Fig. 1

Relative cell movement in wild-type tailbud shows increased fluidity in posterior tissues.

A Schematic of 10 somite stage (SS) zebrafish embryo with the tailbud at top (box), and closeup of major posterior tissues (right; blue and pink arrows are direction of cell motion and axis elongation, respectively). Kupffer’s Vesicle (KV) is indicated (gray oval). B Representative orthogonal confocal projections through 10 SS tailbud of Tg(h2afva:h2afva-GFP) embryo (nuclei; white) showing dorsal, parasagittal and transverse views (N = 5). Colored overlays indicate different tissues. C–F Analysis of cell movements in different posterior tissues (shading: SE). Normalized MSRD (C), velocity spatial (D) and temporal (E) autocorrelation, and average normalized velocity (F). MPZ: n_p = 3370 nuclear pairs (C), n_t = 3831 nuclear tracks (D–F) from N = 6 embryos; pPSM: n_p = 2356 (C), n_t = 2774 (D–F) from N = 6; aPSM: n_p = 1232 (C), n_t = 1479 (D–F) from N = 5; pDorsal: n_p = 2537(C), n_t = 2866 from N = 5; aDorsal: n_p = 2062 (C), n_t = 2348 (D–F) from N = 5. G Example of manual segmentation of the tailbud into dorsal (magenta) and ventral (cyan) tissues. H Representative Fluidity Index plot of nuclei from a single wild-type embryo. I Averaged fluidity index map of wild-type tailbuds (N = 5). J 2D velocity field of averaged cell movements in the tailbud. Arrowheads indicate position of the paired vortices and asterisk indicates position of the stagnation point. K Representative example of maximum intensity confocal projections of dorsal views of the tailbud with detected nuclei manually segmented into cells comprising PSM, notochord and dorsal tissue (N = 4). Nuclei were segmented in a transverse section through the tailbud at 0 min, and then tracked over the course of the 120 min timelapse, revealing relative movement between tissues. Scale bars: 100 µm; KV Kupffer’s Vesicle; MPZ Mesodermal Progenitor Zone; PSM Pre-Somitic Mesoderm. Source data are provided as a Source Data file.