Fig. S1.

(A) a–f, Lateral view of the head region; g, ventral view of the head region; b′–g′, sections at the level of the forming eye stalk as indicated by the red dashed lines. Though pax2, vax1, and mid1 are clearly expressed within the forming eye stalk, their pattern of expression in this part is not identical and appears to follow a proximodistal axis with mid1 more distally, pax2 centrally, and vax1 proximally located. (B) a, dorsal view; a′, anterior view; a1, transversal section as indicated in a. The misexpression of shh upon the microinjection of synthetic 500 pg shh RNA induced the expression of ptc1 strongly at the open neural tube stage (NF stage 15) within the sensorial layer of the ectoderm (a1′) and this induction of ptc1 is maintained though less intense at tadpole stage (see also Fig. 1 B, d–d′). (C) a and b, anterior view. Misexpression of pax2 upon the microinjection of synthetic 100 pg pax2 RNA repressed the expression of pax6 already at the open neural tube stage (NF stage 15) and this suppression of pax6 is maintained at tadpole stage (see also Fig. 1 B, h–h′).