Disruption of the temporal state of the notochord can be observed through notochord cell morphology. (A,C,D) 24 hpf control embryos; notochord cells differentiate in an anterior to posterior manner. High magnification view of notochord cells at the level of the hind yolk extension (C) and at the level of the cloaca (D). (B,E,F) 24 hpf Fstl1/2 morphants. High magnification view of notochord cells at the level of the hind yolk extension (E) and at the level of the cloaca (F). (G-L) 24 hpf tBR embryos heat-shocked at 80% epiboly (G,H) and Bmp4 morphants (I,J). (K-N) Application of cell cycle inhibitors in wild-type (K,L) and Fstl1/2 morphants (M,N). (O) Cell transplantation procedure. See text for details. (P,Q) Wild-type donor cells (green) populating the notochord of tBR embryos do not enlarge and vacuolate prematurely (Q). (R,S) tBR donor cells (green) consistently fail to populate the notochord of wild-type hosts; instead, they contribute to tissues in paraxial mesoderm. All views except R are lateral views of 24 hpf embryos with anterior towards the left. (R) Dorsal view with anterior towards the left. Red outlines indicate notochord cell morphology.
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