-->TAG). These mutations accounted for almost 75% of the total beta-thalassemia chromosomes. We identified 34 different genotypes with a high level of homozygosity. The various beta-thalassemia mutations were characterized using gene amplification with specific oligonucleotide primers, restriction enzyme analysis, denaturing gradient gel electrophoresis and direct sequencing. By combining these three approaches we were able to detect mutations in almost 90% of the chromosomes studied. Our findings provide a sound foundation on which to base a preventive program for thalassemia and we believe that the data that we present will facilitate the improvement of medical services such as carrier screening, genetic counseling, and prenatal diagnosis. Furthermore a detailed knowledge of the molecular pathology of beta-thalassemia will strongly improve the prenatal diagnosis services in Syria.

Preimplantation genetic diagnosis in 10 couples at risk for transmitting beta-thalassaemia major: clinical experience including the initiation of six singleton pregnancies

Preimplantation genetic diagnosis (PGD) offers couples at risk for transmitting an inherited disorder the possibility to avoid the need to terminate affected pregnancies, since it allows the selection of unaffected IVF embryos for transfer. PGD for monogenic diseases is most commonly accomplished by blastomere biopsy from cleavage stage embryos, followed by polymerase chain reaction (PCR)-based DNA analysis. However, PCR-based DNA analysis of single cells is subject to several problems including sample contamination, total PCR failure, or failure of one allele to amplify--a phenomenon known as allelic drop-out (ADO). Furthermore, the molecular heterogeneity of many monogenic diseases requires a diagnostic strategy capable of detecting a spectrum of mutations and compound genotypes. With the above considerations we developed an accurate and reliable strategy for analysis of beta-globin gene mutations, applicable for PGD for the wide spectrum of beta-thalassaemia major genotypes in the Greek population. The strategy involves nested PCR followed by denaturing gradient gel electrophoresis (DGGE) analysis. DGGE is an advantageous method for mutation detection since it facilitates simultaneous analysis of more than one mutation in a single PCR fragment, it identifies the presence of normal alleles and in addition can monitor the occurrence of ADO. This report describes the application of the DGGE-based diagnostic strategy in 11 clinical IVF/PGD cycles, in 10 couples at risk for transmitting beta-thalassaemia major. The transfer of at least one embryo diagnosed as unaffected for beta-thalassaemia major in nine couples has resulted in the initiation of six pregnancies. Four pregnancies have so far been confirmed as unaffected for beta-thalassaemia major by first or second-trimester prenatal diagnosis, two of which have resulted in the birth of two healthy babies. Three singleton pregnancies are still on-going and one ectopic pregnancy was terminated.

Molecular, haematological and clinical studies of the -101 C --> T substitution of the beta-globin gene promoter in 25 beta-thalassaemia intermedia patients and 45 heterozygotes

We report the clinical, haematological, biosynthetic and molecular data of 25 double heterozygote beta-thalassaemia intermedia patients and 45 beta-thalassaemia heterozygotes with the C --> T substitution at nucleotide position -101 from the Cap site, in the distal CACCC box of the beta-globin gene promoter. This mutation is considered the most common amongst the silent beta-thalassaemia mutations in Mediterranean populations. Of the 25 compound heterozygotes for the beta -101 C --> T and common severe beta-thalassaemia mutations, all but one had mild thalassaemia intermedia preserving haemoglobin levels around 9.5 g/dl and haemoglobin F levels < 25%. The only transfused patient was characterized to have an additional alpha-globin gene. Strict assessment of haematological and biosynthetic findings in the heterozygotes for the beta -101 C --> T mutation (excluding six cases with an alpha-globin gene defect) demonstrated that less than half of them had completely normal (silent) haematology; the remainder had either high haemoglobin A2 values (in the range of 3.7-5.1%) and/or low red cells indices and/or raised haemoglobin F values. The alpha/non-alpha-globin chain synthesis ratios were generally raised, with mean 1.44 (1.07-2.10). Amongst the parents of the compound heterozygotes, who were not selected for molecular analysis following haematological screening, half of the cases were completely silent. Interaction with severe beta-thalassaemia mutations always resulted in the clinical phenotype of mild non-transfusion-dependent thalassaemia intermedia.

Fetal hemoglobin expression in the compound heterozygous state for -117 (G-->A) Agamma HPFH and IVSII-745 (C-->G) beta+ thalassemia: a case study

We studied a family in which two inherited defects of the non-alpha-globin cluster segregate: Greek hereditary persistence of fetal hemoglobin (HPFH) and beta-thalassemia. The compound heterozygote is a healthy man with 43% HbF, Ggamma/Agamma ratio (27:73) differing from that of 10 simple heterozygotes for the Greek HPFH (92:8), normal levels of total Hb (13.3 g/dl), and reduced HbA2 levels comparing with the levels of beta-thal heterozygotes for the same mutation. Molecular analysis of the beta-globin genotype revealed the presence of the IVSII-745 (C-->G) beta+ RNA splice mutation in trans with the -117 G-->A Greek HPFH. The beta+ mutation was linked to haplotype VII and the Greek HPFH was associated with haplotype Ia. The father of the compound heterozygote carries the Greek HPFH in trans with the -158 C-->T on the Ggamma promoter, which is linked with haplotype IV. He presented 13.5% HbF with a Ggamma/Agamma ratio 75:25. His daughter was a compound heterozygote for the IVSII-745 mutation in trans with the -158 C-->T, while her HbF levels were 3.7% with a Ggamma/Agamma ratio 31:69.

Beta-thalassemia alleles in Aegean region of Turkey: effect on clinical severity of disease

Beta (beta) globin gene analysis was performed in 54 homozygous beta-thalassemia patients followed up in the Pediatric Hematology Department of Medical School of Ege University. The spectrum of beta-thalassemia alleles and their effect on clinical severity of disease were investigated. Twelve different mutations were determined in our patients. The six most frequent alleles, IVSI-110 (G-A), IVSI-6 (T-C), IVSI-I (G-A), IVSII-745 (C-G), Cd39 (C-T), and FSC8, account for 80.6% of all the disease genes. Eleven percent of the chromosomes could not be identified with the probes used in this study. In 38 patients both of whose beta-thalassemia alleles were identified, the beta-thalassemia alleles were found to be the major determinant of the clinical severity of disease. The clinical progress of disease was also closely related to the degree of iron overload.

Evidence for high-risk haplotypes and (CGG)n expansion in fragile X syndrome in the Hellenic population of Greece and Cyprus

The expansion of the trinucleotide repeat (CGG)n in successive generations through maternal meiosis is the cause of fragile X syndrome. Analysis of CA repeat polymorphisms flanking the FMR-1 gene provides evidence of a limited number of "founder" chromosomes and predisposing high-risk haplotypes related to the mutation. To investigate the origin of mutations in the fragile X syndrome in the Hellenic populations of Greece and Cyprus, we studied the alleles and haplotypes at DXS548 and FRAXAC2 loci of 16 independent fragile X and 70 normal control chromosomes. In addition, we studied 191 unrelated normal X chromosomes for the distribution and frequencies of CGG alleles. At DXS548, 6 alleles were found, 2 (194 and 196) of which were represented on fragile X chromosomes. At FRAXAC2, 6 alleles were found, 4 of which were present on fragile X chromosomes. Sixteen haplotypes were identified, but only 5 were present on fragile X chromosomes. The highest number of CGG repeats (> or = 33) were associated with haplotypes 194-147, 194-151, 194-153, and 204-155. The data provide evidence for founder chromosomes and high-risk haplotypes in the Hellenic population.

Severity of beta-thalassemia due to genotypes involving the IVS-I-6 (T-->C) mutation

Among individuals of Mediterranean or Middle Eastern descent, the IVS-I-6 (T-->C) mutation is one of the most common causes of beta-thalassemia. In this report, we describe the clinical phenotypes of a group of beta-thalassemia patients who are compound heterozygotes for the relatively mild IVS-I-6 (T-->C) beta-thalassemia mutation and more severe beta(+)- or beta (0)-thalassemia mutations. Although most of these patients are transfusion-dependent, the requirement for regular transfusions generally occurred late in childhood. A correlation between concomitant alpha-thalassemia and a mild transfusion-independent phenotype is not apparent, indicating the involvement of other ameliorating determinants.

Molecular characterization of homozygous (high HbA2) beta-thalassemia intermedia in Greece

Homozygous beta-thalassemia is usually characterized by severe anemia requiring regular blood transfusion for survival. For homozygous patients with milder clinical manifestations and no dependence on transfusion therapy, the term thalassemia intermedia is usually applied. Genetic mechanisms that may ameliorate the clinical expression of homozygous beta-thalassemia include coinheritance of alpha-thalassemia, inheritance of mild beta-globin gene mutations, and increased gamma-globin chain production, which may partially compensate for the lack of beta-globin chain synthesis. To identify which of these factors may contribute to the modification of childhood homozygous, high-hemoglobin A2 (HbA2) beta-thalassemia in Greece, the interaction of alpha-thalassemia, types of beta-thalassemia mutations, and the presence of a polymorphic site 5' to the G gamma-globin gene, which has been described as associated with increased gamma-globin chain production in some cases, was assessed. The results were analyzed in light of similar studies in 150 randomly selected, homozygous, high-HbA2 beta-thalassemia patients with the aim of assessing whether thalassemia genotypes can provide information useful for prognosis and/or more appropriate management of homozygous beta-thalassemia patients. The results indicate that, in general, the major factor modifying the clinical expression of homozygous, high-HbA2 beta-thalassemia in Greece is the inheritance of mild beta-thalassemia mutations. Although there is not always a complete correlation of genotype with clinical phenotype, the inheritance of two mild beta-thalassemia alleles results in almost all cases (11 of 12 cases in this study) in thalassemia intermedia phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a novel beta O-thalassaemia mutation in a Greek family and subsequent prenatal diagnosis

We present a case in which a Greek couple was considered not to be at risk of having children with homozygous beta-thalassaemia, an assessment based largely on the father's belief that he carried alpha-thalassaemia. After their first child was diagnosed with homozygous beta-thalassaemia, the case was re-assessed and both parents were shown to have the haematological profile of beta-thalassaemia trait. Screening for the common Mediterranean mutations demonstrated that the mother carries the IVS-1 nt 110 G-->A beta(+)-thalassaemia mutation. Direct nucleotide sequencing of PCR-amplified DNA revealed that the father carries a novel beta O-thalassaemia mutation, frameshift codons 9/10 (+T). The couple's second pregnancy was terminated after prenatal testing revealed that the fetus had inherited both parental mutations. This case illustrates the need to confirm the carrier status of individuals prior to assessing their genetic risks, and highlights the importance of being able to identify rare or novel beta-thalassaemia mutations.

Molecular characterization of beta-thalassemia in north Jordan

We have studied the beta-thalassemia mutations in 91 chromosomes of 43 patients with beta-thalassemia major and five with Hb S-beta-thalassemia, aged 6 months to 24 years. Many are blood transfusion-dependent and are being treated at the major hospital, the Princess Basma Hospital, in Irbid, Jordan. As many as 13 different mutations have been identified; three Mediterranean mutations [IVS-I-110 (G-->A), IVS-II-I (G-->A), and IVS-II-745 (C-->G)] were present in 54% of the chromosomes tested, while six other Mediterranean alleles were found in 24% of the chromosomes, for a total of 78% of Mediterranean origin. Sixteen chromosomes carried mutations which were observed in Arabian, Southeast Asian/Indian, and Iranian/Egyptian or Black populations; four beta-thalassemia mutations remained unidentified.

Hematologic phenotype of the mutations IVS1-n6 (T-->C), IVS1-n110 (G-->A), and CD39 (C-->T) in carriers of beta-thalassemia in Greece

The hematologic phenotype was characterized in heterozygotes for three of the most common beta-thalassemia mutations in the Greek population. The study included 17 carriers of beta++ IVS1-n6 (T-->C), 21 carriers of beta+ IVS1-n110 (G-->A), and 17 carriers of beta 0 CD39 (C-->T). The 55 beta-thalassemia heterozygotes were selected from among parents of patients on regular transfusion regimens, and the beta-thalassemia mutation was identified by means of the polymerase chain reaction to amplify the appropriate region of the beta-globin gene and then by allele-specific oligonucleotide hybridization. The assessment of hematologic phenotype included complete blood count and quantitation of hemoglobin HbA2 and HbF and of the globin chain biosynthesis ratio. Comparison and statistical analysis of the hematologic parameters for the three mutations demonstrated no consistent correlation among the three mutations relative to Hb levels, hematocrit, and red cell indices, although heterozygotes for the IVS1-n6 mutation produce red blood cells with slightly higher mean corpuscular volume; significantly lower values of HbA2 (mean, 3.81% +/- 0.62% with four values less than 3.60%) in IVS1-n6 heterozygotes compared with IVS1-n110 heterozygotes (mean, 4.69% +/- 0.48%) and CD39 heterozygotes (mean, 4.75% +/- 0.50%, P < 0.001); and significantly higher HbF levels in CD39 heterozygotes (mean, 2.31% +/- 1.52%) compared with IVS1-n6 heterozygotes (mean, 0.79% +/- 0.45%, P < 0.01) and IVS1-n110 heterozygotes (mean, 1.17% +/- 0.75%, P < 0.01). With respect to the HbA2 levels, the findings are in agreement with previous studies in Mediterranean populations; the slightly higher levels of HbF in CD39 heterozygotes appear to be reported for the first time.

The spectrum of beta-thalassemia mutations in the Oran region of Algeria

In order to delineate the spectrum of beta-globin gene defects causing beta-thalassemia in the Oran region of Algeria, we have analyzed a representative sample of 31 beta-thalassemia patients. This led to the detection of 10 mutations. Four of them [nonsense codon 39 (C->T), IVS-I-110 (G->A), IVS-I-2 (T->C), and frameshift codon 6 (-A)] account for approximately 77% of the beta-thalassemia chromosomes. Three of these mutants are also widespread in Mediterranean populations, whereas the fourth, IVS-I-2 (T->C), appears typical of the Oranese population. The six other variants are less frequent. The possible origin of these mutated alleles, either by recurrent mutational event or by migration from other populations, is discussed.

History of pediatric hematology and oncology in Greece

The history of pediatric hematology and oncology in ancient and modern Greece is reviewed. Ancient Greek literature concerning cancer starts with Hippocrates, is enriched by Galen during the 2nd century AD, and ends with the end of the Byzantine period. Hematology and oncology in modern Greece were adopted as fields of special interest by a few Greek pediatricians. Their work constituted the basis for and the start of pediatric hematology and oncology, which has followed the advances of science ever since.

Beta thalassaemia in the indigenous British population

We have analysed the molecular basis of beta-thalassaemia in 22 Anglo-Saxon individuals, all of whom were heterozygous for beta-thalassaemia except for one, who was a compound heterozygote. Using a combination of allele-specific priming of the polymerase chain reaction (PCR) and direct sequencing of genomic DNA amplified by the PCR, 20/23 beta-thalassaemic genes were characterized. Nine different mutations were identified; four are commonly found in the Mediterranean, one in Asia, one has been described previously in both Europe and Asia, and three are rare mutations associated with a dominant beta-thalassaemia phenotype. In three individuals the mutation remains uncharacterized despite sequence analysis of the beta-globin gene and its immediate flanking regions. We report our findings and discuss the diversity of these mutations.

The beta-thalassaemia mutations in the population of Cyprus

We have identified the beta-thalassaemia alleles in nearly all known Turkish Cypriot beta-thalassaemia homozygotes and in over 700 Greek Cypriot beta-thalassaemia heterozygotes living on the island of Cyprus. The data confirmed earlier observations that the IVS-I-100 (G-->A) mutation is present for about 74-80%, while three other alleles [IVS-II-745 (C-->G), IVS-I-6 (T-->C), IVS-I-1 (G-->A)] occur at frequencies of 5-8%. Nearly identical percentages were observed for the two Cypriot groups, quite different from those for beta-thalassaemia patients from Greece and Turkey. This suggests close contacts between the two Cypriot communities during many centuries without a major recent influence from Greek or Turkish beta-thalassaemia carriers.

The molecular basis of β-thalassemia in Turkey

By using oligonucleotide hybridization, restriction endonuclease analysis and direct sequencing of amplified genomic DNA, we have been able to characterize 18 different mutations in the beta-globin genes of 161 beta-thalassemia homozygotes and 107 beta-thalassemia heterozygotes from Turkey (429 beta-thalassemia chromosomes). Previous studies dealing with beta-thalassemia in Mediterranean countries have shown that, in most Mediterranean populations, only a few mutations are prevalent. In contrast, beta-thalassemia in Turkey does not seem to be associated with a few predominant mutations. The six most frequent alleles, IVS-I-110 (G----A), IVS-I-6(T----C), FSC-8 (-AA), IVS-I-1(G----A), -30(T----A) and FSC-5 (-CT), account for only 69.3% of the disease genes; indeed, all 26 mutations assayed represent 85.8% of the disease genes, confirming the considerable molecular heterogeneity of beta-thalassemia among Turks, and indicating the possible presence of rare, previously undefined, mutations in the population. Two mutations observed in this study, IVS-I-116 (T----G) and Cd44(-C), have not been reported in the Turkish population to date. Since preventive medical services, such as genetic counseling and prenatal diagnosis, are greatly improved by detailed knowledge of the molecular pathology of beta-thalassemia, we strongly believe that the presented data will facilitate the intended establishment of a prenatal diagnosis center, based on DNA analysis, in Turkey.

Prenatal diagnosis of thalassemia and hemoglobinopathies in Switzerland

During a 10-month period, 10 couples originating from Africa (3), the tropics (1) and the thalassemia-belt region (6), living in Switzerland, requested prenatal diagnosis of hemoglobinopathies. Hb SS (twice), Hb Bart's (Hydrops fetalis) and beta-thalassemia major were diagnosed either by gene mapping or by direct detection of the mutations in DNA amplified by the PCR procedure. Whenever it was possible to obtain fetal blood or tissue, diagnosis was confirmed. In one Vietnamese man, concomitant existence of alpha-thal 1 with beta-thalassemia resulted in an unusually high Hb level because of balanced alpha and beta globin synthesis. The 10 couples examined originated from 7 different countries and presented at least 7 different Hb pathologies. This variety of pathologies represents the main difficulty for prenatal diagnosis of hemoglobinopathies in a non-endemic country. A diagnostic approach to overcome this problem is developed.