Comparison of expression of human globin genes transferred into mouse erythroleukemia cells and in transgenic mice

To examine whether transfer of gamma globin genes into mouse erythroleukemia cells can be used for the analysis of regulatory elements of gamma globin gene promoter, Agamma gene constructs carrying promoter truncations that have been previously analyzed in transgenic mice were used for production of stably transfected mouse erythroleukemia (MEL) cell clones and pools. We found that constructs, which contain a microlocus control region (microLCR) that efficiently protects globin gene expression from the effects of the position of integration in transgenic mice, display position-dependent globin gene expression in MEL cell clones. Agamma globin gene expression among MEL cell clones carrying the muLCR(-201)Agamma and muLCR(-382)Agamma gene constructs ranged 15.5-fold and 17.6-fold, respectively, and there was no correlation between the Agamma mRNA levels and the copies of the transgene (r = .28, P = .18). There was significant variation in per copy Agamma globin gene expression among MEL cell pools composed of 10 clones, but not among pools composed of 50 clones, indicating that position effects are averaged in pools composed by large numbers of clones. The overall pattern of Agamma globin gene expression in MEL cell pools resembled that observed in transgenic mice indicating that MEL cell transfections can be used in the study of cis elements controlling gamma globin gene expression. MEL cell transfections, however, are not appropriate for investigation of cis elements, which either sensitize or protect the globin transgenes from position effects.