Human globin gene expression after gene transfer

Human globin genes can be transferred into mouse and human erythroid cells in culture, and can be appropriately expressed at the mRNA level in these cells. A plasmid containing a human beta globin gene is expressed in mouse erythroleukemia cells (MELC), and another containing a human epsilon or gamma gene is expressed in human erythroleukemia (K562) cells. A neomycin resistance (neoR) gene on the plasmids has been used to select for those cells containing the transferred globin genes; this selection may favor the expression of the globin genes by providing chromosomal positions requiring neoR expression. Analyzing clones resistant to G418, a neomycin analogue, demonstrated globin mRNA expression and induction. Retroviral vectors have also been used to transfer and appropriately express human beta genes in MELC. In addition, a plasmid containing a dihydrofolate reductase (DHFR) gene as well as neoR and beta globin genes has been used to amplify and express beta globin mRNA in MELC. These experiments suggest that high level appropriate expression of human beta globin genes is feasible and provides potentially useful approaches to the long-range goal of gene therapy for sickle cell anemia and beta thalassemia.