Virus Vector-mediated Human β-globin Gene Transfer Research

Human globin gene family resides in different loci, α -globin gene cluster and β -globin gene cluster. The function genes in the clusters can be expressed with the characteristics of erythroid-specificity, development stage-specificity and final product-balance. Once the balance between α and β globin final products was destroyed, thalassemia is coming. Descendance or cessation of the synthesis of β -globin polypeptide caused by deletions or mutations in β -globin gene cluster result in β -thalassemia, one kind of common hereditary disease in hematopoietic system.Till now, no satisfactory strategies can be performed effectively in treatment of β -thalassemia. Theoretically, β -thalassemia is curable by ex vivo gene transfer in which normal human β -globin gene is introduced and integrated into chromosomes of hematopoietic stem cells(HSC) and the transduced HSCs were reinfused into patients when combining with suitable vehicles. The β -globin gene will be present in the progenies of HSC following self-renewal, division and differentiation of HSC.The continual expression of introduced normal gene can ameliorate the anemia syndrome of β -thalassemia. The candidate for human β -globin gene transfer vehicles should be integrative virus vector such as retrovirus(RV) or adeno-associated virus(AAV) vector.The normal expression of β -like globin genes depends upon three regulatory elements: erythroid-specific and general trans-acting factors, proximal in-cis elements(promoters) and the distal in-cis elements--locus control region(LCR). LCR, which is located 20kb upstream of ε -globin gene and consists of five DNaseI hypersensitive sites(HS), directs high-level, position-independent and copy number-dependent globin gene expression in transgenic mice. Among LCR, HS1-HS4 are erythroid -specific and developmental stage-stable, each HS contains a 200-400bp core fragment which is essential for each HS activities and in which many binding motifs for erythroid -specific and general trans-acting factors were distributed. Intact LCR spends 20kb in β -globin gene cluster and exceeds the packaging capacities of virus vectors, however, miniLCR composed with combinations of different HS core...