(A) Time-lapse imaging is carried out on tg(myl7:Gal4FF; UAS:H2A-GFP) embryos. In the 28 hpf panel, the dashed line indicates the position of the transversal section shown in the bottom left corner, in which the superior (S), inferior (I), right (R) and left (L) sides of the heart tube are defined. One representative heart is shown. A: anterior; P: posterior. (B) Total tracks (Ventral View). Each track is color-coded and is assigned an ID number. (C) Track displacement vectors for each single trace. (D) Track displacement vectors to be analyzed are selected, categorized by visual inspection and color-labeled accordingly. (E) Cardiac displacement vectors on the superior side of the ventricle and atrium and (F) on the inferior side of the cardiac chambers. (G) Displacement of cardiomyocytes at the outer curvature (asterisks) and (H) at the inner curvature (arrowheads) of the atrium are compatible with rotation of the chamber. (I–I’’') Computational unfolding and angular velocity measurement. (I-I'') Steps 1 and 2 (I, I') taken to computationally unfold the heart tube, resulting in the vector map shown in I''. The angular velocity of the cardiomyocytes is then calculated in the plane perpendicular to the axis (I'''). A detailed description of the methodology is available in the SI (J) Cumulative rotation angle for the ventricle (shades of red) and atrium (shades of blue) in wild-type hearts. Note the opposite direction of rotation of the two chambers. Positive values represent anti-clockwise rotation and negative values represent clockwise rotation with respect to the outflow of the heart. (K) Comparison of the average angular velocity for each replicate per 1.5 hr time window displayed by the chambers analyzed in (J). Horizontal bars: mean values. Scale bars: 100 µm.
