EXPRESSION OF THE NEOMYCIN-RESISTANCE (NEO) GENE INDUCES ALTERATIONS IN GENE-EXPRESSION AND METABOLISM

The amino 3'-glycosyl phosphotransferase (neo) gene is the selectable marker most widely used in stable transfection or infection protocols. Because the neo gene product has phosphotransferase activity, it migh t modify the phosphorylation state when introduced in mammalian cells. NIH-3T3 fibroblast cells expressing the neo gene, after either infect ion with retroviral vectors or transfection with plasmids, showed a 50 % reduction in both fructose 2,6-bisphosphate (Fru 2,6-P-2) concentrat ion and lactate production compared with control NIH-3T3 cells, indica ting that these neo-expressing cells are less glycolytic. In addition, a marked decrease in the levels of mRNA for the procollagen 1 alpha a nd fibronectin genes was also observed in neo-expressing NIH-3T3 cells . This decrease was concomitant with an increase in the mRNA concentra tion of the endogenous c-myc gene. FTO-2B rat hepatoma cells also show ed modifications in gene expression when the neo gene was introduced b y stable transfection or infection. In these cells an increase in both P-enolpyruvate carboxykinase (PEPCK) and tyrosine aminotransferase (T AT) mRNA was observed. These results suggest that neo gene expression may induce changes in the cells, which should be considered when neo-s elected cells are used to deliver specific genes in different therapy approaches and in embryo manipulation.