Fig. 2

Suppression of pmp2 and sptlc3 in Zebrafish Causes Defects in Motor Axon Pathfinding and Outgrowth

(A–F) Lateral views of a control embryo, an embryo injected with pmp2 morpholino (MO) and embryos injected with pmp2 MO+PMP2_WT and pmp2 MO+PMP2_I43N, PMP2_WT and PMP2_I43N cocktails, respectively, at 2 dpf (days post fertilization). Controls showed even spacing and normal branching of the motor neuron axons (A). In the pmp2 MO-injected embryos, the spacing of neuronal axons is perturbed by exiting the periphery but failing to extend (asterisks) or presenting pathfinding errors (arrows; B). Co-injection of pmp2 MO with human PMP2_WT resulted in restoration of the normal neuronal phenotype (C), but PMP2_I43N did not (D). Overexpression of human PMP2_WT causes mild pathfinding errors (E), suggesting dose sensitivity for PMP2. However, the human PMP2 mutant p.I43N was significantly more severe than PMP2_WT when overexpressed (F) and had similar effects to suppression of pmp2 by MO knockdown.

(G) Percentage of normal versus abnormal embryos under the conditions being evaluated above.

(H–K) Wild-type embryos (H) and sptlc3 morphants (I) in which secondary axons fail to migrate appropriately (white arrows). The phenotype induced by suppression of sptlc3 could be rescued by co-injection with SPTLC3_WT (J) but not SPTLC3_R150W (K).

(L) Quantification of normal embryos versus embryos with motor neuron axon defects. For statistical analyses, Χ² tests were performed.