The association of Gγ XmnI polymorphism with hemoglobin F levels in homozygous hemoglobin E

Abstract

The Gγ -Xmn I polymorphism (-158 C → T) in 131 subjects with homozygous Hb E were investigated. The Xmn I (+/+), (+/-) and (-/-) patterns were identified in 77 (58.8 %), 45 (34.3 %) and 9 (6.9 %) cases, respectively. This result indicates that majority of βE globin genes are linked to the Xmn I + allele. Among 61 cases of Hb E homozygote (Hb > 9 g/dl) who had (bE/bE, aa/aa) genotype, 37 (59.7 %), 20 (32.3 %) and 5 (8.0 %) cases had the Xmn I (+ / +), (+ / -) and (- / -) patterns, respectively. The median levels of Hb E and other Rbc parameters in these groups were not difference. However, the median levels of Hb F as determined by Hb-HPLC analysis, the MCHF (ng) and the Hb F concentration (mg/dl) were significantly higher in the Xmn I (+ / +) group (3.6 %, 731.0 ng and 374.0 mg/dl) as compared to those with the Xmn I (+ / -) (2.4 %, 456.9 ng and 264.4 mg/dl) and the Xmn I (- / -) (2.5 %, 518.0 ng and 245.0 mg/dl) at p-value < 0.01 using Kruskal Wallis One-way Analysis of Variance and Mann-Whitney U-Test. No difference was found between the Xmn I (+ / -) and the Xmn I (- / -) groups. Although the Gγ -Xmn I (+ / +) polymorphism is associated with high Hb F production in Hb E homozygote, it is apparent that other factors requiring further investigation might also be involved.