(A) EM analysis of cortical and hippocampal synapsis derived from the three experimental groups of mice. Synaptic vesicles number per synapse was quantified from ~40 different images (taken from 5 mice for each group), normalized by the length of synaptic cleft and expressed as % of WT. The synaptic density was measured from 20 different images (taken from 5 mice for each group) as the number of synapses/area(#/500μm2) and expressed as % of WT. Arrows indicate the synaptic cleft while asterisks indicate abnormal vacuoles. Values are means ± s.e.m. *P<0.05, Student's t-test: Either MPS-IIIA-empty or MPS-IIIA-myc-CSPα vs WT-empty. Scale bar: 0.2 µm 