Studies on Abnormal Hemoglobins of Umbilical Cord Blood : II. Amino Acid Substitutions of Hb F Yamaguchi and Hb F Iwata

2,750 cord blood specimens collected from several hospitals in Yamaguchi Prefecture were examined electrophoretically for the detection of abnormal hemoglobins. Two γ chain variants were discovered and characterized as follows. 1) Hb F Yamaguchi : γ 80 (EF 4) Asp → Asn (75 Thr, 136 Ala) This γ chain variant was the first example of mutation of the γ^T chain. It comprised 33.6% of the total Hb F, an unusually high percentage for a γ chain variant. 2) Hb F Iwata : γ 72 (E 16) Gly → Arg (75 Ile, 136 Ala) This γ chain concerned with the first report of substitution at E 16. It comprised 11.6% which is comparable to the values usually reported in an A^γ chain variant. No clinical consequences have been observed in association with the hemoglobin variants. The frequency of γ chain variants appears to be very low. From this screening and other reports in Japan (Omura 1970, Sumida 1975), the frequency approximates 0.08% and is estimated to be 1/600--1/3, 100 (90% confidence interval). Non-allelic polymorphism of the γ chain at position 136 (either Gly or Ala) has been well documented and a second polymorphism at position 75 (Ile or Thr) has recently been recognized. The observation on Hb F Yamaguchi demonstrates that the γ^T chain has alanine in position 136, and further confirm an emerging concept of the association of γ 75 Ile/Thr heterogeneity with γ 136 Ala due to allelic polymorphism at Aγ locus.