Fig. 2. Presumptive hypochord precursors express notch5 and her4. (A,B) Dorsal views, anterior towards the top, of 8.5 hpf (A) and 9.5 hpf (B) embryos probed for notch5 expression. Cells near the dorsal midline express notch5 (arrows). (C,D) Dorsal views, anterior towards the top, of 8.5 hpf (C) and 9.5 hpf (D) embryos probed for her4 expression. Cells near the dorsal midline express her4 (arrows). (E) Sagittal section, anterior towards the left, of 9.5 hpf embryo probed for notch5 expression. Deep mesendodermal cells express notch5 (arrows). (F) Transverse section of 9.5 hfp embryo probed for her4 (blue, arrows) and myod (red) expression. Adaxial cells, marked by myod expression, do not express her4. (G) Transverse section of 10 hpf embryo probed for notch5 (blue, arrows) and myod (red) expression. myod-positive adaxial cells do not express notch5. (H) Dorsal view, anterior towards the top, of 9.5 hpf embryo probed for her4 (blue) and ntl (red) expression. Broken lines indicate approximate positions of transverse sections shown in I,J. (I,J) Transverse sections of 9.5 hpf embryo probed for her4 (blue) and ntl (red) expression. (I) Posterior transverse section with several double-labeled cells (arrows). (J) Anterior transverse section in which one her4-positive cell expresses ntl (arrow) whereas two others do not. (K) Transverse section of 9.5 hpf embryo probed for notch5 (blue, arrows) and ntl (red) expression. The notch5-positive cell on the right expresses ntl whereas the one on the left does not. (L) Transverse section of 9.5 hpf embryo probed for notch5 (blue) and her4 expression. Cells bordering the midline express both genes (arrows). (M) Transverse section of 11.5 hpf embryo probed for her4 expression. A single hypochord cell (arrow), ventral to notochord (nc), and neural keel (nk) cells expresses her4. (N) Transverse section of YPC stage embryo probed for notch1a expression. Many dorsal mesoderm cells express notch1a. Scale bar: 100 µm for A-D,H; 50 µm for E; 25 µm for I-N.