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Fig. 3. Otx2 induces ectopic expression of Wnt1, Pax2 and Xgbx2a. Embryos were injected unilaterally with Otx2/GR and LacZ mRNA as a lineage tracer. Dex was added at stage 11. The injected side is marked with an asterisk. The lineage tracer was detected by in situ hybridization with a LacZ probe (turquoise) in (A,B,E,F) or with LacZ enzymatic activity (red) in (C,D). (A) In untreated embryos at stage 20, Wnt1 is expressed at the MHB (black arrow) and along the dorsal midline posterior to rhombomere 2 (white arrow). (B) The expression of Wnt1 in the Otx2/GR-injected side is strongly activated, creating an uninterrupted line of expression from the MHB to the posterior region of the embryo. (C) Pax2 normal expression at stage 22. The two main sites of expression are the MHB (black arrow) and the otic vesicles (white arrow). (D) On the non-injected side Pax2 expression remains unchanged. On the Otx2/GR-injected side, the MHB and the otic vesicle domains of expression are combined creating a large Pax2-expressing patch situated posterior to the normal MHB. (E) Embryo injected with Otx2/GR RNA but not treated with dex. In untreated embryos at stage 18, Xgbx2a is expressed in the MHB and the lateral epidermis. (F) Otx2/GR overexpression resulted in strong ectopic expression of Xgbx2a in the dorsolateral region of the embryo at the edges of the lineage tracer staining. (G) Normal Fgf8 expression in stage 23 embryos. The weak Fgf8 expression across the MHB is observed (black arrow). (H) Fgf8 expression in embryos unilaterally expressing Otx2. The change in the Fgf8 pattern of expression as a result of Otx2 activity can be seen (arrowheads). The Otx2-injected sides are marked (*). |
