[Prenatal diagnosis of beta-thalassemia using genetic engineering techniques].
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Biomedical subjects
Publications and source records attributed to H Kerem.
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The development of fetoscopy and the ability to obtain fetal blood samples have made possible the prenatal diagnosis of diseases not diagnosable by amniocentesis. Foremost among these disorders are the hemoglobinopathies. We report our experience in establishing the first program for fetoscopy and fetal blood sampling in the Middle East. The results demonstrate that the experience and training required for a fetoscopy and fetal blood sampling program can be obtained in about one year. During that year, 23 couples who fetuses were at risk for a hemoglobinopathy learned the genetic status of their fetuses.
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Chromatographic separation of labeled globin chains was performed in stroma-free hemolysates prepared from peripheral blood and bone marrow cells of 11 patients with beta O-thalassemia and 2 patients with sickle cell anemia. A small radioactivity peak, slightly preceding the beta-chain and more prominent in bone marrow cells, was often observed. This peak, which represents synthesis of non-globin proteins, did not exceed 5% of the radioactivity incorporated in the alpha-chain. It is concluded that contamination of the beta-chain with non-globin proteins undoubtedly occurs, but its extent is insufficient to explain the different synthetic ratios which have been repeatedly observed in peripheral blood and in bone marrow cells of patients with heterozygous beta-thalassemia.
Three patients with a relatively mild form of beta O-thalassemia who did not require regular blood transfusions are described. Globin synthesis was studied by gel filtration and urea-carboxymethylcellulose chromatography of stroma-free hemolysates prepared from peripheral blood and bone marrow cells labeled in vitro with 14C-leucine. gamma/alpha Synthetic ratios in peripheral blood were in the same range as in patients with the severe clinical form of beta O-thalassemia, while gamma/alpha synthetic ratios in bone marrow cells were higher than in that group of patients. The size of the free alpha-chain pool measured in one case was smaller than in other patients with "classical" Cooley anemia. It is concluded that the severity of the clinical course in beta O-thalassemia does not correlate with the imbalance in alpha verus gamma chain synthesis in peripheral blood and is determined by the synthetic ratio in bone marrow cells, where the bulk of hemoglobin synthesis takes place.
We report the characterization of the amount of beta mRNA in a Kurdish Jewish population with beta0-thalassemia using the same methods employed for characterization of the Catania and Ferrara beta0 patients. We found very low amounts of beta mRNA sequences, consistent with the presence of beta0-thalassemia of the beta mRNA-negative population type. In addition, no globin gene deletion was detected that could account for the absence of beta mRNA.
Human globin messenger RNA was isolated from reticulocytes of four Jewish patients of Kurdish origin with homozygous beta0-thalassemia. On translation in the wheat-germ cell-free system, messenger RNA from these patients directed extensive synthesis of alpha- and gamma-globin chains, but synthesis of beta-globin chains was not detectable. In contrast, nonthalassemic human globin messenger RNA directed the synthesis of essentially equimolar amounts of alpha- and beta-globin. The patterns of globin synthesized by beta0-thalassemic messenger RNA in the cell-free system were virtually identical to the patterns of globin synthesized in peripheral blood cells of these patients. beta0-thalassemic messenger RNA similarly failed to direct any detectable beta-globin synthesis in a micrococcal nuclease-treated rabbit reticulocyte lysate, even in the presence of an excess of purified eukaryotic initiation factor 2. These results strongly suggest that functional messenger RNA for beta-globin chains is absent in Kurdish Jews with homozygous beta0-thalassemia.
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The parents of a child with homozygous thalassemia of the beta O variety requested prenatal diagnosis during a subsequent pregnancy. At the 19th week of pregnancy, a sample of blood containing fetal cells was obtained by placentocentesis. Radiochromatography of globin chains demonstrated production of a beta-chain with a beta/gamma synthetic ratio of 0.049, which is low for this gestational age. The conclusion that the child would be heterozygous for the beta-thalassemia gene was confirmed after birth.