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Fig. 7. FoxB1 collaborates with Oct-25 in the process of neural induction. (A–H) FoxB1 acts together with Oct-25 to promote neural development. Together with β-gal mRNA, FoxB1 MO (34 ng; A and B), Oct-25 MO (8.6 ng; E and F), or a combination of both MOs (C and D) were injected unilaterally into both dorsal and ventral animal blastomeres of 8-cell stage embryos. Total amount of injected MO (42.6 ng per embryo) was adjusted by adding Control MO in each experimental group. For rescue experiments, a mixture of MOs and either Nmut-FoxB1 (1000 pg; G) or δBMPR mRNA (1000 pg; H) was injected as described above. Inhibition of both FoxB1 and Oct-25 function resulted in a marked reduction in the expression of Sox2 (arrowheads, C), and also caused the expression of epidermal keratin to extend into neural plate territory (arrowheads, D). Expression of Sox2 (A, C, E, G and H) and epidermal keratin (B, D and F) analyzed by in situ hybridization is shown in purple and β-gal is stained in red. The injected side of the embryo is indicated by brackets. A, C, E, G and H: dorsal views with posterior to the top; B, D and F: anterior (front) view with dorsal to the top. (I) FoxB1 is in part required for neuralization of the ectoderm by Oct-25. A mixture of mRNA and MOs was injected into animal poles at the 4-cell stage: GR-Oct-25 mRNA (1000 pg), Nmut-FoxB1 mRNA (500 pg), Control MO (68 ng), and FoxB1 MO (68 ng). Ectodermal explants were isolated at the blastula stage, treated with DEX to activate Oct-25 and cultured until early neurula (st. 16) or late neurula stage (st. 23). The QPCR data are shown as arbitrary units normalized to ODC expression. (J) FoxB1 and Oct-25 form a regulatory network essential for neural induction processes, which resembles the motif of feed-forward loop networks (K). See Discussion for details. |
