cxcr4b or cxcl12a deletion does not affect pronephros cell migration. a Collective cell migration in the zebrafish pronephros was quantified, using a cxcr4b:H2B-RFP; cldnb:GFP double transgenic zebrafish line (upper panel, see Supplementary Movie 4). The transgene cxcr4b:H2B-RFP labels the nuclei of cells that express RFP under the control of the endogenous cxcr4b promoter; cldnb:GFP labels the membranes of pronephric duct cells. The pronephros and the corpuscle of Stannius are outlined with dashed lines. The arrow points to the corpuscle of Stannius (scale bars, 10 µm). A model of collective cell migration was generated (lower panel), using the image tool Imaris. The migration of ca. 40 pronephric nuclei was tracked over 8 h, starting 48 hpf. The tracks for each cell were calculated and represented as lines. The observation times were coded by blue-to-green colors; blue are early time points and green are later ones (see Supplementary Movie 5). b The mean track speed and displacement length, i.e., the length that a cell traveled over the observation period were measured at 36 and 41 hpf for 3 h, and at 48 hpf for 8 h. Deficiency of cxcr4b (left panel) or cxcl12a (right panel) did not affect track speed (left panel). c Deficiency of cxcr4b (left panel) or cxcl12a (right panel) did not affect displacement length. Note that the displacement length is larger in the 48–56-hour-interval, because cells were tracked for a longer time period (8 h) in comparison with the earlier time points (3 h each). In contrast, the speed did not change significantly over time (n.s., not significant; t-test)
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