Figure 4.

Stage 5 blastoderm embryos show a complex pattern of nuclear densities. (a) A schematic representation of how information calculated on the three-dimensional surface constructed from a PointCloud was projected onto a surrounding cylinder and the cylinder was then unrolled to produce a planar map. In these cylindrical projections, anterior is to the left, posterior to the right, the dorsal midline is at the top and bottom, and the ventral midline is in the middle. The distance along the a/p axis is given as a percent egg length (EL). (b-d) Average local nuclear density maps were computed from 294 embryos. The maps in (b,d) were computed from the 'top' and 'bottom' portions of each embryo image only, where the segmentation is most accurate. The map (c) was computed from the 'sides' only. The two maps broadly agree, but on the sides of the embryo images the segmentation algorithm has underestimated the number of nuclei dorsally and overestimated the number ventrally. Isodensity curves were plotted over a color map representing local average densities from 0.025 nuclei/μm² (dark blue) to 0.05 nuclei/μm² (dark red) (b,c). The average expression patterns of eve (green) and snail (red) are shown with the isodensity contour (d). The most anterior stripe of eve follows a ridge of locally high density, and the boundaries of snail expression follow contour lines along about half the length of the embryo.