Supplementary Figure 5: Alignment of polarised cells in the embryo.
(a) Alignment of cells with a shape eccentricity of >0.87 in various domains before and during streak formation. The percentages show how many cells in each domain have eccentricity >0.87. It is evident that all ready at the beginning of development before the onset to motion (1 h) cells in the posterior Area Opaca are aligned perpendicular to the direction of the forming streak and that the number of polarised cells increase during the onset of motion (4.2 h) after which their fraction and orientation decreases again (7.3 h). Scale bar in each panel is 200 μm. (b) Tissue texture tensor (red bars). The tissue texture tensor is calculated from centres of mass of all cells in a given domain as described in detail in methods. The length and spatial orientation of the tensors shows that cells in the posterior embryo are initially aligned along their long axis. With the onset of streak formation the cells become smaller and the alignment becomes less pronounced supporting the data shown in fig S3a, S5a. White scale bar is 200 μm. The yellow scale bar corresponds to the tensor magnitude of 200 μm2 and a domain speed 4 μm/min.
