FIGURE 6.

Somitic mesoderm morphogenesis affects the ratchetting of contraction pulses during apical constriction. (A) Stills from a time lapse recording of a control neuroepithelial cell during apical constriction. Red arrowheads: pulsed medioapical actin accumulation. Scale bar: 20 μm. (A’) Outline of the apical cell surface area at 0 and 34 min showing reduction of apical cell surface area. (B) Stills from a time lapse recording of a neuroepithelial cell overlying Wee2 morphant somitic mesoderm during apical constriction. Red arrowheads: pulsed medioapical actin accumulation. Scale bar: 20 μm. (B’) Outline of the apical cell surface area at 0min and 34 min showing defective reduction of apical cell surface area. (C,D) Quantification of medioapical actin intensity and apical cell surface area over time. (C) 4 control neuroepithelial cells. (D) 4 neuroepithelial cells overlying morphant somitic mesoderm. Medioapical actin accumulation (red line) is followed by reduction of the cell surface area (black line) in control cells. The cell surface area is not reduced upon apical F-actin accumulation in neuroepithelial cells overlying morphant somitic mesoderm.