Fig. 2.

Divided Müllerian duct segments (E14.5–15.5) move caudally without propulsion from a more anterior segment. The Müllerian duct is visualized (A–K) over time by whole mount in situ hybridization for Wnt7a. Intact urogenital ridges harvested at E14.5 (A), and after 10 h (D) or 20 h (G) in organ culture, show normal elongation of the Müllerian duct. Mesonephroi were incised at 200 μm posterior to the Müllerian duct tip (arrow) at E14.5 (B), and incubated for 10 h (E) or 20 h (H). Elongation was blocked at the site of incision (arrow) after 10 h and the tip enlarged relative to the time of incubation. The mesonephroi were incised at 200 μm and 700 μm anterior to the Müllerian duct tip (arrows) at E14.5 (C), and incubated 10 h (F) or 20 h (I). The bulge of the Müllerian duct anterior to the incisions and the Müllerian duct gap posterior to the incisions were seen at each incision site after 10 h. The tip of the most distal segment (red arrowhead) moved at the same rate as did the tip of the intact Müllerian duct (compare D and F; G and I). E 15.5 female rat urogenital ridges incised at 2 sites (J) and incubated for 20 h (K) similarly showed the bulging tip of the Müllerian duct anterior to the incisions and the gap of the Müllerian duct posterior to the incisions (J, K) after 20 h. Transverse sections (L–N) of the mesonephros at the levels of the red line (L), black line (M), and dashed line (N) in (H) stained with H and E, show cell accumulation and enlargement of diameter at (M) and cell accumulation at the distal blocked tip (N) of the Müllerian duct. Arrow, site of incision; red arrowhead, posterior tip of the Müllerian duct. Scale bar: 500 μm in (A)–(K), 100 μm in (L)–(N).