Fig. 6

prrx1a and prrx1b are repressed by Edn1 and activated by Bmp4 signaling.

(A-F) Two-color fluorescent in situs of 36 hpf wild-type embryos show that, relative to all arch NCCs (dlx2a, green), prrx1a and prrx1b (magenta) are expressed in dorsal arch NCCs and mesenchyme surrounding the ear (white arrow), as well as in a more limited ventral arch domain (white arrowhead). prrx1a and prrx1b are upregulated in ventral arch NCCs (white open arrowhead) of edn1 mutants and nearly lost upon overexpression of Edn1 in hsp70I:Gal4; UAS:Edn1 embryos subjected to a 20–24 hpf heat-shock treatment. (G, H) prrx1a/b and barx1 are expressed complementarily in the arches of wild types. (I, J) Overexpression of Bmp4 in hsp70I:Gal4; UAS:Bmp4 embryos heat-shocked from 20–24 hpf resulted in broad upregulation of prrx1a/b throughout the arches, with barx1 restricted to domains showing lower prrx1a/b expression. (K) prrx1b overlaps only slightly with jag1b expression at the dorsal-posterior tips of the first and second arches (yellow arrows). (L) Schematic depicting the expression patterns of prrx1a/b (magenta), barx1 (green), and jag1b (blue). Scale bar = 20 μm.