-GγAγ-thalassemia and γ-chain variants in chinese newborn babies

The occurrence of γ-chain abnormal hemoglobins and of γ-thalassemia in Chinese newborns was evaluated through analyses of the Hb F of over 1,100 babies and of the DNA from one baby and his parents. Gene mapping data identified this baby as a homozygote for -GγAγ-thalassemia, which is caused by a deletion of about 5 kb due to an unequal crossing-over between the -Gγ- and -Aγ- genes. This condition is the same as that observed in Indian and Japanese babies [2,3]. Its gene frequency among babies from the Shanghai area was 0.012. A previously unrecognized Gγ chain variant, Hb F-Shanghai or α2Gγ266(E10)Lys→Arg, was observed in one newborn. This variant was not detected by conventional techniques but only by high performance liquid chromatography, as the Gγ66 Lys and Gγ66 Arg chains had slightly different chromatographic mobilities. Lys at position γ66 participates in contacts with the heme group, and its substitution by another amino acid residue might interfere with physiochemical and/or functional properties. No other γ-chain variants have been detected except the well-known AγT or F-Sardinia chain (f.AγT = 0.076).