Figure 4. The release of at least 1000 Sema3A molecules is necessary to induce GC repulsion.

(a) For N_v = 1900 after VB several filopodia retracted.(b) as in a but for N_v = 1,300. (c) as in a but for N_v = 1,042. In this case only 1 filopodium clearly retracted. (d), (e) and (f) as in a, but for N_v = 275, 19 and 12 respectively. (g) Collected data showing the relation between N_v and N_filolost. The linear least square fit of the experimental data (red curve) with a straight line of parameters a = 1.9 and b = 0.001 (chi-square two-tailed significance = 0.05) suggests that the presence of approximately 1,000 Sema3A molecules inside the vesicle are necessary to induce the repulsion of a single filopodium. Data were confirmed by statistical significance. Note that the results of N = 14 control experiments are illustrated by mean value and dispersion bar. Scale bar: 10 µm.