Fig. 5. Adding FGF2 to slices increased motility of migrating PGCs. The reverse effect was seen in slices cultured with the FGFR inhibitor SU5402. Time-lapse movies are available in the supplementary material. (A) The first (frame 1), middle (frame 50) and last (frame 100) frames from a single movie are shown as an example of cell tracing. Numbered germ cells were traced. Germ cells marked `X' moved out of the plane of focus during filming, and were not traced. When PGCs divided, one of the siblings was traced. (B) Typical trajectories of migrating PGCs in controls, 10 ng/ml FGF2-treated slices, 100 ng/ml FGF7-treated slices and 10 µM SU5402-treated slices. Trajectories of PGCs were acquired using NIH image software. The green lines, connecting notochord (n) and the midline of hind gut (g), indicate the dorsoventral axis. Red arrows show the direction of PGC migration. In all treatments, PGCs showed directional movement towards the genital ridges. Trajectories were extended by FGF2 treatment, and shortened by SU5402 treatment. (C) Summary of PGC velocity data from six control, three FGF2- and FGF7-, and four SU5402-treated slices. Six to eight cells in each slice were analyzed. Mean, mean velocity for the whole culture period; Max., maximum velocity in any 35-minute period of culture. Error bars show the s.e.m. (D) PGCs exhibited exaggerated processes when exposed to FGF2. Every 10 frames, the percentage of PGCs showing processes was scored. In contrast to FGF-treatment, the formation of processes was inhibited in SU5402-treated slices. Pictures of PGCs taken from frame 40 of each treatment are shown in D. Asterisks in C and D indicate a degree of statistical significance (P<0.05) of increase (^*) and decrease (^**) compared with controls. Scale bars: 100 µm for A,B; 50 µm for D.