Application of DNA polymorphisms for prenatal diagnosis of beta thalassemia in Chinese

Forty-seven Chinese suffering from beta thalassemia major and their parents were studied to establish linkage of the beta thal and beta A genes with 11 restriction site polymorphisms. There is marked linkage disequilibrium at the BamH I site 3' to the beta globin gene, such that, in 31% of pregnancies, absence of the site in the fetus can exclude beta thalassemia major. Using four restriction sites (Hinc II psi beta, Ava II beta, Hind III beta, and BamH I beta), prenatal diagnosis is feasible in all families. In 46% of all cases, a definitive diagnosis can be made, and in the remaining cases, a 50% chance of exclusion is possible. Fetal blood globin chain analysis would be required for the failures. Our experience in nine successive beta thalassemia prenatal diagnosis is also reported.     

Delineation of specific beta-thalassemia mutations in high-risk areas of Italy: a prerequisite for prenatal diagnosis

In this study, we defined by haplotype characterization combined with oligonucleotide hybridization or direct restriction endonuclease analysis the specific beta-thalassemia mutations in a representative sample of beta-thalassemia chromosomes from patients with homozygous beta-thalassemia originating from different parts of Italy. We characterized the mutations in 90% of the thalassemia chromosomes and found that three mutations, namely the beta+IVS 1-110, beta degrees -39 and beta+IVS 1-6 are prevalent in the Italian population. Most of the patients investigated were compound heterozygotes for two beta- thalassemia mutations, and only a few were homozygotes for one mutant. On the basis of these findings, we predict that prenatal diagnosis in this population would be feasible in most cases by fetal DNA analysis with the oligonucleotide method using a limited number of oligonucleotide probes selected after screening parents for the most common beta-thalassemia mutations. We have also devised a method based on hybridization with a mixture of two oligonucleotides that allows rapid and simultaneous screening of prospective parents for the two most frequent mutations in Italians, the beta+IVS 1-110 and beta degrees -39 mutants. This method may be applicable to prenatal diagnosis in cases at risk for the genetic compound of these mutations.     

Molecular basis of beta thalassemia in the south of Thailand.

A total of 103 beta thalassemia genes from 78 children (45 with Hb E/beta thalassemia, 8 with beta thalassemia heterozygotes, and 25 with homozygous beta thalassemia) were analyzed using dot-blot hybridization of the polymerase chain reaction-amplified DNA and direct DNA sequencing. Nine mutations were characterized in 98/103 (95%) of beta thalassemia alleles, of which six (a 4 bp deletion in codons 41-42, a G-C transition at position 5 of IVS-1, A-G transition at codon 19, an A-T transition at codon 17, an A-G transition at position -28 upstream of the beta globin gene, a G-T transition at position 1 of IVS-1), accounted for 92%. The spectrum of beta thalassemia mutations in Chinese Thai is similar to that reported among the Chinese from other parts of the world. The distribution of beta thalassemia mutations in Muslim Thai is similar to that reported among Malaysians. The most common beta thalassemia mutation in Thai and Chinese Thai patients is the frameshift mutation at codons 41-42, in comparison with the Muslim Thai in whom the G-C transition at position 5 of the IVS-1 mutation predominates. The heterogeneity of molecular defects causing beta thalassemia should aid in the planning of a prenatal diagnosis program for beta thalassemia in the South of Thailand.     

Reverse dot-blot detection of the African-American beta-thalassemia mutations

DNA-based diagnosis of the beta thalassemias provides accuracy to newborn screening genetic counseling, and prenatal diagnosis. However, the use of polymerase chain reaction (PCR)-based methods is challenged by the great number of different-beta-thalassemia mutations that exist even within defined ethnic groups. In this regard, the reverse dot-blot method offers a means of screening for several mutations with a single hybridization reaction. We have applied the reverse dot-blot method to the detection of the beta-thalassemia mutations of African-Americans. We used two biotin-labeled primer pairs in a duplex reaction to amplify and label two beta-globin target DNA fragments that encompass all known African-American beta-thalassemia mutations. The PCR products were denatured and hybridized to polyT-tailed, membrane-fixed, allele- specific probe pairs for the hemoglobin (Hb) S, Hb C, and 14 beta- thalassemia mutations and their corresponding wild-type sequences. Seven common mutations plus Hb S and Hb C were included on one diagnostic strip, and seven less common beta-thalassemia mutations were included on another strip. Carefully controlled, high stringency hybridization allowed accurate distinction of these alleles. Reverse dot-blot diagnosis of the less common beta-thalassemia mutations precludes the need for alternative, more technically challenging methods. This method provides a rapid, accurate method for diagnosis of beta thalassemia among African-Americans and other ethnic groups in which beta thalassemia occurs.     

Thalassemia and abnormal hemoglobin

Thalassemia and abnormal hemoglobins are common genetic disorders in Asia. Thalassemia is not only an important public health problem but also a socio-economic problem of many countries in the region. The approach to deal with the thalassemic problem is to prevent and control birth of new cases. This requires an accurate identification of the couple at high risk for thalassemia. However, the diagnosis of thalassemia carrier states need several tests which are not practical for screening the population at large. Recently we have used two simple laboratory tests to screen for potential thalassemia carriers and hemoglobin E individuals. There is also a new development in using the automatic HPLC to diagnose thalassemic diseases and the carriers. This system gives both qualitative and quantitative analysis of hemoglobin components in the same run with good precision and reproducibility. The system has been applied to study thalassemia and abnormal Hb in adult and cord blood. This system has enabled us to do both prenatal and postnatal diagnosis of thalassemia within the few minutes. However, none of these screening tests can accurately give specific diagnosis of the thalassemia genotype. Specific thalassemia mutation can be carried out by DNA analysis. Many DNA techniques have been used for point mutation detection and small deletion. For the last few years there is a development of DNA chip technology that has been applied for thalassemia mutation as well. Clinically, thalassemia is very heterogeneous in the manifestation. In spite of seemingly identical genotypes, severity of beta thalassemic patients can vary greatly. Heterogeneity in the clinical manifestation of beta thalassemic diseases may occur from the nature of beta globin gene mutation, alpha thalassemia gene interaction and difference in the amount of Hb F production which is partly associated with a specific beta globin haplotype. However, there is still some beta thalassemia cases that have a mild clinical symptom without those known genetic fators interaction suggesting that there are other additional factors responsible for the mildness of the disease.     

Thalassemia and abnormal hemoglobin

Thalassemia and abnormal hemoglobins are common genetic disorders in Asia. Thalassemia is not only an important public health problem but also a socio-economic problem of many countries in the region. The approach to deal with the thalassemic problem is to prevent and control birth of new cases. This requires an accurate identification of the couple at high risk for thalassemia. However, the diagnosis of thalassemia carrier states need several tests which are not practical for screening the population at large. Recently we have used two simple laboratory tests to screen for potential thalassemia carriers and hemoglobin E individuals. There is also a new development in using the automatic HPLC to diagnose thalassemic diseases and the carriers. This system gives both qualitative and quantitative analysis of hemoglobin components in the same run with good precision and reproducibility. The system has been applied to study thalassemia and abnormal Hb in adult and cord blood. This system has enabled us to do both prenatal and postnatal diagnosis of thalassemia within the few minutes. However, none of these screening tests can accurately give specific diagnosis of the thalassemia genotype. Specific thalassemia mutation can be carried out by DNA analysis. Many DNA techniques have been used for point mutation detection and small deletion. For the last few years there is a development of DNA chip technology that has been applied for thalassemia mutation as well. Clinically, thalassemia is very heterogeneous in the manifestation. In spite of seemingly identical genotypes, severity of.beta thalassemic patients can vary greatly. Heterogeneity in the clinical manifestation of beta thalassemic diseases may occur from the nature of beta globin gene mutation, alpha thalassemia gene interaction and difference in the amount of Hb F production which is partly associated with a specific beta globin haplotype. However, there is still some beta thalassemia cases that have a mild clinical symptom without those known genetic fators interaction suggesting that there are other additional factors responsible for the mildness of the disease.     

Delta + 27 homozygosis in a Sicilian family.

During a screening program to identify at risk couples for beta-thalassemia first-trimester prenatal diagnosis, we were able to detect, by polymerase chain reaction (PCR) and direct genomic sequencing of the PCR product, a homozygosis for the G-T substitution at the first nucleotide of codon 27 of the delta-globin gene in a pregnant Sicilian woman. The possibility of showing an interaction between delta and beta thalassemia is relevant for a thalassemia prevention program because it may hide a beta-thal carrier state.     

Hydrops fetalis due to an unusual form of Hb H disease

The occurrence of Hb H hydrops fetalis is reported for the first time. The mother has zeta-alpha thalassemia 1 (zeta zeta alpha alpha/----) and the father has non-deletion alpha thalassemia [zeta zeta alpha alpha/zeta zeta (alpha alpha)T]. The complete deletion of the zeta alpha cluster on one chromosome was confirmed by quantitation of alpha and zeta gene numbers, the normal alpha and zeta gene patterns arising from the remaining normal chromosome, and the decreased alpha/beta globin chain ratio of 0.57. The non-deletion alpha thalassemia defect could only be identified by the imbalanced alpha/beta globin chain ratio of 0.65 in the presence of normal gene numbers and patterns. The newborn was markedly anemic, unlike those with classical Hb H disease, because the non-deletion alpha thalassemia defect is more severe than alpha thalassemia 2. The decreased zeta genes during fetal life might have additional deleterious effects. In this family, the distinct BamHI restriction fragment length polymorphism in the hypervariable region of the zeta genes may be used for future prenatal diagnosis.     

Early Prenatal Diagnosis of Thalassemia: The First Report of Experience in Mainland China

In this study, we report our experience with chorionic villus sampling (CVS) for prenatal diagnosis of thalassemia in mainland China. During a 4-year period, 308 pregnant women chose to have CVS for prenatal diagnosis. Chorionic villus sampling was successful in all cases, and post-CVS abortion was seen in only two cases (0.6%). DNA diagnosis was correctly done in 307 (99.7%) prenatal samples but maternal contamination was found in one (0.3%) subject. In total, 77 pregnancies were found with an affected fetus, and all of the affected pregnancies were terminated within 1 week after the CVS procedure. Our experience indicates that CVS is a feasible and effective technique for prenatal diagnosis of thalassemia.     

Early prenatal diagnosis of thalassemia: the first report of experience in mainland China

In this study, we report our experience with chorionic villus sampling (CVS) for prenatal diagnosis of thalassemia in mainland China. During a 4-year period, 308 pregnant women chose to have CVS for prenatal diagnosis. Chorionic villus sampling was successful in all cases, and post-CVS abortion was seen in only two cases (0.6%). DNA diagnosis was correctly done in 307 (99.7%) prenatal samples but maternal contamination was found in one (0.3%) subject. In total, 77 pregnancies were found with an affected fetus, and all of the affected pregnancies were terminated within 1 week after the CVS procedure. Our experience indicates that CVS is a feasible and effective technique for prenatal diagnosis of thalassemia.     

Overview of the beta thalassemias: genetic and clinical aspects

There has been much progress in basic studies of the beta-thalassemia disorders in recent years, as well as in the practical aspects of prenatal diagnosis and clinical management. Alterations in a single or a few nucleotides account for most of the types of beta-thalassemia syndromes that have been characterized, and a variety of deletions have been found associated with beta O thalassemia, delta beta thalassemia, gamma delta beta thalassemia, and hereditary persistence of fetal hemoglobin (HPFH). Studies of nondeletional types of HPFH have revealed several single base changes 5' to the G gamma and A gamma genes, suggesting that these regions may be of major importance in the switchover from fetal to adult hemoglobin synthesis and in the relative production of the G gamma and A gamma globin chains during development. Evaluation of restriction enzyme polymorphisms and the assignment of haplotypes in the beta-like globin region of chromosome 11 have allowed delineation of the origin and distribution of thalassemia mutations, and have provided an important means for prenatal diagnosis. These studies have accumulated much new information about the function and expression of eukaryotic genes, and have served as a model for the investigation of human genetic disorders. The clinical management of patients with Cooley's anemia has benefited greatly from changes in transfusion practice, clear guidelines for splenectomy, and the availability of effective chelation therapy for iron overload. Current basic and clinical studies may lead to new approaches to management, treatment and eventual cures for this disease, including safe bone marrow transplantation, oral chelation treatment, and gene therapy.     

Prenatal diagnosis of thalassemia in Songklanagarind Hospital in southern Thailand

A thalassemia screening program for pregnant women has been established in Songklanagarind Hospital since 1992. After genetic counseling, a total of 5078 pregnant women accepted entry into a screening program for thalassemia. Couples at risk who should receive prenatal diagnosis were 2.8%. Total cases who accepted prenatal diagnosis were 135. Total clinical cases were 40 (29.6%) with achievement by prenatal diagnosis of 33 cases (82.5%). Genetic amniocentesis is the most acceptable method for prenatal diagnosis. Five cases (12.5%) were misdiagnosed due to contamination of maternal blood cells in amniotic fluid cases. Questionable results were reported in 2 cases (5%). Abortion occurred in one case (0.7%). Improvement of surgical technic in prenatal diagnosis reduced the complications and contamination of maternal cells. This program shows the feasibility of prevention and control of thalassemia disease in southern Thailand.     

First observation of homozygous hemoglobin hamadan (B 56 (D7) GLY-ARG) and beta thalassemia (-29 G>A)- hemoglobin Hamadan combination in a Turkish family

During screening surveys for beta thalassemia and abnormal hemoglobins in Mugla, a city located in the Aegean Region of Turkey, a hemoglobin variant was detected in two large families residing in two neigboring cities (i.e., Mu?la and Aydin) without any clinical signs. Further analysis of the variant revealed it as Hb Hamadan (B 56 (D7) GLY‐ARG). Family screening revealed the father of the propositus as homozygote Hb Hamadan. The grandfather of the index case was detected as combination of Hb Hamadan with beta thalassemia. The beta thalassemia carrier had a promotor mutation at ?29 G>A, which is also a novel mutation. Furthermore, we described a simple and rapid restriction enzyme digestion protocol (Hha I) for the verification of Hb Hamadan. The clinical and hematologic data of the index case and his father showed that neither homozygous Hb Hamadan nor combination with beta thalassemia has clinical importance. This is also important especially from the prenatal diagnosis point of view. Am. J. Hematol. 74:280–282, 2003. © 2003 Wiley‐Liss, Inc.     

Restriction fragment length polymorphism in the interzeta hypervariable region for prenatal diagnosis of non-deletion alpha thalassemia

A Bam HI restriction fragment length polymorphism in the interzeta hypervariable region (IZ HVR) of the zeta-alpha gene cluster was used for the prenatal diagnosis of a pregnancy at risk for Hb H hydrops fetalis. The parents had zeta-alpha thalassemia 1 and non-deletion alpha thalassemia, respectively, and a previous hydrops was missed using the conventional method of gene detection. In this prenatal diagnosis, linkage to IZ HVR was used to exclude non-deletion alpha thalassemia, and the numbers of zeta and alpha genes in the fetus were quantitated to predict the exact genotype. Confirmation was made by analysis of cord blood at delivery.     

Molecular basis of thalassemia intermedia in Iran

Thalassemia intermedia shows considerable heterogenity in phenotype and molecular basis. The aim of this study was to evaluate the prevalence and effect of different beta-globin mutations, alpha-globin defects and (G)gamma XmnI polymorphisms in Iranian patients. Forty-five Iranian patients with clinical criteria of thalassemia intermedia were studied. The molecular background of the diseases was investigated. The mean age of onset varied from 1.5 to 30 years. Only 22.2% of cases received occasional blood transfusions. The hemoglobin (Hb) level in more than half of the cases was stable (10-12 g/dL) with no need for blood transfusions. In most cases (88.9%) the Hb F level was more than 50%. Sixty-eight point nine percent of patients were homozygous for beta(0)-thalassemia (beta-thal) mutations. The positive XmnI polymorphism with the capability of enhancing Hb F production was seen in 60% of the studied chromosomes. Co-inheritance of alpha-globin gene defects was seen in 22.2% of cases. Only 8.9% of patients had beta(+) or beta(++) mutations. We concluded that the main molecular basis of the thalassemia intermedia phenotype in Iranian cases is co-inheritance of a positive XmnI polymorphism with beta-globin mutations, which can enhance the capability of Hb F production. Co-inheritance of alpha-globin defects and mild beta-globin mutations are second and third causes of thalassemia intermedia phenotypes respectively. These factors must be considered in genetic counseling, prediction of disease prognosis and treatment and prenatal diagnosis.     

Detection of the hemoglobin E mutation using the color complementation assay: application to complex genotyping

The color complementation assay (CCA) is a method of allele-specific DNA amplification by which competitive priming and extension of fluorescently labeled oligonucleotide primers determine the color of DNA amplification product. This diagnostic method precludes the need for radioisotopes, electrophoresis, and multiple high-stringency reaction conditions. The multiplicity of mutant globin genes present in Southeast Asians complicates clinical diagnosis and underscores the importance of DNA-based diagnostic methods. We have applied CCA to distinguish beta A and beta E alleles. Competing 15mer primers were a fluorescein-labeled complement to beta A and a rhodamine-labeled complement to beta E, identical except for their central nucleotides. A common unlabeled primer was used to amplify DNA product, the color of which was determined by the perfectly complementary primer. Color photography and spectrofluorometry, as well as a method of black-white photography that we developed to distinguish fluorescein- and rhodamine- labeled DNA, were used to record results. We applied CCA to define the complex genotype of a Thai woman with thalassemia intermedia, 96% HbE, and 4% HbF whose possible genotypes included several permutations of alpha-thalassemia, beta-thalassemia, and beta E genes. zeta-Globin gene mapping of DNA doubly digested with Bg/II and Asp 718 showed the -alpha 3.7/--SEA genotype, and CCA confirmed homozygous beta E/beta E. The CCA is useful for diagnosing the compound hemoglobin genotypes of Southeast Asians and could be applied also to prenatal diagnosis in this population.     

Prenatal diagnosis of thalassemia in the Chinese

There is a high prevalence of thalassemia in the Taiwan area. Prenatal diagnosis of severe forms of thalassemia is important for the prevention of this disease. We performed prenatal diagnosis in 167 cases, of which 59 cases were diagnosed by chorionic villi biopsy, 91 cases by amniotic fluid analysis, and 17 cases by cord blood analysis. Hb Bart's hydrops was detected by amplifying the break junction area of the α-thalassemia-1 Southeast Asia (SEA)-type gene, and β-thalassemia major was detected by using naturally occurring restriction sites and the amplified created restriction sites (ACRS) method. Screening for hemoglobin (Hg) Bart's hydrops revealed 26 cases of Hb Bart's hydrops, 67 cases of α-thalassemia-1 (including 6 Hb Bart's hydrops falsely diagnosed as α-thalassemia-1 from chorionic villi samples), and 38 normal cases. Screening for β-thalassemia major revealed 8 cases of β-thalassemia major, 17 cases of β-thalassemia minor, and 11 normal cases. In cases of α-thalassemia, maternal tissue contamination in the chorionic villi samples occurred in the diagnosis of the carrier state and further amniotic fluid analysis will be necessary. There were no any false-positive or false-negative results in β-thalassemia major screening. We conclude that prenatal diagnosis is a reliable and accurate screening method for thalassemia and may be valuable in other areas of high prevalence for thalassemia in Southeast Asia and in Southern China. Am. J. Hemat. 55:65-68, 1997. © 1997 Wiley-Liss, Inc.     

Rapid detection of deletions causing delta beta thalassemia and hereditary persistence of fetal hemoglobin by enzymatic amplification

A considerable number of deletions of variable size and position that involve the beta-globin gene complex on chromosome 11 are associated with the clinical entities of hereditary persistence of fetal hemoglobin (HPFH) and delta beta thalassemia. Specific deletions appear to be associated with consistent phenotypes and some are known to be recurrent. To facilitate the molecular diagnosis of uncharacterized patients with HPFH and delta beta thalassemia, oligonucleotide primers have been designed to enzymatically amplify deletion-specific products for nine known deletions, which include those responsible for HPFH-1, HPFH-2, HPFH-3, Spanish (delta beta)zero thalassemia, hemoglobin (Hb) Lepore, Sicilian (delta beta)zero thalassemia, Chinese G gamma(A gamma delta beta)zero thalassemia, Asian-Indian inversion-deletion G gamma(A gamma delta beta)zero thalassemia, and Turkish inversion-deletion (delta beta)zero thalassemia. Using this approach, we have successfully characterized the molecular basis for delta beta thalassemia in 23 individuals from 16 families of diverse ethnic origins. Thirteen individuals from this group were shown to be heterozygous for the 13.4- kb Sicilian deletion, two were heterozygous for the 100-kb Chinese G gamma(A gamma delta beta)zero deletion, four were heterozygous for the Turkish form of inversion-deletion delta beta thalassemia, and three were heterozygous for the Asian-Indian form of inversion-deletion G gamma(A gamma delta beta)zero thalassemia. One Vietnamese subject was heterozygous for a 12.6-kb deletion, which we have fully characterized at the molecular level. Sequence analysis of the breakpoint regions of the Chinese deletion and the Turkish rearrangement indicates that, in each case, the mutation is likely to have arisen from a single origin. This hypothesis is supported by the evident geographical clustering of the various deletions described here.     

The thalassemia syndromes: molecular basis and prenatal diagnosis in 1990

In this review I have outlined the molecular basis and prenatal diagnosis of alpha-thalassemia and then concentrated on the state of our knowledge of the molecular basis of beta-thalassemia and its prenatal diagnosis. I discussed the improved but more complicated genetic counselling now available as a result of our increased knowledge of the effects of various defects in the beta-globin gene. Our knowledge of the heterogeneous molecular basis of the thalassemia syndromes has become very impressive and it is hoped that effective therapy will soon follow. For the present, however, prevention of the birth of affected children is the most effective means of reducing the suffering associated with the thalassemia syndromes, and prevention of this type is succeeding in many parts of the world, including North America.     

Hemoglobin E disease in North Indian population: a report of 11 cases

Hemoglobin E (beta26Glu --> Lys) is the most common hemoglobin (Hb) variant in Southeast Asia and the second most prevalent worldwide. However in India, it is prevalent in Bengal and the north-eastern region, but relatively rare in the rest of the country. Identification of this Hb variant is important, because the doubly heterozygous state for HbE and beta-thalassemia is characterized clinically by thalassemia major, a situation different from other compound heterozygous states for structural beta-chain variants and beta-thalassemia. Thus, the affected individual may be symptomatic and transfusion dependent at an early age. This paper reports four cases with Hb E trait, three cases with hemoglobin E disease and another four cases with Ebeta-thalassemia. Laboratory investigations are based on RBC indices and high performance liquid chromatography (HPLC). A negative correlation has been found to exist between levels of HbA(2) and RBC indices including the MCV and MCH. A similar correlation has been seen between levels of HbF with Hb, RBC count, and MCV. The main aim is to increase the awareness of this relatively rare disorder, so that it can be included in the differential diagnosis of patients presenting clinically like thalassemia intermedia or thalassemia major. This awareness may also help in prenatal diagnosis, genetic counseling and clinical management. The clinical, hematological and laboratory features of this disorder are also discussed.