Fig. 3

Pre-crossing commissural axon pathfinding is influenced by PCP components. a–c Confocal micrographs of CoPA axon pathfinding in WT and fzd3a ^rw689 embryos illustrating examples of CoPA axon trajectories. Anterior is to the left, dorsal is up. a CoPA axons have an anterior–posterior bias as they extend ventrally towards the midline. The majority of CoPA axons traverse ventro-anteriorly (A), straight ventrally (V), while a small proportion extend ventro-posteriorly (P). All CoPAs turn anteriorly by the time they have reached the contralateral spinal cord in wild-type embryos, b in fzd3a ^rw689 mutants, examples of pre-crossing CoPA axons that project ventro-posteriorly (P) and continue posteriorly after midline crossing, and a small number that project ventro-anteriorly before turning posteriorly after midline crossing, c in fzd3a ^rw689 mutants, pre-crossing CoPA axons that project straight ventrally (V) are more likely to make random A–P guidance as post-crossing fibers, d quantitation of the midline crossing points relative to cell body position among genotypes per embryo (*p < 0.05; ♦p < 0.01; Pearson Chi square test). e, f distribution of post-crossing axon trajectory relative to the pre-crossing directional bias in fzd3a ^rw689 and scrib ^rw468 mutants. Superimposed on the graph are representations of the appearance of CoPA trajectories