Fig. 2. Immunostaining of testicular sections with anti-Brdt antibodies. DAB staining produces a brownish color at the site of antibody localization. The -CT antibody was used in the staining. Roman numerals within each tubule denote the stage of the tubule as defined previously (Russell et al., 1990). (A) A wild-type stage XI tubule showing the expression of Brdt protein in the nucleus of pachytene (P) but not zygotene (Z) spermatocytes. (B) A mutant stage IX tubule showing the expression of Brdt^BD1 protein in the nucleus of pachytene (P) but not leptotene (L) spermatocytes. (C) A stage XII wild-type tubule showing that, during the meiotic divisions (M), Brdt protein was distributed throughout the cell, but after the meiotic divisions, Brdt protein was predominantly found in the nucleus. (D) A stage XII mutant tubule showing a similar expression pattern and sub-cellular distribution of the truncated Brdt protein in the Brdt^BD1/BD1 testes. (E) Stage I, V-VI and VIII wild-type tubules showing the expression of Brdt protein in round spermatids (rs) but not in elongating spermatids (es). (F) Stage II-III, IV and IX mutant tubules showing the expression of the truncated Brdt protein in round spermatids (rs) but not in elongating spermatids (es). L, leptotene spermatocytes; Z, zygotene spermatocyte; P, pachytene spermatocyte; M, meiotic M phase; rs, round spermatid; es, elongating spermatid. Scale bar: 40 µm.