Fig. 5. Defects in inner ear formation in Fgf3 and Fgf10 double mutant mice. (A-D) Sections at the level of the otic placode at E8 (eight somites) and the invaginating placode (E8.75) which have been hybridized with the indicated probes. Note the absence of Dlx5 staining in B. At E8.75, the otic placode in the mutant embryo has only initiated its invagination and shows very weak Pax2 expression (D), whereas strong expression is detected in the otic cup formed in the wild-type embryo (C). (E,F) Toluidin Blue stained sections through the otic vesicle of a wild-type and a Fgf3^–/–/Fgf10^–/– mutant littermate at E10.75. Note the absence of the cochlear ganglion in the mutant (indicated by an arrow in the wild-type animal) and a more ventralized position of the vesicle relative to the border of the neural tube (marked by asterisks). (G-P) Expression of the indicated otic marker genes by whole-mount RNA in situ hybridisation in wild-type embryos (G,I,K) and Fgf3^–/–/Fgf10^–/– mutant littermates at E9.5 (H,J,L,O,P). (M,N) Sections corresponding to the embryos shown in K,L. The punctated circle in J,L,N indicates the circumference of the residual otic tissue formed in the mutants. Note the complete absence of Dlx5 staining in the vesicle of the mutant animal in L,N. Scale bars: in A, 40 µm for A-D; in I, 100 µm for E-P.