Fig. 4. DD axon morphology changes over time in unc-119(ed3) mutants. (A) Confocal micrograph of an unc-119(ed3) L1 larvae expressing GFP in the GABA motor neurons. The DD axons (arrows) bifurcated normally at the dorsal nerve cord (arrowhead). (B) The DD neurons in an adult unc-119(ed3) mutant were branched (arrows). There were large gaps in the dorsal nerve cord (arrowhead). (C,D). The number of branched DD axons increased over time in unc-119(ed3) mutants. (C) At 1 hour after hatching 93% ±3.2 of wild-type axons were normal (left, n=12 worms, 71 axons). Most unc-119(ed3) DD axons were also normal at this stage (left, 58% ±8.1, n=15 worms, 79 axons). Some unc-119(ed3) axons reached the dorsal nerve cord but failed to extend normally along the dorsal midline (middle left, 28% ±7.2), which was also true for some wild-type axons at this time (7% ±3.2). Only a small fraction of mutant DD axons were visibly branched (middle right, 7% ±4.0), or failed to reach the dorsal nerve cord (right, 7% ±6.7). (D) At 48 hours after hatching, all wild-type axons were morphologically normal (left, n=16 worms, 96 axons). However, the fraction of normal axons in unc-119(ed3) mutants was significantly reduced (left, 25% ±8.1, n=8 worms, 40 axons). The fraction of axons that failed to extend along the dorsal midline did not change significantly (middle left, 20% ±3.8). The number of branched axons in unc-119(ed3) mutants increased eightfold (middle right, 55% ±5.0). The percentage of axons that failed to reach the dorsal nerve cord did change significantly (0%, right). Significance between time points is indicated by an asterisk (*, P<0.0001, t-test). Error bars represent the standard error of the mean. Scale bars (A,B) 10 µm.
