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Fig. 4. Otx2 is a direct activator of Wnt1, Xgbx2a and Pax2. RNA encoding the hormone-inducible form of Otx2 was injected unilaterally (the injected side is indicated with an asterisk) together with LacZ mRNA. Cycloheximide was added 30 min prior to the activation of Otx2/GR by dexamethasone to inhibit protein synthesis. The embryos were fixed 2.5 h after the addition of dexamethasone and the expression of Wnt1 (A–D), Xgbx2a (E–H) and Pax2 (I–L) was studied. (A) Expression of Wnt1 in the absence of dexamethasone. (B) Activation of Otx2/GR by dexamethasone resulted in Wnt1 expression along the neural tube. (C) Cycloheximide treatment inhibited the normal endogenous expression of Wnt1. (D) Broad ectopic expression of Wnt1 was observed in embryos incubated with dexamethasone and cycloheximide. The endogenous domains of Wnt1 were inhibited by the cycloheximide treatment. (E) Control Xgbx2a expression in the absence of dexamethasone. (F) Activation of Otx2/GR induced broad ectopic activation of Xgbx2a at the edges of the injected region. (G) Inhibition of protein synthesis causes a general increase in Xgbx2a transcription. (H) Xgbx2a is ectopically activated in embryos incubated with dexamethasone in the presence of cycloheximide. (I) In the absence of activator, Otx2/GR does not affect the normal Pax2 expression. (J) Pax2 is broadly activated in embryos treated with dexamethasone. (K) Inhibition of protein synthesis does not affect the MHB-specific expression of Pax2. (L) In the presence of cycloheximide and dexamethasone Pax2 is activated in the injected side (arrow). |
