Whole mount in situ hybridization of Fzd5 mRNA expression showing frontal (A, B), lateral (C) and ventral views (D) of the embryonic mouse head. (A) Fzd5 is expressed in the anterior neural plate at E8 (bracket, 6–8 somites; fg: foregut). (B) At E9, Fzd5 expression is detectable in the anterior forebrain (bracket). (C) At E9.5, Fzd5 is expressed in the optic vesicle (ov) and optic stalk as well as in the olfactory placode (white arrowhead) and lung buds (black arrowhead). (D) By E10.5, Fzd5 is expressed in the ventral forebrain, Rathke’s pouch (rp) and infundibulum (inf). Fzd5 expression was also detected in the olfactory placode (black arrowheads) and along the optic stalks (white arrowheads). E: embryonic day, Lg: lung