Concomitant occurrence of D-type apoptotic cells during neural plate morphogenesis. Time-lapse video of apoptosis during flipping of the neural ridge and bending of the neural plate, as shown in Fig. 3 C. The neural ridge of the midbrain–hindbrain of a SCAT3tg/+ embryo undergoing only closure I was observed. D-type apoptotic cells first appeared and continuously danced at the boundary ridge between the neuroectoderm (neural plate) and surface ectoderm. Some of them tumbled down the neural plate, as shown by tracking in the ECFP image (bottom left). As its ridge flipped and the neural plate bent, apoptotic cells were abundantly observed beneath the flipped neural ridge (the presumed dorsolateral hinge point, shown by arrows in the last frame of the video). Caspase activation is indicated by the V/C (1.0–0.5) using pseudocolor. Live imaging was performed on an inverted confocal microscope (TCS SP5). Frames were taken at intervals of 6 min for 12 h.
