A new DNA polymorphism in the beta-globin gene cluster can be used for antenatal diagnosis of beta-thalassaemia.

Restriction endonuclease analysis of the human beta-globin gene cluster has revealed a new DNA polymorphism at a Pvu II recognition site approximately 3.5 kilobases from the 3' end of the Agamma-globin gene. In patients from the Mediterranean area, the Pvu II polymorphism was associated equally with both normal and beta-thalassaemia chromosomes.

Restriction endonuclease maps of the beta-like globin gene cluster in the British and Greek forms of HPFH, and for one example of G gamma beta + HPFH.

We report here restriction endonuclease maps of the beta-like globin gene cluster for the British form of HPFH and for a case of G gamma beta + HPFH, and also confirm and extend previous reports of the map for the Greek form of HPFH. These results show that all these conditions belong to a group lacking any substantial deletion or rearrangement of DNA sequence in this gene cluster. The absence of any gross disruption of the structure of this region of the genome, together with evidence that the HPFH genotype is either allelic with, or closely linked to, the beta-like globin gene cluster, suggests that the responsible lesions are nearer to being purely regulatory in nature than in forms of HPFH due to substantial deletions.

Linkage analysis of nondeletion hereditary persistence of fetal hemoglobin.

Nondeletion forms of hereditary persistence of fetal hemoglobin may result from regulatory disorders of globin gene expression. The defects in two such conditions were localized by demonstrating a tight genetic linkage between the disorders and polymorphic restriction endonuclease sites within the beta-like globin gene complex. In one instance, the defect probably occurred outside the region of DNA between the epsilon- and beta-globin genes.

Restriction mapping of a new deletion responsible for G gamma (delta beta)o thalassemia.

DNA from individuals heterozygous for (G)gamma(deltabeta)(o) thalassaemia has been studied by restriction endonuclease analysis. The results reveal a new molecular defect associated with this condition. A total of three defects is now responsible for the one single phenotype, thereby emphasising the complex relationship between genotype and phenotype among the disorders of beta-like globin synthesis in man.

A novel rearrangement of the human beta-like globin gene cluster.

The first example of a duplication involving the human beta-like globin genes has been characterised in DNA from a native of Vanuatu. Restriction endonuclease mapping has shown that a 5 kb insert of DNA in the gamma-delta-beta gene cluster is due to duplication of the Ggamma-globin gene and results in a new rearrangement 5'-epsilon-Ggamma-Ggamma-Agamma-delta-beta-3'.

Hemoglobin H disease and mental retardation: a new syndrome or a remarkable coincidence?

Each of three families of northern European origin contains a mentally retarded son with hemoglobin H (Hb H) disease. One parent is a carrier of mild alpha-thalassemia and the other is normal, suggesting that this form of Hb H disease results from the interaction between an inherited defect of alpha-chain production and one member of the pair in chromosome 16 and a new mutation on the other. Restriction-enzyme analysis indicated that the new mutation was not the same in the other three patients, and demonstrated at least two hitherto undescribed lesions involving the alpha-globin gene cluster.

A novel alpha-globin gene arrangement in man.

The human genome has two linked alpha-globin genes on chromosome 16. Deletion of one or more of them, as occurs in alpha-thalassaemia, leads to a reduced output of alpha-globin mRNA in proportion to the number of alpha-globin genes lost. In some racial groups deletion of one of the pair of alpha-globin genes may result from unequal crossing over between the genes on homologous chromosomes by a mechanism resembling that postulated for the formation of the delta beta fusion genes of the Lepore haemoglobins.

Negro alpha-thalassaemia is caused by deletion of a single alpha-globin gene.

Studies in two Jamaican Negro families, including haematological and haemoglobin analysis, haemoglobin synthesis, and globin messenger-RNA assay, have defined two alpha-thalassaemia phenotypes which resemble the severe (alpha-thalassaemia 1) and mild (alpha-thalassaemia 2) forms of the disorder described in Orientals. Genetic analysis suggests that subjects with the alpha-thalassaemia-1 phenotype are homozygous for the alpha-thalassaemia-2 determinant. Restriction-endonuclease mapping shows that alpha-thalassaemia-2 results from the deletion of one of the linked pair of alpha-chain genes.

The molecular basis of alpha-thalassemias: frequent occurrence of dysfunctional alpha loci among non-Asians with Hb H disease.

Study of Asians has previously indicated that deletion of alpha-globin structural genes is the predominant lesion in alpha-thalassemias and that Hb H disease occurs when three of four normal alpha loci per cell are deleted. To test the generality of this model, Hb H disease DNAs of both Asian and non-Asian origin were analyzed by restriction endonuclease mapping using the technique of Southern (1975). Whereas in normal DNA, alpha sequences are present in a single Eco Rl fragment of cellular DNA approximately 22.

Partial deletion of beta-globin gene DNA in certain patients with beta 0-thalassemia.

We have used restriction endonuclease mapping of cell DNA to investigate the structure of the beta-globin gene in beta-thalassemias. Among 17 individuals with beta +- and beta 0-thalassemia, we observed three patients of Indian origin with beta 0-thalassemia whose DNA revealed a consistent mapping abnormality. In one beta allele in each diploid cell, 0.

Characterization of beta-globin mRNA in the beta0 thalassemias.

A number of cases of beta0 thalassemia have been examined for the presence or absence of beta-globin mRNA. Total RNA extracted from peripheral blood was hybridized to purified complementary DNA specific for beta-globin mRNA, and to beta-cDNA probes specific for the 5' and 3' noncoding regions of beta-globin mRNA. Three clear-cut categories of beta0 thalassemia were identified.

The aminoacylation of transfer ribonucleic acid. Recognition of methionine by Escherichia coli methionyl-transfer ribonucleic acid synthetase.

The mechanism of the recognition of methionine by Escherichia coli methionyl-tRNA synthetase was examined by a kinetic study of the recognition of methionine analogues in the ATP-PPi exchange reaction and the tRNA-aminoacylation reaction. The results show that the recognition mechanism consists of three parts: (1) the recognition of the size, shape and chemical nature of the amino acid side chain at the methionine-binding stage of the reaction; (2) the recognition of the length of the side chain at the stage of aminoacyl-adenylate complex-formation; (3) the recognition of the sulphur atom in the side chain at the stage of methionyl-tRNA formation. It is proposed that the sulphur atom interacts with the enzyme to induce a conformational change.

The aminoacylation of transfer ribonucleic acid. Inhibitory effects of some amino acid analogues with altered side chains.

Several amino acid analogues that are able to replace amino acid residues in binding positions of the biologically active C-terminal tetrapeptide amide sequence, Trp-Met-Asp-PheNH2, of the gastrins were examined for their ability to inhibit the aminoacylation of tRNA in an Escherichia coli and rat liver system. Although in both systems the amino acid side chains are involved in the recognition process, the structural requirements of the side chain in the two systems are not comparable. Analogues of methionine and phenylalanine behaved similarly in the E.

A direct estimate of the number of human gamma-globin genes.

The number of genes specifying human gamma-globin has been determined directly by hybridization of complementary DNA to total human DNA. The complementary DNA was enriched in sequences specific for gamma-globin genes by transcribing globin mRNA isolated from fetal reticulocytes with viral reverse transcriptase, and collecting the material which does not back-hybridize to adult globin mRNA. When hybridized in cDNA excess to DNA, very similar values are found for gamma-gene number as for beta-gene number, suggesting two or at most three gamma-globin genes per haploid human genome.