Figure 3.

The mode of cell division is regulated by intrinsic programs, not environmental influences. (A) Quantification of midline crossing for isochronic and heterochronic cells; *P <0.01, KS test. n = number of embryos. (B) Schematic illustrating the three different modes of cell division orientation that occur at neural rod and tube stages. (C) Quantification of the mode of cell divisions for older host cells and younger transplanted cells. A significantly greater proportion of younger transplanted cells divide with a C-mode of division orientation compared to older host cells; *P <0.01, χ² test. (D) Series of frames from a timelapse movie to illustrate a young cell (circled red nucleus) dividing with a C-division orientation, and a neighboring host cell (circled green nucleus) dividing with a D-division orientation. See also Additional file 3: Movie S3. (E) Sequence of timelapse frames of an old cell expressing green fluorescent protein/polarity protein partitioning defective 3 fusion (Pard3-GFP) transplanted into young host. During cytokinesis Pard3-GFP is localized to the abscission plane (arrowed) as is typical of cells at neural rod stages but not at earlier stages of development.