A new unstable variant of the fetal hemoglobinHBG2gene: Hb F-Turritana [Gγ64(E8)Gly→Asp, HBG2:c.194G>A] foundin cisto the Hb F-Sardinia gene [Aγ(E19)Ile→Thr, HBG1:c.227T>C]

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Abstract

A new variant of the fetal hemoglobin (Hb) was observed in a newborn baby subjected to phototherapy due to jaundice, by means of electrophoretic and chromatographic techniques. The variant Hb resulted unstable by the isopropanol stability test. After HBG2 gene sequencing, the G to A transversion at codon 64, position eight of the E helix, was found, which corresponds to the Asp for Gly amino acid substitution. The new variant was called Hb F-Turritana [Gγ64(E8)Gly→Asp, HBG2:c.194G>A]. Incoming aspartic acid residue, bulky and negatively charged, may be responsible for alteration of the heme pocket steric configuration and for instability. The new abnormal HBG2 gene was found to be associated in cis with the mutated HBG1 gene, which characterizes the Hb F-Sardinia [Aγ (E19)Ile→Thr, HBG1:c.227T>C] variant.

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