Hemoglobin Villejuif [beta 123(H1) Thr----Ile]: a new variant found in coincidence with polycythemia vera

Identification of Hb Villejuif [beta123(H1)Thr-->Ile] in Southern Italy

Hb Villejuif [beta123(H1)Thr-->Ile] is a silent and asymptomatic variant described in 1989 in an 87-year-old woman of French origin suffering from coincidental polycythemia vera. This paper reports the second observation of Hb Villejuif in three related subjects from Montesarchio, Southern Italy. All routine techniques for hemoglobin analysis yielded normal results with the exception of a slight increase in the Hb A2 value. The occurrence of a variant beta-globin was rapidly assessed by liquid chromatography mass spectrometric analysis and the abnormal chain purified by high performance liquid chromatography. The amino acid replacement Thr-->Ile at beta123 was determined by tandem electrospray mass spectrometric analysis of the tryptic digest of the variant beta chain. The corresponding DNA mutation was established as C-->T at the second position of codon 123 (ACC-->ATC) by polymerase chain reaction amplification techniques.

Hb Ernz [beta123(H1)Thr-->Asn] and Hb Renert [beta133(H11)Val-->Ala]: two new neutral variants revealed by reversed phase high performance liquid chromatography analysis

Analysis of globin chains by reversed phase high performance liquid chromatography, used as an additional tool for characterizing hemoglobin variants, has led to the discovery of a new class of variants that display only differences in hydrophobicity. Two such variants are here described. Hb Ernz was found in a man of Italian origin who was polycythemic, and in two of his three daughters who were hematologically normal. Hb Renert, a slightly unstable variant, was found in a man from Cape Verde who also carried Hb S and presented with chronic hemolysis. The structural abnormalities were characterized by protein structure methods involving reversed phase high performance liquid chromatographic separations of globins and peptides, followed by mass spectrometry studies (electrospray, ion trap, tandem mass spectrometry).

Hemoglobin Rouen (alpha-140 (HC2) Tyr-->His): alteration of the alpha-chain C-terminal region and moderate increase in oxygen affinity

Hb Rouen (alpha 140(HC2) Tyr-->His) is a moderately high oxygen-affinity variant that was found in coincidence with polycythemia vera in a French patient. This hemoglobin provides an example of an alteration of the C-terminus of the alpha-chain, a region involved in the mechanisms of allosteric regulation. The increase in oxygen-affinity and decrease in cooperativity of this variant is much smaller than that resulting from the same substitution in the beta-chain. This model provides additional evidence for the inequivalence between the alpha- and beta-subunits.

Hemoglobin Redondo [beta 92(F8) His----Asn]: an unstable hemoglobin variant associated with heme loss which occurs in two forms

Hb Redondo [beta 92(F8) His----Asn] illustrates how post-translational structural modifications may modify the phenotypic expression of an unstable hemoglobin. This variant was found in a Portuguese patient suffering from a chronic hemolytic anemia. The electrophoretic pattern demonstrated that it occurred in two forms, both being semi-hemoglobins: the fastest one migrating like HbS and the other like HbA2; after a few days of storage at 4 degrees C the intensity of the slowest Hb fraction decreased while that of the other increased proportionally. In both cases, the RP-HPLC analysis of the tryptic digest of the aminoethylated beta chains demonstrated the presence of an abnormal beta T10 peptide carrying a His----Asx substitution. Microsequence study of these two peptides demonstrated that the slowest abnormal Hb fraction had a beta 92 His----Asn substitution and the fastest a His----Asp at the same site. All these results suggest that the beta 92 His----Asn variant loses readily its heme group and that a deamidation occurs rapidly in vitro, yielding a beta 92 Asp semi-hemoglobin. The oxygen affinity of the patient's red blood cells was increased, leading to a stimulation of erythropoiesis and to a macrocytic hemolytic disease.