Figure 5

Tracking of pioneer axon growth through the optic chiasm highlights differential effects of Slit2 and Slit3 loss I: analysis of axon trajectories and velocities. 2D tracking analysis of RGC axon growth along the optic nerve, optic chiasm and proximal optic tract, from time-lapse experiments starting at 30 hpf, shown in Figure 4. (A). Axon trajectories across the ventro-dorsal and medio-lateral axes, for non-injected and crispant embryos. The gray bracket marks an area of higher spatial dispersion and/or apparent axon growth deviations in the slit2 crispants. (B). Instantaneous growth cone velocities compared to the medio-lateral axis along the optic pathway. The gray bracket marks an area of higher velocity dispersion and/or apparent axon growth deviations in the slit2 crispants. (C). Diagram showing a cross-section of a 30 hpf zebrafish embryo at the level of the optic chiasm, highlighting the approximate area analyzed in the time-lapse tracking experiments, with an example of the trajectory of a wild-type axon. Di: diencephalon; L: lens; NR: neural retina; OC: optic chiasm; ON: optic nerve; OT: optic tract. (D,E). Instantaneous velocities for the four experimental situations, analyzed as a pool (D) or averaged per embryo (E). In all cases, the data were analyzed and compared either for the whole axon path tracked, the optic nerve portion or the optic tract portion, as noted at the top. The gray brackets in (D) highlight several negative velocity values in the slit2 crispants. Mean ± SD; statistical significance is shown as asterisks (*: p < 0.05; ***: p < 0.005) and analyzed using the Brown-Forsythe and Welch test for multiple comparisons.