(C) EM analysis of cortical synapses derived from mice with indicated genotypes. The number of synaptic vesicles per synapse was quantified from 40 different images (taken from 5 different mice for each genotype), normalized by the length of synaptic cleft and expressed as % of WT. The size of synaptic vesicles was quantified from 400-500 vesicles (taken from 5 different mice for each genotype) and expressed as the average of vesicle diameter (nm) Arrows indicate the synaptic cleft. 