Background and Objectives. To explore the role of cis-regulatory sequences within the β globin gene cluster at chromosome 11 on human γ globin gene expression related to Hb E allele, we analyze baseline hematological data and Hb F values together with β globin haplotypes in homozygous Hb E. Patients and Methods. 80 individuals with molecularly confirmed homozygous Hb E were analyzed for the β globin haplotypes and Xmn I polymorphism using PCR-RFLPs. 74 individuals with complete laboratory data were further studied for association analyses. Results. Eight different β globin haplotypes were found linked to Hb E alleles; three major haplotypes were (a) (III), (b) (V), and (c) (IV) accounting for 94% of Hb E chromosomes. A new haplotype (Th-1) was identified and most likely converted from the major ones. The majority of individuals had Hb F？<？5%; only 10.8% of homozygous Hb E had high Hb F (average 10.5%, range 5.8–14.3%). No association was found on a specific haplotype or Xmn I in these individuals with high Hb F, measured by alkaline denaturation. Conclusion. The cis-regulation of γ globin gene expression might not be apparent under a milder condition with lesser globin imbalance such as homozygous Hb E. 1. Introduction Beside producing abnormal variant, hemoglobin E (HbE), the G→A substitution in codon 26 (Glu→Lys) of the β-globin gene (βE) could also produce β+ thalassemia due to decreased functional HbE-mRNA, secondary to alternative splicing mechanism [1]. However, the clinical phenotype in homozygous Hb E (Hb EE) is rather asymptomatic with very mild anemia. In contrast, patients with HbE/β thalassemia have a more diverse clinical phenotype from transfusion dependent to very mild disease [2–5]. Although, understanding of clinical phenotypic diversity in patients with Hb E/β thalassemia has long been a topic of several investigations, at present, the genotype-phenotype correlation of this so-called single gene disorder remains obscure. Variation of postnatal γ globin expression and HbF production in these patients was thought to be one of the main genetic factors responsible for clinical heterogeneity found in Hb E/β thalassemia by reducing globin imbalance and ameliorating ineffective erythropoiesis. Through erythroid development, the γ globin expression was regulated by interactions between cis-acting sequences within the β globin cluster and trans-acting factors such as BCL-11A, cMYB, and TOX [1, 6–8]. The most significant genetic factor in cis associated with high HbF is Xmn I polymorphism located at ？158 upstream to the Gγ globin genes [9]. In a
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