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Fig. 8. Expression of Nieuwkoop, BCNE or Spemann organizer genes is not restored inβ -Catenin/Bmp4/Bmp7-depleted embryos. (A-D) Expression of Xnr6 in the vegetal dorsal side at blastula stage 9 in the Nieuwkoop center requires β-Catenin, is unaffected by knockdown of Bmp4/Bmp7, and is not re-expressed in β-Catenin/Bmp4/Bmp7 triple knockdowns. (E-L) Expression of the BCNE center genes Pintallavis/Hnf3β and Chordin at blastula stage 9 requires β-Catenin, is not affected by the depletion of Bmp4/Bmp7 and fails to be rescued in β-Catenin/Bmp4/Bmp7 triple knockdowns. (M-P) Chordin expression in the Spemann organizer at gastrula stage 10 is eliminated by β-Catenin depletion but is unchanged in Bmp4/Bmp7-depleted embryos. Note that embryos shown in panels D,H,L and P do not express any of the dorsal genes tested, yet still give rise to hyperdorsalized embryos with large head structures. (Q) RT-PCR analysis at stage 9. Dorsal markers are not expressed in embryos lacking β-Catenin orβ -Catenin/Bmp4/Bmp7. (R-V) A simplified model highlighting the interactions taking place at blastula stage between BMP signals and the dorsal BCNE and Nieuwkoop centers. |
