Influence of DNA delivery method on gene targeting frequencies in human cells

Gene targeting can be used for genetic studies of human cell lines and has significant potential for somatic cell gene therapy. These applications are however restricted by the low frequency of homologous recombination in hig her eukaryotes compared to the relatively efficient nonhomologous integrati on of transfected DNA into the genome. As part of our attempts to overcome this problem, we compared two widely used transfection methods for their ef ficiency in gene targeting. To our surprise we found that, for conditions t hat render similar frequencies of nonhomologous integrants, lipofection is much less efficient than electroporation in generating targeted clones. Thi s suggests that nonhomologous and homologous recombination have different r equirements for DNA delivery in human cells.