Fig. 3. Gross morphology and histology of wild-type and Dnmt3L^–/– testes. (A) Gross morphology of testes of wild-type (+/+) and Dnmt3L^–/– (–/–) mice at 1 week and 8 weeks of age. (B-G) Testes from wild-type (B-D) and Dnmt3L^–/– (E-G) mice at 1 week (B,E), 4 weeks (C,F), and 8 weeks after birth (D,G). The number of spermatogonia in 1-week old testes was not significantly different in wild-type and mutant mice. At 4 weeks of age, most seminiferous tubules in Dnmt3L^–/– testes contained very few differentiated spermatocytes. At 8 weeks of age, Dnmt3L^–/– testes contained almost no spermatids or spermatozoa, which are normally present in the lumen of wild-type seminiferous tubules. Scale bar: 100 µm.