Figure 7.

CaP and RoP motor axons grow abnormal branches in N-cadherin mutant embryos. Wild type and cdh2^hi3644Tg embryos were injected at the 1-cell stage with a mix of two plasmids expressing Gal4 under the mnx1 promoter and pren-EGFP under a 14X-UAS element, fixed at 24 hpf, immunolabeled with SV2 and znp1 antibodies, and observed under confocal microscopy. Images in A, C, E, and G show pren-EGFP labeling while images B, D, F, and H show pren-EGFP (green) merged with SV2 and znp1 antibody labeling. A, B) Wild type CaP motor neuron shows the characteristic morphology with an axon extending from the spinal cord, along the common pathway and into the myotome (arrow) ventral to the choice point (bracket). C, D) CaP motor neuron from a cdh2^hi3644Tg embryo. The bracket indicates the choice point, the arrow points to the axon in the ventral myotome, and the double arrows point to an aberrant branch extending in the rostrocaudal axis. E, F) Wild type RoP motor axon shows the characteristic caudal migration before turning ventrally into the myotome. The bracket indicates the choice point where the RoP axon normally stalled. The SV2 and znp1 labeling ventral to the choice point corresponds to the CaP motor axon. G, H) RoP motor neuron from a cdh2^hi3644Tg mutant embryo. The bracket indicates the choice point and the arrow points to aberrant growth of the axon into the ventral myotome together with the CaP motor axon. Scale bars, 10 μm. Rostral is to the left and dorsal is to the top.