Fig. 2 Ntn1a is necessary to prevent a second CaP/VaP axon from extending beyond the muscle pioneers.
Projected confocal stacks of living dye-labeled motoneurons in one spinal hemisegment. A. VaP axon stalled at muscle pioneers (dashed line) at 36 hpf in standard control-MO injected embryo. B. nt1a SBMO injected embryos had two CaP/VaP axons that extended beyond the muscle pioneers. One CaP/VaP cell also extended an ectopic branch (arrow) along the horizontal myoseptum. B′-B′′. The same cells as shown in B. At 25 hpf (B′) the red cell was a CaP, but by 31 hpf (B′′) the red cell had retracted its axon to the muscle pioneers intermediate target and the green cell had become CaP. Scale bars = 9 μm in A, B and 20 μm in B′, B′′.