Fig. 1. Expression of Spalt4 in ectoderm and derived tissues. Whole-mount in situ hybridization of (A) stage 3 chicken embryo, (B) stage 5 chicken embryo (arrows indicate level of sections in D and E), (C) stage 8 chicken embryo (arrow indicates levels of sections in F). (D) Section through embryo in (B) at the level of the notochord. (E) Section through embryo in B at the level of Hensen's node. (F) Section through stage 8 embryo at midbrain level. (G) Expression of Spalt4 in a stage 10 embryo sectioned at hindbrain level. (H) Expression of Spalt4 in the otic pit (opi) of a stage 13 embryo. Arrowhead points to the neural crest. (I) Expression of Spalt4 in the otic vesicle (otv) of a stage 16 embryo. Arrowhead indicates the neural crest. (J) Section through a stage 14 embryo at eye level. (K) Section through a stage 17 embryo at forebrain level. (L) Whole-mount in situ hybridization with Spalt4 in a stage 19 embryo showing strong Spalt4 expression in the forelimb. Arrow shows the level of the section in M. (M) Section through the forelimb in L. (N-Q) Comparison of stage 5 expression of (N). Spalt4 (O). Six1 (P). Eya2 and (Q) Sox3. ps, primitive streak; hn, Hensen's node; no, notochord; otp, otic placode; opi, otic pit; otv, otic vesicle; mb, midbrain; hb, hindbrain; re, retina; le, lens; fb, forebrain; ol, olfactory epithelium; fl, forelimb; d, dorsal; v, ventral; aer, apical ectodermal ridge.