Fig. 1. S1P induces rapid collapse and repulsive turning of Xenopus retinal growth cones. (A) S1P caused collapse in a dose-dependent manner of stage 32 retinal growth cones cultured for 24 hours. (B) S1P (0.1 µM) and LPA (1 µM) induced a transient collapse of stage 32 retinal growth cones cultured for 24 hours. (C) The morphology of a retinal growth cone before bath application of S1P. (D) A collapsed retinal growth cone 10 minutes after S1P application. (E) Recovery of a growth cone after 60 minutes of S1P treatment. For D,E, the concentration of S1P used was 0.1 µM. (F,G) Cumulative frequency graph showing the distribution of growth cone turning angles after 60 minutes in the presence of a S1P or control gradient. Most of the turning angles are negative compared with control, indicating that S1P is repulsive to growth cones. (G) Mean turning graph from data in F. (H) 24-hour cultured stage 32 retinal growth cone before being exposed to a S1P gradient. (I) After 60 minutes the growth cone is repelled by a gradient of S1P. Numbers inside bars indicate growth cones tested. ^*P<0.05, ^**P<0.01, Mann-Whitney U test. Scale bars: in C, 10 µm for C-E; in H, 20 µm for H,I.