Fig. 2. The Stra8 mutation is a null mutation. (A-K) Absence of the STRA8 protein in germ cells from male mutants. (A,B) Show immunodetection of STRA8 (red signal) on histological sections of testes at 8 weeks of age, and the DAPI nuclear counterstain (blue). (C,D) Show immunodetection of STRA8 (red signal) on histological sections of testes at P5 and the DAPI nuclear counterstain (blue). (E-J) Show immunodetection of STRA8 (red signal) on nuclear spreads from testes at 8 weeks of age and the DAPI counterstain (blue). Note that: (1) in G,J, the superimposition of the immunohistochemical signals (red false colour) and of the DAPI nuclear stain (blue false colour) were converted to a bright-field image using Photoshop, and (2) in E-J, the three panels in each column represent the same nuclei. (K) Western blot analysis of testis proteins (100 g) from adult mice with the indicated genotypes, using an anti-STRA8 polyclonal antibody (upper panel). Excision of exons 2-4 resulted in a null allele, as confirmed by the absence of any STRA8 in Stra8^–/– testes (arrow). The asterisk points to an unspecific signal that was detected both in WT and Stra8^–/– extracts. The lower panel, showing detection of actin (ACTA), reveals that similar amounts of protein are loaded on each lane (arrow). (L-O) Absence of oocytes and follicles in ovaries from mutant females at 8 weeks of age. Histological sections were stained with haematoxylin and eosin. The genotypes are as indicated. AF/PF/PRF, antral/primary/primordial follicles; E, ovarian surface epithelium; LY, Leydig cells; PR, preleptotene spermatocytes; ST, ovarian stroma; T, seminiferous tubules. Scale bar: 80 m (A-D); 15 m (E-J); 160 m (L,N); 40 m (M,O).