The temporal state of the notochord changes with the alteration of BMP activity. The expression of chordamesoderm markers in embryos with reduced BMP activity is strongly reduced, resembling older embryos. Fstl1/2 morphant embryos maintain expression of these genes well past equivalently staged controls, resembling the expression patterns observed in younger embryos. (A-D,U-W) ihhb expression in 9-somite (A-D) or 18-somite stage (U-W) embryos. (E-L,X-CC) shha expression in 24 hpf (E-L) and 36 hpf (X-CC) embryos. (I-L,AA-CC) High-magnification view of the trunk. (M-P,DD-FF) ptc1 expression in 24 hpf (M-P) and 36 hpf (DD-FF) embryos. (Q-T,GG-II) col2a1a expression in 36 hpf (Q-T) and 48 hpf (GG-II) embryos; arrows in R-T indicate absence of floorplate expression; arrows elsewhere indicate the shift in chordamesodermal gene expression relative to controls. nc, notochord. All views are lateral, with anterior towards the left. Insets in A-D are flat-mount dorsal views. (Q-T,GG-II) Lateral views of the trunk. Insets in DD-FF indicate higher magnification views of the boxed areas.
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