A. Angius

Polymorphism of DNA Sequence in the β-Globin Gene Region

Abstract We used a restriction endonuclease to analyze the β-thalassemia gene in Sardinia. When we digested human DNA with the restriction enzyme Bam HI, the β-globin gene split into a 5′ portion c...

Isoelectric Focusing of Globin Chains for Antenatal Diagnosis of β°-Thalassemia

A recently developed isoelectric focusing technique for human globin chain separation has been applied to the antenatal diagnosis of β°-thalassemia in Sardinia. Results obtained with this method show a complete concordance with those obtained by the currently-in-use chromatographic separation of globin chains by carboxymethyl-cellulose. The ease with which several samples (up to 20) can be simultaneously processed and analyzed by a single operator and the very simple equipment required make this new method ideal for the antenatal diagnosis of β°-thalassemia and could encourage a more widespread use of prenatal diagnosis of thalassemias.

Interaction of Alpha and Beta Thalassaemia Genes in Two Sardinian Families

Summary. Our paper describes two Sardinian families with α‐β thalassaemia interaction. In the first (family S), the propositus, whose haemoglobin pattern at birth consisted of about 25% Hb Barts and 75% Hb F, successively developed a clinical and haematological picture typical of Cooleys anaemia. Haematological and globin chain synthesis studies together with these findings suggest that he is homozygous for β0 thalassaemia and heterozygous for α thalassaemia‐1 and α thalassaemia‐2. This conclusion is further substantiated by the finding of various combination of α and β thalassemia among his family members.

Prenatal Diagnosis of β Thalassaemia by Fetal Red Cell Enrichment with NH4Cl-NH4HCO3 Differential Lysis of Maternal Cells

Summary. Prenatal diagnosis with globin chain synthesis analysis on fetal red blood cells concentrated by NH4Cl‐NH2HCO3 differential lysis of maternal cells (Ørskov lysis) was carried out in 27 pregnancies at risk for β thalassaemia and one at risk for sickle cell β0 thalassaemia. The β/γ globin chain synthesis ratio was also determined after anti‐i differential agglutination (12 cases), in almost pure fetal samples (six cases) and by extrapolation (one case). Differential lysis permitted the study of samples drawn by placental aspiration containing as little as 3.2% fetal red blood cells. There was no consistent difference between the β/γ ratios observed after differential lysis and those determined after the use of the other approaches. A presumptive diagnosis of homozygous β thalassaemia was made in nine cases. All but one of these pregnancies was terminated. The absence of β chain synthesis was confirmed by the study of fetal blood after abortion in four cases with suitable samples. Of the remaining pregnancies, six proceeded to term and non‐homozygous infants were delivered. The others are still in progress. No fetal loss occurred. ørskov lysis seems to be a very reliable method for prenatal diagnosis of β chain abnormalities. Moreover it can minimize the number and duration of placental aspirations required and thus the risk to the fetus.

Molecular mechanism accounting for milder types of thalassemia major

We carried out alpha-globin gene analysis by restriction endonuclease mapping in 91 Sardinians with homozygous transfusion-dependent beta 0-thalassemia and correlated the clinical findings with the alpha-globin genotype. In patients (n = 6) with deletion of two alpha-globin structural genes, disease onset and transfusion dependence occur later than in those (n = 50) with a full complement of alpha-globin genes. There was no statistically significant difference in the group of patients (n = 35) with deletion of only one alpha-globin gene. Patients with deletion of two alpha-globin genes had significantly higher Hb A2 levels than those with a full complement of alpha-structural genes and those with deletion of a single alpha-globin gene. From this and other studies, it seems that the deletion of two alpha-globin structural genes may convert the common severe clinical picture associated with homozygous beta 0-thalassemia to milder forms, ranging from a later occurring but still transfusion-dependent type to a non-transfusion-dependent form.

PRENATAL DIAGNOSIS OF β THALASSEMIA: EXPERIENCE WITH 133 CASES AND THE EFFECT OF FETAL BLOOD SAMPLING ON CHILD DEVELOPMENT *

Prenatal diagnosis was attempted in 133 pregnancies at risk for beta thalassemia (132 cases) or sickle-cell beta 0 thalassemia (1 case). Of these, 76 couples requested diagnosis because they already had children affected with homozygote beta thalassemia (72 cases) or beta+ thalassemia (4 cases). The others were probably at risk for beta 0 thalassemia since this is by far the predominant thalassemia type in Sardinia. Sufficient fetal blood for analysis was obtained by placental aspiration at 18--24 weeks gestation in 130 cases. Ten fetal losses occurred. The pregnancies were followed and no relevant complications were seen. Of the newborns delivered, 45 were followed from birth with particular attention to congenital malformation, neurological, growth, and maturity assessement. No major adverse effect of placentocentesis on child growth and development was observed. Placental samples were analyzed by globin chain synthesis analysis on carboxylmethylcellulose columns. When the placental samples contained more than 20% maternal red cells, fetal red cell enrichment was carried out by anti-i (53 cases) or anti-AB (2 cases) differential agglutination or NH4Cl-NH4HCO3 differential lysis of maternal cells (17 cases). Of the 130 cases, 32 fetuses had no beta-chain radioactivity and one had a beta/gamma ratio of 0.005. These were presumed to be homozygous and all but one were electively aborted. Absence of beta-chain radioactivity was confirmed in 10 abortuses with suitable cord blood samples. A total of 91 infants have been born and are nonhomozygous. Genotype assessment at 6 months after birth in 33 infants showed that there was only a slight overlap between the ranges of normal (0.095 +/- 0.016) and heterozygous (0.05 +/- 0.01) fetal beta/gamma globin chain synthesis ratios.

Hematological Characteristics of Sardinian α-Thalassemia Carriers Detected in a Population Study

88 adults with thalasseia-like red cell indices, normal serum iron and normal hemoglobin (Hb) A2 and F levels, diagnosed in a mass screening had Hb H inclusion bodies studies (65 subjects)

Diagnosis of the β0 Thalassemia Trait at Birth

This study shows the results of in vitro globin chain synthesis analysis in 33 infants who had been previously evaluated for the presence of thalassemia in the second trimester of gestation and were restudied after the stage of hematological maturity. Four children with α-thalassemia-1, identified in a newborn screening, were also included. Normals and β-thalassemia heterozygotes could be distinguished in the neonatal period by β/α or β/γ ratios. However, as a considerable overlap of α-thalassemia-1 with normals and α-thalassemia-2 with β-thal-assemia heterozygotes were found, biosynthetic studies at birth seem to be inappropriate to make reliable diagnosis of hemoglobin chain deficiences. There were no differences between hematological indices of normal and heterozygous β-thalassemia newborns, while α-thalassemia-l carriers showed a statistically significant difference from normals in mean MCV and MCH.

Hemoglobin H Disease in Sardinia: Phenctypic and Genetic Observations

In this study the clinical and hematological characteristics, the transmission pattern and the relative rates of globin chain synthesis were determined in the members of four Sardinian families with 14 patients affected by hemoglobin H disease. The severity of hemoglobin H disease in Sardinian subjects shows a high degree of variability. Clinically it usually appears intermediate between the hemoglobin H disease found in Oriental and Negro populations. The alpha/beta specific activity ratio was 0.42 +/- 0.10 indicating an analogous biochemical defect like that described in the Chinese. On the basis of hematological data and alpha/beta ratio, the genetics of hemoglobin H disease in Sardinians seem to follow a pattern similar to that observed in Orientals: one parent showing alpha-thalassemia-1 trait and the other alpha-thalassemia-2 trait. Parent offspring transmission of hemoglobin H disease did occur in 2 out of 6 hemoglobin H matings with spouses carrying the alpha-thalassemia-1 gene. This observation indicates either a high frequency of alpha-thalassemia trait in Sardinians or a high incidence of inbreeding. In one family the mating of a patient with hemoglobin H disease and a normal person produces 6/6 offspring with alpha-thalassemia-1. The genetic implications of this transmission pattern are discussed.