Fig. 6.

Fgf signals are required for the generation of sensory epithelial cells in vivo. (A) In ovo electroporation of stage 12 embryos in the olfactory placodal region using pCaggs-GFP together with pCaggs-Fgfr3c-ΔC (n=16) resulted in loss of Hes5 and HuC/D expression and an increase of Msx1/2 and Id3 expression in the nasal epithelial region, when analyzed at stage 22. In the most severely affected embryos, the olfactory epithelial region fails to invaginate (arrowheads). HuC/D and Hes5 can also be detected in the telencephalon. (B) In E10.5 Foxg1:Fgfr1;Fgfr2 mutant mice (n=4) the placodal invagination was absent, the expression of Hes5 and HuC/D was greatly reduced or completely lost, and Msx1/2 and Id3 expression were detected throughout the presumptive olfactory placodal region (arrowheads). E10.5 wild-type mice expressed Hes5 and HuC/D in the anteromedial region and Msx1/2 and Id3 at the rim of the olfactory pit. Hes5 can also be detected in the telencephalon. (C) In ovo Fgfr3c-ΔC-electroporation of stage 21 (n=6) embryos resulted in an increase in Msx1/2⁺ and Id3-positive cells in the sensory epithelial domain when analyzed at stage 27. The sensory epithelium, identified by expression of Hes5 and HuC/D, was reduced in size and appeared thinner (black brackets), while the respiratory epithelium was expanded (white brackets). (D) Higher magnification figures of the sensory epithelial region, as indicated by white boxes in C.