Effect of BCL11A and HMIP QTL upon HbF and F cells. (A) Box plots showing the complete distribution of HbF in 619 Chinese β-thalassemia heterozygotes, expressed as percentage in log scale on the y-axis. Each rectangle represents the data between the 25th and 75th quartiles, and the bar in each rectangle is the median value for the HbF in log scale. rs766432: AA, AC, and CC represent the SNP genotypes for rs766432 in BCL11A on chromosome 2p16. rs9399137: TT, CT, and CC represent the SNP genotypes for rs9399137 in HMIP on chromosome 6q23. (B) Effect of the 3 major HbF QTLs on HbF and F-cell levels in adult β-thalassemia heterozygotes who had HbF and F cells determined. Data are mean ± SD. Control indicates 80 subjects (age, 48.3 ± 9.0 years) who are homozygous for the major alleles for rs7482144 in HBG2 promoter, rs766432 in BCL11A, and rs9399137 in HMIP. rs766432: 8 subjects (age 46.9 ± 9.6 years) with identical HbF QTL genotypes as those in control, except that they are homozygous for the minor allele for rs766432 in BCL11A. rs9399137: 6 subjects (age 40.3 ± 13.8 years) with identical HbF QTL genotypes as those in control, except that they are homozygous for the minor allele for rs9399137 in HMIP.