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Fig. 4
a, b For quantitative analysis, we considered cells circumferentially arrayed in a row (A1–A5, each cell array is shown in a different color in b) as a unit. a Selected images from a confocal time-lapse recording of a Tg(myl7:EGFP-CAAX)ncv536Tg embryo starting at 19–20 hpf. Dorsal view (anterior to the top). Scale bar = 50 µm. b Colored, corresponding images to those in a. Cells in the left primordium (colored cells) were analyzed. Cell arrays are numbered from the inner to the peripheral order (A1–A5). We measured the length of each cell array (black line in c), the length of constituent cells (blue lines in d) and the overlap length between neighboring cells (red lines in d) every 1 h. c A cell array is indicated by magenta. d Enlargement of the region indicated by the box in c. e Relative length changes of cell arrays (black), cells (blue), and loss of the cell lengths caused by the cell overlap (red) in five cell arrays (e1, A1–A5 indicated in b), in the peripheral cell arrays (e2, A3–A5) and in the inner cell arrays (e3, A1–A2). Magenta plots represent the sum of relative changes of cell length (blue) and the length loss by the cell overlap (red). n = 5 cell arrays, 4–8 cells per each cell array (1 embryo). Data are normalized relative to sum of cell lengths at the initial time point to eliminate the effects of each cell array size. Means ± s.d. are shown. Corresponding graphs indicating individual data points are shown in Supplementary Fig. 2. f Model for convergence of the cardiac disc based on our quantitative analysis. Circumferential convergence is initially driven by oriented cell rearrangement and subsequently by cell shortening.