Fig. 1.

Generation of transgenic animals using spermatogonial stem cells. The testis from a fertile male is digested to generate a single-cell suspension. The SSCs can be cultured, transfected, and then microinjected into the lumen of seminiferous tubules of an infertile recipient mouse. Only a spermatogonial stem cell can generate a colony of spermatogenesis in the recipient testis. Mating the recipient male to a wild-type female produces progeny that carry foreign genes