Figure 2.

Shh regulates the expression of markers along the dorsoventral axis of the otic vesicle. Transverse section and whole-mount views of otic vesicles from wild-type (a–d,i–l,q,s,u,w) and Shh^−/− (e–h,m–p,r,t,v,x) embryos analyzed for gene expression by RNA in situ hybridization. (a,e) Otx2 is absent from the ventral otic epithelium of Shh^−/− embryos; (b,c,f,g) Otx1 expression is reduced in Shh^−/− embryos. Red arrowhead in g points to the reduced domain of Otx1 expression. (d,h) Dlx5 is expanded ventrally in the absence of Shh. Brackets mark the distance between the ventral limit of Dlx5 expression and the ventral extent of the otic vesicle. (i,m) Fgf3. (j,k,n,o) Lfng, the ventral shift in Lfng expression in Shh^−/− embryos (o) is marked by a red arrowhead. (l,p) Bmp4; red arrowhead points to the Bmp4 expression domain that is shifted ventrally in Shh^−/− embryos. (q,r) Gli1and (s,t) Ptc are detected in the otic epithelium and periotic mesenchyme of wild-type but not Shh^−/− embryos. Arrowheads in q and s point to faint expression of Gli1 and Ptc in the periotic mesenchyme and medial wall of the otic vesicle. The semblance of expression of Gli1 in r is the result of trapping rather than specific staining. (u,v) Tbx1; expression is detected in the lateral wall of the otic vesicle in both wild-type and Shh^−/− embryos. However, the periotic mesenchyme expression of Tbx1 (bracket) is absent in Shh^−/− mutants. (w,x) Brn4; expression in the condensing mesenchyme (bracket) is absent from Shh^−/− embryos at 10.5 dpc. Asterisk in x marks the branchial arch expression of Brn4, which is unaffected in Shh^−/−embryos. All sections are from embryos at 10.5 dpc except d and h, which are from embryos at 9.5 dpc. M, medial; L, lateral; D, dorsal; V, ventral.