Fig. 7. The lateral canal defects in Shh^-/- and Gli3^-/- mutants are caused by different mechanisms. The inner ears of Gli3^+/- (A-D), Gli3^-/- (E-H), and Shh^-/- (I-L) at 11.75 dpc examined by the paint-fill technique (A,B,E,F,I,J) and in situ hybridization (C,D,G,H,K,L). Red lines in A,E,I represent the levels of sections shown in C,D, G,H, and K,L, respectively. (A,B) At 11.75 dpc, the inner ear shows a vertical pouch (vp; develops into the anterior and posterior semicircular canals) dorsally and a horizontal pouch (hp; develops into the lateral semicircular canal) laterally. The developing cochlear duct (cd) is also shown ventrally. (C,D) The location of the prospective lateral crista (lc) is marked by the co-expression of Bmp4 and Otx1 (arrows). Otx1 is also expressed in the prospective lateral canal region. (E,F) The vertical pouch of Gli3^-/- mutants is smaller than that of heterozygotes. The horizontal pouch is absent or rudimentary. (G,H) The primordial lateral crista is present based on the overlap of expression between Bmp4 and Otx1 (arrows). Yet, the Otx1 expression domain in the canal pouch is much reduced (arrowheads). (I,J) The inner ears of Shh^-/- mutants show the presence of the horizontal pouch. However, Otx1 expression, which is normally found in the horizontal pouch, has shifted to the medial side (arrowheads), such that the Otx1 expression domain no longer overlaps with that of Bmp4 (K,L). Orientations: D, dorsal; A, anterior; L, lateral. Scale bars: 100 µm.