Fig. 3. Morphological and in situ hybridisation analyses of E9.5 and E10.5 Fgf3/Fgf10 double mutant embryos reveal a failure of otic vesicle formation. Whole mount embryos were stained with haemotoxylin and eosin (A,C) or were probed with labelled cDNA for Pax2 (E,G) and Dlx5 (I,K) 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 at the top (A,C) or to the left (E,G,I,K). Comparison of E10.5 control (A,B) and double mutant embryos (C,D) shows the absence of otic vesicles (ov), forelimbs (fl) and hindlimbs (hl) as well as truncation of the tail (t) in double mutants (C,D). In situ hybridisation with Pax2 to E9.5 control (E) and double mutant (G) embryos detects transcripts in the eye (e), kidney (k) and isthmus (i). Pax2 transcripts can be detected in the ventromedial wall of the otic vesicle in control embryos (F) but Pax2 is absent from the comparable region of double mutant embryos (H). In situ hybridisation with Dlx5 to E9.5 control (I) and double mutant (K) embryos detects transcripts in the first and second branchial arches (ba) and forebrain (f). Dlx5 transcripts can be detected in the forelimb and the dorsolateral wall of the otic vesicle in control (I,J) but not double mutant (K,L) embryos. Arrowheads indicate microvesicles (D,H).