Figure 7. Midline crossing of apical protrusions occurs more frequently when KLC function is disrupted.

(A–B) Confocal projections (dorsal views) of partial z-stacks containing only the optical sections in the plane of the RB cell bodies within the spinal cord in a wild-type Tg(–3.1ngn1:gfp-caax) embryo (A), or a klc4^uw314 Tg(–3.1ngn1:gfp-caax) embryo (B), with an apical protrusion from a neuron crossing the midline and reaching the contralateral side (white arrowhead). Scale bars = 20 µm. (C) The percentage of neurons per embryo that had an apical protrusion crossing the midline of the spinal cord was quantified. **p<0.0052, Mann–Whitney test. Mean with SEM displayed over individual data points. Wild type N=608 neurons from 21 embryos, klc4^uw314 N=1496 neurons from 47 embryos, 2% DMSO N=429 neurons from 15 embryos, Kinesore N=595 neurons from 21 embryos. (D–F) Mosaic labeling of individual neurons by injection with –3.1ngn1:gfp-caax DNA into klc4^uw314 mutants (D), DMSO-treated embryos I or kinesore-treated embryos (F) showing that apical protrusions (magenta arrowheads) can fasciculate onto the contralateral central axon.

Figure 7—video 1. Light sheet microscopy of an embryo treated with 100µM Kinesore, showing what appear to be apical protrusions crossing the midline of the spinal cord.

Download video file ^{(5.3MB, mp4)}

This behavior was seen in both Kinesore treated and klc4^uw314 mutant embryos. Anterior is to the right.

Figure 7—video 2. High-speed, high-magnification light sheet microscopy of a klc4^uw314 mutant embryo showing an apical protrusion growing across the midline with a dynamic tip that shows growth-cone like behavior.

Download video file ^{(5MB, mp4)}

Anterior is to the top right corner.

Figure 7—video 3. A cropped portion of Figure 2—video 1 showing normal behavior of apical protrusions in the spinal cord of a wild-type embryo.

Download video file ^{(2.4MB, mp4)}

Video has been rotated to show the spinal cord in a more horizontal position. Anterior to the left.