FIG. 1.

Generation of rat spermatogenesis in mouse testes. a, Testis from 8-week-old transgenic rat (line 14-2) incubated with 5-bromo-4-chloro-3-indole-β-D-galactosidase (X-gal). The transgene was composed of the mouse metallothionein-1 promoter and flanking regions (MT) fused to the Escherichia coli lacZ (lacZ) structural gene, which results in expression of β-galactosidase (β-gal) in the liver and testes of rats, causing blue staining of these tissues after incubation with X-gal (refs 1,2,10 and unpublished results). In rats, Sertoli cells are uniformly stained (light areas) and all germ cells will stain blue depending on substrate penetration (dark areas). b, Testis from 8-week-old non-transgenic rat which does not stain blue after incubation with X-gal. c, Testis from 16-week-old immunodeficient nude (nu/nu) mouse treated with busulphan (32 mg per kg) to destroy endogenous mouse spermatogenesis^1,2,16. d, Testis from busulphan-treated nude mouse that was injected with transgenic rat testis cells (Left testis of 777, Table 1). Enlarged area is site of injection from which some tubules were extruded. Blue tubules represent areas of rat spermatogenesis in the mouse testis. Scale bars: a, b, 5 mm; c, d, 1 mm.

METHODS. Transgenic rats were generated as previously described¹⁷. Technique for isolating testis cells^18,19, microinjection into recipient mouse seminiferous tubules and analysis of testes have also been described^1,2. Roughly 0.5 ml of cell suspension was used to inject the testes of each recipient. Recipient Swiss nude mice were injected with bone marrow cells (~ 3 × 10⁶ per mouse) into the tail vein, 3 days after busulphan treatment, to reduce mortality.