The prenatal diagnosis of thalassaemia.
Explore the source record for details and available documents.
DNA↗
Biomedical subjects
A Cao
Publications and source records attributed to A Cao.
Molecular pathology of haemoglobin H disease in Sardinians.
We investigated the molecular basis for haemoglobin H disease in 50 Sardinian patients by restriction endonuclease analysis. We found that the majority (78% of the cases) are due to gene deletion (- -/- alpha). Among those with a combination of deletion and nondeletion defects (- -/alpha alpha th), the most prevalent nondeletion lesion (70% of the nondeletion defects) was the initiation codon mutation of the alpha 2 gene (alpha Nco alpha), previously discovered in this population. Of the remaining patients with the (- -/alpha alpha th) genotype, two showed the IVS-1 splice junction lesion and one a mutation in the alpha 1 gene, removing the Nco I site within the 5' part of the alpha 1 gene, which may arise from a process of gene conversion from the initiation codon mutant of the alpha 2 gene. A single patient had the homozygous state for the initiation codon mutant of the alpha 2 gene. Study of genotype-phenotype correlations indicates that the (alpha Nco alpha) haplotype is associated with a more severe defect in the alpha-globin chain output than that resulting from the (-alpha) haplotype. We may conclude that restriction endonuclease analysis is a powerful method for the definition of the molecular heterogeneity of haemoglobin H disease.
Adolescent↗
Mitochondrial DNA polymorphisms in Italy. I. Population data from Sardinia and Rome.
The polymorphisms of human mitochondrial DNA were studied in about 150 Sardinians from Cagliari and 100 other Italians living in Rome, using total blood cell DNA and the following restriction enzymes: HpaI, BamHI, HaeII, MspI, AvaII and HincII. 1. Seven different new morphs have been identified, one for HaeII, four for AvaII and two for HincII. 2. 16 and 17 mtDNA types were observed in the Sardinian and Roman samples, respectively. Of these only seven were shared by both groups. The morphs BamHI-3, MspI-4 and AvaII-9 were found associated at a frequency (10.0%) much higher than expected (0.17%). 3. Sardinians can be differentiated from the other Italians for a higher frequency of both morph AvaII-1 (P less than 0.05) and type 1 (2-1-1-1-1) (P approximately less than 0.03), and for a lower intragroup heterogeneity (0.52 v. 0.61). 4. The Italian sample on the whole can also be differentiated from the Caucasian group previously examined for a lower frequency of BamHI morph 2 (P Yates less than 0.01), a higher frequency of HaeII morph 1 (P Yates less than 0.02) and for the presence at a non-negligible incidence (5 individuals out of 229) of the new type 57-2 (2-3-1-4-13-2). The data indicate that mtDNA polymorphisms have not only proved to be a useful tool in detecting differences among major human groups but they can also differentiate populations within the same major ethnic division.
Adult↗
Pitfalls in prenatal diagnosis of beta thalassaemia.
In this paper, we report a pregnancy at risk for beta thalassaemia in which the fetal red blood cell volume was reduced while that of the mother was relatively great, so that the presence of a fetal red blood cell population in a mixed maternal-fetal sample was difficult to recognise. The molecular basis for these haematological phenotypes was clarified by follow up examination and alpha globin gene mapping. These indicated that the fetus was heterozygous for beta thalassaemia and had deletion of three alpha globin structural genes, while the mother, heterozygous for beta thalassaemia, also had deletion of two alpha globin structural genes. When the coinheritance of alpha thalassaemia is suspected, it is necessary to examine carefully the red blood cell distribution of a placental sample, so that the presence of a population of fetal red blood cells is not missed.
Chromosome Deletion↗
Alpha-thalassemia in premature newborns.
In this study we have carried out alpha-globin gene mapping, hemoglobin (Hb) Bart's quantitation serum bilirubin, and red blood cell indices determination in a group of Sardinian appropriate for gestational age premature infants (from 32 to 35 wk gestation) in order to define the incidence in this population of the different alpha-thalassemia syndromes, their expression rate, and the correlation between the alpha-globin genotype and phenotype at this developmental stage. The gene frequencies of deletion (-alpha) and nondeletion (alpha alpha th) alpha-thalassemia were 0.29 and 0.04, respectively, and thus not different from those found in full-term newborns from the same population. The majority of premature newborns with a single alpha-globin gene deletion [(-alpha/alpha alpha) genotype] were hematologically silent. Those who manifested increased Hb Bart's (1.2 to 3.4%) had slightly reduced Hb levels (17.4 +/- 2.6 g/dl), mean corpuscular volume (102.6 +/- 6.3 fl), and mean corpuscular Hb (34.8 +/- 2.0 pg) values. Those infants with the deletion of two alpha-globin structural genes (-alpha/-alpha) showed without exception moderate amount of Hb Bart's in the 3.5-8.1% range and an obvious decrease of Hb levels (16.1 +/- 1.6 g/dl) mean corpuscular Hb (30.6 +/- 3.5 pg), and mean corpuscular volume (88.5 +/- 11.5 fl) values. The only infant with the deletion of 3 alpha-globin structural genes had 25% Hb Bart's associated with a moderate microcytic anemia at birth and developed the clinical picture of Hb H disease. Carriers of nondeletion alpha-thalassemia (alpha alpha/alpha alpha th) showed variable amount of Hb Bart's always associated with thalassemia-like red cell indices.(ABSTRACT TRUNCATED AT 250 WORDS)
Chromosome Mapping↗
Genetic control of the proportion of gamma chains of human fetal haemoglobin.
The relative proportions of gamma chains of human fetal haemoglobin G gamma, A gamma 75 Ileu (A gamma I) and A gamma 75 Thr (A gamma T) were investigated in homogeneous populations of patients in Algeria exhibiting sickle cell disease and in patients in Algeria and Sardinia with beta-thalassaemia. The restriction site haplotypes within the beta gene cluster were known. The results suggest a tight genetic regulation of the G gamma/A gamma + G gamma ratio (G gamma ratio) which is associated with the G gamma Hind III site of polymorphism (p less than 0.0001). From the present results and those in the literature the high G gamma ratio is associated with the presence of 3 polymorphic restriction sites: Xmn1 5' to the G gamma gene, Hind III in the G gamma IVS II and Hinc II in the psi beta gene. Familial studies showed that the expression of the A gamma alleles is genetically determined. The wide variation of the A gamma T/A gamma T + A gamma I ratio (A gamma ratio) between families is most probably related to the various haplotypes bearing the A gamma I alleles.
Algeria↗
Prenatal diagnosis of inherited hemoglobinopathies.
In this paper we reviewed the different methods presently available for prenatal diagnosis of hemoglobin disorders and the impact of this technology in the control of beta-thalassemia in several Mediterranean populations. The vast majority of the inherited hemoglobinopathies can now be detected in the fetus by amniocyte or trophoblast DNA analysis. alpha-thalassemias, delta beta-thalassemias and gamma delta beta-thalassemias, which are usually caused by a gross structural rearrangement of the DNA, may be directly detected by Southern blot analysis. Only a few beta-thalassemia lesions are caused by gene deletion or affect a restriction recognition site and thus may be directly identified by this method. The major part of beta-thalassemia are due to single nucleotide substitution, small deletion or addition which do not alter a restriction recognition site. These mutations may be directly detected by complementary oligonucleotide probes. Alternatively, when normal or affected children are available, fetal diagnosis may be accomplished by linkage analysis with polymorphic restriction sites. Fetal blood analysis is used at present time for those cases presenting too late in the pregnancy for characterization of the molecular defect and in prospective parents in whom the defect is not known. Introduction of prenatal diagnosis in combination with carrier screening in several mediterranean populations led to a consistent reduction in the incidence of homozygous beta-thalassemia.
Base Sequence↗
[Quasi-elastic diffusion of light for the study of emulsions in extremely fine dispersions].
Explore the source record for details and available documents.
Diffusion↗
Prenatal diagnosis of beta-thalassaemia with the synthetic-oligomer technique.
103 couples attending the antenatal clinic in Sardinia were screened for the beta o-39 (nonsense) mutation, which codes for beta-thalassaemia, with the oligonucleotide method. In 94 couples both members had the beta o-39 mutant and thus were eligible for antenatal testing with this method. These pregnancies were monitored with amniocentesis (61) or trophoblast biopsy (33). Prenatal diagnosis in those monitored with amniocentesis was carried out with DNA analysis of uncultivated amniocytes (19) or cultivated cells (38). In 4 pregnancies results were unsatisfactory, and prenatal diagnosis was repeated with fetal-blood analysis. Trophoblast biopsy was unsuccessful in 1 pregnancy and gave a misdiagnosis in another because of maternal contamination. In the latter case the genotype of the fetus was established with amniocyte DNA analysis and globin-chain-synthesis studies.
Amnion↗
Genetic counseling and genetic heterogeneity in the thalassemias.
In this study, we have compared the hemoglobin A2 levels (Hb A2) of alpha-thalassemia carriers (-alpha/-alpha and -alpha/alpha alpha genotypes) with those of double heterozygotes for delta+ and beta thalassemia genes, who were identified by family studies and polymorphic restriction site analysis within the beta-globin gene cluster. We found that double heterozygotes for the delta+ and beta thalassemia have significantly (p less than 0.001) higher Hb A2 levels as compared with carriers of alpha-thalassemia. This finding has practical implications in the genetic counseling of subjects with a thalassemia-like phenotype associated with normal or borderline Hb A2 levels.
DNA Restriction Enzymes↗
Antenatal diagnosis of thalassemia major in Sardinia.
In this report, we summarized our experience, carried out in Sardinia, with antenatal diagnosis in one thousand pregnancies in which the fetus was at risk for homozygous beta-thalassemia. In the majority of these cases, the thalassemia lesion segregating in the family was the nonsense mutation at the codon corresponding to amino-acid 39. At the outset (976 cases) we used globin chain synthesis analysis by column chromatography on fetal blood obtained by placental aspiration, and recently (24 cases) we employed the synthetic oligonucleotide method on amniocyte DNA. Apart from 126 pregnancies still in progress, in all the other cases the diagnosis has been confirmed. In the majority of the cases (99%), we obtained sufficient fetal blood for the analysis. The fetal mortality associated with placental aspiration was 6.1%. The biochemical analysis gave reliable results. We had two misdiagnoses (0.2%): one due to a nonglobin protein comigrating with the beta chains and the other for a misclassification of the type of thalassemia segregating in the family. The oligonucleotide method gave clear-cut results in all the cases tested. The method was sensitive enough to detect the mutation directly in the DNA isolated from 20-25 ml of amniotic fluid in 75% of the pregnancies tested. In one case, we successfully employed this method for the analysis of the DNA isolated from chorionic villi. The oligonucleotide method seems to be the best procedure for monitoring the pregnancies at risk for beta-thalassemia in places where one or a few beta-thalassemia lesions are prevalent.
Amnion↗
Perinatal hepatitis B virus detection by hepatitis B virus-DNA analysis.
Maternal transmission of hepatitis B virus infection in relation to the hepatitis B e antigen/antibody system and serum hepatitis B virus-DNA were evaluated. Results indicate that hepatitis B virus-DNA analysis can identify hepatitis B serum antigen positive mothers who may transmit infection to their offspring.
Autoradiography↗
Osmotic fragility test in heterozygotes for alpha and beta thalassaemia.
This study shows that the combination of heterozygous beta thalassaemia and deletion heterozygous (-alpha/alpha alpha) or homozygous (-alpha/-alpha) alpha+ thalassaemia may result in the production of erythrocytes which have normal mean volume and haemoglobinisation but decreased osmotic fragility. Based on this finding and previous studies, which have shown that beta thalassaemia screening by the osmotic fragility test may miss a significant proportion of beta thalassaemia heterozygotes, we conclude that beta thalassaemia screening in a population in which both alpha and beta thalassaemia are prevalent should combine the one tube osmotic fragility test with electronic measurement of red blood cell indices in the initial screening process.
Genetic Carrier Screening↗
Initiation codon mutation as a cause of alpha thalassemia.
Cloning and sequence analysis of the alpha-globin genes from a Sardinian patient with the nondeletion type of hemoglobin-H disease revealed a new type of thalassemia lesion. A mutation in the alpha 2-globin gene changes the initiation codon ATG to ACG and abolishes the function of this gene. Globin mRNA output from the affected alpha 2 locus is decreased relative to the alpha 1 locus. The mutation is detectable in genomic DNA by restriction analysis with the enzyme NcoI. Of the seven Sardinian patients with nondeletion alpha thalassemia screened with this enzyme, six had the initiation codon lesion.
Base Sequence↗
Fatal Yersinia enterocolitica meningitis in thalassemia major.
A case of meningitis by Yersinia enterocolitica in a patient with thalassemia major is described. The Yersinia has been identified both in the cerebrospinal fluid and in the feces. The clinic syndrome began with gastroenteritis and was suddenly complicated by septicemia and meningitis. In spite of a prompt and specific antibiotic therapy, the disease led the patient to death.
Acute Disease↗
Multiple mutations produce delta beta 0 thalassemia in Sardinia.
In Sardinia the common form of beta thalassemia is a beta 0 thalassemia due to a nonsense mutation at codon 39. delta beta 0 Thalassemia is rare in Sardinia and is associated with increased production of hemoglobin F of the A gamma type. In this study we used a synthetic oligomer assay and detected the beta 39 nonsense mutation on the delta beta 0 thalassemia chromosome. Hence at least two different mutations have occurred on this chromosome; one that increases A gamma globin synthesis and another that silences the beta globin gene.
Chromosomes, Human↗
Alpha thalassaemia in Sardinian newborns.
In this study we describe the correlation between the haematological parameters (red cell indices and Hb Bart's levels) and the alpha-globin genotype in Sardinian newborns. Increased Hb Bart's levels at birth always indicates alpha-thalassaemia, either of the deletion or non-deletion variety. Infants with two alpha-globin genes deleted (- alpha/- alpha and --/ alpha alpha genotypes) had microcytosis, low MCH and Hb Bart's in the 2.0-7.1% range. A minority (38.9%) of infants with the (- alpha/ alpha alpha) globin genotype had detectable Hb Bart's, in the 0.78-2.5% range, frequently associated with minimal microcytosis while the remainder (61.1%) were completely silent. Infants carriers of a non-deletion type of alpha-thalassaemia showed Hb Bart's levels within the range found in the (- alpha / alpha alpha) genotype. The association of heterozygous beta 0-thalassemia seems to have no effect on the expression of any of these alpha-thalassaemia lesions at birth.
Chromosome Mapping↗
Control of homozygous beta-thalassemia by carrier screening and antenatal diagnosis in Sardinians.
This paper reports the present results of an ongoing program aimed at preventing homozygous beta-thalassemia by means of heterozygote screening and antenatal diagnosis in the Sardinian population. Screening based on the knowledge of carrier frequency and types of thalassemia prevalent in this population was designed to discover all heterozygotes except the few silent beta-thalassemia carriers. Most of the couples at risk were informed and accepted testing. Information was conveyed by mass media, midwives and marriage registry offices. Antenatal diagnosis was accepted by the majority of the couples counselled. The results of antenatal testing were very accurate. There was only one misdiagnosis out of 949 pregnancies tested. This risk of fetal loss was 7.5%. The program was highly effective, as shown by the decline of the incidence of the homozygous state from 1:205 live births in 1976 to 1:557 in 1981.
DNA↗