Fig. 1. Conditional inactivation of Bruce in mice results in reduced testis size and germ cell depletion.

a Tamoxifen treatment scheme to generate Bruce cKO (Bruce^loxp/loxp; UBC-Cre-ER^T2) and Ctrl (Bruce^loxp/loxp) mice. Mouse pups were exposed to tamoxifen via intraperitoneal injections once a day on postnatal days 7, 8, and 9 (P7–9). For analyses, all mice were sacrificed at 7 weeks of age (P49). b Evaluation of KO efficiency in testes via PCR (left) and western blot (right) analyses. The PCR primers SC1 and NDEL2 were used (see Fig. S1A, “Materials and methods”). c Photos of testes at 7 weeks of age show smaller testis sizes in Bruce cKO mice compared with Ctrl mice. Testis/body weight ratios are shown in a dot plot to the right. Data are aggregated from 7 Ctrl and 11 cKO mice. Horizontal line, mean. Student’s t test, ***p < 0.001. d Hematoxylin and eosin (H&E) analyses of testis sections at 7 weeks of age. Frequencies of different cell types in Bruce Ctrl and cKO testes are shown in a dot plot to the right. Data are aggregated from two independent Bruce Ctrl-cKO littermate pairs. Horizontal line, mean. Student’s t test, ***p < 0.001. ST Sertoli cells; SG spermatogonia; SP spermatocytes; RS round spermatids; ES elongating spermatids. e Immunohistochemistry (IHC) of SOX9, a marker of Sertoli cells, in Bruce Ctrl and cKO testis sections at 7 weeks of age. Frequencies of Ctrl and cKO tubules bearing only Sertoli cells are shown in a bar graph to the right. Data are aggregated from two independent Bruce Ctrl-cKO littermate pairs (tubule number, Ctrl = 41, cKO = 76). Error bar, standard deviation. Student’s t test, ***p < 0.001. f H&E analyses of epididymis sections from Bruce Ctrl and cKO mice at 7 weeks of age. Frequencies of Ctrl and cKO empty epididymides are shown in a bar graph to the right. Data are aggregated from three independent Bruce Ctrl-cKO littermate pairs (epididymal ducts number, Ctrl = 47, cKO = 214). Error bar, standard deviation. Student’s t test, ***p < 0.001.