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The evolution of globin chain synthesis was studied in larvae treated either with thyroxine or with an antithyroid substance. Thyroxine treatment accelerated the rate of Hb switching; it induced a preferential synthesis of adult globins while the synthesis of larval globins decreased rapidly. Treatment with thiourea did not prevent the Hb transition, which occurred even at concentrations of thyroid hormones that did not permit induction of anatomical metamorphosis.

SummaryThe yak has two hemoglobins sharing a common globin chain. Hb slow appears unique to the yak among the ruminants studied. It is not known if Hb slow is important in high altitude adaptation, but physiologic rather than hematologic adjustments may be more important after acute blood loss, as 2,3-DPG remains nil and no disproportionate hemoglobin production occurs.The authors thank Dr. B. R. Baidya, Director General, and Dr. N. K. Shah, Chief Epidemiologist, His Majesty's Government Directorate of Health Services, Nepal, for their approval and assistance in carrying out this study, and Drs. C. R. Valeri and C. G. Zaroulis of the U.S. Naval Blood Research Laboratory, Chelsea, MA, for the 2,3-DPG, ATP and lactate levels. Supported by PHS Grant No. 5 R07 AI 10048-13.

The applicability of the chromatographic separation of haemoglobin F, A and S on Biorex 70 ( Blouquit et al., 1982) for the prenatal diagnosis of thalassaemia and related conditions was evaluated in comparison to the conventional globin chain separation technique. The method proved reliable, inexpensive and rapid and should be considered as a valuable alternative in laboratories carrying out great numbers of tests and those being newly set up for this purpose.

Continuous lines of erythroleukemia cells, which originate from the spleens of mice with Friend virus-induced leukemia, provide a convenient experimental system in which the molecular control of erythrodifferentiation can be examined in some detail (Friend et al. 1966; Ikawa and Sugano 1966; Ostertag et al. 1972; Freedman and Lilly 1975). The cultures contain cells at various stages of differentiation. The majority are large, primitive erythroid cells with prominent nucleoli, but a few more mature cells recognizable as normoblasts are present. We had developed these lines with the idea of studying leukemia as a disease resulting from a block in maturation, and had hoped to find means of stimulating the cells to differentiate. To a certain extent, we achieved this goal.

The intermittent occurrence of intracellular and extracellular hemoglobins among the invertebrates may be due either to the intermittent presence of functional globin genes or to defects in the mechanism regulating their expression. In the absence of information concerning the structure and expression of invertebrate globin genes, I would like to focus on the identification of common structural themes among these molecules. All the extracellular invertebrate hemoglobins whose subunit structures are known can be classified into four separate groups: (A) single-domain, single-subunit molecules, i. e. monomeric hemoglobins, (B) two-domain, multi-subunit hemoglobins, consisting of aggregates of dimeric polypeptide chains, each containing two heme-binding domains, (C) multi-domain, multi-subunit hemoglobins, consisting of two or more polypeptide chains, each comprising many heme-binding domains and (D) single domain, multi-subunit hemoglobins, consisting of aggregates of monomeric and dimeric subunits and disulfide-bonded trimers or tetramers. A diagrammatic representation of the subunits found in the four classes is shown in figure 1.

An inhibitor of protein synthesis is activated in reticulocytes and in their lysates under high p02. This activation is enhanced by ATP and prevented by glucose-6-phosphate or high concentrations of cAMP. With an apparent molecular weight of about 2.3kD, the high p02 inhibitor is distinct from the hemin-regulated inhibitor (HRI), but, possibily identical with a glutathione disulphide-dependent inhibitor. This inhibitor is a likely component of the cascade system which,through activation of HRI, gives rise to phosphorylation of eukaryotic initiation factor 2 and to inhibition of globin synthesis.

Hemoglobin Indianapolis was first described by Adams et al (1,2) as a very unstable variant with a phenotype similar to severe beta-thalassemia. We have also characterized this variant, but there are several differences in the clinical expression of the variant described in our report and those described in the original case. We found Hb Indianapolis to be unstable, but not to the extent that it could not be detected by routine testing. The four family members heterozygous for the variant were not anemic, showed normal hematologic values, and did not exhibit any severe clinical disadvantages, although there was slight reticulocytosis. The variant could not be resolved from Hb A on cellulose acetate (pH 8.4), but isoelectric focusing showed a double band in the region of Hb A that is probably the variant and Hb A. However, the variant chain was clearly evident by globin chain analyses in acid and alkaline buffers. The condition of additional blood samples did not allow us to determine the oxygen dissociation properties of the variant or the rates of globin chain synthesis.

Prenatal diagnosis of various congenital abnormalities and inherited diseases, with selective termination of affected pregnancies, has been universally accepted and extensively applied for the last 15 years [1, 2]. In particular, prenatal diagnosis of hemoglobinopathies including thalassemia is generally performed by globin chain synthesis studies on fetal blood samples obtained by fetoscopic or ultrasound-guided techniques in the second trimester of pregnancy [3, 4], or by DNA analysis of chorionic villi samples obtained by ultrasound-guided techniques in the first trimester of pregnancy [5, 6]. Ultrasound scanning plays a central role in enhancing the safety and effectiveness of these diagnostic procedures.

Globin chain synthesis was performed with the peripheral blood of a 10-year-old girl, who had acquired aplastic anaemia, at the time of bolus methylprednisolone administration and during recovery. There was no indication of an increase in gamma chain synthesis despite elevation of total foetal haemoglobin.

Thalassemias are characterized by an imbalance in globin chain synthesis. When patients having beta-thalassemia major are given transfusions, globin synthesis is transiently suppressed, particularly the alpha chains. This results in a relatively improved alpha/beta ration that may erroneously be interpreted as indicating stimulation of beta chain synthesis.

Hemoglobin synthesis was studied in vitro in reticulocytes from a patient with the anti-Lepore variant Hb Lincoln Park. Incorporation of L-leucine-3H into the alpha and beta delta chains of Hb Lincoln Park was substantially less than the incorporation into the corresponding globin chains of Hb A, with the rate of synthesis of the beta delta chain being similar to that of the delta chain of Hb A2. Synthesis of the alpha and total non-alpha globin components was unbalanced, with a substantial excess of alpha chain synthesis. These findings help to explain the mild hemolytic disease present in individuals with this hemoglobin variant.

The pace at which information about the thalassemias is accumulating has quickened.* There are a number of excellent reviews21,22,24,26,55,190,249, 269,394,398,402 which cover the historical development of clinical and genetic information, together with concepts to account for the pathophysiology of this group of familial anemias. We have selected highlights of this history in order to draw comparisons with the parallel growth of information concerning control of gene activity. These efforts began for different reasons and depended at first on different experimental systems. The theme for this review is that they now appear to be converging on a common question: what determines the rate of production of a given gene product (hemoglobin) in differentiated cells (erythrocytes) of a eukaryote (man) ?

Summary. Twelve carriers of thalassaemia intermedia were studied. Their clinical and haematological picture was distinctly different from that in both heterozygotes and haematological picture was distinctly different from that in both heterozygotes and homozygotes for β thalassaemia. Several genetic patterns were found responsible for thalassaemia intermedia: β/δβ thalassaemia, α2β/β thalassaemia, β/β thalasaemia-heterocellular HPFH. In a few subjects the genetic picture indicated that the patients were homozygous for β thalassaemia, in spite of the mildness of the clinical sitution. The lack of genetic uniformity was reflected in very wide Hb A2 (2.5–8.7%) and Hb F (7.5–96.9%) ranges, as opposed to the noticeable degree of biochemical uniformity indicated by the very similar imbalance of globin chain synthesis: 0.33–0.54 for the non-α/α chain ratio in the peripheral blood. The mean for this parameter (0.43 ± 0.05) was significantly different (P

A prospective study of 2191 Negro infants in Jamaica showed that approximately 7% of them had detectable levels of Hb Bart's (gamma 4) in the neonatal period. The red cell indices, globin chain biosynthesis and restriction endonuclease mapping of DNA from these infants were used to determine the significance of Hb Bart's at birth. The results indicate that the genotypes alpha alpha/alpha alpha, -- alpha/alpha alpha and -- alpha/ -- alpha are associated with 0%, 0.1-2%, and greater than 2% Hb Bart's respectively. Although trace amounts of Hb Bart's may be associated with the genotype -- alpha/alpha alpha this is not always the case and therefore haemoglobin analysis in the neonatal period cannot be used to diagnose this genotype with any certainty.

Red blood cells (RBC) from 13 patients suffering from dysmyelopoietic syndromes (DMPS) have been studied. About half of these subjects showed an abnormal Na+ and K+ leakage of their RBC, which were incubated at 37 degrees C for 24 h. The mean rate of the glycolytic pathway increased significantly and the glycolysis values correlated well with the Na+ gain. Moreover, 9 out of the 13 patients showed an abnormal biosynthetic ratio of haemoglobin chains in their reticulocytes. Since the multiple defects in DMPS erythrocytes do not seem clearly linked by cause-effect relationships, they probably derive from several cooperating factors in pathological erythroid precursors, leading to RBC membrane damage.

The relative rates of beta-, gamma-, and alpha-globin chain formation in reticulocytes of six newborn infants ,ith hemolytic disease were determined before and in weekly intervals after exchange transfusion. Directly after birth (before exchange transfusion) the beta/alpha, gamma/alpha, and (beta + gamma)/alpha ratios in newborn infants with hemolytic disease (0.35 +/- 0.20, 0.67 +/- 0.12, and 1.06 +/- 0.29) were similar to those of normal newborn infants (0.33 +/- 0.07, 0.65 +/- 0.06, and 0.98 +/- 0.06). The gradual increase in the beta/alpha ratio seen during the postnatal period of eight normal newborn infants was also observed in newborn infants with hemolytic disease after exchange transfusion. In contrast, the gamma/alpha ratio was found to be increased (1.89 +/- 0.25) in all infants with hemolytic disease in the second week after exchange transfusion. The corresponding value for normal newborn infants was 0.48 +/- 0.25. After exchange transfusion the number of hemoglobin F-containing erythrocytes increased. Possible reasohs for this imbalance of globin chain formation after exchange transfusion may be the decreased erythropoiesis and/or the abnormal high hemoglobin A concentration after exchange transfusion or the introduction of an unknown, gamma chain formation-stimulating agent by exchange transfusion. Speculation In newborn infants with hemolytic disease the repression of gamma-globin chain formation normally seen during the postnatal period is replaced by a stimulated gamma-globin chain production after exchange transfusion.

Polycythemia in man is defined as an increase in the hematocrit and hemoglobin concentration above accepted normal values. As such, the finding of polycythemia implies the increased production of erythrocytes. Since red cell production is governed normally by interaction of oxygen (O2) availability, the elaboration of the regulatory hormone, erythropoietin, and marrow function, it is not surprising that derangements in these interrelationships account for virtually all causes of polycythemia. This chapter summarizes briefly various aspects of the regulation of red cell production and focuses on those identified mechanisms which lead to polycythemia.

Various aspects of globin gene segregation and inheritance have been discussed in earlier chapters. In this section the genetics of the hemoglobins and their mutations are considered more systematically, both to define the specific principles of globin gene inheritance, and to formulate a rational basis for genetic counseling of families affected with these disorders.

We describe three basic modifications of our previous method for thalassemia screening by isoelectric focusing of heme-free globin chains: the gel thickness is reduced from 2 mm to 240 microns; the level of the detergent Nonidet P-40 in the gels is decreased from 3% to 0.5%; the polyacrylamide slab is covalently fixed to the supporting glass plate by treatment with silane A-174. By the present method the entire focusing process, starting from gel moulding up to gel destaining and drying, is completed within 4 h, a fraction of the time needed in our previous technique. More than a 100 samples can be analyzed per working day. The present technique also affords increased sensitivity: less than 1 microgram protein/band is detected and less than 200 picomol of hemoglobin are needed for each analysis. Band sharpness and resolution in our ultrathin gels is also considerably increased.

Globin chain synthesis and alpha/beta ratios were determined in a number of normal subjects, alpha-thalassemia-2 homozygotes, and beta-thalassemia trait using three different techniques. Cation exchange high performance liquid chromatography on a Pharmacia Mono-S, HR 5/5 and reversed phase high performance liquid chromatography on a semi-preparative Vydac C4 column were compared with the traditional carboxymethylcellulose chromatography. Both high performance liquid chromatography columns give excellent results when 2 mg of hemoglobin was chromatographed in each analysis. By modifying the protocols for column equilibration and gradient shape for preparative Vydac C4 columns, conditions were found yielding excellent resolutions of the labeled globin chains in less than an hour without the need for substantial increase of the flowrate. This method was found to be superior to other methods and may be a suitable alternative for the classical carboxymethylcellulose chromatography. Up to five specimens could easily be analyzed in a single day with this system.

A reduction of the haemoglobin level induces an increase in bone marrow cell proliferation and red cell production. The response of crythroid elements in bone marrow to erythropoietic stimulation depends on various factors such as the severity of anaemia, the production of erythropoietin, the integrity of the haemopoietic inductive microenvironment, the availability of essential substrates and the specific characteristics of the anaemia (Hillman, 1970).

All forms of thalassaemia are uncommon in North Europeans and alpha thalassaemia to date has not been reported in the Irish context. We describe such a finding in a family with no known foreign ancestry and discuss the haematological investigations which led to its detection.

A resting adult extracts about 5 ml of oxygen (measured at STP) from every 100 ml of circulating blood. During exercise, this figure can increase almost three-fold. Since the solubility of oxygen in plasma is only 0.3 ml/100 ml, it is not surprising that blood contains about 15 g/ 100 ml of an oxygen transporter. This transporter is the protein haemoglobin and is contained entirely within the erythrocyte.

Human globin chain separation, a key procedure in the study of hemoglobinopathies, is routinely performed by chromatography on carboxymethylcellulose. This method, though relatively easy and highly reliable, is expensive and time consuming. A new procedure, based on isoelectric focusing, is presented which allows the simultaneous separation of globin chains from multiple samples (at least 20 per gel slab). The method is rapid, inexpensive and can be easily carried out in clinical laboratories, and its high sensitivity allows the identification of radioactive bands even with minute amounts of labelled material. A new phenomenon, called the 'Nonidet P-40 effect', which greatly enhances the separation between gamma and beta chains by binding to these two chains and shifting their pI values in opposite directions, is described.

Globin chain synthesis and globin mRNA content were studied in blood cells of a patient homozygous for Hb Lepore. Peripheral blood cells incubated with tritiated leucine synthesized approximately 1.5 to 3% as many Lepore globin chains as alpha chains. Globin mRNA in peripheral blood cell RNA was assayed by molecular hybridization assays using human alpha and beta cDNA, and the results indicated the presence of approximately 1% to 2% as much beta-like mRNA (presumably deltabeta Lepore mRNA) as alpha mRNA. The amount of Lepore deltabeta chain mRNA in peripheral blood cells is therefore proportional to the amount of Lepore globin chain synthesis in the same cells. An incidental observation was the finding that peripheral blood cell RNA of this patient, at a time when she was being heavily transfused, contained substantially higher levels of beta-like mRNA (relative to alpha mRNA) than in subsequent studies. Cell-free translation of this mRNA however revealed that it contained authentic beta chain mRNA which must have been derived in some way from the transfused blood cells.

A previously unrecognized hypochromic anemia associated with marked normoblastemia during the newborn period is reported. One male and two female siblings and a first cousin had a hypochromic anemia and marked normoblastemia (300 to 900 normoblast index per 100 white blood cells) at birth. Globin chain synthesis studies on peripheral blood of the proband at birth indicated the presence of alpha-thalassemia trait with possible reduced gamma chain synthesis. Studies of globin chain synthesis on the father, two older affected siblings of the proband, and the proband at 1.5 years of age revealed alpha-thalassemia trait. The data suggest this complex alpha-thalassemia-like condition as a new syndrome associated with marked neonatal normoblastemia.

WE have described structural data for mouse and rabbit embryonic β-like e chains and the conclusions which can be drawn with respect to the evolution of e globin chain genes in both species1. Here we present evidence for crossover events in the ancestral mouse β and e-type chain genes leading to Hb Lepore-like globin chain genes which are functional in mice of recent evolutionary origin.

Globin chain synthesis was studied in a family with both the Greek (Agamma) type of hereditary persistence of fetal haemoglobin and beta thalassaemia. The ratio of alpha/(gamma+beta+delta) chain synthesis in the hereditary persistence of fetal haemoglobin (HPFH) heterozygotes was 0.97 while in the HPFH/beta-thalassaemia heterozygote it was 2.14. However, calculation of the amounts of haemoglobin synthesized per cell suggests that in the HPFH/beta-thalassaemia heterozygote, the beta- and Agamma-chain genes in cis to the HPFH determinant are unable to compensate for the deficiency of chains imposed by the beta-thalassaemia gene in trans and that the increased synthesis of Hb F is directed by the gamma-chain genes located on the beta-thalassaemia chromosome. The data suggest that synthesis of beta and Agamma chains in the Greek HPFH is fixed at a 'preset' level and indicate that the defect might be due to an abnormality in the rate of transcription of the closely linked beta-, delta- and gamma-chain genes.

In the past few years analysis of the genetics and disorders of human hemoglobins has undergone a revolution as new research tools have provided the means to obtain long-sought-after answers regarding gene structure and function. Study of human hemoglobins and their disorders, particularly the thalassemia syndromes, is at the forefront of the interaction of new genetic technology and medicine. It offers the promise of understanding an entire class of diseases at the molecular level in detail totally unforeseen just a short time ago. In this review we will attempt to summarize recent approaches and findings in this rapidly moving area and illustrate how these studies may provide important models for the analysis of other human diseases.

Polyacrylamide gel electrophoresis (PAGE) in the presence of urea, acid, and Triton X-100 was used for determination of the G gamma to A gamma ratio in human Hb F. The data compared most favourable with results obtained by a HPLC procedure and by a chemical procedure. Moreover, its accuracy and reproducibility was determined. The presence of Hb A2 in a sample with Hb F level below 10% interferes with the determination because of the nearly identical electrophoretic mobilities of the delta and G gamma chains. Thus, the removal of Hb A2 is required. Samples free fo Hb A2 but with a Hb F level as low as 2% can be analyzed with an accuracy of about 5%. The PAGE method has been applied to the Hb F of 63 subjects with beta thalassemia and related conditions, and the results of these analyses are included in this communication.

Summary. The thalassaemias are a heterogeneous group of conditions characterized by imbalanced globin chain production. In some forms there is a total absence of globin chain synthesis while in others globin chains are synthesized but at a reduced rate. There is increasing evidence that inefficiently synthesized structural haemoglobin variants can produce an identical clinical picture to thalassaemia. The molecular defect in the β thalassaemias is not yet worked out but in all forms studied, except the Ferrara type, there is an absolute reduction in the amount of β-chain messenger RNA. In the Ferrara type there appears to be messenger RNA present but β-chain synthesis does not occur unless induced by a soluble fraction from normal cells. The molecular pathology of the α thalassaemias is understood better. The severe type, α-thalassaemia 1, results from a deletion of all or most of the α-chain genes. There is good circumstantial evidence that the milder form, α-thalassaemia 2, results from a loss of one of a pair of linked α-chain genes. About half of the individuals with the haematological picture of α-thalassaemia 2 are heterozygous for Hb Constant Spring, a chain-termination mutant which is synthesized inefficiently. The chain-termination mutants form a class of disorders which can produce the clinical picture of thalassaemia due to inefficient production of elongated α chains.

Globin synthesis ratios were measured on reticulocytes from nine patients with primary acquired sideroblastic anaemia (SA), four patients with hereditary or congenital SA, two patients with secondary acquired SA and three patients with iron deficiency (ID). Ten of the samples from patients with SA and all the samples from patients with ID had normal ratios. Samples from three patients had significantly abnormal ratios, one from a patient with SA and acquired Hb H disease (alpha/beta 0 X 26), one from a patient with secondary acquired SA (alpha/beta 0 X 88), and one from a patient who went on to develop acute myeloblastic leukaemia (alpha/beta 1 X 36). Globin synthesis was stimulated by 100 microM haem similarly in normal, SA and ID reticulocytes. Any limitation of globin synthesis in SA and ID is therefore not easily reversible by adding haem. Inhibition of haem synthesis in nonsideroblastic reticulocytes using 4 mM isonicotinic acid hydrazide for 1 h incubation affected neither total globin synthesis nor the alpha/beta ratio. These results contradict the view that decreased haem synthesis decreases globin chain synthesis and decreases the alpha/beta globin chain synthesis ratios in human reticulocytes. Previously reported findings that haem could reverse globin chain synthesis inhibition in SA were good evidence for a primary deficiency of haem synthesis in the erythroblasts of these patients. Our inability to substantiate these findings emphasizes the need for a re-evaluation of the aetiology of sideroblastic anaemia.

In recent years there has been a rapid increase in knowledge about the structure and function of the hemoglobin molecule in health and disease. Many genetic disorders of hemoglobin synthesis have been described and the molecular basis of the associated clinical pictures elucidated. Unfortunately none of these advances have led to an improvement in the clinical management of affected patients.

A simple, rapid technic for cellulose acetate electrophoresis of hemoglobin globin chains is presented. Preparation of the support media and sample application takes only a few minutes. Electrophoresis time is 15 min. at room temperature. The separation of the globin chains compares favorably with the starch gel method.

Globin chain synthesis has been studied in β-thalassemia by incubating red blood cells of 10 homozygous thalassemic patients with [3H] amino acids, and by measuring the incorporation of radioactivity into the globin chains, separated by column chromatography.

Summary. The haemoglobin constitution of 14 infants with the haemoglobin Bart's hydrops syndrome has been examined. Thirteen of the infants were stillborn or lived only a few minutes after delivery, but in one case an exchange transfusion was performed and the pattern of globin chain synthesis examined by an [H3]leucine incorporation experiment utilizing umbilical cord blood. These studies indicate that the syndrome results from a total deficiency of α-chain production. Furthermore, it has been possible to exclude the presence of fragments of α-chain longer than II residues in the cells of these infants. In each infant a small quantity of haemoglobin was found which consisted of normal γ-chains in association with chains of unique constitution. A similar component was found in trace amounts in normal umbilical cord blood. This haemoglobin may be identical with haemoglobin Portland. It is suggested that the non-γ-chain of this haemoglobin is the product of a normal foetal haemoglobin locus which produces very small amounts of gene product in normal infants but which is capable of increased activity in the presence of a partial or total deficiency of α-chains.

Rabbit reticulocytes were incubated in vitro as long as 20 hr with l - O -methyl threonine, the OMT was removed, and the capacity of the cells to synthesize α- and β-globin chains was determined. After 20 hr incubation in vitro , OMT-treated cells can make β chains about twice as well as cells incubated for 20 hr without OMT. However, the capacity of OMT-treated cells to synthesize α chains was only about 60% that of cells incubated without OMT for 20 hr. These results suggest that the capacity of reticulocytes to produce a specific globin chain after an in vitro incubation correlates positively with the number of ribosomes associated with the specific messenger RNA for that chain during the incubation.

Summary: The rate of globin chain production has been studied in patients with homozygous β-thalassaemia, heterozygous β-thalassaemia, haemoglobin E-thalassaemia, and sickle-cell-thalassaemia, and compared with that in non-thalassaemic individuals. A partial or total deficit of β-chain synthesis has been demonstrated in all forms of β-thalassaemia. This results in the production of a large intracellular pool of α-chains, the kinetics of which have been worked out. The α-chains in this pool appear to contain haem and are unstable, rapidly becoming associated with the stromal fraction. These findings are examined in terms of the pathogenesis of the anaemia of thalassaemia.

The clinical, haematological and biosynthetic features of subjects with Hb E variants are described. An association with red cell hypochromia and microcytosis was confirmed, although this was not invariable in Hb E trait. Imbalanced globin chain synthesis was found in the majority of Hb E carriers. A patient doubly heterozygous for Hb E and Hb S, a condition we have not previously seen reported, had a benign clinical course with minor haematological changes, despite a relatively large amount of Hb S (67%).

Newborns with trisomy 13 have elevated hemoglobin (HB) F; those with trisomy 21 have increased HB A. To examine this “switch”, blood was obtained from neonates, incubated with 3H-leucine, and globin chains separated on carboxymethylcellulose columns in urea: β/α ratios were in the range of β-thal trait in trisomy 13, and in 4/6 with trisomy 18. (β+γ)/α was also low. β/α was above normal in 2/6 with trisomy 18, and in trisomy 21. (β+γ)/α was high. Thus the high HB F in trisomy 13 results from normal γ/α synthesis, but a delay in turning on β chain. High HB A in trisomy 21 is due to an early and coordinated switch from γ to β synthesis. Trisomy 18 infants represent both types. Finally these data emphasize that abnormalities other than thal genes may lead to aberrant β/α ratios in neonates and also may affect the β/γ ratios in utero that are used to define hemoglobin phenotypes in prenatal diagnoses.

Globin messenger RNA (mRNA) from reticulocytes of several patients with various β-thal syndromes was studied in two ways: I. partially purified globin mRNA preparations from β-thal reticulocytes were tested for their capacity to promote α and βA globin chain synthesis in a heterologous cell-free system which preferentially synthesized βA chains when incubated with normal human globin mRNA (βA/α = 2-4). In this system, globin mRNA preparations from each of 10 patients with β-thal (βA/α = 0.1-0.3); 2 patients with homozygous β0-thal (βA/α = 0); and 4 patients doubly heterozygous for β0-thal and an abnormal hemoglobin (βA/α = 0) reproduced in every case the defect in β chain synthesis occurring in their intact reticulocytes. II. The actual chemical amounts of β chain specific mRNA sequences (relative to α chain sequences) in the β-thal mRNA's were measured by re-annealing β-thal mRNA, in separate experiments, with synthetic radioactive DMA (cDNA) complementary to purified normal α chain specific or β chain specific mRNA. When measured by these hybridization techniques, β chain mRNA was reduced to 10-30% of normal in the 4 patients tested with β+-thal and was absent in 4 patients with β0-thal. All of the β-thal syndromes studied to date are thus characterized by β chain mRNA which is diminished (β+-thal) or absent (β0-thal) not only in terms of template activity but also in absolute chemical amounts.

Globin chain synthesis and clinical and hematologic findings in double heterozygotes for the silent and classical s-thalassemia genes, and their parents