Table 2.

Morphometric analysis of NMJs in control and Syb1^lew/lewSyb2^−/− embryos^a

Variable	Control	Syb1lew/lewSyb2−/−
Nerve terminal area (μm2)	0.54 ± 0.06	0.46 ± 0.04
Nerve terminal perimeter (μm)	3.45 ± 0.22	2.98 ± 0.16
Synaptic contact length (μm)	1.14 ± 0.08	0.78 ± 0.05**
Synaptic contact proportion	33.5 ± 1.0	27.3 ± 1.0***
Synaptic vesicle number (per terminal)	43.4 ± 4.5	31.9 ± 2.9*
Synaptic vesicle density (per μm2)	91.7 ± 4.3	78.2 ± 3.8*
Docked synaptic vesicle number (per active zone)	1.47 ± 0.09	1.59 ± 0.12
DCV number (per terminal)	0.56 ± 0.08	1.49 ± 0.17***
Ectopic synaptic vesicle cluster (per terminal)	0.023 ± 0.013	0.031 ± 0.015
Vacuole-like structures (per terminal)	1.77 ± 0.18	1.23 ± 0.13
Tubular structures (per terminal)	0.63 ± 0.13	0.38 ± 0.60

^aMorphometric analysis was performed on EM images of the NMJs from control (n = 131 nerve terminal profiles, N = 5 mice) and Syb1^lew/lewSyb2^−/− mice (n = 129 nerve terminal profiles, N = 4 mice) at E18.5. The definition of parameters is described in Material and Methods. Docked synaptic vesicle numbers were counted from 68 nerve terminals in control and 37 nerve terminals in Syb1^lew/lewSyb2^−/− embryos. Data are mean ± SEM.

*p < 0.05;

**p < 0.001;

***p < 0.0001; two-tailed Student's t test.