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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.
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