Fig. 6. Embryonic Sertoli cells are specialised secretory cells. EM of 13.5 dpc testes showing secretory granules in Sertoli cells and germ cells (A-E). (A,D) Low-magnification image showing arrangement of germ cells (gc) and Sertoli cells (sc). (B,C,E) Higher magnification of boxed regions in A, B and D, respectively. Secretory granules (sg) are indicated. Scale bars: 5 µm in A,D; 0.1 µm in B,C,E. (F-I) Immunohistochemistry for SNAREs (brown precipitate) in 13.5 dpc ovaries and testes. (F) Vamp4 (trans-Golgi network) is ubiquitously expressed. (G) Vamp3 (secretory granules, endosomes) is abundant in a subset of cells in male and female gonads. (H,I) Vamp8 (secretory granules, endosomes) and Stx2 (apical plasma membrane) are abundant in testis cords. (J) Non-specific IgG controls show no significant staining. Scale bar: 100 µm.