Figure 3

NMJ morphology in sec8 mutants becomes abnormal during larval growth. A: Confocal images showing NMJs on ventral longitudinal muscles 15, 6/7, 13 and 12 in first instar larvae (24–28 h AEL), visualized using anti-HRP antibodies. Scale bar: 10 μm. B: Confocal images showing NMJs on ventral longitudinal muscles 6 & 7 in third instar larvae (110–120 hr AEL), visualized using anti-HRP antibodies. Scale bar: 20 μm. C: Example of extreme NMJ overgrowth occasionally observed in sec8P1 mutant third instar larvae. The mutant NMJ appears contracted, with an abnormally high number of boutons, compared to controls (c.f. 3B). In addition, long slender neurites (normally not present) extend across the muscle to the right (distally) of the NMJ center. Abnormal NMJ growth such as this was never observed in control animals (N>200). D: Quantification of the number of presynaptic boutons (left) and the number of branches (right) at the 6/7 NMJ in first instar (24–48 h AEL) larvae. E: Quantification of the number of presynaptic boutons (left) and the number of branches (right) at the 6/7 NMJ in third instar (110–120 AEL) larvae. sec8Δ1 mutants die before third instar (skull and crossbones) and thus third instar morphology could not be assayed in that genotype.