Amplification of the human alpha-globin gene enhances its expression

We investigated the effect of globin gene amplification on alpha-globin gene expression. Chinese hamster ovary cells were transformed with a plasmid containing the human alpha-globin gene linked to a functional dihydrofolate reductase gene, and the transformed cells were selected with increasing concentrations of methotrexate in the culture medium. A cell clone which was resistant to 0.1 mM methotrexate showed a 500-fold amplification of the transformed alpha-globin and DHFR genes. Both genes expressed high levels of their respective mRNAs. The mRNAs were functional and were translated to alpha-globin and DHFR proteins. Thus, one strategy for globin gene therapy is to achieve a high copy number of the transformed globin genes.