Hemoglobin Ozieri: a new alpha-chain variant (alpha 71(E20)Ala-->Val). Characterization using FAB- and electrospray-mass spectrometric techniques.

A new silent hemoglobin variant, Hb Ozieri (alpha 71(E20)Ala-->Val), was observed in five apparently unrelated newborn babies during a screening for hemoglobinopathies on the island of Sardinia. This asymptomatic variant was detected by means of isoelectric focusing (IEF), isolated using IEF in an immobilized ultranarrow pH-gradient and characterized at the structural level using FAB- and electrospray-mass spectrometric techniques. A Val for Ala substitution was unambiguously detected at position 71 of the alpha-globin chain. This substitution indicates that a C to T transition occurred in the GCG codon for Ala which contains one of the 35 unmethylated CpG dinucleotides of the alpha-globin gene. This observation brings the number of variants due to a mutation in the alpha-globin gene CpGs (the third instance of a silent mutation) to 13 and raises the possibility that unmethylated CpGs might be hotspots for mutations as the methylated ones.