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Fig. 2 her1 oscillation is induced by Fgf. (A) Expression of fgf8a at the mid (left) and late (right) epiboly stage. (B) her1 expression disappears following treatment with the Fgf inhibitor SU5402. Left and right panels show her1 expression at the stage before (7.0 hpf) and after (9.0 hpf) the emergence of the traveling wave, respectively. (C-G) Ectopic Fgf induces an ectopic her1 traveling wave. (C) Ectopic expression of spry4 was induced by Fgf8b-soaked bead implantation (arrowhead). (D) Ectopic her1 expression (arrow) is first detected in close vicinity to the Fgf bead (left, 0.5 hours after transplantation) and tends to gradually expand with time, forming a band-like expression domain (right, 1.5 hours after transplantation). (E,F) Subcellular localization of induced her1 expression. (Ga-c) Induction of the traveling wave by Fgf bead transplantation occurs only in the hypoblast. Optical sections of the sample shown in E,F along the z-axis (Ga), x-axis (Gb) and y-axis (Gc). x- and y-axes are shown by white and red lines, respectively, in Ga. Hypoblast and epiblast are indicated by arrowheads and asterisks, respectively. (H,I) The regions of Fgf activity, as indicated by spry4 (H), and her1 expression (I) are almost identical. (J) Time-course analysis of the width (in cells) of spry4 and her1 expression. The number of cells showing nuclear signals was manually counted in samples subjected to high-resolution in situ hybridization (images not shown). Error bars indicate s.d. Scale bar: 50 μm.