Fig. 2

nkx2.2b expression during early zebrafish embryogenesis. (A) Onset of nkx2.2b expression at 70% epiboly. Arrowhead points to nkx2.2b positive cells in the ectoderm. (B) Higher magnification of (A). (C) Dosal view of (B). (D) nkx2.2b expression in the developing ventral head at bud stage. (E-G) Lateral view of prospective head regions of embryos at bud stage (anterior to left, dorsal to top) with expression of nkx2.2b (E), shh (F) and flh (G) in bright-field (E,G) and under fluorescence light (F). The asterisk indicates the anterior border of the prechordal plate. Note overlap of nkx2.2b with shh and flh expression in the anterior mesoderm. (H) nkx2.2a expression precedes that of nkx2.2b and is expressed in head mesoderm at 80% epiboly. (I-L) Shh precedes posterior extension of nkx2.2b expression in the ventral neural tube. (I) Expression of shh in notochord and MFP at the 5s stage. Arrowhead indicates posterior front of shh expression in the MFP. (J-L) nkx2.2b expression at 5s (J), 7s (K) and 9s (L) stages. Arrowheads in (J-L) show the posterior front of extending nkx2.2b expression in the LFP. All pictures, except C, are lateral views with anterior to the left; dashed lines indicate the boarder between ectoderm and mesoderm (B,G). Scale bar in (D) represents 100 µm (for A,D), in (H) 30 µm (for B,C,E-H), and in (L) 50 µm (for I-L).