Gene transfer into the germ line of mice and into embryonal carcinoma stem cells

Recombinant genes can be introduced into the germ line of mice by microinjection into the fertilized egg or via embryonal carcinoma stem cells. A regulated, cell-type specific expression of the newly introduced gene following microinjection is usually not found. However, in one series of experiments the insertion of human growth hormone genes in the germ line led to prenatal recessive lethal mutations. Alternatively, embryonal carcinoma stem cells can be used to introduce and express genes in mice, for example after infection with selectable retroviral vectors. In addition, these cells are useful for differentiation studies in vitro following DNA-mediated gene transfer.