Diaphragms of P0 mice were subjected to electron microscopic analysis. (A) Representative electron micrographic images of indicated genotypes. Asterisks, active zones; SBL, synaptic basal lamina; N, nerve terminals; M, muscle fibers; SC, Schwann cells; SV, synaptic vesicle. (B–E) Quantitative analysis of data in A. Data were shown as mean ± SEM; **, p < 0.01; ***, p < 0.001, One-way ANOVA, n = 10.