Table 1.

Summary of ultrastructural analysis

CharacteristicGenotype
+/+Mhc-Gal4 → DGluRIIAMhc-Gal4 → PABPpabpEP0310/df
Number of branches analyzed  4   4  10   5
Total length of branches sectioned (μm) 37.8 39.4 83.8 41.1
Total junction surface sectioned (μm2)174.0241.1368.1228.2
Total number dense areas observed144 178 268 141
Number dense areas with one T-bar 70 108 158  99
Number of dense areas with more than one T-bar  9  17  33  10
Number dense areas without T-bar 65  58  77  32
Mean size dense areas (μm2)0.285  ± 0.0150.329  ± 0.0180.225  ± 0.0100.287  ± 0.015
Dense areas/surface area (μm2)0.83  ± 0.080.74  ± 0.090.74  ± 0.080.64  ± 0.06
Dense areas with T-bars/surface area (μm2)0.46  ± 0.060.54  ± 0.090.53  ± 0.060.49  ± 0.07
Dense areas without T-bar/surface area (μm2)0.37  ± 0.080.20  ± 0.050.21  ± 0.040.15  ± 0.07
Size of entire NMJ (%)100  ± 4158  ± 5183  ± 13196  ± 6
(number of boutons/muscle surface area)(1.59  ± 0.06)(2.52  ± 0.08)(2.91  ± 0.20)(3.11  ± 0.09)
Total number dense areas per entire NMJ (%)100  ± 8141  ± 9163  ± 17151  ± 8
(1.38  ± 0.10)(1.86  ± 0.18)(8.15  ± 0.22)(1.99  ± 0.11)
Dense areas with T-bars per entire NMJ (%)100  ± 11188  ± 18211  ± 29208  ± 15
(0.70  ± 0.08)(1.36  ± 0.12)(1.54  ± 0.21)(1.52  ± 0.11)
Dense areas without T-bar per entire NMJ (%)100  ± 1785  ± 15103  ± 3480  ± 19
(0.59  ± 0.10)(0.50  ± 0.09)(0.61  ± 0.20)(0.47  ± 0.11)
Active zones (%) 56  72  73  76
  • Summary of scored and derived data obtained from serial reconstructions of junctional branches. The number and density of dense areas of the reconstructed branches were extrapolated to entire NMJs of the respective genotypes by multiplying normalized junction size (arbitrary units; Sigrist et al., 2000) by density of synapses (see Materials and Methods). Genotypes with larger NMJs show a significantly higher percentage of active zones (dense areas that harbor a T-bar) compared with wild type (p< 0.05). All data were obtained from individual branches and then combined to mean values ± SEM per genotype.