Figure 8

(A–L) Embryos were injected with 75 pg of Sqt^{ActβB[loopβ8]} mRNA (A–C), 75 pg of Sqt^{ActβA[loopβ8]} mRNA (D–F), 200 pg of Vg1^{ActβB[loopβ8]} mRNA (G–I), or 200 pg Act^{Sqt[Finger1-loopβ8]} mRNA (J–L). Embryos were further double-injected with either 500 pg of LacZ mRNA (A, D, G, and J), 100 pg of lefty1 and 400 pg LacZ mRNAs (B, E, H, and K), or 500 pg of lefty1 mRNA (C, F, I, and L). gsc mRNA expression in wild-type zebrafish embryos is shown at shield stage, animal pole view. Note that both levels of Lefty1 cannot inhibit the ectopic gsc expression induced by Sqt^{ActβB[loopβ8]} (B and C), Sqt^{ActβA[loopβ8]} (E and F), and Vg1^{ActβB[loopβ8]} (H and I). In contrast, Lefty1 can inhibit Act^{Sqt[Finger1-loopβ8]} (K and L).

(M) Wild-type embryos were injected with 75 pg of either Sqt^{ActβB[loopβ8]}, Sqt^{ActβA[loopβ8]}, Vg1^{ActβB[loopβ8]}, or 200 pg of Act^{Sqt[Finger1-loopβ8]} mRNA. Embryos were further double-injected with 500 pg of LacZ mRNA, 100 pg of lefty1, and 400 pg of LacZ mRNAs, or 500 pg of lefty1 mRNA. Smad2 pathway activation was measured by an Activin response element luciferase reporter, A3-luc. Values are folds over wild-type control injected with 500 pg of LacZ mRNA and A3-luc reporter. An asterisk indicates a significant difference from the level of activation with ligand and LacZ expression alone (Student's t-test, p < 0.05).