(A) Drosophila embryonic hindgut visualized by UAS-myr-GFP (membrane in green) and UAS-redstinger (nuclei in magenta) driven by byn-Gal4, starts to rotate at late stage 12, when the germ band is almost completely retracted (dashed line in A1). The hindgut rotates anticlockwise (A2) and completes the rotation in 2 hr, exhibiting a rightward pointing hook shape (A3). Time after the start of rotation is indicated at upper right. (B) Schematic of the hindgut before rotation. Lateral (left), dorsal (right), and posterior (bottom) views are shown. The hindgut is LR symmetric with the hook shape pointing in the ventral direction. The regions observed in the displacement measurements are indicated by red (dorsal) and blue (ventral) rectangles. (C, D) Cell nuclei in the dorsal (C) and ventral (D) sides of the hindgut, schematically shown as red and blue circles in B (posterior view), respectively, visualized by byn-Gal4 and UAS-redstinger (C) or UAS-stinger (D). Three central columns of cells are marked by colored circles. Cells slid leftward on both the dorsal and ventral sides. (E) Schematic of the displacement quantification. The coordinates of two cells located along the anterior-posterior axis at two time points were observed. The subjacent cell was set at (0,0), and the relative displacement of the upper cell in the x direction was measured. (F) Quantification of the cell movement during wild-type hindgut rotation. Dorsal cells showed minus directional movement (red bar, n = 126, N = 5) while ventral cells showed plus directional movement (blue bar, n = 78, N = 12), indicating that the cells on both sides moved leftward. Cells in the rectum region (shown as a control, ctl) did not show LR displacement (open bar, n = 91, N = 5). Error bars indicate SEM. *, p<0.05. For all images, anterior is up. A, anterior; P, posterior; L, left; R, right.