Transgenic mice produced by retroviral transduction of male germ-line stemcells

Male germ-line stem cells are the only cell type in postnatal mammals that have the capability to self-renew and to contribute genes to the next gener ation. Genetic modification of these cells would provide an opportunity to study the biology of their complex self-renewal and differentiation process es, as well as enable the generation of transgenic animals in a wide range of species. Although retroviral vectors have been used as an efficient meth od to introduce genes into a variety of cell types, postnatal male germ-lin e stem cells have seemed refractory to direct infection by these viruses. I n addition, expression of genes transduced into several types of stem cells , such as embryonic or hematopoietic, is often attenuated or silenced. We d emonstrate here that in vitro retroviral-mediated gene delivery into sperma togonial stem cells of both adult and immature mice results in stable integ ration and expression of a transgene in 2-20% of stem cells. After transpla ntation of the transduced stem cells into the testes of infer-tile recipien t mice, approximately 4.5% of progeny from these males are transgenic, and the transgene is transmitted to and expressed in subsequent generations. Th erefore, there is no intrinsic barrier to retroviral transduction in this s tem cell, and transgene expression is not extinguished after transmission t o progeny.