Fig. 1. Fgf3 and Fgf10 are expressed in sites relevant to early otic development. Whole mount embryos were probed with labelled cDNA for Fgf3 (A,C) and Fgf10 (E,G,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 to the left. Fgf3 is expressed in the developing neurectoderm (n) and surface ectoderm (se) from 3 (A,B) to 12 (C,D) somites. Fgf10 is expressed in the mesenchyme (m) that underlies the otic ectoderm at zero somites (E,F), 7 somites (G,H) and at E8.75 (I,J). By E9.0, Fgf10 expression is induced in the otic cup (oc) (K,L). Fgf10 transcripts can also be detected in the neurectoderm (G-J) and the pharyngeal endoderm (pe) (J,L).