Additional file 3.

Analyses of Ea/Ep internalization and apical dynamics. (A) Morphometric analysis of apical cell shape. (Top left) Drawing depicting the directions in which the measurements were performed. Flatness was calculated using the depicted formula 20]. Shapes were measured from two-dimensional (2D) confocal images (mean ± SD, n = 3). (B) Ea/Ep are arc-shaped during internalization. Ventral (blue), sagittal (green)m and transverse (yellow) views of the Ea/Ep apical surfaces generated by projecting three-dimensional (3D) volume data in the respective direction. (C) Flows of contractile foci on Ea shortly after cell birth and during internalization. Superimposition of five consecutive frames from cortical projection stills recorded at 2-second intervals. Streams of non-muscle myosin (NMY)-2 foci are highlighted by arrowheads. (D) Kymographs of contractile flows on Ea starting at time points corresponding to (A), and generated along a line similar to the white dashed line in Figure 1A. Arrows indicate local contractile flow convergence that led to extension advancement. (E) Transient covering of cells by lateral extensions. (Top) Cortical views of ABplapp. Dashed lines outline the extensions of surrounding cells, and progression of covering and resurfacing is shown in the bottom right frame. (Bottom) Quantification of the degree of covering over time (mean ± SD, n = 3). (F) Apical dynamics of Partitioning defective (PAR)-6 (representations as in Figure 1A). White arrows mark the accumulation of PAR-6 on the apical surface of Ea, red arrow marks the accumulation on ABalppp, which later internalized later (see Figure B). White lines denote sister cells. (G) Repolarization of Ea/Ep during internalization. (Left) Side view of Ea with average projection of 2 focal planes at 1 um apart in the middle of the embryo. (Right) Quantification of PAR-2::GFP along the perimeter of Ea (inside the white dashed lines) in counterclockwise direction from the gray arrow to the black arrow.

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Pohl et al. BMC Biology 2012 10:94   doi:10.1186/1741-7007-10-94