Fig. 6. Pax2 and Dlx5 expression in Fgf3^-/- embryos, Fgf10^-/- embryos and embryos with three mutant Fgf alleles reveals quantitative and unequal roles for Fgf3 and Fgf10 in otic development. Whole mount embryos were probed with labelled cDNA for Pax2 (A,C,E,G) and Dlx5 (I,K,M,O) and sectioned in the transverse plane. A section taken through the otic region (the plane is indicated by a line through each embryo) is shown in the panel to the right of each whole embryo. Rostral is to the left. The control and double mutant embryos for comparison are located in Fig. 3 and are shown at the same magnification. Pax2 and Dlx5 transcripts can be detected in the ventromedial (B,D,F,H) and dorsolateral (J,L,N,P) wall of the otic vesicle (ov), respectively. The size and location of the otic vesicle as well as the pattern of Dlx5 expression are altered in Fgf3^-/- mutants (D,L). In Fgf3^-/-;Fgf10^+/- and Fgf3^+/-;Fgf10^-/- embryos, the otic vesicles are reduced in size when compared to Fgf3^-/- or Fgf10^-/- embryos (F,H,N,P). In Fgf3^-/-;Fgf10^+/- embryos (H,P), the otic vesicles are also located ventrally relative to the otic vesicles in Fgf3^-/- (D,L) or Fgf10^-/- (B,J) embryos and Pax2 expression is expanded both dorsally and laterally (H). In embryos carrying either combination of three mutant alleles, Dlx5 expression is reduced relative to that seen in the branchial arches (N,P).