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Fig. 2
Apical constriction undergoes pulsatile activity.
(A) Maximum projection of Z-planes extracted from a spinning-disk confocal TL sequence performed on a 48 hpf Tg(fli1:Gal4; UAS:RFP; UAS:eGFP-ZO1) embryo. Yellow arrowheads: regions enriched with eGFP-ZO1, at the two opposite poles of the EHT cell contacting endothelial neighbors and converging until coalescence (see Figure 2—video 1). Time is indicated in hr:min. Scale bars, 10 μm. (B–C) Spatio-temporal analysis of two cells (see also Source code 1). Top panels obtained from the cell visualized in (A) and bottom ones from a second cell. (B) Tracking of two spots delineating regions of eGFP-ZO1 densification, after maximum projection. Top and bottom panels are showing tracks of antero (black) and posterior (green) eGFP-ZO1 spots for a single cell each. X and Y correspond to the antero-posterior and dorso-ventral axis, respectively. Each point corresponds to the position in X,Y of the spot at a given time point. The lines link two successive time points. Note that when one spot is not detected, the line is interrupted. The anterior track is the longest track in 30% of cases, n = 10 (not shown); The posterior track is the longest track in 60% of cases, n = 10 (bottom panel); note that in 1/10 cells, the displacement of the antero and posterior spots were virtually equal (top panel). (C) Evolution as a function of time of distances (green) and closing speeds (red) of the two eGFP-ZO1 spots. Note that breaking of tracks and lines result from sporadic loss of signal. (D) Representation of the calculated periods of oscillatory closing speeds (39.7 min ±2.6 min). Error bars represent mean values ± SEM (n = 8 TL sequences).