-G gamma A gamma-Thalassemia and gamma-chain variants in Chinese newborn babies

Abstract

The occurrence of gamma-chain abnormal hemoglobins and of gamma-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 -G gamma A gamma-thalassemia, which is caused by a deletion of about 5 kb due to an unequal crossing-over between the -G gamma- and -A gamma- 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 G gamma chain variant, Hb F-Shanghai or alpha 2 G gamma 266(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 G gamma 66 Lys and G gamma 66 Arg chains had slightly different chromatographic mobilities. Lys at position gamma 66 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 gamma-chain variants have been detected except the well-known A gamma T or F-Sardinia chain (f.A gamma T = 0.076).