Genetics of fetal hemoglobin in Tanzanian and British patients with sickle cell anemia.
Makani J., Menzel S., Nkya S., Cox SE., Drasar E., Soka D., Komba AN., Mgaya J., Rooks H., Vasavda N., Fegan G., Newton CR., Farrall M., Thein SL.
Fetal hemoglobin (HbF, α(2)γ(2)) is a major contributor to the remarkable phenotypic heterogeneity of sickle cell anemia (SCA). Genetic variation at 3 principal loci (HBB cluster on chromosome 11p, HBS1L-MYB region on chromosome 6q, and BCL11A on chromosome 2p) have been shown to influence HbF levels and disease severity in β-thalassemia and SCA. Previous studies in SCA, however, have been restricted to populations from the African diaspora, which include multiple genealogies. We have investigated the influence of these 3 loci on HbF levels in sickle cell patients from Tanzania and in a small group of African British sickle patients. All 3 loci have a significant impact on the trait in both patient groups. The results suggest the presence of HBS1L-MYB variants affecting HbF in patients who are not tracked well by European-derived markers, such as rs9399137. Additional loci may be identified through independent genome-wide association studies in African populations.