α -globin gene expression is highly regulated by several multi-species conserved sequences (MCS-R) or enhancers located 30–70 kb upstream of HBA1/2.[44] In this region, we identified an association signal for red cell traits in our study of African Americans (previously reported in European populations[19]) that normalizes red cell parameters in individuals who carry the −α3.7 deletion and negates the protective effect of α-thalassemia for stroke in individuals with HbSS. This evidence concerns the gene HBA1 and thalassemia.