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The gamma chain heterogeneity of fetal hemoglobin in black beta- thalassemia and HPFH heterozygotes

1981; Elsevier BV; Volume: 58; Issue: 1 Linguagem: Inglês

10.1182/blood.v58.1.62.62

1528-0020

T. H. J. Huisman, ME Gravely, B. B. Webber, Kehinde O. Okonjo, J. B. Henson, A. L. Reese,

Blood groups and transfusion

Abstract High pressure liquid chromatography (HPLC) was applied to the HbF isolated from blood of numerous black patients with beta-thalassemia trait or homozygosity, G gamma-delta beta-thalassemia trait, G gamma A- gamma HPFH heterozygosity, or the G gamma-[delta+ beta+]-HPFH condition. The method allowed an accurate evaluation of the relative quantities of three types of gamma-chain (G gamma, A gamma I, A gamma T) in the fetal hemoglobins. The results have shown the following. (A) The incidence of the A gamma T-chain in beta-thal heterozygotes and G gamma A gamma-HPFH heterozygotes is about the same as has been observed in black newborn; about one of five blacks are heterozygous for this A gamma-chain variant. The A gamma T-chain was not detected in the nine G gamma-delta beta-thal heterozygotes nor in the eight G gamma-[delta+ beta+]-HPFH heterozygotes. (B) In most cases, the A gamma T-chain was produced by the A gamma gene in trans to the beta-thal or HPFH determinant. The contribution by the gamma-chain genes in trans to the beta-thal or HPFH determinant is about 15% of the total gamma-chain production in both conditions. (C) Three black beta-thal heterozygotes (and five additional relatives) had the A gamma T gene in cis to the beta-thal determinant. Four of these patients had a low levels of G gamma-chain (the “adult” level), and the contribution by the A gamma gene in cis to the beta-thal determinant was about three times that of the A gamma gene in trans. The four additional patients, all members of one family, had a high level of G gamma-chain (the “newborn” level), and the contribution of the A gamma gene in cis was half of that seen in the previously mentioned four patients while that of the A gamma gene in trans was essentially the same. These limited data suggest that the genetic anomaly causing high high G gamma levels in adult beta-thal heterozygotes is linked to the beta-thal determinant and that one of its primary effects is a decreased synthetic expression of the A gamma gene in cis to the beta-thal determinant.