Figure 5—figure supplement 1.

Figure 5—figure supplement 1.

(A) The cartoon illustrates the stereotyped morphology of CaP motor neurons, which have a large cell body located dorsally in the spinal cord and an axon that grows into the ventral myotome where it branches and forms synapses on fast twitch muscle fibers (Myers et al., 1986; Westerfield et al., 1986). (B) EGFP (left column), or iR4H (middle column) or aR3H (right column) fusion proteins with EGFP (green) were co-expressed in motor neurons with a presynaptic marker, synaptophysin-mCherry (Syn-mCherry, red). Live images of CaP motor neurons were obtained at 48 hpf using a laser scanning confocal microscope. Representative maximum intensity projections are shown. Top row, EGFP fluorescence; middle row, mCherry fluorescence; bottom row, merged images. Images were traced for three-dimensional reconstruction and synapses were counted using Imaris software. (C–H) Panels show mean values ± SEM obtained from traced images for (C) synapse number; (D) distal branch number, where distal indicates below the midline (dashed line in cartoon shown in part A); (E) distal branch length; (F) length of the main axon shaft; (G) proximal branch number, where proximal indicates at or above the midline (dashed line shown in cartoon in part A); and (H) proximal branch length. Statistical significance was assessed by one-way ANOVA Kruskal-Wallis test, followed by Dunn’s multiple comparison test. *, p<0.05; **, p<0.01. EGFP, n = 12 neurons; iR4H, n = 33 neurons; aR3H, n = 19 neurons.