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Fig. 5 ISH of manipulated embryos at 80% epiboly stage. Dorsal views. Insets show ventral views. (A) myf5 and myod mRNAs flank the dorsal midline in siblings (sib), but are absent or greatly diminished in tbx16−/− mutants. fgf4 mRNA injection widened notochord and induced ectopic myod and myf5 mRNA around the germ marginal zone of siblings, but did not rescue expression in tbx16−/− embryos. (B) tbxta mRNA reveals widened notochord (bars) in wild-type embryos injected with fgf4 mRNA. Both tbxta and tbx16 mRNAs show clumping in the germ ring after overexpression of fgf4. (C,D) ISH at 80% epiboly stage for myf5 and myod mRNAs in wild-type control or tbx16 mRNA-injected embryos treated with SU5402 at 10 µM (C) or 60 µM (D). myf5 and myod mRNAs are ectopically induced in posterior mesoderm by Tbx16 expression, but decreased by administration of 10 µM SU5402 in wild type, and rescued in SU5402-treated embryos by overexpression of tbx16. High dose SU5402 prevents MRF expression, even after tbx16 mRNA injection. Scale bars: 100 µm.