Hb F-Sassari: a novel G gamma variant with a threonine residue at position gamma 75, characterized by mass spectrometric techniques

Disorders of the synthesis of human fetal hemoglobin

Fetal hemoglobin (HbF), the predominant hemoglobin in the fetus, is a mixture of two molecular species (alpha(2)(G)gamma(2) and alpha(2)(A)gamma(2)) that differ only at position 136 reflecting the products of two nonallelic gamma-globin genes. At the time of birth, HbF accounts for approximately 70% of the total Hb. The (G)gamma:(A)gamma globin ratio in the HbF of normal newborn is 70:30 whereas in the trace amounts of HbF that is found in the adult it reverses to 40:60 because of a gamma- to beta-globin gene switch. Alterations of these ratios are indicative of a molecular defect at the level of the HbF synthesis. Qualitative hemoglobinopathies due to (G)gamma and (A)gamma chain structural variants, and quantitative hemoglobinopathies affecting the synthesis of HbF such as gamma-thalassemias, duplications, triplications, and even sextuplications of the gamma-globin genes, which may be detected in newborn blood lysates, have been described. Moreover, several pathological and nonpathological conditions affecting the beta-globin gene cluster, such as beta-thalassemia, sickle cell disease, deltabeta-thalassemia, and hereditary persistence of HbF syndromes, are characterized by the continued synthesis of gamma-globin chains in the adult life. Studies of these natural mutants associated with increased synthesis of HbF in adult life have provided considerable insight into the understanding of the control of globin gene expression and Hb switching.

Alteration in the ubiquitin structure and function in the human lens: a possible mechanism of senile cataractogenesis

High-performance liquid chromatography purification followed by mass spectrometry analyses highlighted that human senile cataractous lens includes a 8182 Da species which is absent in the normal lens, whereas a 8566/8583 Da species is present in both lenses. Western blot analysis identified both species as ubiquitin. The species at lower molecular weight is a shorter form due to the cleavage of the C-terminal residues 73-76. As it is the last amino acid of ubiquitin which is involved in the protein degradation mechanism, we suggest that this structure modification compromises the function of ubiquitin and consequently the physiologically occurring degradation of the lens proteins.

Compound heterozygosity for Hb Lepore-Boston and Hb Neapolis (Dhonburi) [beta 126(H4)Val-->Gly] in a patient from Naples, Italy

The simultaneous presence of two hemoglobin variants has been detected in a 14-month-old patient affected by thalassemia intermedia. The two variants were characterized by a combination of allele-specific amplification methods and mass spectrometric procedures carried out on isolated globins. These were identified as Hb Lepore-Boston and Hb Neapolis (also known as Hb Dhonburi) or beta 126 (H4)Val-->Gly. Hb Lepore-Boston is the most common hybrid variant detected in Campania and several cases of Hb Neapolis which causes a mild hypochromic microcytic anemia have been identified in this region in the last few years. This is the first report of a double heterozygosity involving Hb Lepore-Boston and Hb Neapolis.