Electroporation of Embryonic Stem Cells for Generating Transgenic Mice and Studying In Vitro Differentiation

The ability to transfect mammalian cell lines stably in culture has enabled countless scientific advances to be made in just a few decades. However, not until about 10 years ago did the true potential for the genetic manipulation of cells become a reality, with the ability to alter a mammalian gene precisely by targeted homologous recombination (1 –3 ). This powerful tool was first devised for gene therapy approaches, but was quickly adopted for the transfection (4 ) and genetic disruption of genes in embryonic stem (ES) cell lines to produce transgenic animals (5 ,6 ). Currently, the most common cell line used is the mouse ES cell, but ES cells have recently been derived for other species (rabbit, rat, and hamster) (7 –9 ).