Fig. 8. Effects of FGF and SU5402 treatments prior to canal pouch formation. (A-F) Bmp2 expression in FGF-(B,D) or SU5402-treated (F) otocysts. A, C and E show left untreated ears of the same embryos that are shown in B, D and F, respectively. Otocysts implanted with an FGF2-soaked bead at E2.5 (B), infected with RCAS-Fgf3 at E2 (D), or implanted with SU5402-soaked beads at E3 (F) were analyzed 24 hours later. At E3-E3.5, Bmp2 expression in control inner ears is barely detectable (arrows, A,C), but it is upregulated with FGF2 and RCAS-Fgf3 treatments (white arrowhead in B and D). By E4, the two wedge-shaped Bmp2 expression domains are evident in the control ear (E), and this expression is downregulated in the SU5402-treated ear (F). The reduction of Bmp2 expression is more pronounced in the posterior domain (arrowhead) than the anterior domain (arrow). (G-J) Paint-filled inner ears treated with medium (G,I) and high (H,J) doses of SU5402 at E2.5 and harvested at E6 (G,H) or E9 (I,J). (G,I) A medium dose of SU5402 causes the loss of the posterior canal pouch at E6 (asterisk, G) and prevents formation of the posterior canal and ampulla at E9 (asterisk, I). (H,J) A high dose of SU5402 causes a severely deformed canal pouch at E6 (arrows, H) and absence of all three canals and ampullae, but the common crus is intact (arrows, J). Arrowhead in J indicates the presence of the anterior ampulla. Orientations in A apply to C and E; orientations in B apply to D and F; orientations in G apply to H-J.