Fig. S3

Behavior of the nVII motor neurons compared with the neighboring neuroepithelial cells. (A,B) To compare the behavior of the nVII motor neurons with the neighboring neuroepithelial cells, we observed mosaic embryos obtained by the transplantation of WT>WT (A) and ord>ord (B) Isl1-GFP embryos. The donor cells labeled with rhodamine-conjugated dextran (red) were incorporated into the neuroepithelium. Behavior of the nVII motor neurons (green) was shown at the time indicated in each panel (hpf). In the wild-type embryo, the nVII motor neurons migrated caudally relative to the neighboring cells and they were associated with the pial surface of the brain (A). By contrast, in the ord embryo, one of the nVII motor neurons (indicated by arrows) became detached from the pial surface of the brain (B). Single optical planes are shown in dorsal view. Pial surfaces of the brain are indicated by lines. Double-headed arrows indicate midlines of the embryos. (A′,B′) Schematic drawings of each panel. (C,C′) Single optical plane of a cross section at r5 from a mosaic embryo obtained by the transplantations of WT>WT Isl1-GFP embryos at 24 hpf. The donor cells labeled with rhodamine-conjugated dextran (red) were incorporated into the neuroepithelium. Most of the labeled neuroepithelial cells were round in shape (C). However, when the images were obtained at a higher amplified gain (C′), long processes associated with ventricular and pial surfaces were detected (arrows in C′). These results suggest that the rhodamine-conjugated dextran strongly stained cell bodies around the nuclei, but weakly stained cellular processes in the neuroepithelial cells. Pial and ventricular surfaces are indicated by broken lines. Because most of the mosaic embryos were observed at lower gains to reduce the noise, the long neuroepithelial processes were not imaged.