Figure 1.

Characterization of degeneration at the Drosophila NMJ and in motoneuron axons after injury. A, The axonal membrane (red) at muscle 4 NMJ synapses is labeled by immunostaining with anti-HRP antibodies. The MAP1B homolog Futsch (green) disappears most rapidly from distal boutons and concentrates within proximal boutons (12 h, arrow). By 24 h, Futsch has completely disappeared from boutons and forms sphere-shaped fragments in segmental nerves (arrowheads) and HRP staining becomes discontinuous (inset). B, Presynaptic active zones, stained by anti-Brp antibodies (red) also disappear from NMJ boutons in a distal-to-proximal manner (12 h, arrow). Postsynaptic receptors, detected by GluRIII staining (green) become diffuse but do not disappear (24 h). C, The time course of NMJ degeneration was quantified by measuring the length of muscle 4 NMJ nerve terminus (defined by HRP staining), which does not contain Futsch (as described in Materials and Methods). The onset of degeneration is significantly delayed at the lower temperature (dotted line), and inhibited by expression of the WldS mutation (blue line). D, In segmental nerves distal to the injury site, Futsch (red) and mCD8::GFP-labeled single axons, using the m12-Gal4 driver (green), are extensively fragmented by 12 h after injury. Nerves are oriented with the side proximal to the injury on the left. E, F, To quantify the time course of axonal degeneration, axons were scored by researchers blind to genotype using a scale ranging from completely continuous (0%) to continuous with varicosities (25%) to partially discontinuous (50%) to mostly fragmented with a few segments of continuity (75%) to completely fragmented (100%). Scale bars, 25 μm.