Homologous Recombination in Human Embryonic Stem Cells

Homologous recombination provides a precise mechanism for defined modifications of genomes in living cells and has been used extensively with mouse embryonic stem (ES) cells to investigate gene function and to create mouse models of human diseases. The ability to modify the mouse genome in mouse in a predetermined manner has revolutionized biomedical research involving mice. The HPRT1 gene is located on the X-chromosome, so a single, homologous recombination event can lead to complete loss of function in XY cells. A gene-targeting vector that was able to ablate parts of the human HPRT1 gene was designed and used to optimize transfection protocols in human ES cells. Homologous recombination in human ES cells will be important for studying gene function in vitro and for lineage selection. It is a powerful approach for understanding the function of any human gene. For therapeutic applications in transplantation medicine, controlled modification of specific genes should be useful for purifying specific ES cell-derived, differentiated cell types from a mixed population and for altering antigenicity of ES cell derivatives. Additionally, it should be possible to give cells new properties to combat specific diseases.