DEV02578 Supplementary Material

Files in this Data Supplement:

• Supplemental Figure 1 -

  Fig. S1. Graphical representation of a round cell that shows the geometrical definition of each division type by its angle range (A) and the surface area corresponding to this angle on the sphere (A,B). The apical domain, which is normally pigmented, is shown as a brown ‘cap’. Divisions where the cleavage plane (light-blue line) does not bisect the apical domain are perpendicular, those where the apical domain is cleaved unequally are oblique, whereas those that cleave the apical domain about equally are parallel. Perpendicular divisions take place when the spindle axis (purple) falls within α1, oblique within α2 and parallel within α3. Although these angles are equal (α1=α2=α3=30^o), the surface area of the sphere that corresponds to each of these is not equal (shown by red, green and blue, respectively in A and B). The corresponding surface areas were calculated trigonometrically and expressed as percentages of the total surface of the sphere. From this geometrical argument, proportions of 13% perpendicular, 36% oblique and 51% parallel are expected in randomly dividing round cells when division outcome is scored with respect to the pigmented cap on the surface. These proportions correspond well with the percentages of division types we have found in isolated cells (see Fig. 2B,C). If divisions are random, the smaller the surface area, the less chance that the division would bisect it.

• Movie 1 -

  Movie 1. Rotation of the 3D reconstruction of the parallel dividing pair of cells shown in Fig. 1I. This pair of cells was generated by a previous parallel division as indicated by the position of the midbody remnant.

• Movie 2 -

  Movie 2. Rotation of the 3D reconstruction of the pair of cells shown in Fig. 1J. One will divide perpendicularly and one parallel. They are the product of an oblique division as indicated by the position of the midbody remnant and unequal apical surface size.

• Movie 3 -

  Movie 3. Time-lapse movie of the divisions of an early Xenopus embryo. (Time interval between frames is 1 minute.) A cell is framed that undergoes two consecutive perpendicular divisions, generating one inner and one outer cell in each division. This cell has a small apical surface and is the product of an oblique division. As this cell divides perpendicularly, when viewed from the surface it appears not to divide, whereas the neighbours do. The divisions of the early Xenopus embryo are synchronous.

• Movie 4 -

  Movie 4. Long axis division (LA) in Fig. 4A. Cell of an embryo injected with tau-GFP. The spindle is set up in the long axis before metaphase. Time interval between frames: 100 seconds.

• Movie 5 -

  Movie 5. Rotation into long axis (RLA) division in Fig. 4A. Cell of an embryo injected with tau-GFP. At prometaphase the spindle axis is not aligned with the long axis of the cell. Rotation into the long axis occurs at late metaphase. Time interval between frames 80 seconds.

• Movie 6 -

  Movie 6. Rotation into the short axis (RSA) division. The occurrence of these divisions is rare. Time intervals between frames: 95 seconds.

• Movie 7 -

  Movie 7. Corresponds to Fig. 7A. Cell of an embryo injected with EB1-GFP. EB1 signals become reduced before metaphase, are absent during metaphase and increase again at anaphase onset. Image stacks of ∼15 μm imaging depth were collected on a spinning disc confocal microscope. 101 frames are shown and the time intervals between frames are 15.3 seconds.