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Fig. 7 zic3 E1 is regulated by Wnt, BMP and FGF signaling, and zic3 E2 is regulated by Wnt and BMP signaling. (A-F) dkk1 was overexpressed by heat shock in embryos with zic3 E1:GFP or zic3 E2:GFP. dkk1 overexpression beginning with a 75% epiboly heat shock decreases zic3 E1 activity (100%, n=23) (B versus A) and slightly decreases zic3 E2 activity (88%, n=50) (E versus D). The NPB activity of both enhancers is almost completely lost, with dkk1 overexpression induced with a shield stage heat shock [E1, C versus A (100%, n=21); E2, F versus D (100%, n=55)]. (G-L) bmp2b was overexpressed by heat shock. zic3 E1 loses activity in the posterior NPB and shifts medially in the anterior (H, bar) upon bmp2b induction with 75% epiboly heat shock (93%, n=29) (H versus G). Shield-stage heat shock causes a dramatic reduction of E1 activity throughout and causes a drastic medial shift (I, bar) (96%, n=23) (I versus G). zic3 E2 activity does not change when bmp2b overexpression is induced with a 75% epiboly heat shock (79% with wild-type GFP level, n=38) (K versus J), but decreases with a shield-stage heat shock (100%, n=24) (L versus J). (M-P) SU5402 treatment beginning at 65% epiboly dramatically decreases zic3 E1 activity (100%, n=27) (N versus M), but not zic3 E2 activity (81% with wild-type GFP level, n=22) (P versus O). All E1 pictures are dorsal views of the trunk with anterior upwards; all E2 pictures are anterior dorsal views with anterior upwards.