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Fig. 5. Activation of Otx2 target genes is required for trigeminal placode specification. (A), (B) Otx2-EnR inhibits Runx3 at stage 23 ((A); 59%, n=26; arrowhead: trigeminal placode on uninjected side). This is rescued by co-injection of Otx2 ((B) inhibition reduced to 17%, n=36). Inserts show higher magnification of the trigeminal region. (C), (D) At stage 28 the profundal and trigeminal placodes can be distinguished; both are reduced after Otx2-EnR injection (78%, n=18). Compare control (C) and injected side (D). (E), (F) Injection of Gbx2 splice and translation blocking morpholinos ((F) 0% affected, n=25) does not affect Runx3; compare uninjected (E) and injected side (F). (G), (H). Injection of Gbx2-EnR does not affect Runx3 ((H); 3% affected, n=31); compare control (G) and injected side (H). (I)–(K) Activation of Otx2-EnR-GR at stage 10 inhibits Pax3 the profundal placode ((J) 49%, n=33); no change is observed without DEX ((I) 5% affected, n=61; PR: profundal placode) or when added at stage 14 ((K) 5% affected, n=42). Magnifications show profundal region (dotted outline) on the uninjected (top) and injected side (bottom; FDX: turquoise). All embryos were injected into the A3 blastomere at the 32-cell stage. |
