SYN1 and early-onset autosomal dominant Alzheimer disease: As shown in Fig. 2A and B, many of the SNARE complex genes involved in presynaptic vesicle exocytosis were significantly downregulated in Alzheimer’s disease, including SNAP-25, STX1A, SYT1 and VAMP2, while STX2, SYN1 and VAMP3 were not changed.